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Genetic Diversity and the Survival of Populations
Abstract
: In this comprehensive review, a range of factors is considered that may influence the significance of genetic diversity for the survival of a population. Genetic variation is essential for the adaptability of a population in which quantitatively inherited, fitness-related traits are crucial. Therefore, the relationship between genetic diversity and fitness should be studied in order to make predictions on the importance of genetic diversity for a specific population. The level of genetic diversity found in a population highly depends on the mating system, the evolutionary history of a species and the population history (the latter is usually unknown), and on the level of environmental heterogeneity. An accurate estimation of fitness remains complex, despite the availability of a range of direct and indirect fitness parameters. There is no general relationship between genetic diversity and various fitness components. However, if a lower level of heterozygosity represents an increased level of inbreeding, a reduction in fitness can be expected. Molecular markers can be used to study adaptability or fitness, provided that they represent a quantitative trait locus (QTL) or are themselves functional genes involved in these processes. Next to a genetic response of a population to environmental change, phenotypic plasticity in a genotype can affect fitness. The relative importance of plasticity to genetic diversity depends on the species and population under study and on the environmental conditions. The possibilities for application of current knowledge on genetic diversity and population survival for the management of natural populations are discussed.
... Populations with high GD tend to have a higher adaptive potential to cope with changing environments (Markert et al., 2010;Ellegren and Galtier, 2016), which is becoming increasingly important in the context of global change (Francisco-Ortega et al., 2000;Reusch et al., 2005). Therefore, great efforts have been made to understand the factors that influence GD in order to design management strategies for target species, such as endangered and invasive species (Booy et al., 2000;DeWoody et al., 2021). Many endangered species have important economic, cultural and ecological value (Hooper et al., 2005;Hooper et al., 2012;Estrada et al., 2017), while invasive species often have significant negative impacts on ecosystems (Mitchell and Power, 2003;Pysek and Richardson, 2010). ...
... The populations of endangered species have declined or remained small, while those of invasive species have expanded, representing two opposite species statuses (Colautti et al., 2017). Given that population GD is closely related to fitness (Booy et al., 2000;Leimu et al., 2006) and population size (Reed and Frankham, 2003;Leimu et al., 2006), it might be associated with the species status, i.e., with whether they experienced or are experiencing population decline or expansion (Abrams, 2002;Coates et al., 2007). Numerous studies have shown low GD in small populations (Frankham, 1996;Leimu et al., 2006;Azizan et al., 2023), making them more vulnerable to disturbances, pests or diseases and thus in greater danger of becoming extirpated (Woodworth et al., 2002). ...
... This knowledge gap greatly impedes our understanding of the role that GD plays in the processes of becoming endangered or invasive, to design more effective management strategies to prevent species extinction and control biological invasions. There is thus an urgent need to clarify the overall patterns of population GD in species with contrasting species status and its key influencing factors (Booy et al., 2000;Teixeira and Huber, 2021), which is the aim of the present study. Based on the current theory and evidence found from quantitative synthesis about endangered (rare) or invasive (introduced) organisms separately (Table 1), two opposite scenarios are possible. ...
Genetic diversity (GD) in populations is important in determining the adaptive potential of populations and is thus thought to influence whether populations decrease or increase in abundance. Yet, a robust evaluation of this premise is needed. By integrating data of 1636 observations from 589 studies globally, we evaluated the relative GD (measured as log response ratio of expected heterozygosity, lnRR) of endangered and invasive plant species compared to control (common or native) species. We also evaluated the variables that influence the variation in population GD within each plant group. Results suggest that the decline in GD is lagging behind the population decline of most endangered plants and that a lower GD did not limit the population expansion of most invasive plants. The effect of inbreeding and gene flow on the relative GD of invasive species was mediated by population size, whereas gene flow directly but nonlinear impacted that of endangered plants, and inbreeding influenced it through an indirect pattern. Mating system was the most important life-history and ecological characteristic to drive relative GD of both endangered plants and invasive plants. The relative GD of endangered plants was also influenced by life form, distribution and rarity form. Overall, genetic diversity was not found to determine species status (endangered or invasive), but species characteristics and genetic factors do have a clear influence on species' evolutionary potential. Understanding the factors that influence GD is key to prioritize management actions on endangered and invasive plants with low and high GD, respectively.
... These primers were used to amplify DNA from seven Zanthoxylum accessions (9, 30, 35, 42, [14]. was also conducted using DNA from the same seven Zanthoxylum accessions (9,30,35,42,67,70,71) (Supplementary Table S1). Again, primers that yielded clear ampli cation bands, high polymorphism, and high stability were selected. ...
... Over an extended period, the combination of natural and arti cial selection has limited genetic exchange between these Zanthoxylum populations, leading to signi cant differentiation. Generally, higher genetic diversity indicates greater complexity of plant diversity and greater potential for environmental adaptation [42]. Among the three populations, the Z. bungeanum population (Pop1) exhibited the highest genetic diversity, while the Z. piperitum population (Pop3) displayed the lowest. ...
Zanthoxylum is a versatile economic tree species utilized for its spice, seasoning, oil, medicinal, and industrial raw material applications, and it has a lengthy history of cultivation and domestication in China. This has led to the development of numerous cultivars. However, the prevalence of mixed varieties and naming confusion significantly obstruct the effective use of Zanthoxylum resources and industry development. Consequently, conducting genetic diversity studies and variety identification on Zanthoxylum are crucial. This research analyzed the genetic traits of 80 Zanthoxylum cultivars using SSR and iPBS molecular markers, leading to the creation of a DNA fingerprint. This study identified 206 and 127 alleles with 32 SSR markers and 10 iPBS markers, respectively, yielding an average of 6.4 and 12.7 alleles ( Na ) per marker. The average polymorphism information content ( PIC ) for the SSR and iPBS markers was 0.710 and 0.281, respectively. The genetic similarity coefficients for the 80 Zanthoxylum accessions ranged from 0.0947 to 0.9868 and from 0.2206 to 1.0000, with mean values of 0.3864 and 0.5215, respectively, indicating substantial genetic diversity. Cluster analysis, corroborated by principal coordinate analysis (PCoA), categorized these accessions into three primary groups. Analysis of the genetic differentiation among the three Zanthoxylum ( Z. bungeanum , Z. armatum , and Z. piperitum ) populations using SSR markers revealed a mean genetic differentiation coefficient ( Fst ) of 0.335 and a gene flow ( Nm ) of 0.629, suggesting significant genetic divergence among the populations. Molecular variance analysis (AMOVA) indicated that 65% of the genetic variation occurred within individuals, while 35% occurred among populations. Bayesian model-based analysis of population genetic structure divided all materials into two groups. The combined PI and PIsibs value of the 32 SSR markers were 4.265 × 10 − 27 and 1.282 × 10 − 11 , respectively, showing strong fingerprinting power. DNA fingerprints of the 80 cultivars were established using eight pairs of SSR primers, each assigned a unique numerical code. In summary, while both markers were effective at assessing the genetic diversity and relationships of Zanthoxylum species, SSR markers demonstrated superior polymorphism and variety discrimination compared to iPBS markers. These findings offer a scientific foundation for the conservation and sustainable use of Zanthoxylum species.
... The second argument is that plant fitness allows populations to be distinguished by differences in habitat quality (VERGEER et al., 2003). According to BOOY et al. (2000), low levels of genetic variation may decrease plant fitness and limit a population's capacity to react to changing environmental circumstances via selection and adaptation. Twenty-five percent of genetic variation was gained within populations, while 75% of genetic variance was obtained between the examined groups. ...
... The breeding system of plant species is an important component in influencing the distribution of genetic diversity (DUMINIL, 2007). Couvet (BOOY et al., 2000) demonstrated that one migrant each generation is insufficient to ensure the long-term survival of relatively small populations. The number of migrants is determined by life history characteristics and population genetics (VERGEER et al., 2003). ...
Yellow hornpoppy (Glaucium flavum Crantz.) is a herbaceous plant with gray-green leaves in coastal sands, rocky areas, and heavily eroded soils up to 500 meters above sea level. Glaucium flavum is native to Northern Africa, temperate zones in Western Asia and Europe, and is indigenous to Iran. The plant has been widely recognized for its aporphine-type isoquinoline alkaloids, which are pharmacologically active. Thus, we conducted a combination of morphological and molecular data analysis on such species because of the plant species' relevance. One hundred seven randomly collected plants from 14 natural populations in 5 provinces were evaluated using ISSR markers and morphological traits. The evaluation of molecular variance (AMOVA) demonstrated significant genetic divergence between the examined populations. It indicated that 25% of overall genetic variability was related to intra-population variety, whereas 75% was due to inter-population genetic differentiation. ISSR primers discovered 156 bands, 139 (83 %) of which have been polymorphic, each primer containing an average of 13 bands. The Polymorphic Bands (PPB) Percentage (ISSR-6) varied from 50% to 100%. (ISSR-1, ISSR-4, and ISSR-5). The average polymorphic information content (PIC), Shannon's information indexes (I), and several effective alleles (Ne) were correspondingly 0.39, 0.26, and 1.2.
... The second reason is the fact that plant fitness differentiates populations based on variations in habitat quality (Vergeer et al., 2003;Peng et al., 2021). According to Booy et al. (2000), low levels of genetic diversity could reduce plant fitness and restrict a population's ability to respond to changing environmental conditions through selection and adaptation. Genetic diversity (17%) was obtained within populations, whereas 83% of genetic variation was obtained between the evaluated populations. ...
... One of the key factors determining the distribution of genetic variation is the breeding system in plant species (Duminil, 2007). Couvet (Booy et al., 2000) revealed that one migrant per generation cannot be existed to guarantee the long-term survival of small populations and that the number of migrants is demonstrated through life history characters and population genetics (Vergeer et al., 2003). ...
The genus Malva L., popularly known as mallow, grows spontaneously in almost all of Europe and the Mediterranean region. This genus is morphologically very diverse and its species are used in the treatment of respiratory, urinary, and digestive problems, but some species are hardly distinguishable based on morphological features. We, therefore, performed a molecular data analysis for this genus. Amplification of genomic DNA of 90 randomly selected samples of six species of Malva using 5 primers produced 83 bands, of which 77 were found to be polymorphic (90.99%). The high average PIC and MI values revealed the high capacity of ISSR primers to detect polymorphic loci among Malva species. The genetic similarities of the six collections were estimated from 0.73 to 0.90. ISSR analysis revealed that Malva parviflora and M. vericillata had the lowest similarity whereas, M. neglecta and M. sylvestris had the highest similarity. Bangladesh J. Plant Taxon. 29(2): 193-202, 2022 (December)
... Molecular methods can help to understand the demographic and evolutionary processes that are essential for the adaptability of a population, in which quantitatively inherited fitness-related traits are considered crucial to its survival (Booy et al., 2000;Roderick, 1996). Identifying the origin and history of a species range through genetic structure is crucial for understanding the distribution patterns of a species and thus for assessing potential future invasion (Mech et al., 2019;Zahiri et al., 2019). ...
The phylogeography of economically important forest pests is important for understanding their demographic and evolutionary history. Linking the genetic data obtained with the bioclimatic models helps reveal future demographic trends of the pest species studied. Lymantria monacha is a polyphagous species that feeds on numerous coniferous and deciduous trees throughout the Palaearctic and is known to cause catastrophic defoliation, particularly in Europe. In addition, data from various mapping programmes over the last decade have revealed changes in the distribution of L . monacha . Therefore, in this study, we decided to clarify the evolutionary and demographic history of this important forest species using genetic data complemented by bioclimatic modelling. Our results confirmed the systematic status and monophyly of L . monacha . However, the lack of a geographical pattern between the studied regions suggests that the current genetic structure may be the result of recent dispersal events. Moreover, we found that the areas of high genetic diversity are consistent with potential past range shifts and survival of changes in climate and host plant availability. These two main variables also seem to determine the future range of L . monacha . Also, our modelling confirmed a poleward shift in its range and with a significant retraction from its current southern edge of distribution.
... Therefore, the stand should maintain relatively uniform in growth. The advantage of cultivating genotypes of different geographical origins together could lie in the fact that genetically more diverse communities are generally more resistant to various pathogens and pests outbreaks [46][47][48]. ...
Background
Afforestation of non-forestland is a new measure by the European Union to enhance climate mitigation and biodiversity. Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) is among the suitable tree species for afforestation to produce woody biomass. However, the best performing genotypic material for intensive biomass production and its physiological adaptation capacity is still unclear. We compared 22 hybrid aspen genotypes growth and leaf physiological characteristics (stomatal conductance, net photosynthesis, intrinsic water-use efficiency) according to their geographical north- or southward transfer (European P. tremula parent from 51° to 60° N and North American P. tremuloides parent from 45° to 54° N) to hemiboreal Estonia (58° N) in a completely randomized design progeny trial. We tested whether the growth ranking of genotypes of different geographical origin has changed from young (3-year-old) to mid-rotation age (13-year-old). The gas exchange parameters were measured in excised shoots in 2021 summer, which was characterised with warmer (+ 4 °C) and drier (17% precipitation from normal) June and July than the long-term average.
Results
We found that the northward transfer of hybrid aspen genotypes resulted in a significant gain in growth (two-fold greater diameter at breast height) in comparison with the southward transfer. The early selection of genotypes was generally in good accordance with the middle-aged genotype ranking, while some of the northward transferred genotypes showed improved growth at the middle-age period in comparison with their ranking during the early phase. The genotypes of southward transfer demonstrated higher stomatal conductance, which resulted in higher net photosynthesis, and lower intrinsic water-use efficiency (iWUE) compared with northward transfer genotypes. However, higher photosynthesis did not translate into higher growth rate. The higher physiological activity of southern transferred genotypes was likely related to a better water supply of smaller and consequently more shaded trees under drought. Leaf nitrogen concentration did not have any significant relation with tree growth.
Conclusions
We conclude that the final selection of hybrid aspen genotypes for commercial use should be done in 10–15 years after planting. Physiological traits acquired during periods of droughty conditions may not fully capture the growth potential. Nonetheless, we advocate for a broader integration of physiological measurements alongside traditional traits (such as height and diameter) in genotype field testing to facilitate the selection of climate-adapted planting material for resilient forests.
... In general, a species' adaptability is difficult to be directly assessed because it involves complex interactions between genetic, physiological, ecological, and behavioral factors, which are difficult to measure comprehensively and simultaneously 22 . Nevertheless, several proxies exist that can serve as estimates for an organism's resilience to environmental changes, and genetic diversity might serve as one of the most reliable estimators because high genetic diversity within a population relates to a higher likelihood of adaptive responses to selective pressures from changing environments 23 . The genetic diversity in immune response genes is directly translated into amino acid sequences, and hence, accessing genetic diversity is more closely tied to the immediate immune function 24 . ...
Our study examines the declining Jaguar populations in Central and South America, assessing the impact of habitat loss and fragmentation on genetic diversity and local adaptation. We investigated population structure and immunome variability in 25 jaguars to identify unique genetic diversity for informed, differentiated conservation. Our genome-wide analyses revealed three distinct geographic populations corresponding to Central America, South American lowland, and South American highland regions. While the highland population displayed lower overall immunome-wide variability, specific innate (Natural killer cell complex, Toll-like receptor) and adaptive (Major histocompatibility complex-class-II) immune genes crucial for adaptive responses showed promising diversity. Nonetheless, South American highland and Central American jaguars are severely threatened. Therefore, we propose re-evaluating evolutionary significant units to prioritize conservation efforts, preserving crucial genetic and adaptive diversity essential for the species' resilience and long-term survival.
... The genetic diversity of trees directly affects their evolutionary potential and adaptability to environmental changes. Higher genetic diversity indicates stronger evolutionary potential and ability to match the environment (Xia, 1999;Booy et al., 2000). The genetic Mantel between genetic distance and geographical distance of 10 A. odoratissima subpopulations. ...
Background
This study aimed at exploring unique population genetic characteristics of Albizia odoratissima (Linn. f) Benth on Hainan Island to provide a scientific basis for its rational utilization and protection.
Methods
It analyzed the genetic diversity and structure of 280 individuals from 10 subpopulations of A. odoratissima from Hainan Island and Baise City using 16 expression sequence markers - simple sequence repeat markers.
Results
The genetic diversity of Hainan population (I = 0.7290, He = 0.4483) was lower than that of the Baise population (I = 0.8722, He = 0.5121). Compared with the Baise population (Nm = 2.0709, FST = 0.1077), the Hainan Island population (Nm = 1.7519, FST = 0.1249) exhibited lower gene flow and higher degree of genetic differentiation. Molecular variance and genetic differentiation analyses showed that the main variation originated from individuals within the subpopulation. There were significant differences in the genetic structure between Hainan and Baise populations. It grouped according to geographical distance, consistent with the Mantel test results (R² = 0.77, p = 0.001). In conclusion, the genetic diversity of the island A. odoratissima population was lower than that distributed on land, the two populations exhibited obvious genetic structure differences. Both the degrees of inbreeding and genetic differentiation were higher in the island population than in the land population.
... Many assisted-migrant populations retain genetic diversity lost from their native conspecific populations (Bradshaw et al., 2006;Marchesini et al., 2021;Todd et al., 2022). Genetic diversity is itself an element of biodiversity, considered by many to have intrinsic value (Crozier, 1997); is important for future evolutionary dynamics; and may be a lifeline to the persistence of these species globally (Booy et al., 2000). Moreover, active conservation efforts in the native ranges of some of these species are difficult, if not impossible (e.g., the remaining 23-200 native African wild asses occur in areas occupied by warring groups [IUCN, 2018]). ...
International and national conservation policies almost exclusively focus on conserving species in their historic native ranges, thus excluding species that have been introduced by people and some of those that have extended their ranges on their own accord. Given that many of such migrants are threatened in their native ranges, conservation goals that explicitly exclude these populations may overlook opportunities to prevent extinctions and respond dynamically to rapidly changing environmental and climatic conditions. Focusing on terrestrial mammals, we quantified the number of threatened mammals that have established new populations through assisted migration (i.e., introduction). We devised 4 alternative scenarios for the inclusion of assisted‐migrant populations in mainstream conservation policy with the aim of preventing global species extinctions. We then used spatial prioritization algorithms to simulate how these scenarios could change global spatial conservation priorities. We found that 22% (70 species out of 265) of all identified assisted‐migrant mammals were threatened in their native ranges, mirroring the 25% of all mammals that are threatened. Reassessing global threat statuses by combining native and migrant ranges reduced the threat status of 23 species (∼33% of threatened assisted migrants). Thus, including migrant populations in threat assessments provides a more accurate assessment of actual global extinction risk among species. Spatial prioritization simulations showed that reimagining the role of assisted‐migrant populations in preventing species extinction could increase the importance of overlooked landscapes, particularly in central Australia, Europe, and the southwestern United States. Our results indicated that these various and nonexhaustive ways to consider assisted‐migrant populations, with due consideration of potential conservation conflicts with resident taxa, may provide unprecedented opportunities to prevent species extinctions.
... In the case of anemophily, there may be higher genetic diversity than the parent population owing to the wide migration distance of pollen [123,124]. However, for cross-fertilized plants, low genetic diversity in the parental population reduces seed production and quality, and it negatively impacts population survival and maintenance [125][126][127]. Therefore, the opportunity to increase genetic diversity arises from seed dispersal and subsequent ontogeny. ...
Rhododendron sobayakiense is an endemic and near-threatened species (Korean Red List, NT) found in the alpine regions of South Korea that requires conservation. This study investigated the species’ genetic variations and seed germination characteristics and predicted its potential habitat change according to climate change scenarios. The genetic diversity of R. sobayakiense at the species level (P = 88.6%; S.I. = 0.435; h = 0.282) was somewhat similar to that observed for the same genus. The inter-population genetic differentiation was 19% and revealed a relatively stable level of gene exchange at 1.22 in each population. The main cause of gene flow and genetic differentiation was presumed to be the Apis mellifera pollinator. Seed germination characteristics indicated non-deep physiological dormancy, with germination at ≥10 °C and the highest percent germination (PG) of ≥60% at 15–25 °C, while the PG was ≥50% at 30 °C. The PG increased at constant temperature than at variable temperatures; the mean germination time decreased as temperature increased. The climate scenarios SSP3 and SSP5 were analyzed to predict future R. sobayakiense habitat changes. The variables of the main effects were Identified as follows: elevation > temperature seasonality > mean diurnal range.
... Introduction Genetic diversity is a fundamental element to represent evolution, and the process of adaptation and speciation are the foundation materials on which this genetic diversity depends [1]. High levels of genetic diversity in any population are generally considered a healthy characteristic, providing resistance to diseases, parasites, and predators, and to environmental changes [2]. The evolutionary trajectory of genetic diversity represents a critical phenomenon within the broader realm of the living community, reaching its peak of significance, particularly in comparison to the vector insect community [3]. ...
Background:
Phlebotomus argentipes complex is the primary vector for cutaneous leishmaniasis, a burgeoning health concern in contemporary Sri Lanka, where effective vector control is important for proper disease management. Understanding the genetic diversity of the P. argentipes population in Sri Lanka is vital before implementing a successful vector control program. Various studies have indicated that genetic divergence, caused by genetic drift or
selection, can significantly influence the vector capacity of arthropod species. To devise innovative control strategies for P. argentipes, exploring genetic diversity and phylogeography can offer valuable insights into vector competence, key genetic trait transfer, and impact
on disease epidemiology. The primary objective is to analyze the genetic diversity and phylogeography of the P. argentipes complex in Sri Lanka, based on two mitochondrial genomic regions in modern representatives of P. argentipes populations.
Methodology:
A total of 159 P. argentipes specimens were collected from five endemic areas of cutaneous leishmaniasis and identified morphologically. Two mitochondrial regions (Cytochrome c oxidase subunit I (COI) and NADH dehydrogenase subunit 4 (ND4) were amplified using the total DNA and subsequently sequenced. Partial sequences of those mitochondrial genes were utilized to analyze genetic diversity indices and to explore phylogenetic and phylogeographic relationships.
Principal findings:
Among five sampling locations, the highest genetic diversity for COI and ND4 was observed in Hambantota (Hd—0.749, π—0.00417) and Medirigiriya (Hd—0.977, π—0.01055), respectively. Phylogeographic analyses conducted using COI sequences and GenBank retrieved sequences demonstrated a significant divergence of P. argentipes haplotypes found in Sri Lanka. Results revealed that they have evolved from the Indian ancestral haplotype due to historical- geographical connections of the Indian subcontinent with Sri Lanka.
Conclusions:
Utilizing high-mutation-rate mitochondrial genes, such as ND4, can enhance the accuracy of genetic variability analysis in P. argentipes populations in Sri Lanka. The phylogeographical analysis of COI gene markers in this study provides insights into the historical geographical relationship between India and P. argentipes in Sri Lanka. Both COI and ND4 genes exhibited consistent genetic homogeneity in P. argentipes in Sri Lanka, suggesting minimal impact on gene flow. This homogeneity also implies the potential for horizontal gene transfer across populations, facilitating the transmission of genes associated with traits like insecticide resistance. This dynamic undermines disease control efforts reliant on vector control strategies.
... One component of the management of the species is the maintenance of plants ex situ in living collections. Ex situ living collections act as safeguards to extinction for threatened species and help to preserve genetic diversity, which is the basis for evolutionary change and is intrinsically linked to the adaptability and fitness of populations (Booy et al. 2000). For this reason, maximizing genetic diversity in seed banks and ex situ living collections is a priority for the conservation of threatened species. ...
Zieria buxijugum, Z. formosa, and Z. parrisiae are three closely related, Critically Endangered species of questionable taxonomic validity that occur within six kilometres of each other on the south coast of New South Wales, Australia. We investigated genetic relationships and diversity of these species, along with two related but taxonomically distinct congeners, Z. granulata and Z. tuberculata, and a possible undescribed taxon, Z. aff. tuberculata. Double-digest restriction-site associated sequencing (ddRADseq) was used to generate anonymous genomic loci that were used for phylogenetic, network, and genetic structure analyses, and for estimating genetic diversity of the threatened species. Our results support the current taxonomic status of Z. buxijugum, Z. formosa, and Z. parrisiae, and suggest that Z. aff. tuberculata warrants recognition as a distinct species. We detected no evidence of inbreeding in the three Critically Endangered species, and found their genetic diversity to be similar to that of the more widespread species Z. granulata and Z. tuberculata. Comparison of plant material held in ex situ collections at the Australian National Botanic Gardens with wild plants highlighted several genotypes of the Critically Endangered species that are not represented in the ex situ collection, and we provide suggestions for the future inclusion of those unrepresented genotypes.
... The sterile and parthenocarpy nature of bananas, with the vegetative mode of propagation coupled with its genetic uniformity, make them particularly vulnerable to diseases and abiotic stress [68,81]. The low genetic diversity may compromise the crop's ability to adapt to changing environmental conditions, making them more prone to extinction [91,92]. ...
Sweet fig ( M . acuminata cv. Sotoumon) is an economically important dessert banana in Benin, with high nutritional, medicinal, and cultural values. Nevertheless, its productivity and yield are threatened by biotic and abiotic stresses. Relevant knowledge of the genetic diversity of this economically important crop is essential for germplasm conservation and the development of breeding programs. However, very little is known about the genetic makeup of this cultivar in Benin. To advance the understanding of genetic diversity in sweet fig banana germplasm, a Genotype-By-Sequencing (GBS) was performed on a panel of 273 accessions collected in different phytogeographical zones of Benin. GBS generated 8,457 quality SNPs, of which 1992 were used for analysis after filtering. The results revealed a low diversity in the studied germplasm (He = 0.0162). Genetic differentiation was overall very low in the collection as suggested by the negative differentiation index (Fstg = -0.003). The Analysis of Molecular Variance (AMOVA) indicated that the variation between accessions within populations accounted for 83.8% of the total variation observed (P < 0.001). The analysis of population structure and neighbor-joining tree partitioned the germplasm into three clusters out of which a predominant major one contained 98.1% of all accessions. These findings demonstrate that current sweet fig banana genotypes shared a common genetic background, which made them vulnerable to biotic and abiotic stress. Therefore, broadening the genetic base of the crop while maintaining its quality attributes and improving yield performance is of paramount importance. Moreover, the large genetic group constitutes an asset for future genomic selection studies in the crop and can guide the profiling of its conservation strategies.
... In evolutionary biology, it is generally accepted that species with larger genetic variation have better survival rates (e.g., Booy et al., 2000). Applied to legal systems, survival rates can be seen in terms of public support or legitimacy of the legal system. ...
Technological developments increasingly enable monitoring and steering the behavior of individuals. Enforcement of the law by means of technology can be much more effective and pervasive than enforcement by humans, such as law enforcement officers. However, it can also bypass legislators and courts and minimize any room for civil disobedience. This significantly reduces the options to challenge legal rules. This, in turn, can impede the development of legal systems. In this paper, an analogy is made with evolutionary biology to illustrate that the possibility to deviate from legal rules and existing norms is sometimes necessary for the further development of legal systems. Some room to break the law, for instance, through civil disobedience or imperfect enforcement of the law, will ensure sufficient variation. This allows for properly evolving legal systems that can continue to provide fair solutions, even when society and concepts of fairness further develop.
... Die niedrigen Überlebens-und Etablierungsraten von Scorzonera humilis könnten im hohen Alter und der geringen Verjüngung der wenigen noch bestehenden Spenderpopulationen begründet sein (COLLING et al. 2002, COLLING & MATTHIES 2006, RECKINGER et al. 2010. Da sich die mit der Populationsgröße rückläufige genetische Variabilität negativ auf deren Anpassungsfähigkeit an veränderte Umweltbedingungen auswirkt, könnte dies auch die Entwicklung der Wiederansiedlungen beeinträchtigt haben (BOOY et al. 2000, MIX et al. 2006. Studien zum Einfluss der genetischen Vielfalt auf den Etablierungserfolg von Populationen zeigen, dass sich die Nutzung mehrerer Spenderpopulationen und die damit einhergehende Erhöhung der genetischen Variabilität positiv auf den Erfolg von Wiederansiedlungen auswirkt und Inzuchtdepressionen vorbeugen kann (VERGEER et al. 2005, MENGES 2008, RECKINGER et al. 2010, COMMANDER et al. 2018. ...
Feuchtwiesen und deren Kennarten sind heute stark im Rückgang begriffen. In Luxemburg gehören dazu auch typische Vertreter der Pfeifengraswiesen wie Oenanthe peucedanifolia, Scorzonera humilis, Stachys officinalis, Succisa pratensis und Serratula tinctoria. Um solche gefährdeten Arten gezielt zu fördern, werden sie seit 2012 durch das Naturschutzsyndikat SICONA vermehrt und In situ ausgebracht. Ziel dieser Untersuchung war es, den langfristigen Erfolg solcher Wiederansiedlungsmaßnahmen zu beurteilen. Dabei wurde überprüft, zu welchem Erfolg die Maßnahmen bei den fünf Zielarten nach vier bis neun Jahren geführt haben. Folgende drei Fragestellungen wurden bearbeitet: (1) Wie erfolgreich verlief die Wiederansiedlung, (2) wie unterschieden sich vegetative und generative Merkmale – als Kenngrößen der Vitalität und Fitness – zwischen wiederangesiedelten und bestehenden Populationen und (3) welchen Einfluss hatten die Standortbedingungen auf den Etablierungserfolg? Dazu wurden auf jeweils sechs Ansiedlungsflächen pro Art die Überlebens-, Reproduktions- und Etablierungsraten bestimmt. Der Vergleich von Vitalität und Fitness auf den Ansiedlungs- und Bestandsflächen erfolgte durch den Vergleich phänometrischer und reproduktionsbiologischer Merkmale. Zur standörtlichen Charakterisierung dienten die aus Vegetationsaufnahmen ermittelten Zeigerwerte. Bei drei Zielarten – Stachys officinalis, Succisa pratensis und Oenanthe peucedanifolia – wurde festgestellt, dass sich die neu etablierten Populationen erfolgreich angesiedelt hatten und selbst verjüngten. Etablierungsraten zwischen 327 und 763 % bestätigen eine erfolgreiche Wiederansiedlung. Bei Serratula tinctoria überlebte ein Viertel der gepflanzten Individuen; es kam aber kaum zur Verjüngung. Bei diesen vier Zielarten und in 60 % aller 30 Wiederansiedlungsplots kam es zu einer Zunahme der Populationsgröße. Weniger erfolgreich verlief die Wiederansiedlung von Scorzonera humilis, die mit durchschnittlich 7,5 % die niedrigste Etablierungsrate aufwies. Während die Vitalität bei den wiederangesiedelten Populationen oft schon ein ähnlich hohes Niveau erreichte wie bei den Bestandspopulationen, lag die reproduktive Fitness meist deutlich niedriger. Der Vergleich der Zeigerwerte verdeutlichte, dass die Lebensbedingungen für die Zielarten auf vielen der Ansiedlungsflächen gut mit denen der Bestandsflächen übereinstimmten. Auf einigen Ansiedlungsflächen wiesen die Zeigerwerte allerdings auf eine höhere Basen- und Stickstoffversorgung und eine größere Trockenheit als auf den Bestandsflächen hin. Die weniger gute Entwicklung der Zielarten auf solchen Ansiedlungsflächen belegt die große Bedeutung passender Standortbedingungen für den Renaturierungserfolg. Die Nachzucht und Auspflanzung hat sich also als gut geeignete Methode erwiesen, um die rückläufigen Vorkommen von Kennarten der Pfeifengraswiesen zu stärken und es bestehen gute Chancen, dass die meisten Zielarten auch langfristig auf den Ansiedlungsflächen vorkommen werden. Dennoch verlief die Wiederansiedlung nicht bei allen Zielarten erfolgreich. Serratula tinctoria gelangte kaum zur Reproduktion und bei Scorzonera humilis waren sowohl die Überlebens- als auch die Reproduktionsraten sehr niedrig. Als Ursachen hierfür werden artspezifische Faktoren wie mangelnder genetischer Austausch oder Überalterung der Spenderpopulationen diskutiert. Zudem wird die Wiederansiedlung auch durch praxisrelevante Faktoren wie der Mangel an für stenöke Arten geeigneter Standorte und die fehlende Möglichkeit zur Wiedervernässung eingeschränkt. Die Studie belegt auch die Bedeutung langjähriger Erfolgskontrollen bei In situ-Erhaltungsmaßnahmen, die in der Renaturierungspraxis bislang kaum verbreitet sind.
Abstract
Today, wet meadows and their typical flora are in sharp decline. In Luxembourg, these include characteristic species of Molinion meadows such as Oenanthe peucedanifolia, Scorzonera humilis, Stachys officinalis, Succisa pratensis and Serratula tinctoria. To support such species, the nature conservation syndicate SICONA has practiced propagation and in situ plantation since 2012. The aim of this study was to assess the long-term success of such reintroduction measures. We examined the establishment of the five target species four to nine years after reintroduction. Three questions were addressed: (1) how successful was the reintroduction, (2) how did vegetative and generative traits - as key indicators of vitality and fitness - differ between newly established and extant populations, and (3) what influence did site conditions have on establishment success? For this purpose, survival, reproduction, and establishment rates were determined on six reintroduction plots per species. Vitality and fitness in newly established (introduction sites) and sites with natural populations (reference sites) were compared using phenometric and reproductive traits. Ellenberg indicator values determined from vegetation surveys were applied to characterize site conditions. For three target species, Stachys officinalis, Succisa pratensis, and Oenanthe peucedanifolia, the newly planted populations showed successful establishment and reproduction, underlined by establishment rates between 327 and 763%. In Serratula tinctoria, one quarter of planted individuals survived, while little regeneration occurred. For these four target species and in 60% of all 30 re-introduction plots population size increased. Only for Scorzonera humilis establishment was less successful, averaging 7.5%. Whilst, for all five species, most of the newly planted individuals reached a vitality similar to that of extant populations, their reproductive fitness usually ranged lower. Comparison of Ellenberg indicator values illustrated that habitat conditions for the target species at most of the restoration sites well matched with conditions at the reference sites. In some introduction sites, indicator values suggest higher base and nitrogen supply and a lower water availability than on the long existing sites. Weaker development of the target species in such sites proves the great importance of suitable site conditions for restoration success. Nursery propagation and on-site plantation were demonstrably a well-suited method to strengthen declining populations of threatened Molinion meadow species and it seems likely that newly established populations can remain viable in the long term. Nevertheless, not all target species showed successful establishment. Serratula tinctoria barely managed to reproduce and for Scorzonera humilis both survival and reproduction rates were very low. Species-specific factors such as insufficient genetic exchange or over-aging of donor populations are discussed as potential causes. In addition, reintroduction can also be constrained by practice-related factors such as the shortage of sites suitable for stenoecious species and the lack of suitable sites for re-wetting. This study also demonstrates the importance of monitoring the long-term success of in situ conservation measures, which has received insufficient attention in restoration practice so far.
... In recent years, due to the global warming and drying of climate, deterioration of soil conditions, overgrazing, and other reasons (Wei et al. 2019; Du et al. 2015), the resources of Astragalus polycladus have declined dramatically, so there is an urgent need to protect the wild Astragalus polycladus resources. Phenotypic diversity is a prerequisite for the conservation of Astragalus polycladus, and it is widely used in genetic diversity research because it can directly re ect the genetic diversity of the population and has the characteristics of simplicity and intuition (Liu et al. 2023; Booy et al. 2000). ...
To explore the phenotypic diversity of wild Astragalus polycladus resources, 150 wild Astragalus polycladus resources from 6 regions of Qinghai Province were used as materials, and 18 phenotypic traits were analyzed. The results showed that Astragalus polycladus had abundant phenotypic diversity in Qinghai Province, and the coefficient of variation of 18 phenotypic traits ranged from 1%-23%. Among them, the fertile tillers’ coarseness, fertile tillers’ length, and crown width are the most variable characteristics. Correlation analysis showed that there were significant or extremely significant correlations among other traits except for root number and stem length. At the same time, the phenotypic traits of Astragalus polycladus were related to latitude and longitude, altitude, and soil pH, and different traits were affected by different geographical factors, among which the corolla number was the most affected. Four principal components with eigenvalues greater than 1 were selected by principal component analysis, and the cumulative contribution rate was 77.151%, which contained most of the information about the phenotypic traits of Astragalus multicladus. Crown width and plant height had the greatest influence on the phenotypic traits diversity of Astragalus polycladus. These results indicate that the phenotypic traits of Astragalus polycladus resources in Qinghai Province are rich in diversity and have great potential for exploitation and utilization. This study provided a scientific basis for the breeding and preservation of superior germplasm resources of Astragalus polycladus .
... According to Bednorz (2007), protection of small populations or even single trees is vital to ensure connectivity and gene flow among populations of rare and scattered tree species such as Turkish hazel. The genetic diversity of tree populations should be kept at an appropriate level to maintain short-term viability and long-term evolutionary potential (Boyle, 2000;Booy et al., 2000, Young et al.,1996. The aim should be to conserve and protect the Turkish hazel populations under the environmental conditions covered by this tree species (in-situ). ...
Climate change is already affecting all forest ecosystems and threatening species therein. By establishing mixed forests incorporating other tree species (e. g. scattered broadleaves) adaptation of forest stands to changing environmental conditions can be improved and the risks minimized. Turkish hazel (Corylus colurna L.) has been currently discussed as a valuable so-called alternative tree species in some European regions because it is well adapted to difficult environmental conditions. However, in its natural distribution area Turkish hazel has been overexploited because of its valuable wood and can only be found in small and isolated populations. Therefore, we examined the genetic structure and variation of Turkish hazel covering most of its natural distribution range in Asia Minor, the Caucasus, and the Balkan Peninsula. Altogether, 689 Turkish hazel trees from 25 populations were analysed at 15 nuclear and five chloroplast microsatellite markers. Both data sets revealed distinct genetic clusters of Turkish hazel in its natural distribution range, suggesting separate refugia and migration pathways during the Holocene. Medium to high level genetic variation was found, with somewhat lower values in Georgia and Turkey compared to the Balkan populations. Overall, our results highlight the need to delineate provenance regions, identify gene conservation units (GCUs) and seed stands for Turkish hazel which are essential for species conservation, provenance research and possible assisted migration attempts. Based on our results each country is able now to start conservation programs and select GCUs for Turkish hazel.
... The Cape gannet, having experienced a dramatic population decline since the late 1990s (Sherley et al. 2019), has already lost some genetic diversity (Reed and Frankham 2003), with consequences for population resilience to disruptions (Booy et al. 2000;Bradshaw and Holzapfel 2008;Vandewoestijne et al. 2008). Our results suggest that aging female gannets expend more energy than males to obtain food to sustain themselves and their chick while replenishing the resources lost from earlier investment in reproduction i.e. egg-laying. ...
Senescence is the irreversible decline in physiological functioning and survival with age. While this phenomenon has been studied in a range of different taxa, including seabirds, it has seldom been assessed for both sexes of monomorphic species, and in conservation contexts. Here, we studied the effect of age and sex on the foraging trip characteristics and energetics of the monomorphic Cape gannet (Morus capensis). Between 2017 and 2020, we used GPS recorders and miniaturised three-dimensional accelerometers to obtain data on the foraging trip characteristics and energy expenditure of 39 Cape gannets rearing chicks on Malgas Island, South Africa. This sample included 11 females and 28 males between the ages of 4 and 23 years. No difference in foraging trip characteristics was apparent between sexes or individuals of different ages. The energy expenditure of aging females (> 17 years) was higher than that of aging males. Aging females spent both more energy flying and less energy resting than males, despite similar foraging trip durations and distances. Males spent more energy diving and taking off from the water than females. The age-related sexual differences in energy expenditure presented in our study might reflect niche and/or risk partitioning strategies to ensure adequate provisioning to the chick, or a possible earlier onset of senescence in females relative to males. The higher energy expenditure of aging females, which presumably requires a concomitantly higher energy intake, likely reduces their resilience to environmental change.
... Species in areas of rapidly changing climates need to adapt and/or shift their distribution to avoid possible extinction (Bindoff et al., 2019;Doney et al., 2012;Poloczanska et al., 2016). The ability to adapt depends on underlying population genetic diversity (Booy et al., 2000), and thus it is essential to maintain high levels of genetic polymorphism in both wild and farmed mussels. The recent discovery of a novel pathogen form, transmissible cancer cell lines, in blue mussels from both the northern and southern hemispheres (Bramwell et al., 2021;Metzger et al., 2015;Metzger et al., 2016;Yonemitsu et al., 2019) further emphasises the urgency to investigate the genetic diversity of wild and farmed populations of Australian mussels in this climate change hot spot. ...
... Genetic diversity is essential for the adaptability of a species, though there is no general relationship between genetic diversity and various fitness components, a lower level of heterozygosity may lead to a reduction in fitness [30]. For example, a positive correlation was found between population growth rate and allelic richness in an endangered orchid [31], favorable climate conditions may have facilitated the growth of juvenile pine individuals with higher genetic diversity [32], reduced heterozygosity is associated with reduced seedling survival in a tropical forest tree species [11], and lower genetic diversity increased the probability of mortality [33]. ...
Understanding the adaptation of plant species will help us develop effective breeding programs, guide the collection of germplasm, and improve the success of population restoration projects for threatened species. Genetic features correlate with species adaptation. Acer yangbiense is a critically endangered plant species with extremely small populations (PSESP). However, no information was available on its seed germination and seedling growth in populations with different genetic characteristics. In this study, we investigated seed germination and compared the performance of 566 seedlings in 10 maternal half-sib families cultivated in Kunming Botanical Garden. The results showed that A. yangbiense seeds required an average of 44 days to start germinating, with a 50% germination rate estimated to take about 47–76 days, indicating slow and irregular germination. There is a trade-off between the growth and survival in A. yangbiense seedlings, with fast growth coming at the cost of low survival. Groups that were able to recover from a recent bottleneck consistently had higher relative growth rates. High genetic diversity and low levels of inbreeding are likely to be responsible for their improved survival during drought conditions and rapid growth under optimal environmental conditions. Our results suggest that maternal genetic traits might be used as indicators for conservation and population restoration. These findings provide us with new information that could be applied to support ex situ conservation and reintroduction of threatened species.
... However, the genetic diversity of the species in the native ranges was within the average of that of the herbaceous perennial plant species [92,93]. Plant species with a high genetic diversity showed better potential for adaptation to various environmental conditions [94,95]. ...
Pueraria montana var. lobata is native to East Asia, and was introduced to many countries due to its potential for multiple uses. This species escaped under the management conditions soon after its introduction, and became a harmful weed species. This species has been listed in the top 100 of the world’s worst invasive alien species. P. montana stands expand quickly and threaten the native flora and fauna including microbiota. This species affects the concentration of carbon and nitrogen in soil and aquatic environments, and increases the amount of pollutants in the local atmosphere. Its infestation also causes serious economic losses on forestry and agriculture. Its characteristics of fast growth, thick canopy structure, enormous vegetative reproduction, and adaptative ability to the various environmental conditions may contribute to the invasiveness and naturalization of this species. The characteristics of P. montana regarding their defense functions against their natural enemies and pathogens, and allelopathy may also contribute to the invasiveness of this species. Potential allelochemicals such as xanthoxins, p-coumaric acid, caffeic acid, methyl caffeate and daidzein, and two isoflavones with anti-virus activity were identified in this species. In addition, fewer herbivore insects were found in the introduced ranges. These characteristics of P. montana may be involved in the invasive mechanisms of the species. This is the first review article focusing on the invasive mechanisms of this species.
... The populations gradually decreased in size and increased in spatial isolation, resulting in a decrease in genetic diversity due to genetic drift or inbreeding (Young et al. 1996; Tang et al. 2008; Ahn et al. 2017). Low levels of genetic variation within a population limit their ability to adapt to environmental changes, and reduce seed production and seedling emergence, resulting in population decline and ultimately extinction (Booy et al. 2000;Hamrick 2004;Tang et al. 2008;Broadhurst and Boshier 2014). Therefore, preserving genetic diversity is important for the maintenance and conservation of sub-alpine coniferous forest in preparation about changing environmental conditions due to climate change ). ...
A strategy is required for selecting appropriate materials for the restoration of Abies koreana on Mt. Jirisan, where the habitat of A. koreana is continuously shrinking. The current study aimed to analyze the genetic characteristics of A. koreana in three subpopulations (Banyabong, Byeoksoryeng, and Cheonwangbong) on Mt. Jirisan using 10 nuclear simple sequence repeat (nSSR) markers and calculate the sampling distance for each subpopulation for avoiding genetically similar samples. Based on the calculated sampling distance, we proposed the size of a sample containing more than 95% of the alleles at a frequency greater than 0.05. AMOVA showed that the difference in genetic variation across subpopulations of A. koreana on Mt. Jirisan was small, approximately 3% of the total. Spatial genetic structure analysis results suggested that it would be appropriate to collect samples of the Banyabong subpopulation at intervals of 10 m or more, when sampling A. koreana , whereas for the Byeoksoryeong and Cheonwangbong subpopulations, samples should be collected at intervals of 20 m or more. Results of random sampling of 5 to 30 individuals indicated that, by applying a 10 m distance within the Banyabong subpopulation, more than 95% of the total alleles with a frequency ≥ 0.05 were secured when more than 25 individuals were extracted. Therefore, as a restoration strategy for A. koreana on Mt. Jirisan, we proposed the collection of more than 25 samples, keeping 10 m distance within the Banyabong subpopulation, which has a relatively high genetic diversity.
... Severe environmental disasters can have serious long-term effects on populations of biological organisms. Plants, being sessile and unable to flee severe weather events, are particularly prone to habitat fragmentation, which can lead to isolation and reduction in population size (Booy et al., 2000;Lienert, 2004). Of course, the loss of reproducing individuals directly results in genetic bottlenecks and deficits in diverse heritable material. ...
Abstract
Hurricane Sandy struck the New York metropolitan region on October 29, 2012. The storm severely impacted the physical state of Barnegat Bay, New Jersey with its heavy storm surge, affecting many forms of benthic life and ripping up extensive beds of Zostera marina. Pre-Sandy studies of the genetic status of Z. marina in Barnegat Bay indicated low levels of heterozygosity and high levels of inbreeding. This present study examines the long-term effects of Hurricane Sandy on the eelgrass meadows of New Jersey. Heterozygosity analysis (mean Ho= 0.482 ± 0.013 and mean He= 0.498± 0.009) of the five Barnegat populations studied suggest an improvement in diversity from pre-Sandy values of 2008. Mean inbreeding levels (overall Fis = 0.077 ± 0.034) also indicated reduced inbreeding, and the fixation index (overall mean pairwise Fst = 0.064 ±0.006) suggested increased connectivity between populations with low levels of differentiation. Although we found no indication of bottlenecks in the last 2–3 years, by employing m-ratio calculations, there was strong evidence for long-term, historical bottlenecks in all populations, potentially due to the mass wasting disease epidemic in the 1930s. Unexpectantly, the post-Sandy genetic health and diversity of Z. marina in Barnegat Bay appears to have improved since it was last surveyed in 2008, supporting the “Storm Stimulus” hypothesis.
... The consequences of genotype or species extinction for population viability, community structure and ecosystem function depend on the degree of functional redundancy in the system. Reductions in genetic diversity can hinder population adaptability in ever changing environments [87][88][89]. Elimination of keystone species would however have the greatest impact on communities, though studies have not linked toxin-sensitive competitors to their ecological functions. Where toxin-sensitive competitors outnumber toxin-resistant competitors, killer phenotypes may radically change community composition and structure despite toxin-sensitive competitors not providing keystone functions. ...
Ecological interactions influence evolutionary dynamics by selecting upon fitness variation within species. Antagonistic interactions often promote genetic and species diversity, despite the inherently suppressive effect they can have on the species experiencing them. A central aim of evolutionary ecology is to understand how diversity is maintained in systems experiencing antagonism. In this review, we address how certain single-celled and dimorphic fungi have evolved allelo-pathic killer phenotypes that engage in antagonistic interactions. We discuss the evolutionary pathways to the production of lethal toxins, the functions of killer phenotypes and the consequences of competition for toxin producers, their competitors and toxin-encoding endosymbionts. Killer phenotypes are powerful models because many appear to have evolved independently, enabling across-phylogeny comparisons of the origins, functions and consequences of allelopathic antagonism. Killer phenotypes can eliminate host competitors and influence evolutionary dynamics, yet the evolutionary ecology of killer phenotypes remains largely unknown. We discuss what is known and what remains to be ascertained about killer phenotype ecology and evolution, while bringing their model system properties to the reader's attention.
... The value of genome-wide heterozygosity (5.538 × 10 -6 ) was lower than most Endangered species, such as crested ibis Nipponia nippon (430 × 10 -6 ) (Li et al., 2014), mountain gorilla Gorilla beringei (640 × 10 -6 ) (Xue et al., 2015) and island fox Urocyon li oralis (1.33 ± 30 × 10 -6 ) (Robinson et al., 2018). As genetic diversity determines the adaptive potential of a species to environmental change, it plays a key role in their long-term survival (Booy et al., 2000;Supple & Shapiro, 2018). While strong deleterious mutations can be removed through genetic purifying to mitigate inbreeding depression in small populations, moderate deleterious mutations can still accumulate during prolonged bo lenecks (Xie et al., 2022), reducing population viability. ...
... The value of genome-wide heterozygosity (5.538 × 10 -6 ) was lower than most Endangered species, such as crested ibis Nipponia nippon (430 × 10 -6 ) (Li et al., 2014), mountain gorilla Gorilla beringei (640 × 10 -6 ) (Xue et al., 2015) and island fox Urocyon li oralis (1.33 ± 30 × 10 -6 ) (Robinson et al., 2018). As genetic diversity determines the adaptive potential of a species to environmental change, it plays a key role in their long-term survival (Booy et al., 2000;Supple & Shapiro, 2018). While strong deleterious mutations can be removed through genetic purifying to mitigate inbreeding depression in small populations, moderate deleterious mutations can still accumulate during prolonged bo lenecks (Xie et al., 2022), reducing population viability. ...
Captive-breeding is a commonly proposed conservation strategy for species whose populations have become too
small to be genetically viable in the wild, such as the Endangered Eld’s deer subspecies Rucervus eldii siamensis. These
programmes require extensive management and maintenance of high genetic diversity within the captive population.
The Phnom Tamao Wildlife Rescue Centre and surrounding forests in Takeo, Cambodia, are home to a captive and a
released breeding population of Eld’s deer that are descended from two founders con scated from the illegal wildlife
trade in 2001. As the captive population grew, it was separated into two herds which remained isolated until small
groups were released in 2018. We assessed the level of inbreeding and genetic diversity of the population (27 animals)
by re-sequencing genome wide variants using blood samples from eight captive individuals. A low level of genetic
diversity was found in the animals. The average heterozygosity rate and nucleotide diversity () were 5.538 × 10-6
± 1.854 × 10-6 and 5.475 × 10-5, respectively. The mean inbreeding coe cient (FROH) was 0.026 ± 0.060, and most individuals
were in second degree kinship. Demographic records from January 2009 to April 2022 for the captive population
revealed average neonatal mortality was 26.85%, which suggests the population does not currently su er striking
hazards from inbreeding. Our results suggest that the captive and released semi-wild herds at the centre may be a suitable
source population for future reintroductions, although they would bene t from the addition of new individuals to
protect against genetic erosion.
... Based on climatic variables only, the habitat suitability for native hens is predicted to decrease overall across their Tasmanian range, most notably in areas that are presently highly suitable. Moreover, this will have the potential to be exacerbated by other factors such as the frequency and/or intensity of extreme events and the native hens' low genetic diversity [46,47], which could limit their potential to withstand the deleterious effects of major environmental changes or adapt to them [48,49]. However, as human settlements and land use can buffer unsuitability over large regions, future distribution will also depend on how these develop in Tasmania. ...
Identifying environmental characteristics that limit species' distributions is important for contemporary conservation and inferring responses to future environmental change. The Tasmanian native hen is an island endemic flightless rail and a survivor of a prehistoric extirpation event. Little is known about the regional-scale environmental characteristics influencing the distribution of native hens, or how their future distribution might be impacted by environmental shifts (e.g. climate change). Using a combination of local fieldwork and species distribution modelling, we assess environmental factors shaping the contemporary distribution of the native hen, and project future distribution changes under predicted climate change. We find 37% of Tasmania is currently suitable for the native hens, owing to low summer precipitation, low elevation, human-modified vegetation and urban areas. Moreover, in unsuitable regions, urban areas can create ‘oases’ of habitat, able to support populations with high breeding activity by providing resources and buffering against environmental constraints. Under climate change predictions, native hens were predicted to lose only 5% of their occupied range by 2055. We conclude that the species is resilient to climate change and benefits overall from anthropogenic landscape modifications. As such, this constitutes a rare example of a flightless rail to have adapted to human activity.
... Genetic variation in natural populations is a source of biodiversity (Booy et al., 2000;Munk 2000; Vellend and Geber 2005;Hughes et al., 2008). Individuals of a population differ genetically, and these different genotypes respond differentially to environmental change; this process gives rise to different phenotypes (Munk 2000;Lampert and Trubetskova 1996;Weider et al., 2008;Hamrová et al., 2011;Jiang et al., 2013). ...
... Genetic variation in fitness is the raw material natural selection acts on, and determines a population's rate of adaptive evolution in the face of environmental change and genetic degradation caused by deleterious mutation, maladaptive gene flow, genetic drift and inbreeding depression (Burt, 1995;Hendry et al., 2018). Despite the critical role of intraspecific genetic variation to species adaptation and survival (Booy et al., 2000), the amount of genetic diversity in many natural populations remains largely unknown. Whereas much recent work has focused on the genetic structure of endangered populations, it is equally important to understand how genetic variation may contribute to the successes of populations that thrive. ...
... It is considered a fundamental and essential component of biodiversity. Genetic diversity level is critical in determining the long-term survivability and evolutionary capacity of a specific species [14]. A decrease in genetic diversity can lead to a reduction in species' fitness, ultimately increasing their risk of extinction. ...
Suaeda aralocaspica, which is an annual halophyte, grows in saline deserts in Central Asia with potential use in saline soil reclamation and salt tolerance breeding. Studying its genetic diversity is critical for effective conservation and breeding programs. In this study, we aimed to develop a set of polymorphic microsatellite markers to analyze the genetic diversity of S. aralocaspica. We identified 177,805 SSRs from the S. aralocaspica genome, with an average length of 19.49 bp, which were present at a density of 393.37 SSR/Mb. Trinucleotide repeats dominated (75.74%) different types of motifs, and the main motif was CAA/TTG (44.25%). We successfully developed 38 SSR markers that exhibited substantial polymorphism, displaying an average of 6.18 alleles with accompanying average polymorphism information content (PIC) value of 0.516. The markers were used to evaluate the genetic diversity of 52 individuals collected from three populations of S. aralocaspica in Xinjiang, China. The results showed that the genetic diversity was moderate to high, with a mean expected heterozygosity (He) of 0.614, a mean Shannon’s information index (I) of 1.23, and a mean genetic differentiation index (Fst) of 0.263. The SSR markers developed in this study provide a valuable resource for future genetic studies and breeding programs of S. aralocaspica, and even other species in Suaeda.
... The spatial distribution of genetic variation reflects evolutionary processes, including drift, migration, and selection, which shape standing variation and the evolutionary potential of populations. Therefore, quantifying spatial genetic structure and the factors shaping it can help assess the degree of population connectivity, the scale of and potential for local adaptation to environmental variation, and, consequently, the persistence of plant populations faced with environmental change (Bauert et al., 1998;Booy et al., 2000;Manel et al., 2003). Such analyses can also be used to guide conservation and restoration decisions using biologically meaningful information (Carvalho et al., 2021;Ottewell et al., 2016). ...
Analyses of the factors shaping genetic variation in widespread plant species are important for understanding the evolutionary history and local adaptation and have applied significance for guiding conservation and restoration decisions. Thurber's needlegrass (Achnatherum thurberianum) is a widespread, locally abundant grass that inhabits heterogeneous arid environments of western North America and is of restoration significance. It is a common component of shrubland steppe communities in the Great Basin Desert, where drought, fire, and invasive grasses have degraded natural communities. Using a reduced representation sequencing approach, we generated SNP data at 5677 loci across 246 individuals from 17 A. thurberianum populations spanning five previously delineated seed zones from the western Great Basin. Analyses revealed a pronounced population genetic structure, with individuals forming consistent geographical clusters across a variety of population genetic analyses and spatial scales. Low levels of genetic diversity within populations, as well as high population estimates of linkage disequilibrium and relatedness, were consistent with self-fertilization as a contributor to population differentiation. Variance partitioning and partial redundancy analysis (pRDA) indicated local adaptation to environment as additionally influencing the spatial distribution of genetic variation. The environmental variables driving these results were similar to those implicated in recent geneco-logical work which inferred local adaptation for seed zone delineation. Our analyses also revealed a complex evolutionary history of A. thurberianum in the Great Basin, where previously delineated seed zones contain distantly related populations. Our results indicate evolutionary history, mating system, and differentiation across distinct geographic and environmental scales have shaped genetic variation in A. thur-berianum and illustrate how numerous aspects of population genetic variation might require consideration for restoration planning.
... Genetic diversity is the most fundamental, central and important dimension for ecosystem diversity, species diversity and biodiversity [17]. Meanwhile, genetic diversity is necessary for species to adapt to environmental changes and to resist pests and diseases [18]. The level of genetic diversity determines the long-term viability and evolutionary potential of a species. ...
Michelia crassipes Y. W. Law (Magnoliaceae) is endemic to China and is the only species with purple flowers in the genus Michelia. It is commonly used as an important parent for flower color improvement and hybrid breeding. M. crassipes is recognized as an endangered plant. An urgent need exists to explore the genetic diversity of M. crassipes to efficiently select hybrid parents and develop efficient conservation strategies. In this study, a total of 128 samples were selected from seven natural populations of M. crassipes to explore their genetic diversity and structure. A total of 14 microsatellite (SSR) markers with high polymorphism and repeatability were developed, and 218 alleles were detected. This study mainly revealed three results: (1) The parameters of expected heterozygosity (He = 0.536) and mean Shannon’s information index (I = 1.121) revealed moderately high levels of genetic diversity for the M. crassipes natural population; (2) The genetic differentiation coefficient (Fst = 0.108) showed that there was a low level of genetic differentiation, and AMOVA indicated that genetic variation existed mainly within populations and that there was frequent gene exchange between populations; and (3) The population genetic structure analysis showed that seven natural populations originated from two ancestral groups, and the Mantel test revealed that genetic and geographical distances between populations were significantly correlated. Our study is the first to explore the genetic diversity and structure of the M. crassipes natural population, which provides an important reference for the collection, conservation and utilization of Michelia crassipes germplasm resources.
... Genetic diversity plays a very crucial role in maintaining the higher chance of long-term survival [4]. However, if the species lack genetic diversity due to a low population or species isolation, they are prone to a vulnerability that may result in fluctuations among the populations caused by climate change, habitat fragmentation, or diseases [5]. ...
The term "biodiversity" refers to the diverse variety of living things that exist in our natural environment including not just plants and animals, but also fungi and even microscopic organisms such as bacteria. Since there are still millions of species that have not been identified, the overall biodiversity of our world is immense. The biodiversity of our planet plays a significant role in ensuring the health of our ecosystems. Because of habitat destruction, industrialization, urbanization, and the ever-increasing population of humans, many animal and plant species are classified as being either vulnerable, endangered, or in imminent danger of becoming extinct. In addition, there is a high risk of extinction for a large number of species in the event that management and conservation strategies are not immediately put into effect. The goal of the initiative known as "citizen science" is to increase scientific understanding by encouraging collaboration and participation from the general public in scientific research. Individual people have the opportunity to nurture their scientific temperament in the field through involvement in citizen science, which also allows communities an ability to study nature and protect it through collective efforts. In order to monitor and conserve biodiversity together with professionals in the scientific and academic communities to develop solutions to environmental problems, it is important to establish additional citizen science projects for citizen scientists.
... However, the genetic composition of restoration material is often overlooked and can be a possible explanation for the decreased success of many reintroduction efforts (Mijangos et al., 2015). Previous studies have shown that the survival rates of reintroduced plants increases when genetic diversity is considered in the project design (Godefroid et al., 2011), providing developmental stability and increasing population fitness (Booy et al., 2000). The consideration of genetic diversity is especially important for species such as A. crassispatha that are threatened by decreases in annual precipitation (Timyan and Cinea, 2018) and are likely to continue experiencing novel conditions (Mijangos et al., 2015). ...
Imperiled plant species can benefit from ex situ cultivation to safeguard against loss of genetic diversity and possible extinction in the wild. Few studies use genetic monitoring in endangered plant species to evaluate how well current management practices maintain genetic diversity and limit inbreeding and relatedness after plants are brought into cultivation. We examine this question using Attalea crassispatha, a palm species with fewer than 100 palms surviving worldwide, and only 25 remaining in their native habitat. We sampled all accessible palms of this species (both in situ and ex situ) to (1) investigate how well garden collections capture in situ genetic diversity, (2) evaluate how well genetic diversity is carried forward into subsequent generations ex situ, (3) determine the number of wild and founding individuals contributing to ex situ breeding efforts, and (4) identify optimal breeding pairs that would maximize diversity and limit inbreeding. We found higher genetic diversity in situ and that current propagation practices lead to self-fertilization in the ex situ population and therefore fail to adequately steward genetic diversity in the conservation collection. Using relatedness analyses, we identified optimal breeding pairs in collections at different locations, highlighting the need for coordinated breeding efforts to maximize diversity ex situ. We also identified putative A. crassispatha that are genetically unrelated to the rest of the study cohort and are likely mislabeled. This study highlights the utility of genetic monitoring and the importance of careful coordination and record keeping within and among collections to ensure genetic diversity is maintained for future conservation efforts.
... The levels of genetic diversity are essential for a species' ability to adapt to environmental change and the emergence of disease resistance. They define the viability and evolutionary potential of populations and are widely used to estimate species trends and future hazards (Booy, 2000). ...
... In traditional methods, phylogenetic tree drawing is based on morphological characteristics, but today, due to the large volume of available molecular data, sequence information in the gene bank (nucleic acid or protein) is used (Patwardhan et al. 2014). Genetic diversity is necessary for the survival of organisms (Booy et al. 2000). Plant viruses use a variety of mechanisms to create large amounts of genetic diversity within and between species. ...
Cauliflower Mosaic Virus (CaMV) is a plant Pararetrovirus with a double-stranded DNA genome distributed worldwide. This study analyzed migration, evolution, and synonymous codon pattern of CaMV and the factors that shape it. We extracted genomic sequences of 121 isolates of CaMV, which were reported from various regions-hosts, from the NCBI database. The evolution of viruses has been widely studied by analyzing their nucleotides and coding regions/codons using different methods. Analysis of the CaMV phylogenetic tree shows that it divides most of the sequences into two main groups: Group I includes Irananin, Japanese, and American-European subgroups, and Group II includes Grecian, Turkish, and Iranian subgroups. Analysis of effective codon count, and relative codon deoptimization index, showed that natural selection is a major driving force in CaMV. Furthermore, Relative synonymous codon usage (RSCU) and neutrality analyses show that CaMV prefers A-ending codons and that one codon, namely GGA, was overrepresented. Analysis of dinucleotide composition demonstrates that nucleotide A was the most abundant in the CaMV coding sequences, and that the most frequent nucleotide at the third position of the codon was A3S. In CaMV, host adaptation was highest for Brassica oleracea and lowest for Raphanus sativus. Therefore the CaMV codon pattern is mostly shaped by the need to escape antiviral responses associated with host dinucleotides and translational efficiency. These values indicate that the study provides useful information on the codon usage analysis of CaMV and can be used to understand host adaptation to the virus environment and its evolution. This is the first study on codon usage bias of CaMV in the world.
... In response to environmental changes, particularly climate change, organisms may use heritable adaptation strategies to increase their intrinsic fitness, genetic diversity, and adaptive potential (Becker et al., 2013). Thus, measurements of genetic diversity are often used as an indicator to evaluate the current survival status of a species and populations (Ellegren & Galtier, 2016;Mhemmed et al., 2008) to investigate population differentiation and relationships and to provide valuable information from a conservation perspective (Booy et al., 2000). Characterizing adaptive genetic variation and investigating the molecular mechanisms underlying adaptation are critical to understand the resilience of an organism to environmental change (Hoffmann et al., 2015). ...
Genetic diversity reflects the survival potential, history, and population dynamics of an organism. It underlies the adaptive potential of populations and their response to environmental change. Reaumuria trigyna is an endemic species in the Eastern Alxa and West Ordos desert regions in China. The species has been considered a good candidate to explore the unique survival strategies of plants that inhabit this area. In this study, we performed population genomic analyses based on restriction‐site associated DNA sequencing to understand the genetic diversity, population genetic structure, and differentiation of the species. Analyses of 92,719 high‐quality single‐nucleotide polymorphisms (SNPs) indicated that overall genetic diversity of R. trigyna was low (HO = 0.249 and HE = 0.208). No significant genetic differentiation was observed among the investigated populations. However, a subtle population genetic structure was detected. We suggest that this might be explained by adaptive diversification reinforced by the geographical isolation of populations. Overall, 3513 outlier SNPs were located in 243 gene‐coding sequences in the R. trigyna transcriptome. Potential sites under diversifying selection occurred in genes (e.g., AP2/EREBP, E3 ubiquitin‐protein ligase, FLS, and 4CL) related to phytohormone regulation and synthesis of secondary metabolites which have roles in adaptation of species. Our genetic analyses provide scientific criteria for evaluating the evolutionary capacity of R. trigyna and the discovery of unique adaptions. Our findings extend knowledge of refugia, environmental adaption, and evolution of germplasm resources that survive in the Ordos area.
... The importance of gene flow on the magnitude and distribution of genetic diversity of plant species is widely recognized (Frankham 1995(Frankham , 2005Couvet 2002). Gene flow connects populations over long distances and increases effective population sizes, ameliorating the eroding effects of genetic drift on diversity (Booy et al. 2000;Couvet 2002). Gene flow also maintains genetic variability within populations and understanding how this genetic diversity is geographically structured provides valuable information on how different landscape components such as habitat availability (Dick and Heuertz 2008), habitat fragmentation (Fuchs et al. 2003;Fuchs and Hamrick 2011;Aguilar et al. 2019), urban development (Delaney et al. 2010), and topographic barriers (Antonelli 2017) shape gene dispersal patterns among plant populations. ...
Gene flow connects populations and is necessary to sustain effective population sizes, and genetic diversity. In the Lower Central American (LCA) region, the complex topographic and climatic history have produced a wide variety of habitats resulting in high biodiversity. Phylogeographic studies of plants from this area are scarce, and to date none have been conducted on palms. We used SSR and chloroplast DNA (cpDNA) markers to study the genetic diversity and structure of populations of the understory palm Chamaedorea tepejilote in Costa Rica. We found that populations of C. tepejilote have moderate to high nuclear simple sequence repeat (SSR) genetic diversity, likely due to large population sizes and its outcrossing mating system. Habitat loss and fragmentation may have contributed to increased genetic structure within slopes. High-elevation mountain ranges appeared to be a significant barrier for gene flow among populations in the Caribbean and Pacific slopes; however, ranges are permeable through low-elevation passes. In contrast, most populations had a single distinct cpDNA haplotype, supporting the hypothesis of several isolated populations that experienced decline that likely resulted in eroded cytoplasmic genetic diversity within populations. The haplotype network and Bayesian analysis linked populations in the Caribbean and the southern Pacific coast, suggesting that gene flow between Pacific and Caribbean populations may have occurred through the southern extreme of the Talamanca Mountain range in Panama, a colonization pathway not previously suggested for LCA plants. This is one of the first phylogeographic studies conducted on tropical palms in the LCA region and the first in the genus Chamaedorea, which sheds light on possible gene flow and dispersal patterns of C. tepejilote in Costa Rica. Our results also highlight the importance of mountain ranges on shaping gene flow patterns of Neotropical plants.
... In this study, we evaluated the level and degree of genetic variation within and among populations, as well as the connectedness among populations of Z. tyaihyonii to provide useful information for the effective conservation planning of this endemic and rare plant. Genetic diversity is especially important for preserving the latent evolutionary capacity of a species to deal with changing environments [68]. In addition, information about genetic variation within and among populations in endangered and rare plants plays an important role in the process of formulating conservation and management strategies [69]. ...
Zabelia tyaihyonii (Nakai) Hisauti and H. Hara is a perennial shrub endemic to Republic of Korea that grows naturally in only a very limited region of the dolomite areas of Gangwon-do and Chungcheongbuk-do Provinces in the Republic of Korea. Given its geographical characteristics, it is more vulnerable than more widely distributed species. Despite the need for comprehensive information to support conservation, population genetic information for this species is very scarce. In this study, we analyzed the genetic diversity and population structure of 94 individuals from six populations of Z. tyaihyonii using a genotyping-by-sequencing (GBS) approach to provide important information for proper conservation and management. Our results, based on 3088 single nucleotide polymorphisms (SNPs), showed a mean expected heterozygosity (He) of 0.233, no sign of within-population inbreeding (GIS that was close to or even below zero in all populations), and a high level of genetic differentiation (FST = 0.170). Analysis of molecular variance (AMOVA) indicated that the principal molecular variance existed within populations (84.5%) rather than among populations (17.0%). We suggested that six management units were proposed for conservation considering Bayesian structure analysis and phylogenetic analysis, and given the various current situations faced by Z. tyaihyonii, it is believed that not only the in situ conservation but also the ex situ conservation should be considered.
The great Himalayas are continuously facing a lot of biotic and abiotic challenges like climate change, anthropogenic pressure , etc. since the last decade which as a result is putting the native vegetation, especially of alpine regions, under immense pressure, pushing a number of plants near to the brink of extinction. The present study was done on Swertia speciosa which is a popular substitute of Swertia chirayita, endemic to the Himalayan region and enlisted as endangered in the IUCN Red Data book. Genetic diversity studies on S. speciosa can enable us to understand its adaptability and chances of survival in the near future which can ultimately serve the purpose of conservation and reduce the overexploitation of S. chirayita by serving as a suitable substitute. To assess the genetic diversity, a cluster analysis using the dendrogram method from eight different germplasm of S. speciosa collected from different regions of Uttarakhand Himalayan Ranges (2800-4000 masl) was done, where 15 sets of RAPD primers were used for generating 248 discernible and reproducible bands among the analyzed population with 230 polymorphic and 18 monomorphic bands. The (UPGMA) cluster analysis exposed three distinct clusters: I, II, and III. The cluster I was represented by the S.speciosa population collected from Kedarnath (3500 m asl), Dayara (3408 m asl), Madhyamaheswar (3478 m asl), Sunderdunga (3593 m asl), Bansinaryan (3618 m asl) and Harkidoon (3525 m asl). Cluster II included collection from Bednibugyal (3305 m asl). Cluster III was represented by collection from Tungnath (3361 m asl) and populations were also independent of variations in altitude and geographical locations. The best genetic variation (0.384) was observed in Harki-doon (3525 m asl) population as compared to other populations of S. speciosa which may be possible due to varied altitudinal, habitat, and environmental related factors.
Cauliflower mosaic virus (CaMV) has a double‐stranded DNA genome and is globally distributed. The phylogeny tree of 121 CaMV isolates was categorized into two primary groups, with Iranian isolates showing the greatest genetic variations. Nucleotide A demonstrated the highest percentage (36.95%) in the CaMV genome and the dinucleotide odds ratio analysis revealed that TC dinucleotide (1.34 ≥ 1.23) and CG dinucleotide (0.63 ≤ 0.78) are overrepresented and underrepresented, respectively. Relative synonymous codon usage (RSCU) analysis confirmed codon usage bias in CaMV and its hosts. Brassica oleracea and Brassica rapa , among the susceptible hosts of CaMV, showed a codon adaptation index (CAI) value above 0.8. Additionally, relative codon deoptimization index (RCDI) results exhibited the highest degree of deoptimization in Raphanus sativus . These findings suggest that the genes of CaMV underwent codon adaptation with its hosts. Among the CaMV open reading frames (ORFs), genes that produce reverse transcriptase and virus coat proteins showed the highest CAI value of 0.83. These genes are crucial for the creation of new virion particles. The results confirm that CaMV co‐evolved with its host to ensure the optimal expression of its genes in the hosts, allowing for easy infection and effective spread. To detect the force behind codon usage bias, an effective number of codons (ENC)‐plot and neutrality plot were conducted. The results indicated that natural selection is the primary factor influencing CaMV codon usage bias.
Declines and extirpations of American pika ( Ochotona princeps) populations at historically occupied sites started being documented in the literature during the early 2000s. Commensurate with global climate change, many of these losses at peripheral and lower elevation sites have been associated with changes in ambient air temperature and precipitation regimes. Here, we report on a decline in available genetic resources for an iconic American pika metapopulation, located at the southwestern edge of the species distribution in the Bodie Hills of eastern California, USA. Composed of highly fragmented habitat created by hard rock mining, the ore dumps at this site were likely colonized by pikas around the end of the 19 th century from nearby natural talus outcrops. Genetic data extracted from both contemporary samples and archived natural history collections allowed us to track population and patch-level genetic diversity for Bodie pikas across three distinct sampling points during the last half- century (1948–1949, 1988–1991, 2013–2015). Reductions in within-population allelic diversity and expected heterozygosity were observed across the full time period. More extensive sampling of extant patches during the 1988–1991 and 2013–2015 periods revealed an increase in population structure and a reduction in effective population size. Furthermore, census records from the last 51 years as well as archived museum samples collected in 1947 from a nearby pika population in the Wassuk range (Nevada, USA) provide further support of the increasing isolation and genetic coalescence occurring in this region. This study highlights the importance of museum samples and long-term monitoring in contextualizing our understanding of population viability.
Beyond climate change, the planet faces several other environmental challenges that are at least as threatening, such as the loss of biodiversity. In each case, the problems are driven by similar factors, such as fossil fuels and intensive livestock farming. This paper presents a legal analysis concerning the binding nature of the Convention on Biological Diversity’s (CBD) overarching objective to halt biodiversity loss, within the framework of international environmental and human rights law. Using the established legal techniques encompassing grammatical, systematic, teleological, and historical interpretations, the article demonstrates that the CBD’s objective to halt biodiversity loss is indeed legally binding and justiciable. This conclusion is directly drawn from interpreting Article 1 CBD. Furthermore, a comparable obligation emerges indirectly from international climate law. The imperative to curtail biodiversity loss also finds grounding in human rights law, albeit necessitating a re-evaluation of certain aspects of freedom, similar to what has been explored in the context of climate protection. Moreover, the article underscores that various other biodiversity-related regulations within international law, including those laid out in the CBD, the Aichi Targets, and the Kunming–Montreal Global Biodiversity Framework, also carry partial legal significance. Nonetheless, it is crucial to note that these regulations, including the Kunming–Montreal Framework, do not modify the obligation mandate to halt biodiversity loss, which was established at the latest when the CBD entered into force in 1993. Because this obligation has been violated since then, states could potentially be subject to legal action before international or domestic courts for their actions or inactions contributing to global biodiversity loss.
Turkey is one of the world's nations with the greatest flora diversity. Moreover, it possesses a high level of plant genetic diversity. Garden Grass (Dactylis glomerata L.) is one of the most important fodder species used during cool seasons since it is a hardy and perennial plant. The identification of Orchardgrass cultivars is essential for maximizing cultivar utilization, and safeguarding breeders' intellectual property. Dactylis L. is an allogamous, variable, monospecific genus with multiple subspecies distinguished by morphology, chromosomal count, and distribution. This genus has a single species, Dactylis glomerata, which is comprised of multiple subspecies whose traits have not been exhaustively characterized. Using DNA assays that evaluated the transferability of nine SSR primers designed for wheat loci, the genetic diversity of 44 orchardgrass genotypes from eight naturally distributed locales in the Eastern Anatolia Area of Turkey was calculated. On average, 6.78 alleles were discovered for each of the nine SSR primers, for a total of 61 alleles. A total of 54 polymorphic alleles were identified, with an average of six per primer. Polymorphism information content (PIC) values ranged from 0.320 to 0.626%. The average polymorphism rate of 88.89% suggests a high amount of genetic diversity among all studied genotypes. The average expected heterozygosity (He) ranged between 0.178 to 0.882. The genetic separation ranged from 0.01 to 0.66. In conclusion, our findings indicate that the Dactylis glomerata genotypes gathered in Eastern Anatolia are a rich source of genetic variability, supplying a vast array of genetic material for orchardgrass breeding efforts.
In light of the dramatic decline in amphibian biodiversity, new cost-efficient tools to rapidly monitor species abundance and population genetic diversity in space and time are urgently needed. It has been amply demonstrated that the use of environmental DNA (eDNA) for single-species detection and characterization of community composition can increase the precision of amphibian monitoring compared to traditional (observational) approaches. However, it has been suggested that the efficiency and accuracy of the eDNA approach could be further improved by more timely sampling; in addition, the quality of genetic diversity data derived from the same DNA has been confirmed in other vertebrate taxa, but not amphibians. Given the availability of previous tissue-based genetic data, here we use the common frog Rana temporaria Linnaeus, 1758 as our target species and an improved eDNA protocol to: (i) investigate differences in species detection between three developmental stages in various freshwater environments; and (ii) study the diversity of mitochondrial DNA (mtDNA) haplotypes detected in eDNA (water) samples, by amplifying a specific fragment of the COI gene (331 base pairs, bp) commonly used as a barcode. Our protocol proved to be a reliable tool for monitoring population genetic diversity of this species, and could be a valuable addition to amphibian conservation and wetland management.
Himalayacalamus falconeri is a socio-economically important temperate woody bamboo of north-western Himalayas, which has been investigated for genetic diversity and population genetic structure across distribution range in western Himalayas using genomic STMS markers. The calculated diversity measures have indicated a high gene diversity in H. falconeri at population level (Ho = 0.637; He = 0.714; Ar = 5.05). Despite the larger proportion of genetic variation (88%) confined within the populations, a moderate level of genetic differentiation (FST = 0.121) was detected with relatively lower gene flow (Nm = 1.891). Furthermore, clustering and STRUCTURE analysis displayed high genetic heterogeneity in a metapopulation, where populations in both the spatially disconnected regions of the Uttarakhand state, Garhwal and Kumaon, were clustered in different groups. Whereas, nested sub clustering and between-population genetic admixing were not correlated to their physical proximity. Also, the Mantel test supports the isolation by distance model showing a significant correlation between genetic and horizontal geographic distances. For conservation implications, diverse hotspots with high allelic richness were also identified in both the geographical regions of Uttarakhand state. To the best of our knowledge, it is a pioneer study presenting in depth knowledge of metapopulation in any Indian temperate bamboo, which will be of paramount importance to the researchers, foresters, and policymakers for guiding future conservation decisions of H. falconeri in the Indian Himalayan Regions (IHRs).
Models of founder events have focused on the reduction in the genetic variation following a founder event. However, recent work (Bryant et al., 1986; Goodnight, 1987) suggests that when there is epistatic genetic variance in a population, the total genetic variance within demes may actually increase following a founder event. Since the additive genetic variance is a statistical property of a population and can change with the level of inbreeding, some of the epistatic genetic variance may be converted to additive genetic variance during a founder event. The model presented here demonstrates that some of the additive-by-additive epistatic genetic variance is converted to additive genetic variance following a founder event. Furthermore, the amount of epistasis converted to additive genetic variance is a function of the recombination rate and the propagule size. For a single founder event of two individuals, as much as 75% of the epistatic variance in the ancestral population may become additive genetic variance following the founder event. For founder events involving two individuals with free recombination, the relative contribution of epistasis to the additive genetic variance following a founder event is equal to its proportion of the total genetic variance prior to the founder event. Traits closely related to fitness are expected to have relatively little additive genetic variance but may have substantial nonadditive genetic variance. Founder events may be important in the evolution of fitness traits, not because they lead to a reduction in the genetic variance, but rather because they lead to an increase in the additive genetic variance.
Mayr (1963) proposed that small isolated propagules from a large panmictic population would occasionally undergo a genetic revolution due to loss of genetic variability. More recently Templeton (1980a) has suggested that founder events may be much more important in systems that have strong epistasis. Because of the work of these and other authors it becomes an interesting theoretical problem to study the distribution of epistatic variance in a population following a founder event. In the model presented here measures of coancestry (Cockerham, 1967, 1984; Cockerham and Weir, 1973; Weir and Cockerham, 1973, 1977; Tachida and Cockerham, unpubl.) are used to examine the effect of founder events on additive-by-additive epistasis. Using this approach, the coancestries, or intraclass correlations, within individuals and within demes, together with the genetic variance components in the ancestral population are used to obtain the variance within and among demes following a founder event. Examples are analyzed for single founder events of 1-25 individuals and multiple founder events of two individuals. Following a single founder event, the contribution of the additive variance to the variance within demes relative to the additive variance in the ancestral population is always less than one. However, the contribution of epistatic variance to the variance within demes relative to the epistatic variance in the ancestral population is always greater than one. Thus, while a founder event decreases the contribution of additive variance to the variance within demes, it increases the contribution of epistatic variance to the variance within demes. The contribution of epistatic variance to the variance among demes following a single founder event is not qualitatively different from the contribution of additive variance to the variance among demes. These results indicate that epistatic variance is less likely than additive variance to cause a genetic revolution following a single founder event. When populations undergo multiple founder events the situation changes considerably. Epistatic variance may contribute as much as four times its original value to the variance among demes, while additive variance can contribute maximally twice its original value to the variance among demes. Thus, epistasis, which is relatively unimportant following a single founder event, may have major evolutionary implications if drift is allowed to continue for several generations.
Molecular techniques are proving invaluable in determining the phylogenetic status of potentially endangered species, for investigating mechanisms of speciation, and for measuring the genetic structure of populations. It is increasingly important for ecologists and evolutionary and conservation biologists to understand and use such molecular techniques, but most workers in these areas have not been trained in molecular biology. This book lays out the principles and basic techniques for the molecular tools appropriate for addressing issues in conservation, and it presents case studies showing how these tools have been used successfully in conservation biology. Examples include the genetic analysis of population structure, various uses of DNA in conservation genetics, and estimation of migration parameters from genetic data. Wildlife managers, as well as researchers in these areas, will find this a valuable book.
Plant population sizes vary in space and time both within and among species. This variability is the result of complex interactions among the life-history features of populations, local environmental conditions, and the historical ecology of particular species. Populations range in size from many thousands, as in some forest trees and savannah grasses, to small colonies of a few plants in rare orchids and certain parasitic plants. Considering the sessile habit of plants and the ease with which they can be counted, data on population sizes are surprisingly sparse in the botanical literature.
The existing levels of genetic diversity and the maintenance of these levels of diversity are major issues in conservation biology. Genetic diversity became an issue when Frankel (1970) postulated that genetic variation is essential for the long-term survival of endangered species. Genetic variation is a necessary prerequisite for any future adaptive change or evolution; presumably, species that lack adequate genetic variation are at greater risk of extinction. In terms of conservation, maintenance of genetic variation is essential if populations are to be successfully reintroduced in the wild or introduced to new habitats.
This book is the result of the 12 keynote addresses, delivered at the third IOBC International Symposium held in Montpellier, France in October 2002, focusing on recent developments in genetics and evolutionary biology, and their relevance to biological control. Chapters are organized around the following themes: genetic structure of pest and natural enemy populations; molecular diagnostic tools in biological control; tracing the origin of pests and natural enemies; predictive evolutionary change in pests and natural enemies; compatibility of transgenic crops and natural enemies; and genetic manipulation of natural enemies. This book will interest readers in entomology and pest management, genetics, ecology and evolution.
What is the minimum viable population (MVP) of a particular species? Besides the obvious implications for conservation, especially of endangered species, this question raises important issues in population biology. MVP obviously varies with demographic, life history and environmental factors, but also depends upon genetic load and genetic variability. This book addresses the most recent research in the rapidly developing integration of conservation biology with population biology. Chapters consider the roles of demographic and environmental variability; the effects of latitude, body size, patchiness and metapopulation structure; the implications of catastrophes; and the relevance of effective population size on inbreeding and natural selection. Other topics addressed include the role of decision theory in clarifying management alternatives for endangered species, and the opportunities for improved co-operation between agencies responsible for management. The book concludes with a forward-looking and plain-speaking summary on future research and its application for conservation practice.
What is the minimum viable population (MVP) of a particular species? Besides the obvious implications for conservation, especially of endangered species, this question raises important issues in population biology. MVP obviously varies with demographic, life history and environmental factors, but also depends upon genetic load and genetic variability. This book addresses the most recent research in the rapidly developing integration of conservation biology with population biology. Chapters consider the roles of demographic and environmental variability; the effects of latitude, body size, patchiness and metapopulation structure; the implications of catastrophes; and the relevance of effective population size on inbreeding and natural selection. Other topics addressed include the role of decision theory in clarifying management alternatives for endangered species, and the opportunities for improved co-operation between agencies responsible for management. The book concludes with a forward-looking and plain-speaking summary on future research and its application for conservation practice.
What is the minimum viable population (MVP) of a particular species? Besides the obvious implications for conservation, especially of endangered species, this question raises important issues in population biology. MVP obviously varies with demographic, life history and environmental factors, but also depends upon genetic load and genetic variability. This book addresses the most recent research in the rapidly developing integration of conservation biology with population biology. Chapters consider the roles of demographic and environmental variability; the effects of latitude, body size, patchiness and metapopulation structure; the implications of catastrophes; and the relevance of effective population size on inbreeding and natural selection. Other topics addressed include the role of decision theory in clarifying management alternatives for endangered species, and the opportunities for improved co-operation between agencies responsible for management. The book concludes with a forward-looking and plain-speaking summary on future research and its application for conservation practice.
We compile and analyze data on the population genetic structure of broad-sense clonal plant populations where sexual recruitment is rare or absent. The data from 27 studies show a common theme: multiclonal populations of intermediate diversity and evenness tend to be the rule, most clones are restricted to one or a few populations, and widespread clones are exceptional. While a few studies have demonstrated that ecological differences among sympatric clones do occur, more experimental and theoretical studies are necessary to determine the role of selection and other evolutionary forces in maintaining clonal polymorphism.
Straying between wild anadromous salmon populations is a natural process, and it is likely that the amount of gene migration from straying fish results from and reflects coadaptation between local populations. In contrast, introgression from cultured or transplanted fish may be disruptive. Data used to describe the genetic structure of populations usually come from biochemical genetic traits which may not reflect the strong selection that affects life-history characteristics. Simulations of a simple model of populations which included selection, genetic exchange and gene sampling error were conducted to examine the influences of these processes on population structure within the system. Results of these simulations indicate that data from loci not influenced by natural selection may provide a very different picture of population structure than data from loci subject to dispersive selection. Even relatively small decreases in average population fitness (0.0075) that accompany relatively weak selection can produce divergence between populations in the presence of local immigration rates of between 1 and 10%. Because of natural or anthropogenic causes, many population systems may not be in genetic equilibrium. Estimates from these simulations of parameters such as Ne, GST, Nem, and the G-statistic for heterogeneity, which are used to describe population genetic structure, may differ substantially from equilibrium values and from expectations for neutral loci. Statistically significant divergence between populations can occur even in the presence of 10 immigrants per generation. Results of simulations provide a means to examine potential results of introgression of alien fish into natural populations; but without knowing the extent of gene migration which occurs among wild populations and the magnitude of loss in average fitness of populations which results from introgression, it is not possible to predict what the impact will be.
Models of mating-system evolution commonly assume that inbreeding depression is independent of the genotype at loci determining the mating system. Because of the association that develops between genotypes at different loci in inbred populations, an individual that is heterozygous at a mating-type locus is more likely to be heterozygous at a fitness locus than is a randomly chosen individual. A modifier model for the evolution of self-fertilization in plants demonstrates that inbreeding depression is not an adequate descriptor of the relative fitness of inbred and outbred progeny. If inbreeding depression is primarily a result of segregation at overdominant loci, intermediate rates of self-fertilization may be favored, even if the inbreeding depression is less than 30%. Indeed, in some cases, mutants that cause some outcrossing can be introduced into completely selfing populations when the inbreeding depression is as little as 1%. If inbreeding depression is primarily a result of the expression of recessive lethals in inbred progeny, selfing can evolve in an initially random mating population, even when the inbreeding depression is over 70%.
Most models of mating-system evolution predict inbreeding depression to be low in inbred populations due to the purging of deleterious recessive alleles. This paper presents estimates of outcrossing rates and inbreeding depression for two highly selfing, monoecious annuals Begonia hirsuta and B. semiovata. Outcrossing rates were estimated using isozyme polymorphisms, and the magnitude of inbreeding depression was quantified by growing progeny in the greenhouse produced through controlled selfing and outcrossing. The estimated single-locus outcrossing rate was 0.03 ± 0.01 (SE) for B. hirsuta and 0.05 ± 0.02 for B. semiovata. In both species, the seed production of selfed flowers was on average 12% lower than that of outcrossed flowers (B. hirsuta P = 0.07, B. semiovata P < 0.05, mixed model ANOVAs). There was no significant effect of crosstype on germination rate or survival, but selfed offspring had a lower dry mass than outcrossed offspring 18 weeks after planting in both species (on average 18% lower in B. hirsuta and 31% lower in B. semiovata). Plants that were the products of selfing began flowering later than plants produced through outcrossing in B. semiovata, but not in B. hirsuta. The effects of crosstype on seed production (B. semiovata), days to first flower and offspring dry mass (both species) varied among maternal parents, as indicated by significant crosstype x maternal parent interactions for these characters. Both species showed significant inbreeding depression for total fitness (estimated as the product of seed production, germination rate, survival and dry mass at 18 weeks). In B. hirsuta, the average total inbreeding depression was 22% (range -57%-98%; N = 23 maternal parents), and in B. semiovata, it was 42% (-11%-84%; N = 21). This study demonstrates that highly selfing populations can harbor substantial inbreeding depression. Our findings are consistent with the hypothesis that a high mutation rate to mildly deleterious alleles contributes to the maintenance of inbreeding depression in selfing populations.
Multivariate phenotypic differentiation in eight morphometric traits was examined in bottleneck lines of the housefly initiated with one, four, or 16 pairs of flies from a natural outbred population. Differentiation was assessed using a Mahalanobis' distance metric in units of additive genetic variance and covariance estimated from the ancestral population (i.e., generalized genetic distance). This distance metric was partitioned into contributions of size and shape to total distance. Bottleneck lines of all sizes diverged significantly from the ancestral line, but the direction of these shifts differed among the lines of different initial founding size. Those populations founded with single pairs diverged from the ancestral line mostly in shape; the 16-pair lines differentiated almost entirely in size, and the four-pair lines were intermediate in the relative contribution of shape to differentiation from the control. Bottlenecks serve to alter the genetic relationships among traits within the derived populations and in doing so could promote speciation by permitting differentiation of the populations along evolutionary trajectories less accessible to the base population.
Four natural populations of Clarkia tembloriensis, whose levels of heterozygosity and rates of outcrossing were previously found to be correlated, are examined for developmental instability in their leaves. From the northern end of the species range, we compare a predominantly selfing population (t̂ = 0.26) with a more outcrossed population (t̂ = 0.84), which is genetically similar. From the southern end of the range, we compare a highly selfing population (t̂ = 0.03) with a more outcrossed population (t̂ = 0.58). We measured developmental stability in the populations using two measures of within-plant variation in leaf length as well as calculations of fluctuating asymmetry (FA) for several leaf traits. Growth-chamber experiments show that selfing populations are significantly more variable in leaf length than more outcrossed populations. Developmental instability can contribute to this difference in population-level variance. Plants from more homozygous populations tend to have greater within-plant variance over developmentally comparable nodes than plants from more heterozygous populations, but the difference is not significant. At the upper nodes of the plant, mature leaf length declines steadily with plant age, allowing for a regression of leaf length on node. On average, the plants from more homozygous populations showed higher variance about the regression (MSE) and lower R(2) values, suggesting that the decline in leaf length with plant age is less stable in plants from selfing populations than in plants from outcrossing populations. Fluctuating asymmetry (FA) was calculated for four traits within single leaves at up to five nodes per plant. At the early nodes of the plant where leaf arrangement is opposite, FA was also calculated for the same traits between opposite leaves at a node. Fluctuating asymmetry is significantly greater in the southern selfing population than in the neighboring outcrossed population. Northern populations do not differ in FA. Fluctuating asymmetry can vary significantly between nodes. The FA values of different leaf traits were not correlated. We show that developmental stability can be measured in plants using FA and within-plant variance. Our data suggest that large differences in breeding system are associated with differences in stability, with more inbred populations being the least stable.
https://deepblue.lib.umich.edu/bitstream/2027.42/137516/1/evo00989.pdf
We have mapped genes causing life-history trade-offs, and they behave as predicted by ecological theory. Energetic and quantitative-genetic models suggest a trade-off between age and size at first reproduction. Natural selection favored plants that flower early and attain large size at first reproduction. Response to selection was opposed by a genetic trade-off between these two components of fitness. Two quantitative-trait loci (QTLs) influencing flowering time were mapped in a recombinant inbred population of Arabidopsis. These QTLs also influenced size at first reproduction, but did not affect growth rate (resource acquisition). Substitutions of small chromosomal segments, which may represent allelic differences at flowering time loci, caused genetic trade-offs between life-history components. One QTL explained 22% of the genetic variation in flowering time. It is within a few centiMorgans (cM) of the gigantea (GI) locus, and may be allelic with GI. Sixteen percent of the genetic variation was explained by another QTL, FDR1, near 18 cM on chromosome II, which does not correspond to any previously identified flowering-time locus. These life-history genes regulate patterns of resource allocation and life-history trade-offs in this population.
Estimates of inbreeding depression obtained from the literature were used to evaluate the association between inbreeding depression and the degree of self-fertilization in natural plant populations. Theoretical models predict that the magnitude of inbreeding depression will decrease with inbreeding as deleterious recessive alleles are expressed and purged through selection. If selection acts differentially among life history stages and deleterious effects are uncorrelated among stages, then the timing of inbreeding depression may also evolve with inbreeding. Estimates of cumulative inbreeding depression and stage-specific inbreeding depression (four stages: seed production of parent, germination, juvenile survival, and growth/reproduction) were compiled for 79 populations (using means of replicates, N = 62) comprising 54 species from 23 families of vascular plants. Where available, data on the mating system also were collected and used as a measure of inbreeding history. A significant negative correlation was found between cumulative inbreeding depression and the primary selfing rate for the combined sample of angiosperms (N = 35) and gymnosperms (N = 9); the correlation was significant for angiosperms but not gymnosperms examined separately. The average inbreeding depression in predominantly selfing species (δ = 0.23) was significantly less (43%) than that in predominantly outcrossing species (δ = 0.53). These results support the theoretical prediction that selfing reduces the magnitude of inbreeding depression. Most self-fertilizing species expressed the majority of their inbreeding depression late in the life cycle, at the stage of growth/reproduction (14 of 18 species), whereas outcrossing species expressed much of their inbreeding depression either early, at seed production (17 of 40 species), or late (19 species). For species with four life stages examined, selfing and outcrossing species differed in the magnitude of inbreeding depression at the stage of seed production (selfing δ = 0.05, N = 11; outcrossing δ = 0.32, N = 31), germination (selfing δ = 0.02, outcrossing δ = 0.12), and survival to reproduction (selfing δ = 0.04, outcrossing δ = 0.15), but not at growth and reproduction (selfing δ = 0.21, outcrossing δ = 0.27); inbreeding depression in selfers relative to outcrossers increased from early to late life stages. These results support the hypothesis that most early acting inbreeding depression is due to recessive lethals and can be purged through inbreeding, whereas much of the late-acting inbreeding depression is due to weakly deleterious mutations and is very difficult to purge, even under extreme inbreeding.
Studies of spatial variation in the environment have primarily focused on how genetic variation can be maintained. Many one-locus genetic models have addressed this issue, but, for several reasons, these models are not directly applicable to quantitative (polygenic) traits. One reason is that for continuously varying characters, the evolution of the mean phenotype expressed in different environments (the norm of reaction) is also of interest. Our quantitative genetic models describe the evolution of phenotypic response to the environment, also known as phenotypic plasticity (Gause, 1947), and illustrate how the norm of reaction (Schmalhausen, 1949) can be shaped by selection. These models utilize the statistical relationship which exists between genotype-environment interaction and genetic correlation to describe evolution of the mean phenotype under soft and hard selection in coarse-grained environments. Just as genetic correlations among characters within a single environment can constrain the response to simultaneous selection, so can a genetic correlation between states of a character which are expressed in two environments. Unless the genetic correlation across environments is ± 1, polygenic variation is exhausted, or there is a cost to plasticity, panmictic populations under a bivariate fitness function will eventually attain the optimum mean phenotype for a given character in each environment. However, very high positive or negative correlations can substantially slow the rate of evolution and may produce temporary maladaptation in one environment before the optimum joint phenotype is finally attained.
The effective population size (Ne ) depends strongly on mating system and generation time. These two factors interact such that, under many circumstances, Ne is close to N/2, where N is the number of adults. This is shown to be the case for both simple and highly polygynous mating systems. The random union of gametes (RUG) and monogamy are two simple systems previously used in estimating Ne , and here a third, lottery polygyny, is added. Lottery polygyny, in which all males compete equally for females, results in a lower Ne than either RUG or monogamy! Given nonoverlapping generations the reduction is 33% for autosomal loci and 25% for sex-linked loci. The highly polygynous mating systems, harem polygyny and dominance polygyny, can give very low values of Ne /N when the generation time (T) is short. However, as T is lengthened, Ne approaches N/2. The influence of a biased sex ratio depends on the mating system and, in general, is not symmetrical. Biases can occur because of sex differences in either survival or recruitment of adults, and the potential for a sex-ratio bias to change Ne is much reduced given a survival bias. The number of juveniles present also has some influence: as the maturation time is lengthened, Ne increases.
Houle (1994) showed that marker-associated heterosis due to general inbreeding depression could not be distinguished from direct overdominance at the marker locus by examining mean genotypic fitnesses, in the one-locus case. Indeed, both hypotheses equally fit the same regression model, referred to as the "adaptive distance model" (Smouse 1986). I here extend the analysis to several loci and to the relationship between marker genotype and variance in fitness. Several predictions differ between the overdominance and inbreeding hypotheses: (1) all locus-specific effects are equal under inbreeding, whereas they are not under overdominance; (2) the adaptive distance model has an increasingly low fit when the number of loci increases, under inbreeding, whereas it always explains the whole variance in fitness under overdominance; (3) a negative relationship is predicted between mean fitness and the variance in fitness, under inbreeding, which is not predicted under overdominance. Some statistical tests are derived from these predictions, that help to identify the genetic basis of heterosis. Simulations show that the power of these tests allows their application to real datasets.
Relationships between growth rate and the degree of individual heterozygosity at ten nuclear RFLP loci were examined in two populations of the Atlantic cod, Gadus morhua, from northern Norway. A highly significant positive correlation was observed between growth rate and DNA heterozygosity in one population (Balsfjord) but not in the other (Barents Sea). Our results provide support for an important prediction of the associative overdominance hypothesis that heterozygosity-fitness correlations can be detected at neutral genetic markers and suggest that environmental conditions might play a dominant role in the manifestation of the correlation.
A marker-based method for studying quantitative genetic characters in natural populations is presented and evaluated. The method involves regressing quantitative trait similarity on marker-estimated relatedness between individuals. A procedure is first given for estimating the narrow sense heritability and additive genetic correlations among traits, incorporating shared environments. Estimation of the actual variance of relatedness is required for heritability, but not for genetic correlations. The approach is then extended to include isolation by distance of environments, dominance, and shared levels of inbreeding. Investigations of statistical properties show that good estimates do not require great marker polymorphism, but rather require significant variation of actual relatedness; optimal allocation generally favors sampling many individuals at the expense of assaying fewer marker loci; when relatedness declines with physical distance, it is optimal to restrict comparisons to within a certain distance; the power to estimate shared environments and inbreeding effects is reasonable, but estimates of dominance variance may be difficult under certain patterns of relationship; and any linkage of markers to quantitative trait loci does not cause significant problems. This marker-based method makes possible studies with long-lived organisms or with organisms difficult to culture, and opens the possibility that quantitative trait expression in natural environments can be analyzed in an unmanipulative way.
Population response to selection depends on the presence of additive genetic variance for traits under selection. When a population enters an alien environment, environment-induced changes in the expression of genetic variance may occur. These could have large effects on the response to selection. To investigate the environment-dependence of genetic variance, we conducted a reciprocal transplant experiment between two ecotypically differentiated populations of Impatiens pallida using the progeny of a standard mating design. The floodplain site was characterized by high water availability, moderate temperatures, and continuous dense stands of Impatiens. The hillside site was drier, with larger temperature extremes and supported only scattered patches of Impatiens with significantly lower seed production and earlier mortality. Estimates of heritability were low for each of the 13 traits measured in each population and site (range from 0-28%). Additive genetic variance for life-history traits tended to be larger than for morphological traits, but genetic variance in fitness was estimated to be not significantly different from zero in all cases. Significant heritability was detected in both populations for one trait (date of first cleistogamous flower) known to be closely related to fitness on the hillside. In general, heritability was reduced for populations when grown in the hillside site relative to the floodplain site, suggesting that stress acts to reduce the expression of genetic variance and the potential to respond to selection there. Consistent reductions in heritability associated with more stressful environments suggest that populations invading such sites may undergo little adaptive differentiation and be more prone to local extinction.
We studied deterministic models of multilocus systems subject to mutation-selection balance with all loci unlinked, and with multiplicative interactions of the loci affecting fitness, in partially self-fertilizing populations. The aim was to examine the fitnesses of the zygotes produced by outcrossing and by selling, and the magnitude of inbreeding depression, in populations with different levels of inbreeding. The fates of modifiers of the outcrossing rate were also examined. With biologically plausible parameter values, inbreeding depression can be very large in moderately selfing populations, particularly when the mutant alleles are fairly recessive and selection is weak. A modifier allele reducing the selfing rate can be favored under these circumstances. In more inbred populations, inbreeding depression is lower, and selection favors alleles that increase the selfing rate. When inbreeding depression is caused by mutant alleles with strong selective disadvantage, modifiers causing large increases in selfing can often be favored even when the inbreeding depression exceeds one-half, though in these circumstances modifiers increasing selfing by smaller amounts are usually eliminated. Weaker selection appears to be more favorable to the maintenance of outcrossing.
Inbreeding depression is commonly observed in natural populations. The deleterious effects of forced inbreeding are often thought to be less pronounced in populations with self-pollinating mating systems than in primarily outcrossing populations. We tested this hypothesis by comparing the performance of plants produced by artificial self- and cross-pollination from three populations whose outcrossing rate estimates were 0.03, 0.26, and 0.58. Outcrossing rates and inbreeding coefficients were estimated using isozyme polymorphisms as genetic markers. Analysis of F statistics suggests that biparental inbreeding as well as self-fertilization contribute to the level of homozygosity in the seed crop. Biparental inbreeding will reduce the heterozygosity of progeny produced by outcrossing, relative to random outcrossing expectations, and hence will reduce the effects of outcrossing versus self-fertilization. Heterotic selection may increase the average heterozygosity during the life history. Selfed and outcrossed seeds from all three populations were equally likely to germinate and survive to reproduce. However, inbreeding depression was observed in fecundity traits of plants surviving to reproduction in all three populations. Even in the population whose natural self-fertilization rate was 97%, plants grown from seed produced by self-pollination produced fewer fruits and less total seed weight than plants grown from outcrossed seed. There was no detectable inbreeding depression in estimated lifetime fitness. Inbreeding effects for all reproductive yield characters were most severe in the accession from the most outcrossing population and least severe in the accession from the most self-fertilizing population.
We found relatively high heritabilities in the narrow sense for seven of eight meristic characters in a population of rainbow trout using regression of mean progeny values on mid-parent values. In sharp contrast, there is no statistically significant additive genetic variance controlling developmental stability, as measured by fluctuating asymmetry (h(2) = 0.02). However, there is a significant correlation between the average heterozygosity of each family at isozyme loci and the average number of asymmetric traits per individual. We have previously reported a strong correlation between heterozygosity at protein loci and decreased fluctuating asymmetry in this and other salmonid populations. Thus, there is little or no additive, but substantial dominance, genetic variation affecting fluctuating asymmetry. This suggests that there has been directional selection for increased developmental stability.
Adaptive phenotypic plasticity is the predicted evolutionary response to fine-grained fluctuation in major environmental factors, such as soil moisture in plant habitats. This study examines genotypes from two natural populations of Polygonum persicaria, one from a relatively homogeneous, moderately moist site, and one from a site in which severe drought and root flooding occur within single growth seasons. Norms of reaction (phenotypic response curves) were determined for a random sample of eight and ten cloned genotypes, respectively, from each of the populations over a controlled moisture gradient ranging from drought to flooding.
The mutational genetic load was calculated assuming mutation-selection-inbreeding equilibrium and applied to homosporous ferns. Diploid species with past inbreeding should have a low genetic load while outcrossers should have a high genetic load. These predictions are consistent with the bimodal pattern of genetic load found in 18 diploid homosporous fern species. The prediction that tetraploids should have a low genetic load is also consistent with estimates of genetic load in several species.
The amounts of inbreeding depression upon selfing and of heterosis upon outcrossing determine the strength of selection on the selfing rate in a population when this evolves polygenically by small steps. Genetic models are constructed which allow inbreeding depression to change with the mean selfing rate in a population by incorporating both mutation to recessive and partially dominant lethal and sublethal alleles at many loci and mutation in quantitative characters under stabilizing selection. The models help to explain observations of high inbreeding depression (> 50%) upon selfing in primarily outcrossing populations, as well as considerable heterosis upon outcrossing in primarily selfing populations. Predominant selfing and predominant outcrossing are found to be alternative stable states of the mating system in most plant populations. Which of these stable states a species approaches depends on the history of its population structure and the magnitude of effect of genes influencing the selfing rate.
Fifty-two inbred populations of Drosophila melanogaster, each founded from a single pair, and a large number of control, outbred flies were measured for fitness and a set of six traits. A survey of the literature on the effects of inbreeding and population bottlenecks demonstrates that the commonly observed pattern of an apparent variance among characters and among species in changes of phenotypic variance may in fact be largely the result of sampling error, given the pattern of change that we demonstrate within a species for the same character. In our study, population bottlenecks on average decrease the amount of phenotypic variance for a suite of wing characteristics and size, but there is large and significant variation among lines in the amount of phenotypic variance. As a result, several lines increased in variance in spite of the average decrease. Interestingly, the changes in phenotypic variance for fitness are in sharp contrast to those seen for phenotypic variance for morphological traits. The amount of phenotypic variance for fitness varies highly significantly among lines but, on average, is increased by bottlenecks. The changes in phenotypic variance as a result of population bottlenecks are large enough to significantly affect the probability of peak shifts by the variance-induced peak shift model.
Although genetic variation in characters closely related to fitness is expected to either become depleted by selection or masked by environmental variation, "good gene" models of sexual selection require moderate to high heritabilities of secondary sexual characters to explain the occurrence of costly female mate preferences. In this study, I investigated whether the estimated heritability of a condition-dependent secondary sexual character (i.e., the white forehead badge) in the collared flycatcher varied depending on environmental conditions experienced during offspring growth. The data were collected over a period of 14 years making it possible to exploit natural variation in natal conditions. In addition, natal conditions were experimentally altered through brood size manipulations. During unfavorable conditions caused by generally poor weather or experimentally enlarged brood size, no significant heritability based on father-sons regressions could be demonstrated (0.19 ⩽ h(2) ⩽ 0.27). In contrast, sons reared during years with favorable weather or in experimentally reduced broods significantly resembled their fathers (0.44 ⩽ h(2) ⩽ 0.65). In addition, the heritability estimates declined with increasing maternal age. The strong effect of natal environmental condition on the estimated heritability of forehead badge size suggests that the potential genetic benefit from mate choice vary according to environmental conditions (e.g., the benefit is reduced during unfavorable rearing conditions). Because sons reared during poor conditions have probably experienced a natal environment different from that experienced by their fathers, the low heritability estimates obtained under poor conditions seem to be caused by low additive genetic variation expressed in such environments and/or a low genetic correlation between the expression of the trait in the two different environments (i.e., good vs. bad). Both of these explanations imply the presence of genotype-by-environment interactions. If such interactions frequently affect the expression of secondary sexual characters, this may offer an explanation of the high heritabilites sometimes reported for such traits, despite their exposure to long-term directional selection.
Meta-analyses of published correlation coefficients between multilocus heterozygosity (MLH) and two fitness surrogates, growth rate and fluctuating asymmetry, suggested that the strength of these correlations are generally weak. A variety of plants and animals was included in the meta-analyses. A statistically homogeneous group of MLH-growth rate correlation coefficients that included both plants and animals yielded a common correlation of rz = 0.133. A common correlation of rz = -0.170 was estimated for correlations between MLH and fluctuating asymmetry in three species of salmonid fishes. These results suggest that selection, including overdominance, has at most a weak effect at allozyme loci and cast some doubt on the widely held notion that heterozygosity and individual fitness are strongly correlated.
There is a growing body of literature suggesting that the fitness of an individual increases with the observed number of heterozygous loci. Broad theoretical considerations indicate that under various sorts of balancing selection, this is what one should generally expect in a population of multiple-locus genotypes. To date, however, it has not been possible to distinguish between two potential explanations of the phenomenon. The first explanation is that the loci examined are themselves responsible for the fitness differences observed (or, equivalents, are very closely linked to those that do). The genetic variation in question is thought to be maintained in polymorphic equilibrium by some form of balancing selection. The second explanation assumes that the observed loci are themselves selectively irrelevant but that their heterozygosity reflects that of the total genome. Genomic heterozygosity is thought to be predictive of fitness, being an obverse measure of generalized inbreeding depression. We provide a formal derivation of an explicit relationship between fitness and multiple-locus genotype for a simple form of the first explanation, the multiplicative overdominance model. The inbreeding depression model is a degenerate special case of this more general formulation. A formal estimation and testing framework is constructed that should facilitate evaluation of the two models with empiric data on heterozygosity and fitness.
The coexistence and coevolution of sexual and asexual species under resource competition are explored with three models: a nongenetic ecological model, a model including single locus genetics, and a quantitative-genetic model. The basic assumption underlying all three models is that genetic differences are translated into ecological differences. Hence if sexual species are genetically more variable, they will be ecologically more variable. Under classical competition theory, this increased ecological variability can, in many cases, be an advantage to individual sexual genotypes and to the sexual species as a whole. The purpose of this paper is to determine the conditions when this advantage will outway three disadvantages of sexuality: the costs of males, of segregation, and of the additive component of recombination.
A generalized expression for coefficients of consanguinity and relationship with previous inbreeding is presented to examine various breeding strategies in subdivided populations. Conditions that would favor inbreeding are developed for: 1) nonfamilial inbreeding within a deme versus outbreeding; 2) altruistic inbreeding by females versus outbreeding; 3) sib-mating versus outbreeding; and 4) sib-mating versus nonfamilial breeding within a deme. Inbreeding behavior is advantageous under certain conditions but depends on the types of mating, the previous breeding history of the deme, the rate of accumulation of inbreeding depression, and the cost of migration. In polygynous mating systems it is genetically more advantageous for males to migrate, because female emigration may 1) leave a related male with no mate or one fewer mate, or 2) force both male and female to risk the cost of migration. Nonfamilial breeding is always a better strategy than sib-mating given previous inbreeding within the deme. Even when the cost of migration is zero, inbreeding is favored if the coefficient of relationship among relatives is greater than the ratio of the probabilities of offspring inviability to offspring viability. Although high inbreeding coefficients are probably not adaptive unless the costs of migration are great or inbreeding depression constants are small, low levels of inbreeding are advantageous in many situations. Therefore, increased genetic representation by way of inbreeding and inclusive fitness is a major component of the evolutionary process.