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Correlation between forest age and the proportion of mixed samples in six populations of the moss Plagiomnium affine (p=0.131). See text for details regarding sampling.
Source publication
We screened six populations of the clonal forest floor moss Plagiomnium affine
from forests of different ages for genetic variation at 23 allozyme loci. Samples
consisting of two adjacent, unconnected shoots were taken at regular intervals
along one transect from each population. Transect lengths varied from
22 to 52 m, depending on the size of the...
Context in source publication
Context 1
... proportion of mixed samples (i.e. samples with two different genotypes) ranged from 0 in popula- tion 6 to 25% in population 4. The correlation be- tween forest age and the proportion of mixed sam- ples (Fig. 5) was positive, but not significant (r=0.688, p=0.131). The relationship between the number of detected haplotypes and the number of detected alle- les was linear (r=0.796), suggesting that no popula- tion had reached the inflection point on the curve because most alleles have reached that particular population. ...
Citations
... Genetic diversity of the bryophyte Plagiomnium affine (Bland) T.Kop. was higher in older spruce forest stands than in younger plantations (Cronberg et al. 2005). A study on Hylocomium splendens (Hedw.) ...
... For example, Plagiomnium spp. are the first colonizers in spruce forests after disturbances and are common in spruce forest stands (Cronberg et al., 2005). Simpson's evenness indices were similar among stands, except for the over-mature stand, which indicates a rather similar biological diversity in these stands (Hart & Chen, 2008). ...
The long-term (50 years) effect of whole-tree harvesting (stump harvesting) on ground vegetation in experimental drained Norway spruce ( Picea abies (L.) Karst.) stands was studied. We used a chronosequence approach to assess the long-term impact of whole-tree harvesting (WTH) on stands’ ground vegetation. WTH stands were compared with four control stands with different age and with the same forest type: young stand (15 years), middle-aged stand (45 years), mature stand (110 years) and over-mature stand (140 years). Species richness was similar between the WTH stand and middle-aged stand (61 and 60 species, respectively). Shannon-Wiener diversity indices in the WTH and middle-aged stand (3.40 and 3.19, respectively) indicated that the stands were similar to each other. A community similarity analysis showed that the composition of vegetation was similar between the WTH and middle-aged stand, although some species like Lycopodium clavatum and Diphasiastrum complanatum occurred only in the WTH stand. The study showed that a period of 50 years is sufficient for ground vegetation of a typical drained spruce forest to recover after WTH management.
... Our results indicate that the genetic diversity of native epiphytic moss L. smithii decreases along gradients of anthropogenic disturbance, consistently with previous studies that have highlighted a lower molecular diversity of bryophytes and vascular plants in human-altered habitats (Patiño et al., 2010;Wyatt, 1992;Cronberg et al., 2005;Wang et al., 2006;Baucom et al., 2005). The Mediterranean region is still poorly surveyed in this respect, although numerous traits, like anthropogenic pressure, climate change and widespread natural sources of phytotoxic compounds, such as active volcanoes, fumaroles and geothermal fields, can affect the vegetation biodiversity. ...
We determined genetic variation and metal and polycyclic aromatic hydrocarbon
concentrations in Leptodon smithii moss collected in holm oak stands at cities, outskirts
and remote areas of Campania and Tuscany (Italy) to investigate if anthropogenic
pressure (pollutant emissions and land use change) affects moss genetic richness. In
both regions, metal and polycyclic aromatic hydrocarbon concentrations reflected the
trend urban > outskirts > remote areas, excepting Tuscany remote site. In both regions, the moss gene diversity increased fromurban to remote areas. The findings suggest the extent
and the fragmentation of urban green areas, as drivers of moss genetic richness.
... A positive association between genetic variation (allelic richness and/or gene diversity, H S ) and habitat age (possibly as a result of a long history of recruitment events) is confirmed by several studies of forest bryophytes (Wyatt et al., 1989;Cronberg, 2002;Cronberg et al., 2003Cronberg et al., , 2005Wyatt et al., 2005;Wang et al., 2006). Hence, old populations of bryophytes in forests appear not only to make a central contribution to sexual reproduction, and thereby gene flow via spores, but also represent reservoirs of genetic diversity. ...
Sporophyte production and female fertility were investigated in seventeen calcareous grassland demes of the moss Homalothecium lutescens (Hedw.) H. Rob. on the Baltic island of Oland, with the aim of understanding the relationships between sexual reproduction, habitat age, genetic variation and factors related to growth conditions. The overall proportion of fertile female shoots (with perichaetia) was 35%. Fertility status at the level of individual shoots was positively associated with shoot length and density, while within deme fertility was positively associated with bush cover. There was no association between female fertility and habitat age, genetic diversity (HS) or allelic richness. Out of 1344 investigated shoots, only two were normal-sized fertile males. Dwarf males were also extremely rare, and found almost exclusively on shoots with sporophytes. Few sporophytes were observed (in the two demes with highest fertility and bush cover). No relationship between genetic variation and the frequency of sporophytes and males was found. The lack of a relationship between sexual reproduction and genetic variation suggests that sexual reproduction may not occur in the same grassland fragments as the recruitment of new clones (from spores or vegetative fragments). The majority of the dry, open grassland habitats, where H. lutescens is typically found in the study area, appear to be suboptimal for both dwarf males and fertilization. Sexual reproduction is more likely to occur in shaded (although grazed) grassland patches, where moisture levels are likely to be higher and the moss colonies are generally more vigorous.
... A positive association between genetic variation (allelic richness and/or gene diversity, H S ) and habitat age (possibly as a result of a long history of recruitment events) is confirmed by several studies of forest bryophytes (Wyatt et al., 1989;Cronberg, 2002;Cronberg et al., 2003Cronberg et al., , 2005Wyatt et al., 2005;Wang et al., 2006). Hence, old populations of bryophytes in forests appear not only to make a central contribution to sexual reproduction, and thereby gene flow via spores, but also represent reservoirs of genetic diversity. ...
... Low levels of recruitment should result in a long-term association between the number of alleles and the number of colonization events in haploid bryophytes. In contrast, the point where new colonization events make a negligible contribution to allelic richness (A) may be expected to be reached more rapidly in vascular plants (Cronberg et al. 2005). An increase in genetic variability over time (possibly as a result of a long history of recruitment events) is confirmed by several studies that have shown a positive association between genetic variation (A and within-deme gene diversity (H S )) in bryophyte populations and habitat age in forested areas (Wyatt et al. 1989; Cronberg 2002; Cronberg et al. 2003 Cronberg et al. , 2005 Wyatt et al. 2005; Wang et al. 2006). ...
... In contrast, the point where new colonization events make a negligible contribution to allelic richness (A) may be expected to be reached more rapidly in vascular plants (Cronberg et al. 2005). An increase in genetic variability over time (possibly as a result of a long history of recruitment events) is confirmed by several studies that have shown a positive association between genetic variation (A and within-deme gene diversity (H S )) in bryophyte populations and habitat age in forested areas (Wyatt et al. 1989; Cronberg 2002; Cronberg et al. 2003 Cronberg et al. , 2005 Wyatt et al. 2005; Wang et al. 2006). Gene flow and recruitment in bryophytes is facilitated by sexual reproduction, because the spores are small and have the potential for wind dispersal over distances that are greater than those for vegetative bryophyte fragments or the seeds of most vascular plants (Muños et al. 2004; Frahm 2008 ). ...
... As in earlier bryophyte studies (Wyatt et al. 1989; Cronberg 2002; Cronberg et al. 2003 Cronberg et al. , 2005 Wyatt et al. 2005; Wang et al. 2006), there was a positive association between gene diversity (H S R) and the age of the habitat. In addition to the association with habitat age, the model explaining H S R also included a negative association with vascular plant species richness (Fig. 3). ...
Relationships between genetic (allozyme) variation and landscape age and structure were investigated in 17 calcareous grassland demes of the moss Homalothecium lutescens (Hedw.) H. Rob. on the Baltic island of Öland. Mean within-deme gene diversity (HS = 0.152) was moderate compared with other bryophyte studies, and the between-deme proportion of the total diversity (GST = 0.100, Jost's D = 0.011) was low but significantly different from zero. Clonal mixing, measured as the proportion of two adjacent shoots having different haplotypes, was relatively high (mean 0.32 over all demes). HS was higher in old grassland fragments, but negatively related to vascular plant species richness. Allelic richness (A) was positively associated with the area of old (≥ 280 years) grassland in the surroundings: although demes in old grasslands are genetically more variable than those in younger grasslands, proximity to large areas of old grassland may promote genetic variability even in younger grassland demes. The importance of management continuity for species diversity has been stressed in many earlier grassland studies. Here, we conclude that grassland fragments with a long history of grazing continuity are also positively associated with variability at within-species level, as exemplified by the bryophyte H. lutescens.
... The forest age, which is associated with the number and availability of microhabitats, thus influences the probability of colonisation by bryophytes (Snä ll, Ehrlén & Rydin, 2005; Pereira & Cavalcanti, 2007; Hutsemekers, Dopagne & Vanderpoorten, 2008). Several studies have shown a relationship between population history (related to human-induced disturbances) and the levels of genetic variation in temperate and boreal forests (Cronberg et al., 2005; Wang et al., 2006; Spagnuolo et al., 2007a). By contrast, very few molecular studies have analysed epiphytes or have been carried out in disturbed (sub-) tropical forests (e.g. ...
... Zartman, McDaniel & Shaw, 2006). Furthermore, most available studies have exclusively analysed well-established populations that remain in old forest patches (for exceptions see Cronberg et al., 2005; Wang et al., 2006). As a result, genetic factors have rarely Journal of Bryology (2010) 32: 220–231 been integrated into forest restoration or management programmes designed to protect viable bryophyte populations (Pohjamo, Korpelainen & Kalinauskaité, 2008). ...
... Our results showed that genetic diversity parameters of the moss I. myosuroides were higher in populations from ancient forest stands than in recolonised disturbed forest stands. This is consistent with some previous studies that have pointed to a lower molecular diversity of bryophytes and vascular plants in human-altered habitats (Wyatt, 1992; Cronberg et al., 2005; Wang et al., 2006; Baucom et al., 2005; for an exception see Zartman et al., 2006). Across both study areas, the lowest genetic diversity was found in P. radiata plantations from Enchereda. ...
Human-induced disturbances threaten the genetic variation of wild plant populations. The genetic diversity and spatial population structure of the moss Isothecium myosuroides, a late-successional forest species, was investigated in subtropical cloud forests (La Gomera, Canary Islands) using inter-simple sequence repeat (ISSR) markers. Inter- and intrapopulation genetic variability was assessed in two ancient and four disturbed forest stands, which were classified according to their vegetation, forest age and type of disturbance. ISSR analysis of 144 epiphyte colonies with eight primers resulted in 211 reliably amplified bands. Our findings show that in disturbed forest stands, the population structure is increased, and the genetic diversity decreased compared with the levels observed in ancient forests. Although ancient and disturbed stands were located relatively close to each other, the (re-) established epiphyte populations did not reach their original genetic condition, 40 years following disturbance. Strong differentiation among populations of I. myosuroides at several spatial scales and differences in genetic diversity are mainly related to the local environmental conditions and the availability of suitable microhabitats in anthropogenically disturbed forest stands.
Two competing predictions regarding highly dispersible clonal plants, such as bryophytes, expect levels of genetic diversity to either increase or decrease over time following a disturbance that opens habitat for colonization. Following up on previous research that found higher levels of genetic variation in bryophytes from relatively undisturbed forest sites, we examined unisexual, haploid species of a moss (Plagiomnium ciliare), a leafy liverwort (Porella platyphylloidea), and a thalloid liverwort (Conocephalum conicum sensu lato) from the Mountains, Piedmont, and Coastal Plain of the southeastern United States. In terms of time since last disturbance, sites were ranked Mountains > Piedmont > Coastal Plain. Measures of genetic variation, including percentage of loci polymorphic, mean number of alleles per locus, mean expected heterozygosity, and number of multilocus genotypes, all fit the prediction that genetic diversity should increase over time. We also examined several components of reproductive success expected to influence levels of genetic variation, including colony size, colony mixing, sex expression, phenotypic sex ratio, and sporophyte production (percentage of females producing sporophytes). Most, but not all, of our predictions for populations of varying time since last disturbance were fulfilled, although other ecological differences related to soil, climate, and vegetation are also likely to influence reproductive success.
Available at <http://digitalcommons.mtu.edu/bryophyte-ecology/>
