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![Life-cycle. The typical haploid-diploid life cycle of Gracilaria species, with the alternation of meiosis and syngamy connecting tetrasporophytes and gametophytes individuals (modified from Kain & Destombe [61] and Guillemin et al. [62]](publication/329077189/figure/fig1/AS:695214238863360@1542763399697/Life-cycle-The-typical-haploid-diploid-life-cycle-of-Gracilaria-species-with-the.png)
Life-cycle. The typical haploid-diploid life cycle of Gracilaria species, with the alternation of meiosis and syngamy connecting tetrasporophytes and gametophytes individuals (modified from Kain & Destombe [61] and Guillemin et al. [62]
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Conditional differentiation is one of the most fundamental drivers of biodiversity. Competitive entities (usually species) differ in environmental or ecological niche enabling them to co-exist. Conditional differentiation of haploid and diploid generations is considered to be a requirement for the evolutionary stability of isomorphic b...
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... chilensis is a red macroalga occurring in the intertidal along the Chilean shore that plays a highly relevant role in the agar market worldwide. Individuals are fixed to rocky bottom by a holdfast and may survive and re-grow new fronds after the older were lost [22]. This species has a complex isomorphic biphasic life- cycle ( Fig. 1), also known as haploid-diploid life-cycle, al- ternating free living tetrasporophytes (diploid) and ga- metophytes (haploid). The gametophyte males release gametes that fertilize the gametophyte females. From the fertilized oogonia develops a short-lived diploid epi- phytic stage (the carposporophyte), acquiring nutrients from the ...
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This experimental study investigated the growing and viability of the red seaweed Gracilaria salicornia for commercial extraction of agar; which has varied industrial uses. The study was carried out from January to December 2017 in Kibuyuni, South Coast Kenya, using the 'off-bottom' seaweed farming method. G. salicornia can withstand hash environme...
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... Although in their classical study, Littler et al. [39] reported the functional similarity in physiological or ecological performances between gametophyte and sporophyte in an isomorphic species, many recent empirical studies have reported various types of functional differences between haploids and diploids. Specifically, chemical composition [40], resistance to physical stress [41], fecundity [22,28], survivorship [29,42,43], resistance to predators [44], resistance to epiphyte infection [45], growth rate [46][47][48], dispersal ability of the reproductive cells [49], and viability of the reproductive cells [50] are reported. Based on these facts, this article analyses a mathematical model that explicitly considers the differences in life history parameters of haploid gametophytes and diploid sporophytes, and aims to express stable ploidy ratios in a haploid-diploid population using a mathematical expression as simple as possible. ...
Macroalgal populations often consist of free-living haploid (gametophyte) and diploid (sporophyte) stages. Various ecological studies have been conducted to examine the demographic diversity of haploid-diploid populations with regard to the dominant stage. Here, I relaxed the assumption of classical research that the life history parameters of haploids and diploids are identical and developed a generalized haploid-diploid model that explicitly accounts for population density dependence and asexual reproduction. Analysis of this model yielded an exact solution for the abundance ratio of haploids to diploids in a population in which the ratio is determined by the balance of four demographic forces: sexual reproduction by haploids, sexual reproduction by diploids, asexual reproduction by haploids, and asexual reproduction by diploids. Furthermore, the persistence of a haploid-diploid population and its total biomass are shown to be determined by the basic reproductive number ( R 0 ), which is shown to be a function of these four demographic forces. When R 0 is greater than one, the haploid-diploid population stably persists, and the ploidy ratio obtained by the analytical solution is realized.
... Large differences in mortality, fecundity, or both can drive shifts in expected ploidy ratios (Thornber & Gaines 2004). Survival differences among spores (Destombe et al. 1992;Roleda et al. 2004Roleda et al. , 2008Vieira et al. 2018b), juveniles (Destombe et al. 1993;Guillemin et al. 2013;Vieira et al. 2018a) and adults (Vieira et al. 2018a) have been found to influence ploidy ratios in red algae. Similarly, the fertilization rate and the number of carpospores produced can lead to ploidy bias (Fierst et al. 2005). ...
... Large differences in mortality, fecundity, or both can drive shifts in expected ploidy ratios (Thornber & Gaines 2004). Survival differences among spores (Destombe et al. 1992;Roleda et al. 2004Roleda et al. , 2008Vieira et al. 2018b), juveniles (Destombe et al. 1993;Guillemin et al. 2013;Vieira et al. 2018a) and adults (Vieira et al. 2018a) have been found to influence ploidy ratios in red algae. Similarly, the fertilization rate and the number of carpospores produced can lead to ploidy bias (Fierst et al. 2005). ...
... Despite their morphological similarity, conditional differentiation between haploid and diploid generations has been found (Engel et al. 2001; Thornber and Gaines 2004;Krueger-Hadfield et al. 2016;Vieira et al. 2018aVieira et al. , b, 2021Vieira et al. , 2022 and is considered fundamental for their evolutionary stability and natural occurrence (Hughes and Otto 1999). This conditional differentiation affects traits such as growth (Krueger-Hadfield et al. 2016;Vieira et al. 2021), survival (Engel et al. 2001;Thornber and Gaines 2004;Vieira et al. 2018a), and reproduction (Engel et al. 2001;Thornber and Gaines 2004;Vieira et al. 2018b) that are essential for the production and biomass yield of farmed populations. Hence, it becomes necessary to optimize the management of life cycle phases for farming practices and commercial production. ...
Gracilaria dura is commercially important due to its agarose quality. Thus, production in aquaculture is increasing. Maximizing its yield requires mastering its life cycle. The distinct generations and stages of its isomorphic biphasic life cycle have been observed to diverge their biomechanical properties and eco-physiological responses. Functional traits such as growth, regeneration, pigments, antioxidant capacity, and productivity related to growth and survival can explain the differences observed among stages and/or among sites. We tested for differences in several functional traits among life stages (female gametophyte and tetrasporophyte) of G. dura originated from two locations (Adri and Veraval) along the Indian coast and grown in an open sea farm. A Principal Component Analysis (PCA) showed associations among pigments, antioxidant activity, and productivity. In the largest association, pigments R-PE and R-PC were negatively correlated with productivity (NPP and GPP). In the second-largest association, pigments R-PC and R-PE were negatively correlated to antioxidant capacity (CUPRAC and TAC). These results indicate that G. dura in the Indian Ocean is resource-limited and must partition its use of resources between traits that promote growth and traits that promote survival. Both ploidy phases, collected from different locations, when cultivated in the same environment, showed similar eco-physiological responses. This suggests that G. dura populations from each of these locations are genetically and phenotypically similar, and thus equally suited for optimized farming.
... It is an economically important macroalga that is mostly artificially cultivated on a large scale worldwide because of the quantity and quality of its agar. Due to its economic importance, macroalgae of this genus are used as a model organism for a large range of competitive studies, such as allelopathy(Xu et al. 2012), invasive species(Monteiro et al. 2009;Martinez et al. 2012;Wang et al. 2013), competition against corals(Martinez et al. 2012), mechanisms against grazers(Monteiro et al. 2009;Rodríguez-Barreras et al. 2016), competition for light(Rivers and Peckol 1995;Ursi et al. 2003;Chen et al. 2015), settlement(Garza-Sánchez et al. 2000;Andersson et al. 2006;Vieira et al. 2018), and nutrient ...
Marine macroalgae are the ecological basis in most of the marine environments. Light and space, added to nutrients rank among the most important elements influencing their distribution in the marine environment. Thus, this work aimed to identify and quantify the current and past literature on marine macroalgae competitive interactions and to address the main questions on the competitive patterns and their consequences for community structure, as well as to compare the competitive capacity among different macroalgal taxa. To do so, a quantitative literature search was performed based on papers published from 1934 to 2022, using the following combination of Boolean operators and keywords: “Seaweed OR macroalgae OR macroalga, AND ecolog *, AND competiti *”. A total of 173 articles were then compiled and selected. Our results compiled 124 different macroalgae genera with 546 studied taxa on competition processes. Among them, 38% of the compiled taxa belonged to Ochrophyta; 31% Rhodophyta and 18% Chlorophyta. The most-studied genera were Dictyota (6.8%), Sargassum (6.8%), Ulva (4.9%) and Lobophora (4.2%). Space was the most analyzed limiting factor (40.9%), followed by papers related to herbivory (26.1%), and lastly by competition over nutrients (15.1%). Our results, while attesting to the overarching complexity of competitive interactions, nevertheless allowed us to summarize the current knowledge regarding the patterns of competitive interactions on macroalgae, thus providing a useful synthesis for new perspectives on marine systems and research.
... However, they had the highest levels of spore colonization and germination, together with tetrasporophytes from natural populations, suggesting that the antioxidant response could be explained by a correlation between epiphyte load and physiological stress. This poor performance of males was also observed in terms of growth rate and survival in natural populations (Guillemin et al. 2014;Vieira et al. 2018a;, and probably explains their absence or strong underrepresentation in farms (Guillemin et al. 2008). Females had the greatest capacity to repel spore colonization and inhibit spore germination, a result that was not correlated with physiological and antioxidant parameters. ...
... This study found that females, which are usually absent from farms, are the most resistant to epiphyte infections. Other studies have also shown that females are more resistant to stressful environments (Vieira et al. 2018a). Taken together, these observations may suggest that the cultivation of females could have a long-term advantage for farms: even though tetrasporophytes grow faster than other life cycle stages, females could reduce biomass losses under stressful conditions and epiphyte invasions in farms. ...
The red seaweed Gracilaria chilensis, a species extensively cultivated in Chile for agar extraction, was subjected to a bioassay to determine the susceptibility of tetrasporophytes, female and male gametophytes collected from natural and cultivated populations, to the red epiphyte Acrochaetium sp. and the brown epiphyte Ectocarpus sp. The settlement, attachment and germination of epiphytic algal spores on G. chilensis thalli were evaluated, and the photosynthetic responses and the concentration of total phenolic compounds were determined as a possible response of G. chilensis to biotic stress. The results showed that when the thalli were exposed to Acrochaetium infection, female individuals had a significantly lower percentage of germinated spores than other phases of the life cycle. After infection with Ectocarpus spores, males showed the highest % germination of the epiphyte. For both epiphytes, the response of tetrasporophytes from natural and cultivated populations shows a similar trend. The total content of phenolic compounds showed that, in general, the individuals infected with Acrochaetium had a higher defense capacity, whereas the infection with the brown alga did not induce a significant release of phenolic compounds. Despite the heterogeneous results observed for photosynthetic activity, a higher photoinhibition of the maximum fluorescence quantum yield (Fv/Fm) was observed in thalli with the Acrochaetium epiphyte, confirming that G. chilensis was subjected to stress after infection. Taken together, these observations may suggest that the cultivation of females could be of long-term benefit to farms by reducing biomass losses under stressful conditions and epiphyte invasions on farms.
... However, they had the highest levels of spore colonization and germination, together with tetrasporophytes from natural populations, suggesting that the antioxidant response could be explained by a correlation between epiphyte load and physiological stress. This poor performance of males was also observed in terms of growth rate and survival in natural populations (Guillemin et al. 2014;Vieira et al. 2018a;, and probably explains their absence or strong underrepresentation in farms (Guillemin et al. 2008). Females had the greatest capacity to repel spore colonization and inhibit spore germination, a result that was not correlated with physiological and antioxidant parameters. ...
... This study found that females, which are usually absent from farms, are the most resistant to epiphyte infections. Other studies have also shown that females are more resistant to stressful environments (Vieira et al. 2018a). Taken together, these observations may suggest that the cultivation of females could have a long-term advantage for farms: even though tetrasporophytes grow faster than other life cycle stages, females could reduce biomass losses under stressful conditions and epiphyte invasions in farms. ...
The red seaweed Gracilaria chilensis, a species extensively cultivated in Chile for agar extraction, was subjected to a bioassay to determine the susceptibility of tetrasporophytes, female and male gametophytes collected from natural and cultivated populations, to the red epiphyte Acrochaetium sp. and the brown epiphyte Ectocarpus sp. The settlement, attachment and germination of epiphytic algal spores on G. chilensis thalli were evaluated, and the photosynthetic responses and the concentration of total phenolic compounds were determined as a possible response of G. chilensis to biotic stress. The results showed that when the thalli were exposed to Acrochaetium infection, female individuals had a significantly lower percentage of germinated spores than other phases of the life cycle. After infection with Ectocarpus spores, males showed the highest % germination of the epiphyte. For both epiphytes, the response of tetrasporophytes from natural and cultivated populations shows a similar trend. The total content of phenolic compounds showed that, in general, the individuals infected with Acrochaetium had a higher defense capacity, whereas the infection with the brown alga did not induce a significant release of phenolic compounds. Despite the heterogeneous results observed for photosynthetic activity, a higher photoinhibition of the maximum fluorescence quantum yield (Fv/Fm) was observed in thalli with the Acrochaetium epiphyte, confirming that G. chilensis was subjected to stress after infection. Taken together, these observations may suggest that the cultivation of females could be of long-term benefit to farms by reducing biomass losses under stressful conditions and epiphyte invasions on farms.
... Juvenile G. gracilis (Destombe et al., 1989) and adult G. vermiculophylla (Krueger-Hadfield & Ryan, 2020) gametophytes have higher mortality compared to tetrasporophytes. In G. chilensis, female gametophytes had higher survival (Vieira et al., 2018a) and growth rates (Vieira et al., 2021), but terasporophytic germlings outperformed gametophytic germlings at very low and very high densities of adult fronds (Vieira et al., 2018b). In contrast, carpospore survival in G. chilensis was higher compared to tetraspores (Vieira et al., 2018b). ...
Meiosis and syngamy generate an alternation between two ploidy stages, but the timing of these two processes varies widely across taxa, thereby generating life cycle diversity. One hypothesis suggests that life cycles with long-lived haploid stages are correlated with selfing, asexual reproduction, or both. Though mostly studied in angiosperms, selfing and asexual reproduction are often associated with marginal habitats. Yet, in haploid-diploid macroalgae, these two reproductive modes have subtle but unique consequences whereby predictions from angiosperms may not apply. Along the western Antarctic Peninsula, there is a thriving macroalgal community, providing an opportunity to explore reproductive system variation in haploid-diploid macroalgae at high latitudes where endemism is common. Plocamium sp. is a widespread and abundant red macroalga observed within this ecosystem. We sampled twelve sites during the 2017 and 2018 field seasons and used ten microsatellite loci to describe the reproductive system. Overall genotypic richness and evenness were high, suggesting sexual reproduction. Eight sites were dominated by tetrasporophytes, but there was strong heterozygote deficiency, suggesting intergametophytic selfing. We observed slight differences in the prevailing reproductive mode among sites, possibly due to local conditions (e.g., disturbance) that may contribute to site-specific variation. It remains to be determined whether high levels of selfing are characteristic of macroalgae more generally at high latitudes, due to the haploid-diploid life cycle, or both. Further investigations of algal life cycles will likely reveal the processes underlying the maintenance of sexual reproduction more broadly across eukaryotes, but more studies of natural populations are required.
... Individuals tend to be short-lived and small. During our monitoring experiment (Vieira et al., 2018a(Vieira et al., ,b, 2021, Corral plots were dominated by recruits or young individuals that did not survive for long (5.26 months on average) nor grew large (2.76 cm 3 on average), whereas individuals in Niebla plots generally grew slightly older (6.36 months on average) and larger (9.3 cm 3 on average). Ramets are fixed to rocky bottom by a holdfast and, even if fronds are lost, holdfasts may survive and re-grow new fronds (Guillemin et al., 2013;Vieira et al., 2018a). ...
... During our monitoring experiment (Vieira et al., 2018a(Vieira et al., ,b, 2021, Corral plots were dominated by recruits or young individuals that did not survive for long (5.26 months on average) nor grew large (2.76 cm 3 on average), whereas individuals in Niebla plots generally grew slightly older (6.36 months on average) and larger (9.3 cm 3 on average). Ramets are fixed to rocky bottom by a holdfast and, even if fronds are lost, holdfasts may survive and re-grow new fronds (Guillemin et al., 2013;Vieira et al., 2018a). This species has an isomorphic biphasic life cycle, alternating free living tetrasporophytes (diploids) and dioecious gametophytes (haploids). ...
... This property was not editable. The t = 122 day corresponded to the 4-month intervals of the original A. chilense survey (Vieira et al., 2016(Vieira et al., , 2018a(Vieira et al., ,b, 2021. (d) The census seasons corresponded to the 3 months when census were done during the monitoring experiment (Vieira et al., 2018a(Vieira et al., ,b, 2021, namely, February ('Feb'), June ('Jun') and October ('Oct'). ...
Algal demographic models have been developed mainly to study their life cycle evolution or optimize their commercial exploitation. Most commonly, structured-aggregated population models simulate the main life cycle stages considering their fertility, growth and survival. Their coarse resolution results in weak predictive abilities since neglected details may still impact the whole. In our case, we need a model of Agarophyton chilense natural intertidal populations that unravels the complex demography of isomorphic biphasic life cycles and be further used for: (i) introduction of genetics, aimed at studying the evolutionary stability of life cycles, (ii) optimizing commercial exploitation, and (iii) adaptation for other species. Long-term monitoring yield 6,066 individual observations and 40 population observations. For a holistic perspective, we developed an Individual-Based Model (IBM) considering ploidy stage, sex stage, holdfast age and survival, frond size, growth and breakage, fecundity, spore survival, stand biomass, location and season. The IBM was calibrated and validated comparing observed and estimated sizes and abundances of gametophyte males, gametophyte females and tetrasporophytes, stand biomass, haploid:dipoid ratio (known as H:D or G:T), fecundity and recruitment. The IBM replicated well the respective individual and population properties, and processes such as winter competition for light, self-thinning, summer stress from desiccation, frond breakage and re-growth, and different niche occupation by haploids and diploids. Its success depended on simulating with precision details such as the holdfasts’ dynamics. Because “details” often occur for a reduced number of individuals, inferring about them required going beyond statistically significant evidences and integrating these with parameter calibration aimed at maximized model fit. On average, the population was haploid-dominated (H:D > 1). In locations stressed by desiccation, the population was slightly biased toward the diploids and younger individuals due to the superior germination and survival of the diploid sporelings. In permanently submerged rock pools the population was biased toward the haploids and older individuals due to the superior growth and survival of the haploid adults. The IBM application demonstrated that conditional differentiation among ploidy stages was responsible for their differential niche occupation, which, in its turn, has been argued as the driver of the evolutionary stability of isomorphic biphasic life cycles.
... The natural populations are maintained by sexual reproduction and spore recruitment (Guillemin et al. 2008). In these populations fertile tetrasporophytes, male and female gametophytes are frequently encountered (Meneses 1996;Vieira et al. 2018a). On the other hand, farmed populations-growing on muddy or sandy beds-are composed by a high proportion of genetically identical units (Guillemin et al. 2008), mainly maintained through human-assisted thallus breakage and embedding. ...
... Nevertheless, no clear results have been obtained regarding the diminished reproductive output as a consequence of domestication process in macroalgae yet. Field studies focused on natural populations of A. chilense have shown that the probability of a frond to become fecund is size-dependent (Vieira et al. 2018a(Vieira et al. , 2018b. In the present study, a positive relationship between the size of the primary fronds and the number of cystocarps produced was observed in the natural population (Dichato). ...
... According to life-history theory, reproductive cost implies trade-offs in resource distribution, expressed as changes in future growth, fecundity, and/or survival (Stearns 1992;Álvarez-Cansino et al. 2010;Vieira et al. 2018aVieira et al. , 2018b. In this context, some empirical studies in plants have documented trade-offs in terms of allocation of energy and limited resources, particularly between reproduction and vegetative growth (Ashman 1994;Campbell 2000;Ehrlén and Groenendael 2001;Henriksson 2001;Obeso 2002Obeso , 2004Bañuelos and Obeso 2004;Álvarez-Cansino et al. 2010). ...
Macroalgal domestication and farming can induce significant ecological and biological changes in exploited species. In the red macroalga, Agarophyton chilense, marine farming is based on clonal propagation by cuttings of the largest plants. This type of mass selection by farmers can have a considerable impact on the life history characteristics of cultivated strains. In this study we investigated the potential effect of this type of selection on the reproduction in A. chilense, comparing female gametophytes from the natural and farmed populations. Our results showed strong differences between these two types of populations. As expected, individuals were larger in the farm than in the wild population. On the other hand, the number of cystocarps per centimeters of fronds was ten times lower in the farm than in the natural population. These differences suggest that artificial selection and cultivation environment significantly modify life-history traits in this macroalga. Moreover, the positive relationship between female size and number of cystocarps per centimeters of fronds observed in Dichato point out to the possible existence of cost of reproduction in A. chilense, with bigger females allocating more resources or energy to reproductive structures in natural populations.
... Typical triphasic life cycle consists of morphologically isomorphic gametophytic (separate male and female individuals), tetrasporophytic and carposporophytic generation. These life cycle stages have been found to have niche partitioning and clear ecological differentiation (Guillemin et al. 2013;Vieira et al. 2018a). The variation in functional traits related to survival and growth provides ample opportunity to select appropriate cultivar in clonally propagated seaweeds (Santelices 1992). ...
The red alga Gracilaria dura is economically important due to its high-quality agarose. Previous studies with wild populations reported the existence of specific differences in functional traits as well as agar characteristics among life cycle stages. In farmed populations, such differences can be exploited for commercial gains. For that, the variation among stages still needs to be well established under farming scenarios. Here, we compared the life cycle stages of G. dura regarding morphological and anatomical structures, growth performance under preliminary field trials, characteristics of agarose of cultivated biomass with biochemical (NMR) and molecular profiling (SCoT). The male gametophyte was found to have a significantly higher growth rate of 6.23 ± 0.59% day−1 than the tetrasporophyte (5.10 ± 0.14% day−1) and cystocarpic female gametophyte (2.67 ± 0.32% day−1). A maximum agarose yield of 28.6 ± 1.53% was obtained from the tetrasporophyte, significantly higher than 27.4 ± 0.60% in cystocarpic female gametophyte and 25.2 ± 0.36% in male gametophyte. The gel strength of agarose from male gametophytes was 2384 ± 124.13 g cm−2, which was significantly higher than the 1900 ± 50 g cm−2 and 2122 ± 124.03 g cm−2 recorded from tetrasporophytes and cystocarpic female gametophytes, respectively. A metabolomic study by NMR spectroscopy showed critical differences in alanine, lactate and isethionic acid among stages. The genetic correlation studied with the SCoT marker showed an average polymorphism of 47.02%. The average heterozygosity and Shannon-Wiener index were 0.63 and 1.06 respectively. This study of characterising and differentiating isomorphic life phases of G. dura by a decisive biomarker could be a valuable reference point to select an appropriate cultivar for commercial farming and breeding programmes.
