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- Laenen, Benjamin, et al.
(författare)
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Geographical range in liverworts : does sex really matter?
- 2016
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 43:3, s. 627-635
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Tidskriftsartikel (refereegranskat)abstract
- AimWhy some species exhibit larger geographical ranges than others remains a fundamental, but largely unanswered, question in ecology and biogeography. In plants, a relationship between range size and mating system was proposed over a century ago and subsequently formalized in Baker's Law. Here, we take advantage of the extensive variation in sexual systems of liverworts to test the hypothesis that dioecious species compensate for limited fertilization by producing vegetative propagules more commonly than monoecious species. As spores are assumed to contribute to random long-distance dispersal, whereas vegetative propagules contribute to colony maintenance and frequent short-distance dispersal, we further test the hypothesis that monoecious species exhibit larger geographical ranges than dioecious ones. LocationWorldwide. MethodsWe used comparative phylogenetic methods to assess the correlation between range size and life history traits related to dispersal, including mating systems, spore size and production of specialized vegetative propagules. ResultsNo significant correlation was found between dioecy and production of vegetative propagules. However, production of vegetative propagules is correlated with the size of geographical ranges across the liverwort tree of life, whereas sexuality and spores size are not. Moreover, variation in sexual systems did not have an influence on the correlation between geographical range and production of asexual propagules. Main conclusionsOur results challenge the long-held notion that spores, and not vegetative propagules, are involved in long-distance dispersal. Asexual reproduction seems to play a major role in shaping the global distribution patterns of liverworts, so that monoecious species do not tend to display, on average, broader distribution ranges than dioecious ones. Our results call for further investigation on the spatial genetic structure of bryophyte populations at different geographical scales depending on their mating systems to assess the dispersal capacities of spores and asexual propagules and determine their contribution in shaping species distribution ranges.
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- Laenen, Benjamin, et al.
(författare)
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Increased diversification rates follow shifts to bisexuality in liverworts
- 2016
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 210:3, s. 1121-1129
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Tidskriftsartikel (refereegranskat)abstract
- Shifts in sexual systems are one of the key drivers of species diversification. In contrast to angiosperms, unisexuality prevails in bryophytes. Here, we test the hypotheses that bisexuality evolved from an ancestral unisexual condition and is a key innovation in liverworts. We investigate whether shifts in sexual systems influence diversification using hidden state speciation and extinction analysis (HiSSE). This new method compares the effects of the variable of interest to the best-fitting latent variable, yielding robust and conservative tests. We find that the transitions in sexual systems are significantly biased toward unisexuality, even though bisexuality is coupled with increased diversification. Sexual systems are strongly conserved deep within the liverwort tree but become much more labile toward the present. Bisexuality appears to be a key innovation in liverworts. Its effects on diversification are presumably mediated by the interplay of high fertilization rates, massive spore production and long-distance dispersal, which may separately or together have facilitated liverwort speciation, suppressed their extinction, or both. Importantly, shifts in liverwort sexual systems have the opposite effect when compared to angiosperms, leading to contrasting diversification patterns between the two groups. The high prevalence of unisexuality among liverworts suggests, however, a strong selection for sexual dimorphism.
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- Ledent, Alice, et al.
(författare)
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What do tropical cryptogams reveal? Strong genetic structure in Amazonian bryophytes
- 2020
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 228:2, s. 640-650
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Tidskriftsartikel (refereegranskat)abstract
- Lowland tropical bryophytes have been perceived as excellent dispersers. In such groups, the inverse isolation hypothesis proposes that spatial genetic structure is erased beyond the limits of short-distance dispersal. Here, we determine the influence of environmental variation and geographic barriers on the spatial genetic structure of a widely dispersed and phylogenetically independent sample of Amazonian bryophytes. Single nucleotide polymorphism data were produced from a restriction site-associated DNA sequencing protocol for 10 species and analyzed through F-statistics and Mantel tests. Neither isolation-by-environment nor the impact of geographic barriers were recovered from the analyses. However, significant isolation-by-distance patterns were observed for 8 out of the 10 investigated species beyond the scale of short-distance dispersal (> 1 km), offering evidence contrary to the inverse isolation hypothesis. Despite a cadre of life-history traits and distributional patterns suggesting that tropical bryophytes are highly vagile, our analyses reveal spatial genetic structures comparable to those documented for angiosperms, whose diaspores are orders of magnitude larger. Dispersal limitation for tropical bryophytes flies in the face of traditional assumptions regarding their dispersal potential, and suggests that the plight of this component of cryptic biodiversity is more dire than previously considered in light of accelerated forest fragmentation in the Amazon.
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- Patino, Jairo, et al.
(författare)
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Range size heritability and diversification patterns in the liverwort genus Radula
- 2017
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 106, s. 73-85
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Tidskriftsartikel (refereegranskat)abstract
- Why some species exhibit larger geographical ranges than others, and to what extent does variation in range size affect diversification rates, remains a fundamental, but largely unanswered question in ecology and evolution. Here, we implement phylogenetic comparative analyses and ancestral area estimations in Radula, a liverwort genus of Cretaceous origin, to investigate the mechanisms that explain differences in geographical range size and diversification rates among lineages. Range size was phylogenetically constrained in the two sub-genera characterized by their almost complete Australasian and Neotropical endemicity, respectively. The congruence between the divergence time of these lineages and continental split suggests that plate tectonics could have played a major role in their present distribution, suggesting that a strong imprint of vicariance can still be found in extant distribution patterns in these highly mobile organisms. Amentuloradula, Volutoradula and Metaradula species did not appear to exhibit losses of dispersal capacities in terms of dispersal life-history traits, but evidence for significant phylogenetic signal in macroecological niche traits suggests that niche conservatism accounts for their restricted geographic ranges. Despite their greatly restricted distribution to Australasia and Neotropics respectively, Amentuloradula and Volutoradula did not exhibit significantly lower diversification rates than more widespread lineages, in contrast with the hypothesis that the probability of speciation increases with range size by promoting geographic isolation and increasing the rate at which novel habitats are encountered. We suggest that stochastic long-distance dispersal events may balance allele frequencies across large spatial scales, leading to low genetic structure among geographically distant areas or even continents, ultimately decreasing the diversification rates in highly mobile, widespread lineages.
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