| 1. |
- Desamore, Aurelie, et al.
(author)
-
High migration rates shape the postglacial history of amphi-Atlantic bryophytes
- 2016
-
In: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 25:21, s. 5568-5584
-
Journal article (peer-reviewed)abstract
- Paleontological evidence and current patterns of angiosperm species richness suggest that European biota experienced more severe bottlenecks than North American ones during the last glacial maximum. How well this pattern fits other plant species is less clear. Bryophytes offer a unique opportunity to contrast the impact of the last glacial maximum in North America and Europe because about 60% of the European bryoflora is shared with North America. Here, we use population genetic analyses based on approximate Bayesian computation on eight amphi-Atlantic species to test the hypothesis that North American populations were less impacted by the last glacial maximum, exhibiting higher levels of genetic diversity than European ones and ultimately serving as a refugium for the postglacial recolonization of Europe. In contrast with this hypothesis, the best-fit demographic model involved similar patterns of population size contractions, comparable levels of genetic diversity and balanced migration rates between European and North American populations. Our results thus suggest that bryophytes have experienced comparable demographic glacial histories on both sides of the Atlantic. Although a weak, but significant genetic structure was systematically recovered between European and North American populations, evidence for migration from and towards both continents suggests that amphi-Atlantic bryophyte population may function as a metapopulation network. Reconstructing the biogeographic history of either North American or European bryophyte populations therefore requires a large, trans-Atlantic geographic framework.
|
|
| 2. |
|
|
| 3. |
- Laenen, Benjamin, et al.
(author)
-
Evolutionary origin of the latitudinal diversity gradient in liverworts
- 2018
-
In: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 127, s. 606-612
-
Journal article (peer-reviewed)abstract
- A latitudinal diversity gradient towards the tropics appears as one most recurrent patterns in ecology, but the mechanisms underlying this pattern remain an area of controversy. In angiosperms, the tropical conservatism hypothesis proposes that most groups originated in the tropics and are adapted to a tropical climatic regime, and that relatively few species have evolved physiological adaptations to cold, dry or unpredictable climates. This mechanism is, however, unlikely to apply across land plants, and in particular, to liverworts, a group of about 7500 species, whose ability to withstand cold much better than their tracheophyte counterparts is at odds with the tropical conservatism hypothesis. Molecular dating, diversification rate analyses and ancestral area reconstructions were employed to explore the evolutionary mechanisms that account for the latitudinal diversity gradient in liverworts. As opposed to angiosperms, tropical liverwort genera are not older than their extratropical counterparts (median stem age of tropical and extra-tropical liverwort genera of 24.35 +/- 39.65 Ma and 39.57 +/- 49.07 Ma, respectively), weakening the `time for speciation hypothesis'. Models of ancestral area reconstructions with equal migration rates between tropical and extra-tropical regions outperformed models with asymmetrical migration rates in either direction. The symmetry and intensity of migrations between tropical and extra-tropical regions suggested by the lack of resolution in ancestral area reconstructions towards the deepest nodes are at odds with the tropical niche conservatism hypothesis. In turn, tropical genera exhibited significantly higher net diversification rates than extra-tropical ones, suggesting that the observed latitudinal diversity gradient results from either higher extinction rates in extra-tropical lineages or higher speciation rates in the tropics. We discuss a series of experiments to help deciphering the underlying evolutionary mechanisms.
|
|
| 4. |
- Laenen, Benjamin, et al.
(author)
-
Geographical range in liverworts : does sex really matter?
- 2016
-
In: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 43:3, s. 627-635
-
Journal article (peer-reviewed)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.
|
|
| 5. |
- Laenen, Benjamin, et al.
(author)
-
Increased diversification rates follow shifts to bisexuality in liverworts
- 2016
-
In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 210:3, s. 1121-1129
-
Journal article (peer-reviewed)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.
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Patino, Jairo, et al.
(author)
-
Range size heritability and diversification patterns in the liverwort genus Radula
- 2017
-
In: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 106, s. 73-85
-
Journal article (peer-reviewed)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.
|
|
| 9. |
|
|
| 10. |
- Vanderpoorten, Alain, et al.
(author)
-
Early divergence of anAzorean endemic species in the moss genus Rhynchostegiella(Brachytheciaceae)
- 2015
-
In: Phytotaxa. - : Magnolia Press. - 1179-3155 .- 1179-3163. ; 210, s. 60-69
-
Journal article (peer-reviewed)abstract
- Using the moss genus Rhynchostegiella (Brachytheciaceae) as a model, we address the question of whether taxonomic shortcomings account for the extremely low rates of endemism reported in the Azorean bryophyte flora. Eight accessions initially assigned to three of the four previously reported species in the Azores were identified as a distinct species using the Generalized Mixed Yule Coalescent method in the context of a molecular phylogenetic analysis of the genus. Rhynchostegiella azorica sp. nov. is therefore described as a new species that is endemic to the Azores. Its morphological features intergrade with those observed in other species, with a seta that ranges from almost smooth to rough; a length to width ratio of the laminal cells that matches the one of the R. curviseta group; but a leaf apex that is typical of the R. tenella group. This suggests that previous reports of four Rhynchostegiella species from Azores are erroneous and that a single, morphologically variable species, R. azorica, occurs in the archipelago. Rhynchostegiella azorica is sister to the remainder of the species of the genus, whose most recent common ancestor was dated at 4–20 Ma. This points to a more ancient origin in comparison with other Macaronesian endemic species of the genus. The unexpected discovery of an Azorean endemic species in Rhynchostegiella suggests that patterns of endemicity in the Azorean bryophyte flora are not well estimated from traditional taxonomic knowledge and point to the necessity of an extensive integrative taxonomic revision.
|
|
