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It remains hotly debated whether latitudinal diversity gradients are common across taxonomic groups and whether a single mechanism can explain such gradients. Investigating species richness (SR) patterns of European land plants, we determine whether SR increases with decreasing latitude, as predicted by theory, and whether the assembly mechanisms differ among taxonomic groups. SR increases towards the south in spermatophytes, but towards the north in ferns and bryophytes. SR patterns in spermatophytes are consistent with their patterns of beta diversity, with high levels of nestedness and turnover in the north and in the south, respectively, indicating species exclusion towards the north and increased opportunities for speciation in the south. Liverworts exhibit the highest levels of nestedness, suggesting that they represent the most sensitive group to the impact of past climate change. Nevertheless, although the extent of liverwort species turnover in the south is substantially and significantly lower than in spermatophytes, liverworts share with the latter a higher nestedness in the north and a higher turn-over in the south, in contrast to mosses and ferns. The extent to which the similarity in the patterns displayed by spermatophytes and liverworts reflects a similar assembly mechanism remains, however, to be demonstrated.

It remains hotly debated whether latitudinal diversity gradients are common across taxonomic groups and whether a single mechanism can explain such gradients. Investigating species richness (SR) patterns of European land plants, we determine whether SR increases with decreasing latitude, as predicted by theory, and whether the assembly mechanisms differ among taxonomic groups. SR increases towards the south in spermatophytes, but towards the north in ferns and bryophytes. SR patterns in spermatophytes are consistent with their patterns of beta diversity, with high levels of nestedness and turnover in the north and in the south, respectively, indicating species exclusion towards the north and increased opportunities for speciation in the south. Liverworts exhibit the highest levels of nestedness, suggesting that they represent the most sensitive group to the impact of past climate change. Nevertheless, although the extent of liverwort species turnover in the south is substantially and significantly lower than in spermatophytes, liverworts share with the latter a higher nestedness in the north and a higher turn-over in the south, in contrast to mosses and ferns. The extent to which the similarity in the patterns displayed by spermatophytes and liverworts reflects a similar assembly mechanism remains, however, to be demonstrated

It remains hotly debated whether latitudinal diversity gradients are common across taxonomic groups and whether a single mechanism can explain such gradients. Investigating species richness (SR) patterns of European land plants, we determine whether SR increases with decreasing latitude, as predicted by theory, and whether the assembly mechanisms differ among taxonomic groups. SR increases towards the south in spermatophytes, but towards the north in ferns and bryophytes. SR patterns in spermatophytes are consistent with their patterns of beta diversity, with high levels of nestedness and turnover in the north and in the south, respectively, indicating species exclusion towards the north and increased opportunities for speciation in the south. Liverworts exhibit the highest levels of nestedness, suggesting that they represent the most sensitive group to the impact of past climate change. Nevertheless, although the extent of liverwort species turnover in the south is substantially and significantly lower than in spermatophytes, liverworts share with the latter a higher nestedness in the north and a higher turn-over in the south, in contrast to mosses and ferns. The extent to which the similarity in the patterns displayed by spermatophytes and liverworts reflects a similar assembly mechanism remains, however, to be demonstrated.

As opposed to angiosperms, moss species richness is similar among tropical regions of the world, in line with the hypothesis that tropical bryophytes are extremely good dispersers. Here, we reconstructed the phylogeny of the pantropical moss genus Pelekium to test the hypothesis that high migration rates erase any difference in species richness among tropical regions. In contrast with this hypothesis, several species considered to have a pantropical range were resolved as a complex of species with a strong geographic structure. Consequently, a significant phylogeographical signal was found in the data, evidencing that cladogenetic diversification within regions takes place at a faster rate than intercontinental migration. The shape of the Pelekium phylogeny, along with the selection of a constant-rate model of diversification among species in the genus, suggests, however, that the cladogenetic speciation patterns observed in Pelekium are not comparable to some of the spectacular examples of tropical radiations reported in angiosperms. Rather, the results presented here point to the constant accumulation of diversity through time in Pelekium. This, combined with evidence for long-distance dispersal limitations in the genus, suggests that the similar patterns of species richness among tropical areas are better explained in terms of comparable rates of diversification across tropical regions than by the homogenization of species richness by recurrent migrations.

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.

The disjunction of floras between East Asia, Southeast North America, West North America, and Southwest Eurasia has been interpreted in terms of the fragmentation of a once continuous mixed mesophytic forest that occurred throughout the Northern Hemisphere due to the climatic and geological changes during the late Tertiary. The sword moss, Bryoxiphium, exhibits a distribution that strikingly resembles that of the mesophytic forest elements such as Liriodendron and is considered as the only living member of an early Tertiary flora in Iceland. These hypotheses are tested here using molecular dating analyses and ancestral area estimations. The results suggest that the extant range of Bryoxiphium results from the fragmentation of a formerly wider range encompassing North America and Southeast Asia about 10 million years ago. The split of continental ancestral populations is too recent to match with a continental drift scenario but is spatially and temporally remarkably congruent with that observed in Tertiary angiosperm relict species. The timing of the colonization of Iceland from Macaronesian ancestors, about two million years ago, is, however, incompatible with the hypothesis that Bryoxiphium is the only living member of an early Tertiary flora of the island. Alaska was recurrently colonized from East Asia. The ability of Bryoxiphium to overcome large oceanic barriers is further evidenced by its occurrence on remote oceanic archipelagos. In particular, Madeira was colonized twice independently from American and East Asian ancestors, respectively. The striking range disjunction of Bryoxiphium is interpreted in terms of its mating system, as the taxon exhibits a very singular pattern of spatial segregation of the sexes.

[Background and Aims] The settling velocity of diaspores is a key parameter for the measurement of dispersal ability in wind-dispersed plants and one of the most relevant parameters in explicit dispersal models, but remains largely undocumented in bryophytes. The settling velocities of moss spores were measured and it was determined whether settling velocities can be derived from spore diameter using Stokes' Law or if specific traits of spore ornamentation cause departures from theoretical expectations., [Methods] A fall tower design combined with a high-speed camera was used to document spore settling velocities in nine moss species selected to cover the range of spore diameters within the group. Linear mixed effect models were employed to determine whether settling velocity can be predicted from spore diameter, taking specific variation in shape and surface roughness into account., [Key Results] Average settling velocity of moss spores ranged from 0·49 to 8·52 cm s. There was a significant positive relationship between spore settling velocity and size, but the inclusion of variables of shape and texture of spores in the best-fit models provides evidence for their role in shaping spore settling velocities., [Conclusions] Settling velocities in mosses can significantly depart from expectations derived from Stokes' Law. We suggest that variation in spore shape and ornamentation affects the balance between density and drag, and results in different dispersal capacities, which may be correlated with different life-history traits or ecological requirements. Further studies on spore ultrastructure would be necessary to determine the role of complex spore ornamentation patterns in the drag-to-mass ratio and ultimately identify what is the still poorly understood function of the striking and highly variable ornamentation patterns of the perine layer on moss spores.

Oceanic islands are of fundamental importance for the conservation of biodiversity because they exhibit high endemism rates coupled with fast extinction rates. Nowhere in Europe is this pattern more conspicuous than in the Macaronesian biogeographic region. A large network of protected areas within the region has been developed, but the question of whether these areas will still be climatically suitable for the globally threatened endemic element in the coming decades remains open. Here, we make predictions on the fate of the Macaronesian endemic bryophyte flora in the context of ongoing climate change. The potential distribution of 35 Macaronesian endemic bryophyte species was assessed under present and future climate conditions using an ensemble modelling approach. Projections of the models under different climate change scenarios predicted an average decrease of suitable areas of 62-87% per species and a significant elevational increase by 2070, so that even the commonest species were predicted to fit either the Vulnerable or Endangered IUCN categories. Complete extinctions were foreseen for six of the studied Macaronesian endemic species. Given the uncertainty regarding the capacity of endemic species to track areas of suitable climate within and outside the islands, active management associated to an effective monitoring program is suggested.

Sexual traits are often the most divergent characters among closely related species, suggesting an important role of sexual traits in speciation. However, to prove this, we need to show that sexual trait differences accumulate before or during the speciation process, rather than being a consequence of it. Here, we contrast patterns of divergence among putative male sex pheromone (pMSP) composition and the genetic structure inferred from variation in the mitochondrial cytochrome oxidase 1 and nuclear CAD loci in the African butterfly Bicyclus anynana (Butler, 1879) to determine whether the evolution of “pheromonal dialects” occurs before or after the differentiation process. We observed differences in abundance of some shared pMSP components as well as differences in the composition of the pMSP among B. anynana populations. In addition, B. anynana individuals from Kenya displayed differences in the pMSP composition within a single population that appeared not associated with genetic differences. These differences in pMSP composition both between and within B. anynana populations were as large as those found between different Bicyclus species. Our results suggest that “pheromonal dialects” evolved within and among populations of B. anynana and may therefore act as precursors of an ongoing speciation process.

Understanding the speciation process usually involves the study of the geographic and ecological factors influencing reproductive isolation, as well as the action of evolutionary forces. Recently it was proposed that the type of communication channel, if it offers large possibilities in the direction of evolution of the signals, could help species to differentiate in a similar way as an ecosystem with empty ecological niches would. Olfactory communication could be such a modality since compared to other modes of communication, acoustic or visual, it benefits from a large variety of signals, thanks to the tremendous diversity of chemical compounds that can be used. In addition, the specificity of the olfactory receptors necessary to detect particular chemical compounds confers a strong privacy to the information transfer, regarding illicit receivers like predators. This thesis aimed at investigating the importance of olfactory sexual communication in the evolution of reproductive isolation in the butterfly genus Bicyclus. We first compared the composition of putative male sex pheromone (pMSP) across 32 species in a phylogenetic perspective. We observed that pMSP composition was very diverse, species specific, rapidly evolving, and that stronger differences of composition likely allow species to recognise each other when sharing the same ecosystem. In a second time, we investigated the diversity of the pMSP within species and discovered similar differences as between species. This supports the hypothesis that pMSP diversification can predate speciation and can therefore be a cause of this enigmatic process. Overall, our results strongly suggest that the evolution of male sex pheromone is involved in speciation in the Bicyclus genus, and support the hypothesis that olfactory communication allows a large diversity of signals, evolving without obvious constraint, and which could rapidly lead to reproductive isolation., (SC - Sciences) -- UCL, 2015

Dans l’hémisphère Nord, le climat des deux derniers millions d’années a été marqué par une alternance de périodes froides et de brefs intervalles chauds. Cette succession d’évènements a laissé des traces durables au niveau de l’arrangement spatial de la diversité et de la structure génétique au sein des espèces.En décrivant la répartition spatiale des lignées d’une espèce au moyen d’informations génétiques, la phylogéographie vise à identifier les processus évolutifs responsables de cette répartition. La phylogéographie comparée permet de gagner en compréhension en confrontant les patrons de variation génétique présents chez plusieurs espèces codistribuées :en étudiant des espèces partageant une même histoire au moyen de plusieurs sources d’information indépendantes (par exemple, plusieurs fragments d’ADN ou des données bioclimatiques historiques externes), il est possible de mettre en évidence des éléments de cette histoire commune tels que des refuges glaciaires ou des routes de recolonnisation post-glaciaires. Par contre, il est aussi possible que les caractéristiques biologiques intrinsèques à chaque espèce, telles que des stratégies dispersives ou reproductives différentes, engendrent une différenciation dans la structure et la diversité de cette variation génétique. Dans cette thèse de doctorat nous nous sommes intéressés à deux espèces inféodées à un même hôte (Picea abies) et appartenant à une même sous-famille taxonomique (Coleoptera :Curculionidae, Scolytinae). Il sagit du typographe, Ips typographus et du dendroctone, Dendroctonus micans. Au moyen de plusieurs fragments génétiques spécialement identifiés pour cette étude ainsi que par le recours à des modèles bioclimatiques et des tests statistiques basés sur la théorie de la coalescence, nous avons étudié la phylogéographie de ces espèces.Les résultats obtenus au cours de ce travail ont permis de mettre en évidence l’influence contrastée de stratégies écologiques différentes sur l’arrangement de, Doctorat en Sciences agronomiques et ingénierie biologique, info:eu-repo/semantics/nonPublished

J.P. and A.V. gratefully acknowledge financial support from the Belgian National Fund for Scientific Research (FNRS; grants 1.5036.11 and 2.4557.11) and the University of Liège (Grant C 11/32). R.M.R. and F.L. acknowledge financial support from the Spanish Ministry of Science and Innovation and the FEDER program from the EU (Grants CGL2008-00275/BOS and CGL2012-22936/BOS to R.M.R. and CGL2010–15693 and CGL2011–28857/BOS to F.L.), and J.M.G.M. from the Canarian Government (P1042004-028)., Aim. Our aims were: to determine the evolutionary origin of the single-island endemic moss Orthotrichum handiense; to assess whether its endemicity results from a recent origin or founder event, a loss of dispersal ability, specific habitat requirements, or contraction of a formerly wider range; and to make predictions about its ability to face ongoing climate change. Location. Fuerteventura, Canary Islands. Methods. The evolutionary origin of O. handiense was determined by phylogenetic analysis and molecular dating. The spatial genetic structure and demographic history of 48 individuals of O. handiense were analysed with inter-simple sequence repeat (ISSR) markers through analyses of molecular variance, Mantel tests, mismatch distributions and bottleneck analyses. The macroclimatic envelope of the species was modelled using an ensemble approach of eight species distribution models, and its suitable areas predicted for extant, past (21 ka) and future (2050, 2080) conditions. Results. Orthotrichum handiense was resolved as sister to the Californian O. underwoodii and their most recent common ancestor was dated to early Miocene–Pliocene. ISSR analyses revealed extremely low levels of genetic diversity and provided evidence for a recent bottleneck and for isolation-by-distance at the local scale. The different models investigated all pointed to the mismatch between the limited extant distribution and the extent of macroclimatically suitable areas. All models predicted climatic unsuitability on Fuerteventura and Lanzarote at 21 ka, but were conflicting in other areas. A dramatic reduction and loss of suitable areas were predicted for 2050 and 2080, respectively. Main conclusions The phylogenetic position of O. handiense points to a long-distance dispersal event from a western North American ancestor and emphasizes the differences in the origin of Macaronesian endemic bryophytes and angiosperms. The predicted absence of suitable macroclimatic conditions in Fuerteventura, Belgian National Fund for Scientific Research, University of Liège, Gobierno de Canarias, European Commission, Ministerio de Ciencia, Innovación y Universidades (España), Depto. de Biodiversidad, Ecología y Evolución, Fac. de Ciencias Biológicas, TRUE, pub

Hydrochory plays a key role in the maintenance, diversity and evolution of aquatic plants and has traditionally been thought to (i) decrease or erase patterns of isolation-by-distance, (ii) increase outbreeding, and (iii) result in a downstream increase of genetic diversity. These hypotheses, which are especially relevant in organisms with water-mediated fertilization and a high ability to disperse vegetatively, are tested here from fine-scale spatial analyses of genetic variation at both the haploid and diploid phases in the aquatic moss Rhynchostegium riparioides (Hedw.) Cardot. A substantial geographical partitioning of genetic variation was found at the scale of the river basin and indirect measures of dispersal point to an overall weaker dispersal ability of the moss diaspores than pollen or wind-dispersed seeds. These observations, as well as the high Fis observed at the diploid stage and the very close proximity of potential fathers of the heterozygous diploid genotypes, strongly challenge the hypothesis that water enhances sperm and diaspore-mediated gene flow. In R. riparioides, the severe dispersal limitations revealed by the spatial analyses of genetic structure suggest that shoot fragments rather than spores are involved in local dispersal, which is fully consistent with the low levels of genetic diversity observed within populations. Extremely limited routine dispersal by unspecialized vegetative diaspores, coupled with discrete episodes of local population extinctions and colonizations by spores, account for the absence of a downstream increase of genetic diversity. As a result, although spore-producing plants are typically seen as most efficient dispersers, and although streams are traditionally seen as dispersal corridors, severe limitations of clonal dispersal at the local scale and discrete opportunities of random spore dispersal and establishment among colonies, both explain why typical metapopulation processes also apply to aquatic mosses. © 2013, SCOPUS: ar.j, info:eu-repo/semantics/published

The definition of biogeographic regions provides a fundamental framework for a range of basic and applied questions in biogeography, evolutionary biology, systematics and conservation. Previous research suggested that environmental forcing results in highly congruent regionalization patterns across taxa, but that the size and number of regions depends on the dispersal ability of the taxa considered. We produced a biogeographic regionalization of European bryophytes and hypothesized that (1) regions defined for bryophytes would differ from those defined for other taxa due to the highly specific eco-physiology of the group and (2) their high dispersal ability would result in the resolution of few, large regions. Species distributions were recorded using 10,000 km2 MGRS pixels. Because of the lack of data across large portions of the area, species distribution models employing macroclimatic variables as predictors were used to determine the potential composition of empty pixels. K-means clustering analyses of the pixels based on their potential species composition were employed to define biogeographic regions. The optimal number of regions was determined by v-fold cross-validation and Moran’s I statistic. The spatial congruence of the regions identified from their potential bryophyte assemblages with largescale vegetation patterns is at odds with our primary hypothesis. This reinforces the notion that post-glacial migration patterns might have been much more similar in bryophytes and vascular plants than previously thought. The substantially lower optimal number of clusters and the absence of nested patterns within the main biogeographic regions, as compared to identical analyses in vascular plants, support our second hypothesis. The modelling approach implemented here is, however, based on many assumptions that are discussed but can only be tested when additional data on species distributions become available, highlighting the substantial importance of developing inte

Doctorat en Sciences, info:eu-repo/semantics/nonPublished

The main factor of differentiation at six nuclear microsatellite and seven cpDNA loci in Salicornia from the Mediterranean and Atlantic coasts of France is cytotypic identity, suggesting the presence of a strong reproductive barrier among sympatric cytotypes. Within cytotypes, a substantial proportion of the differentiation between species is due to confounded phylogeographic signal. Conspecific individuals tend to be significantly more related than individuals from different species at the population scale, but mean kinship coefficients among pairs of conspecific and nonconspecific individuals from different populations are not significantly different, suggesting the absence of reproductive isolation among species of the same cytotype. The observed association between morphology and genetic variation within populations would thus result from the selfing mating system (F-is, SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

Eight nuclear microsatellite loci were identified using the method of microsatellite-enriched libraries in the glasswort genus Salicornia. These markers yield specific alleles for discriminating diploid and tetraploid lineages and thus provide a reliable and efficient tool for routine determination of ploidy level in the genus. Within both the diploid and tetraploid lineages, the microsatellites further display a clear biogeographic signal. A significant partitioning of genetic differentiation was found between the diploid populations (F-st, SCOPUS: no.j, info:eu-repo/semantics/published

Genetic diversity and structure are described in the aquatic moss Platyhypnidium riparioides to assess its dispersal ability at a regional scale and to determine whether patterns of genetic differentiation correlate with environmental variation. Variation at six nuclear microsatellite loci from 50 populations in southern Belgium was investigated through Mantel tests, partial Mantel tests and spatial analysis of molecular variance. Overall patterns of genotypic variation showed strong differentiation among populations at a regional scale (F-ST, SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

The co-evolution between hosts and parasites has long been recognized as a fundamental driver of macro-evolutionary patterns of diversification. The effect of co-differentiation on parasite diversification is, however, often confounded by underlying geographic patterns of host distribution. In order to disentangle the confounding effects of allopatric versus host speciation, the mitochondrial cytochrome b (cyt b) gene was sequenced in seventy individuals of the parasitic nematode genus Heligmosomoides sampled in the six Apodemus mice species common in the western Palearctic region. The nuclear internal transcribed spacers (ITS) 1 and 2 were also sequenced in fifteen parasites to confirm the mitochondrial data. All lineages differentiated according to a geographic pattern and independently from the sampled host species. This suggests that host speciation did not involve concurrent parasite speciation. However, the geographic distribution range of some parasite lineages mirrors that of A. sylvaticus lineages in SW Europe, and that of A. flavicollis lineages in the Balkans and in the Middle East. Thus, regional co-differentiation likely occurred between the parasite and the two sister Apodemus hosts in different parts of their distribution range. We suggest that differences in regional abundances of A. sylvaticus and A. flavicollis are responsible for generating this pattern of regional co-differentiation. This study highlights the importance of integrating both geography and biogeographic information from potential hosts to better understand their parasite phylogeography. © 2008 Elsevier Inc. All rights reserved.

Eight microsatellite loci from the aquatic moss Platyhypnidium riparioides were identified using the method of microsatellite-enriched libraries. Polymorphism was assessed in a sample of four populations of 20 individuals each from four streams of the Meuse hydrographic basin in southern Belgium. The markers amplified three to seven alleles per locus. Comparison of observed and expected heterozygosities as well as F-statistics (F-ST, FLWIN, info:eu-repo/semantics/published