Biology subjects

Dufresnes, C.

Publications and source records attributed to Dufresnes, C..

5 recordsLinked to original sources

bioRxiv2026

Shared phylogeographic structuring and recurrent hybridization underlie the diversification of Microhyla frog complexes in the Indochinese biodiversity hotspot

Comparative phylogeography provides a powerful framework to identify the historical processes shaping biodiversity hotspots by testing whether co-distributed species exhibit shared patterns of diversification. Southeast Asia harbors exceptional biodiversity, yet the extent to which common paleogeographic and climatic drivers have structured diversification across taxa remains poorly understood. Here, we investigated the evolutionary history of five widespread Microhyla species complexes distributed across the Indochinese Peninsula and adjacent regions using dense mitochondrial sampling (1,388 individuals) combined with genome-scale ddRAD sequencing (280 individuals). Across all complexes, both approaches recovered multiple lineages and remarkably congruent phylogeographic breaks and contact/intergradation zones associated with major Indochinese regions, including Myanmar, the Tenasserim-Malay Peninsula, southern Vietnam, and northern Vietnam-southern China, supporting the hypothesis that Indochina functions as a mosaic of stable biogeographic units. However, lineage divergence varied substantially among complexes, suggesting that common biogeographic drivers interacted with species-specific demographic histories. Phylogenomic analyses and cyto-nuclear discordance further revealed historical introgression in every complex, indicating that diversification involved both long-term allopatric isolation and reticulate evolution. These findings portray the Indochinese biodiversity hotspot as a dynamic evolutionary system where cycles of fragmentation and reconnection have repeatedly reshaped lineage boundaries. Moreover, the complex phylogeographic structure recovered exemplifies the urgent need for taxonomic revisions, for which genome-scale data provide an essential framework to validate mitochondrial hypotheses and assess admixture patterns for species delimitation. Finally, regions such as the southern Annamites and Tenasserim Hills emerged as recurrent hotspots of genetic diversity across independent lineages, highlighting their importance for conserving not only species/lineage richness but also the evolutionary processes and adaptive potential that sustain biodiversity.

zoology↗

bioRxiv2026

The Hindu Kush, not the Indus Valley, divides amphibian biogeographic realms

The boundary between the Palearctic and Oriental biogeographic realms is one of the oldest unresolved problems in Eurasian biogeography. In Central and South Asia, this transition is remarkable and has often been linked to the Indus River Valley, yet the role of adjacent mountain systems and arid landscapes has remained largely untested because critical regions, especially Afghanistan, have been chronically under-sampled due to difficult, long-term socio-political situation. Here we use a unique amphibian material from Afghanistan and adjacent northwestern Pakistan to test whether the Hindu Kush marks the effective boundary between these two realms. Combining molecular barcoding across all seven amphibian genera inhabiting the region with updated distribution records, we find a strikingly consistent lineage turnover centered on the eastern Hindu Kush and adjacent arid systems. Palearctic taxa reach their southeastern limits along the massif, whereas Oriental taxa extend only to its southern foothills. By contrast, Oriental lineages cross the Indus River without detectable phylogeographic break, indicating that the river valley does not function as a major biogeographic boundary for the taxa examined. The Hindu Kush also harbors endemic relict taxa of both Palearctic and Oriental affinities, revealing a dual role as both refugium and dispersal barrier. Thus, our results identify the Hindu Kush as the de facto boundary between the Palearctic and Oriental realms in this part of Eurasia and show that under-sampled arid-montane regions can disproportionately improve global biogeographic frameworks.

evolutionary biology↗

bioRxiv2024

Genomic, phenotypic and environmental correlates of speciation in the midwife toads (Alytes)

Speciation, i.e., the formation of new species, implies that diverging populations evolve genetic and phenotypic factors that promote reproductive isolation (RI), but the adaptive vs. neutral origin of these factors and their relative contributions across the speciation continuum remain elusive. Here we test which of genomic, bioacoustic, morphological and environmental differentiation best predicts RI across the midwife toads (genus Alytes), a diversification of Mediterranean amphibians. Hybrid zone analyses in the A. obstetricans complex support that without strong geographic barriers to dispersal, the extent of introgression (which should reflect the strength of RI) covaries with genomic divergence irrespective of other factors. Phenotypic divergence become important later along the continuum, namely between non-admixing species attributed to distinct subgenera. Our results suggest that by putatively causing intrinsic incompatibilities in hybrids, the genetic mutations accumulating randomly between allopatric populations act as the initial trigger of RI, while substantial ecological and behavioral differentiation is a long-term consequence of species divergence that ultimately promotes sympatry. Whereas speciation is usually claimed to be primarily adaptive, our study corroborates recent findings that new species may also be a neutral outcome of gradual phylogeographic divergence, which has practical implications for species delimitation.

evolutionary biology↗

bioRxiv2023

Exploring the impact of read clustering thresholds on RADseq-based systematics: an empirical example from European amphibians.

Restriction site-Associated DNA sequencing (RADseq) has great potential for genome-wide systematics studies of non-model organisms. However, accurately assembling RADseq reads into orthologous loci remains a major challenge in the absence of a reference genome. Traditional assembly pipelines cluster putative orthologous sequences based on a user-defined clustering threshold. Because improper clustering of orthologs is expected to affect results in downstream analyses, it is crucial to design pipelines for empirically optimizing the clustering threshold. While this issue has been largely discussed from a population genomics perspective, it remains understudied in the context of phylogenomics and coalescent species delimitation. To address this issue, we generated RADseq assemblies of representatives of the amphibian genera Discoglossus, Rana, Lissotriton and Triturus using a wide range of clustering thresholds. Particularly, we studied the effects of the intra-sample Clustering Threshold (iCT) and between-sample Clustering Threshold (bCT) separately, as both are expected to differ in multi-species data sets. The obtained assemblies were used for downstream inference of concatenation-based phylogenies, and multi-species coalescent species trees and species delimitation. The results were evaluated in the light of a reference genome-wide phylogeny calculated from newly generated Hybrid-Enrichment markers, as well as extensive background knowledge on the species systematics. Overall, our analyses show that the inferred topologies and their resolution are resilient to changes of the iCT and bCT, regardless of the analytical method employed. Except for some extreme clustering thresholds, all assemblies yielded identical, well-supported inter-species relationships that were mostly congruent with those inferred from the reference Hybrid-Enrichment data set. Similarly, coalescent species delimitation was consistent among similarity threshold values. However, we identified a strong effect of the bCT on the branch lengths of concatenation and species trees, with higher bCTs yielding trees with shorter branches, which might be a pitfall for downstream inferences of evolutionary rates. Our results suggest that the choice of assembly parameters for RADseq data in the context of shallow phylogenomics might be less challenging than previously thought. Finally, we propose a pipeline for empirical optimization of the iCT and bCT, implemented in optiRADCT, a series of scripts readily usable for future RADseq studies.

evolutionary biology↗

bioRxiv2022

Combining RADseq and contact zone analysis to decipher cryptic diversification in reptiles: insights from Acanthodactylus erythrurus (Reptilia: Lacertidae)

Linnaean and Wallacean shortfalls (Uncertainties on species taxonomy and distribution, respectively) are major factors hampering efficient conservation planning in the current context of biodiversity erosion. These shortfalls concern even widespread and abundant species in relatively well-studied regions such as the Mediterranean biodiversity hotspot which still hosts a large fraction of unrecognised biodiversity, notably in small vertebrates. Species delimitations have long been based on phylogenetic analyses of a small number of standard markers, but accurate lineage identification in this context can be obscured by incomplete lineage sorting, introgression or isolation by distance. Recently, integrative approaches coupling various sets of characters or analyses of contact zones aiming at estimating reproductive isolation (RI) have been advocated instead. Analyses of introgression patterns in contact zone with genomic data represent a powerful way to confirm the existence of independent lineages and estimate the strength of their RI at the same time. The Spiny-footed Lizard Acanthodactylus erythrurus (Schinz, 1833) is widespread in the Iberian Peninsula and the Maghreb and exhibits a large amount of genetic diversity, although the precise number and distribution of its genetic lineages remain poorly understood. We applied a RADseq approach to obtain a genome wide SNPs dataset on a contact zone in central Morocco between the previously described Rif and Middle-Atlas lineages. We show that these two lineages exhibit strong RI across this contact zone, as shown by the limited amount and restricted spatial extant of gene flow. We interpret these results as evidence for species-level divergence of these two lineages. Our study confirms the usefulness of RADseq approaches applied on contact zones for cryptic diversity studies and therefore to resolve Linnaean and Wallacean shortfalls.

genomics↗