Biology subjects

van Elst, T.

Publications and source records attributed to van Elst, T..

3 recordsLinked to original sources

bioRxiv2026

Understanding cryptic diversity within the honeypot ant species complex of Myrmecocystus mendax

Cryptic species diversity, overlooked due to extreme morphological similarity, is a common phenomenon among ants. The "honeypot ant" genus Myrmecocystus (Wesmael, 1838; Formicinae: Lasiini) likely features multiple cryptic species, as previously suggested by phylogenetic studies based on ultraconserved elements (UCEs). Here, this work is expanded upon by examining 140 specimens and 2,508 UCE loci, with a particular focus on the M. mendax species complex from the southwestern USA and northern Mexico. Phylogenomic and population genomic analyses revealed five distinct M. mendax-like lineages and identified two potential cases of cryptic species diversity, one within samples matching the morphology of M. mendax and another within samples conforming to M. placodops. Most specimens morphologically identified as M. mendax formed a well-supported monophyletic group sister to M. melliger assigned individuals, with evidence for ongoing hybridization between both species in the Madrean Sky Islands along the USA-Mexico border. Patterns in the main M. mendax clade also suggest adaptive divergence across ecological gradients, warranting further investigation. Overall, these findings highlight the power of UCE-based genomic data in phylogenetic reconstructions and population genetic analyses to better resolve cryptic species diversity, and clarify complex evolutionary histories shaped by introgression and incomplete lineage sorting.

genomics↗

bioRxiv2025

Species-specific responses to paleoclimatic changes and landscape barriers drive contrasting phylogeography of co-distributed lemur species in northeastern Madagascar

Madagascar is a megadiverse island with exceptionally high levels of endemism, which resulted mainly from allopatric speciation promoted by the islands complex physical geography and paleoclimatic cycles. Northeastern Madagascar is uniquely suited to test the relative importance of river barriers, topography and climatic conditions for lemur genetic differentiation. Based on restriction site-associated DNA sequences, we inferred phylogeny, population structure, genetic diversity and rates of gene flow in four mouse lemur (genus Microcebus) and two woolly lemur (genus Avahi) species. In addition, we employed isolation-by-resistance models to test the importance of topography, river barriers, climate and forest cover in restricting intraspecific gene flow. Our results show that significant differences in genetic diversity and connectivity can be explained by varying responses to landscape features and species-specific phylogeographic histories. Rivers present a general barrier to gene flow, and dispersal between inter-river systems is predominantly mediated through high-elevation headwater regions. While this led to high connectivity and genetic diversity in M. lehilahytsara and A. laniger, gene flow among M. jonahi populations is limited by low climatic niche suitability at higher elevations. In addition, topographic complexity promotes connectivity among Microcebus populations, potentially by buffering impacts of seasonal or historic changes in climatic conditions. Finally, the more restricted distributions of M. macarthurii, A. mooreorum and, to some extent, M. simmonsi likely resulted from refugial dynamics and sea level fluctuations which led to geographic isolation, microendemism and secondary contact zones. Our findings generated informed hypotheses regarding the colonization history of the studied species while also having important implications for their conservation.

evolutionary biology↗

bioRxiv2025

Ecological plasticity explains the distribution of sympatric and allopatric mouse lemurs (Microcebus spp.) in northeastern Madagascar

Species distributions are shaped by complex biotic and abiotic interactions. We studied major ecological drivers of the distribution of four cryptic mouse lemur species (Microcebus spp.) in northeastern Madagascar, across sympatric and allopatric ranges. Using structural habitat characteristics, adaptability to habitat degradation, bioclimatic niches, and morphology, we estimated n-dimensional hypervolumes of niche sizes and overlaps. Annual body mass variability was analyzed as an indicator of heterothermy, a potential indicator for ecological plasticity. M. jonahi and M. simmonsi were found almost equally often in forest- and fallow-derived habitats (52% and 58%, respectively), while M. lehilahytsara predominantly occupied fallow habitats (71%), likely driven by the coexistence with other species. M. lehilahytsara exhibited the largest niche and range size, followed by M. jonahi and M. simmonsi. In contrast, M. macarthurii was restricted to a narrow niche and range. M. jonahi and M. simmonsi displayed significant fat deposition before the austral winter, indicating heterothermy as an adaptation to unpredictable environmental conditions. These species were only found in allopatry, likely due to competition for critical resources like sleeping sites. The smaller M. lehilahytsara coexisted with M. jonahi and M. macarthurii potentially by adjusting its niche to avoid competition with these larger-bodied species. We hypothesize that heterothermy allowed M. jonahi, M. simmonsi, and M. macarthurii to persist in lowlands during Pleistocene climatic challenges but that it did not promote coexistence. In contrast, M. lehilahytsara may have lost lowland distributions due to a lower ability to store fat. Our findings require further testing but provide a plausible explanation for a complex distributional pattern of sympatric and allopatric occurrences.

ecology↗