Biology subjects

Escuer, P.

Publications and source records attributed to Escuer, P..

3 recordsLinked to original sources

bioRxiv2025

How did evolution halve genome size during an oceanic island colonization?

Red devil spiders of the genus Dysdera colonised the Canary Islands and underwent an extraordinary diversification. Notably, their genomes are nearly half the size of their mainland counterparts ([~]1.7 vs. [~]3.3 Gb). This offers a unique model to solve long-standing debates regarding the roles of adaptive and non-adaptive forces on shaping genome size genome size evolution. To address these, we conducted comprehensive genomic analyses based on three high-quality chromosome-level assemblies, including two newly generated ones. We find that insular species experienced a reduction in genome size, affecting all genomic elements, including intronic and intergenic regions, with transposable element (TE) loss accounting for most of this contraction. Additionally, autosomes experienced a disproportionate reduction compared to the X chromosome. Paradoxically, island species exhibit higher levels of nucleotide diversity and recombination, lower TE activity in recent times, and evidence of intensified natural selection, collectively pointing to larger long-term effective population sizes in species from the Canary Islands. Overall, our findings align with the non-adaptive mutational hazard hypothesis, supporting purifying selection against slightly deleterious DNA and TE insertions as the primary mechanism driving genome size reduction.

genomics↗

bioRxiv2024

Population genomics of adaptive radiations: Exceptionally high levels of genetic diversity and recombination in an endemic spider from the Canary Islands

The spider genus Dysdera has undergone a remarkable diversification in the oceanic archipelago of the Canary Islands, [~]60 endemic species originated during the 20 million years since the origin of the archipelago. This evolutionary radiation has been accompanied by substantial dietary shifts, often characterized by phenotypic modifications encompassing morphological, metabolic and behavioral changes. Hence, these endemic spiders represent an excellent model for understanding the evolutionary drivers and to pinpoint the genomic determinants underlying adaptive radiations. Recently, we achieved the first chromosome-level genome assembly of one of the endemic species, D. silvatica, providing a high-quality reference sequence for evolutionary genomics studies. Here, we conducted a low-coverage based resequencing study of a natural population of D. silvatica from La Gomera island. Taking advantage of the new high-quality genome, we characterized genome-wide levels of nucleotide polymorphism, divergence, and linkage disequilibrium, and inferred the demographic history of this population. We also performed comprehensive genome-wide scans for recent positive selection. Our findings uncovered exceptionally high levels of nucleotide diversity and recombination in this geographically restricted endemic species, indicative of large historical effective population sizes. Furthermore, we identified genomic regions potentially under positive selection, shedding light on relevant biological processes, such as vision and nitrogen extraction as possible targets of adaptation and eventually, as drivers of the species diversification. This pioneering study in spiders endemic of an oceanic archipelago lays the groundwork for broader population genomics investigations aimed at understanding the genetic mechanisms driven adaptive radiations in island ecosystems.

evolutionary biology↗

bioRxiv2020

Smelling in the dark: phylogenomic insights on the chemosensory system of a subterranean beetle

The chemosensory system has experienced relevant changes in subterranean animals, facilitating the orientation into darkness via the perception of specific chemical signals critical to survive in this particular environment. However, the genomic basis of chemoreception in cave-dwelling fauna is largely unexplored. We generated de novo transcriptomes for antennae and body samples of the troglobitic beetle Speonomus longicornis (whose characters suggest an extreme adaptation to the deep subterranean) in order to interrogate the evolutionary origin and diversification of the chemosensory gene repertoire across coleopterans through a phylogenomic approach. Our results suggested a diminished diversity of odorant and gustatory gene repertoires compared to polyphagous epigean beetles. Moreover, S. longicornis showed a large diversity of odorant-binding proteins, suggesting an important role of these proteins in capturing airborne chemical cues. We identified a gene duplication in the ionotropic co-receptor I R25a, a highly conserved single-copy gene in protostomes involved in thermal and humidity sensing. In addition, no homologous genes to sugar receptors or the ionotropic receptor IR41a were detected. Our findings suggest that the chemosensory gene repertoire of this cave beetle may have been reshaped by the low complexity of chemical signals of this particular environment, and that gene duplication and loss may have played an important role in the evolution of genes involved in chemoreception. Altogether, our results shed light on the genomic basis of chemoreception in a cave-dwelling invertebrate and pave the road towards understanding the genomic underpinnings of adaptation to the subterranean lifestyle at a deeper level.

evolutionary biology↗