Abstracts (first author)
Multi-loci Bayesian inference of the Anguilla sp. genus radiation and comparative population genetics of the main lineages
Anguilla sp. dispersal and putative spawning areas have divided the scientific community for decades. The rise of the Atlantic species is an unsolved question for which the most supported hypotheses are incompatible: either A. anguilla and A. rostrata came through the Tethys Corridor (closed ~30Mya) or through the Panama Isthmus (open until ~3 Mya). Our study focuses on reconstructing the evolutionary history of freshwater eels. The goal is to ascertain the global demographic dynamics through time for species from the major oceanic basins. Our analyses include TMRCA and diversity calculations, neutrality tests and molecular clock calibration. Using Sanger technology, we sequenced 5 mitochondrial markers, for a total of 304 fish from 10 species. With Bayesian coalescent inference, we estimated genealogies, branch lengths, substitution model parameters and population parameters through time. To infer the timing of demographic events and attach a real-time scale, we used prior information available in the literature. The estimated mutation rate (1.82E-9/bp.yr) and nodes ages were similar to widely accepted reports based on much smaller data sets. However, our results clearly favor the Panama Isthmus route hypothesis over the most popular Tethys route scenario for the settling of the Atlantic eels. Although most species are outside safe ecological limits, we detect genetic signatures of expansion in nearly all sampled populations (10 to 100 fold increases of Ne). These expansions (~400 000 to 720 000 ya) succeeded the mid-Pleistocene transition, a major change in glacial-interglacial cycles. Post-MPT warmth yielded a re-organization of the ocean circulation at intermediate depth and the egress of low-frequency variability in Paciﬁc surface temperatures, impelling a demographic rise. The reported severe decline calls for a better hold of the impact of climate and anthropogenic factors on the resilience potential of these fascinating catadromous fish.