Résumé
Hydrothermal vents form archipelagos of ephemeral deep-sea habitats that
raise interesting questions about the evolution and dynamics of the
associated endemic fauna, constantly subject to extinction-recolonization
processes. These metal-rich environments are coveted for the mineral
resources they harbor, thus raising recent conservation concerns. The
evolutionary fate and demographic resilience of hydrothermal species
strongly depend on the degree of connectivity among and within their
fragmented metapopulations. In the deep sea, however, assessing
connectivity is difficult and usually requires indirect genetic
approaches. Improved detection of fine-scale genetic connectivity is now
possible based on genome-wide screening for genetic differentiation. Here,
we explored population connectivity in the hydrothermal vent snail
Ifremeria nautilei across its species range encompassing five distinct
back-arc basins in the Southwest Pacific. The global analysis, based on 10
570 single nucleotide polymorphism (SNP) markers derived from double
digest restriction-site associated DNA sequencing (ddRAD-seq), depicted
two semi-isolated and homogeneous genetic clusters. Demo-genetic modeling
suggests that these two groups began to diverge about 70 000 generations
ago, but continue to exhibit weak and slightly asymmetrical gene flow.
Furthermore, a careful analysis of outlier loci showed subtle limitations
to connectivity between neighboring basins within both groups. This
finding indicates that migration is not strong enough to totally
counterbalance drift or local selection, hence questioning the potential
for demographic resilience at this latter geographical scale. These
results illustrate the potential of large genomic datasets to understand
fine-scale connectivity patterns in hydrothermal vents and the deep sea.