Comparative phylogeography among hydrothermal vent species along the East Pacific Rise reveals vicariant processes and population expansion in the South

Abstract

The use of sequence polymorphism from individual mitochondrial genes to infer past demography has recently proved controversial because of the recurrence of selective sweeps acting over genes and the need for unlinked multilocus data sets. However, comparative analyses using several species for one gene and/or multiple genes for one species can serve as a test for potential selective effects and clarify our understanding of historical demographic effects. This study compares nucleotide polymorphisms in mitochondrial cytochrome oxidase I across seven deep-sea hydrothermal vent species that live along the volcanically active East Pacific Rise. Approximate Bayesian Computation (ABC) method, developed to trace shared vicariant events across species pairs, indicates the occurrence of two across species divergence times, and suggests that the present geographical patterns of genetic differentiation may be explained by two periods of significant population isolation. The oldest period dates back 11.6 Ma and is associated with the vent limpet Lepetodrilus elevatus, while the most recent period of isolation is 1.3 Ma, which apparently affected all species examined and coincides with a transition zone across the equator. Moreover, significant negative Tajima's D and star-like networks were observed for all southern lineages, suggesting that these lineages experienced a concomitant demographic and geographical expansion about 100 000-300 000 generations ago. This expansion may have initiated from a wave of range expansions during the secondary colonization of new sites along the Southern East Pacific Rise (founder effects below the equator) or recurrent bottleneck events because of the increase of eruptive phases associated with the higher spreading rates of the ridge in this region.

Evolutionary and ecological genomics in deep-sea organisms

“…Evidence suggestive of non-equilibrium dynamics has been presented in populations of some of vent species, particularly in populations from fastspreading ridges (Vrijenhoek 2010 Hurtado et al 2004;Plouviez et al 2009;Teixeira et al 2011;Thaler et al 2011;Beedessee et al 2013;Thaler et al 2014). Nonetheless, minor allele frequency spectra for vent barnacle populations in this study were consistent with mutation-drift equilibrium, as a majority of the alleles in each population have low frequencies , with a long tail of alleles at intermediate frequencies approaching zero proportions.…”

Insights into Symbiont Population Structure among Three Vestimentiferan Tubeworm Host Species at Eastern Pacific Spreading Centers

“…Comparisons of the composition of vent-associated macrofauna communities (42) and the genetic structure of vestimentiferan worms (33) provide evidence that the northeast Pacific and EPR vent communities have been isolated by the development of discontinuities along the Pacific midocean ridge caused by the tectonic fracturing of the Farallon Plate about 30 million years ago (42,43). Similar dichotomies attributed to later plate fragmentation events were observed in populations of various invertebrate species spanning multiple ridge systems in the northeast Pacific (44)(45)(46). It is therefore reasonable to assume that "Ca.…”

Exploring the Ecology of Deep-Sea Hydrothermal Vents in a Metacommunity Framework

“…The studies have led to a series of discoveries of common or varying geographical subdivisions among diverse vent taxa, which, in turn, have deepened our understanding about the effect of several environmental (e.g., geomorphology of oceanic ridges, spatial and temporal stability of vent habitats, and deep-sea currents) and biological (e.g., species-specific life histories, larval duration, motility and behavior) factors on the connectivity of vent metapopulations (reviewed in Vrijenhoek, 2010). Population connectivity and genetic diversity are influenced by historical factors such as vicariance, range and/or demographic expansion through dispersal, and introgressive hybridization (backcrossing of an interspecific hybrid with one of its parent species), both in mid-ocean ridge and arc-backarc systems (Young et al, 2008;Plouviez et al, 2009;Johnson et al, 2014;Yahagi et al, 2015;Zhang et al, 2015;Jang et al, 2016).…”

“…For example, Young et al (2008) found a general southward pattern of migration along the northeast Pacific system, and larger effective population sizes of the siboglinid tubeworm Ridgeia piscesae in the southern populations compared to those in the north. Coalescent approaches have also been implemented to measure long-term migration rates in mollusk and polychaete species along the EPR (Plouviez et al, 2009(Plouviez et al, , 2010(Plouviez et al, , 2013, crustacean and mollusk species in the Indian Ocean ridges (Thaler et al, 2011;Beedessee et al, 2013;Chen et al, 2015), alvinocaridid shrimp from the MidCayman Spreading Center (Plouviez et al, 2015) and the Mid-Atlantic Ridge (Teixeira et al, 2012(Teixeira et al, , 2013. Despite the evident advantages of coalescent approaches over traditional Fstatistics, the migration estimates obtained through many of these approaches are considered long-term because of necessary equilibrium assumptions over the last ∼4N e generations (i.e., average time to coalescence).…”