Deep-sea octocorals and antipatharians show no evidence of seamount-scale endemism in the NW Atlantic

Abstract

Seamounts are undersea mountains commonly characterized by accelerated currents, exposed hard-substrates, and relatively high biomass and biodiversity. Hydrographic features associated with seamounts have led authors to hypothesize that benthic invertebrate populations from geographically separated seamounts (and the continental slope) may experience varying degrees of genetic isolation, resulting in high levels of endemism. While this hypothesis has been tested for multiple taxonomic groups in the Pacific, it has rarely been addressed in the Atlantic. We tested the null hypothesis that the geographic ranges of corals from NW Atlantic seamounts are restricted to individual seamounts. We examined 188 octocoral and 50 antipatharian colonies (representing 6 and 2 genera, respectively) from 14 seamounts, spanning 1700 km, and the adjacent continental margin and estimated their genetic variation using mitochondrial loci (msh1 for all octocorals, as well as an intergenic region for isidids, and 3 multi-gene spanning segments for antipatharians). Well-sampled haplotypes were not geographically isolated on individual seamounts, thus refuting the hypothesis of local endemism of coral fauna on the New England and Corner Seamounts. The narrow geographic distribution of rare haplotypes is most likely due to undersampling rather than endemism. Our results do not preclude that cryptic variation and endemism not revealed by mitochondrial DNA may become evident should more variable markers be developed.

New Cheilostomata (Bryozoa) from NE Atlantic seamounts, islands, and the continental slope: evidence for deep-sea endemism

“…Results of studies of particular taxonomic groups or community assemblages from seamounts are contrasted in terms of the geographical range of species: a particularly high proportion of endemics is revealed by some of them (e.g., Richer de Forges et al 2000;George & Schminke 2002;Gofas 2007;McClain et al 2009) while, in contrast, other studies show a lack of endemism within seamount assemblages (e.g., Samadi et al 2006;Thoma et al 2009). The set of bryozoan species described here provides a striking example of endemism linked to geographic isolation between the various seamounts, islands and sites from the bathyal continental slope.…”

Diversity, distribution and spatial structure of the cold-water coral fauna of the Azores (NE Atlantic)

“…This prediction is being currently challenged by increasing reports of seamount megafaunas characterized by species with broad geographical distributions and few endemics (e.g. Samadi et al, 2006;O'Hara, 2007;McClain et al, 2009a), including coral assemblages in the North Atlantic (Cairns and Chapman, 2001;Thoma et al, 2009). Our study is in agreement with the latter given that the Azores region hosts a coral fauna of mixed zoogeographic affinities and only 23 of the 164 species (14 %) are apparent endemics (Table 5).…”

Phylogeographic Estimates of Colonization of The Deep Atlantic by The Protobranch Bivalve Nucula Atacellana

“…In contrast, Brix and Svavarsson (2010) found that many Atlantic deep−sea isopod species boundaries coincide with the GIF Ridge, implying that, while Nordic Sea and Arctic Ocean faunas may reflect Transarctic exchange, fewer species extend farther south into the Atlantic proper across the GIF. In keeping with this idea, Atlantic colonization from the Pacific via the Central American Seaway with no evidence of Transarctic exchange has been established for sev− eral deep−sea coral species (Thoma et al 2009;Herrera et al 2012;Pante et al 2012) and a clade of the mysid genus Pseudomma (Meland 2004); a similar pat− tern was found in a shallow−water bryozoan (Schwaninger 2008).…”