The Antarctic Circumpolar Current as a diversification trigger for deep-sea octocorals

Abstract

BackgroundAntarctica is surrounded by the Antarctic Circumpolar Current (ACC), the largest and strongest current in the world. Despite its potential importance for shaping biogeographical patterns, the distribution and connectivity of deep-sea populations across the ACC remain poorly understood. In this study we conducted the first assessment of phylogeographical patterns in deep-sea octocorals in the South Pacific and Southern Ocean, specifically a group of closely related bottlebrush octocorals (Primnoidae: Tokoprymno and Thourella), as a test case to study the effect of the ACC on the population structure of brooding species. We assessed the degree to which the ACC constitutes a barrier to gene flow between northern and southern populations and whether the onset of diversification of these corals coincides with the origin of the ACC (Oligocene-Miocene boundary).ResultsBased on DNA sequences of two nuclear genes from 80 individuals and a combination of phylogeographic model-testing approaches we found a phylogenetic break corresponding to the spatial occurrence of the ACC. We also found significant genetic structure among our four regional populations. However, we uncovered shared haplotypes among certain population pairs, suggesting long-distance, asymmetrical migration. Our divergence time analyses indicated that the separation of amphi-ACC populations took place during the Middle Miocene around 12.6 million years ago, i.e., after the formation of the ACC.ConclusionWe suggest that the ACC constitutes a semi-permeable barrier to these deep-sea octocorals capable of separating and structuring populations, while allowing short periods of gene flow. The fluctuations in latitudinal positioning of the ACC during the Miocene likely contributed to the diversification of these octocorals. Additionally, we provide evidence that the populations from each of our four sampling regions could actually constitute different species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0574-z) contains supplementary material, which is available to authorized users.

Population genetic structure and connectivity of deep‐sea stony corals (Order Scleractinia) in the New Zealand region: Implications for the conservation and management of vulnerable marine ecosystems

“…The results of the present study, and those of previous genetic connectivity studies for various species around New Zealand (Bors et al., ; Boschen, Rowden, Clark, & Gardner, ; Dueñas et al., ; Knox et al., ; Miller et al., ) provide genetic connectivity information at different spatial scales. Not surprisingly, their connectivity patterns vary across the range of taxa with differing ecological characteristics.…”

Following the Antarctic Circumpolar Current: patterns and processes in the biogeography of the limpetNacella(Mollusca: Patellogastropoda) across the Southern Ocean

“…For instance, most of the extant nothothenioid species‐rich clades diversified 11.6–5.3 Ma, more than 10 Ma after their origin (Near et al ., ). Similarly, the levels of genetic divergence between amphi‐ACC octocoral populations indicate that the separation occurred during the Middle Miocene 12.6 Ma (Dueñas et al ., ). Levels of mtDNA divergence between Antarctic and South‐American marine invertebrates (González‐Wevar et al ., ; Poulin et al ., ), including echinoderms of the genera Sterechinus (Díaz et al ., ), Astrotoma (Hunter & Halanych, ) and Odontaster (Janosik et al ., ), bivalves like Limatula (Page & Linse, ) and Yoldia (González‐Wevar et al ., ), suggest that their respective radiations occurred no more than 8 Ma.…”

Key stages in the evolution of the Antarctic marine fauna

“…Mid‐Miocene phases of Antarctic diversification have been identified in both a deep‐sea octopus clade (Strugnell, Rogers, Prodöhl, Collins, & Allcock, ) and primnoid bottlebrush octocorals (Dueñas et al., ). Limpet gastropods of the genus Nacella show a distinct radiation at 7.0–8.5 Ma (González‐Wevar et al., ), and predatory muricid gastropods of the subfamily Pagodulinae have a postulated Late Eocene origin ( c. 40 Ma) but did not diversify in the Southern Ocean until the latest Miocene–Pliocene (Barco, Schiaparelli, Houart, & Olivero, ).…”