Closely related octopus species show different spatial genetic structures in response to the Antarctic seascape

Abstract

Determining whether comparable processes drive genetic divergence among marine species is relevant to molecular ecologists and managers alike. Sympatric species with similar life histories might be expected to show comparable patterns of genetic differentiation and a consistent influence of environmental factors in shaping divergence. We used microsatellite loci to quantify genetic differentiation across the Scotia Arc in three species of closely related benthic octopods, Pareledone turqueti, P. charcoti, and Adelieledone polymorpha. The relative importance of environmental factors (latitude, longitude, depth, and temperature) in shaping genetic structure was investigated when significant spatial genetic structure was uncovered. Isolated populations of P. turqueti and A. polymorpha at these species’ range margins were genetically different to samples close to mainland Antarctica; however, these species showed different genetic structures at a regional scale. Samples of P. turqueti from the Antarctic Peninsula, Elephant Island, and Signy Island were genetically different, and this divergence was associated primarily with sample collection depth. By contrast, weak or nonsignificant spatial genetic structure was evident across the Antarctic Peninsula, Elephant Island, and Signy Island region for A. polymorpha, and slight associations between population divergence and temperature or depth (and/or longitude) were detected. Pareledone charcoti has a limited geographic range, but exhibited no genetic differentiation between samples from a small region of the Scotia Arc (Elephant Island and the Antarctic Peninsula). Thus, closely related species with similar life history strategies can display contrasting patterns of genetic differentiation depending on spatial scale; moreover, depth may drive genetic divergence in Southern Ocean benthos.

Phylogeography of the insular populations of common octopus, Octopus vulgaris Cuvier, 1797, in the Atlantic Macaronesia

“…The deep open ocean surrounding insular habitats presents barriers to dispersal-driven population differentiation in octopuses [56]. We describe strong population structure along the northeastern Atlantic coast, except for samples from neighboring sites in the Macaronesia central core.…”

The Antarctic Circumpolar Current isolates and connects: Structured circumpolarity in the sea star Glabraster antarctica

“…Connectivity patterns in G. antarctica indicate that the Magellanic zoogeographic province may include Shag Rocks, despite its location south of the Antarctic Convergence and proximity to South Georgia. Tests of population differentiation across the Antarctic Convergence show a strong genetic break between Shag Rocks and South Georgia for G. antarctica (Table , Figure ); Magellanic haplotypes are shared with Shag Rocks but no other Scotia Arc samples (Figures and ).Divergence between Shag Rocks and South Georgia was also recovered for the octopus Pareldone turqueti (Allcock, Brierley, Thorpe, & Rodhouse, ; Strugnell, Allcock, & Watts, ), and these authors initially proposed the deep water (maximum 1750 m) separating the sites as a strong barrier, limiting pelagic dispersal. However, other organisms with long pelagic stages have shown connectivity across this putative barrier, for example fish species Dissostichus eleginoides (Shaw, Arkhipkin, & Al‐Khairulla, ) and Champsocephalus gunnari (Kuhn & Gaffney, ), and the nemertean Parborlasia corrugatus , which has a long PLD and extended pelagicism after metamorphosis (Thornhill, Mahon, Norenburg, & Halanych, ).…”

“…Divergence between Shag Rocks and South Georgia was also recovered for the octopus Pareldone turqueti (Allcock, Brierley, Thorpe, & Rodhouse, 1997;Strugnell, Allcock, & Watts, 2017), and these authors initially proposed the deep water (maximum 1750 m) separating the sites as a strong barrier, limiting pelagic dispersal. However, other organisms with long pelagic stages have shown connectivity across this putative barrier, for example fish species Dissostichus eleginoides (Shaw, Arkhipkin, & Al-Khairulla, 2004) and Champsocephalus gunnari (Kuhn & Gaffney, 2006), and the nemertean Parborlasia corrugatus, which has a long PLD and extended pelagicism after metamorphosis (Thornhill, Mahon, Norenburg, & Halanych, 2008).…”

Interactions in the Deep Sea

“…Genetic differentiation by depth, hypothesized to occur due to physiological gradients (see Rex and Etter, 2010) has been identified in other benthic deep-sea invertebrates apart from corals, including molluscs (Jennings et al, 2013, Strugnell et al, 2017, polychaetes (Schüller, 2011, Brasier et al, 2017 among others (reviewed in Morrison et al, 2017 andRoterman, 2017). Noting the relatively wide depth band of their lower bathyal, Watling et al (2013) acknowledged a potential need for further subdivision by depth in some oceans and this appears to be supported by available molecular data.…”