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

Jan M Strugnell,Phillip C Watts,A Louise Allcock

doi:10.1002/ece3.3327

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.

Highlights

The marine environment presents various physical features that can affect population connectivity, such as deep water (Baums, Boulay, Plato, & Hellberg, 2012; Knutsen, Jorde, Bergstad, & Skogen, 2012), currents, fronts, and gyres (Galarza et al, 2009; Galindo, Olson, & Palumbi, 2006; Young et al, 2015)
Results of regression analyses performed in GESTE to examine the proportion of genetic structure explained by variation in environmental factors
The present study shows that closely related octopod species with similar life history characteristics display a generally similar pattern of genetic differentiation at large geographic scales, but contrasting patterns of population genetic structure at a regional scale across the Scotia Arc region

Summary

Introduction

The marine environment presents various physical features that can affect population connectivity, such as deep water (Baums, Boulay, Plato, & Hellberg, 2012; Knutsen, Jorde, Bergstad, & Skogen, 2012), currents, fronts, and gyres (Galarza et al, 2009; Galindo, Olson, & Palumbi, 2006; Young et al, 2015). Available data are likely confounded by seasonal and interannual oceanographic variation and inadequate knowledge about target species’ life histories (e.g., data on timing and duration of spawning, fecundity, and mortality rates). In remote areas, such as the Southern Ocean, where obtaining relevant seascape and biological data is impractical, an alternative strategy to identify the presence of major dispersal barriers is to quantify spatial genetic structure in multiple species simultaneously

Objectives

Results

Conclusion