Detecting glacial refugia in the Southern Ocean

Abstract

Throughout the Quaternary, the continental‐based Antarctic ice sheets expanded and contracted repeatedly. Evidence suggests that during glacial maxima, grounded ice eliminated most benthic (bottom‐dwelling) fauna across the Antarctic continental shelf. However, paleontological and molecular evidence indicates most extant Antarctica benthic taxa have persisted in situ throughout the Quaternary. Where and how the Antarctic benthic fauna survived throughout repeated glacial maxima remain mostly hypothesised. If understood, this would provide valuable insights into the ecology and evolution of Southern Ocean biota over geological timescales. Here we synthesised and appraised recent studies and presented an approach to demonstrate how genetic data can be effective in identifying where and how Antarctic benthic fauna survived glacial periods. We first examined the geological and ecological evidence for how glacial periods influenced past species demography in order to provide testable frameworks for future studies. We outlined past ice‐free areas from Antarctic ice sheet reconstructions that could serve as glacial refugia and discussed how benthic fauna with pelagic or non‐pelagic dispersal strategies moved into and out of glacial refugia. We also reviewed current molecular studies and collated proposed locations of Southern Ocean glacial refugia on the continental shelf around Antarctica, in the deep sea, and around sub‐Antarctic islands. Interestingly, the proposed glacial refugia based on molecular data generally do not correspond to the ice‐free areas identified by Antarctic ice sheet reconstructions. The potential biases in sampling and in the choice of molecular markers in current literature are discussed, along with the future directions for employing testable frameworks and genomic methods in Southern Ocean molecular studies. Continued data syntheses will elucidate greater understanding of where and how Southern Ocean benthic fauna persisted throughout glacial periods and provide insights into their resilience against climate changes in the future.

Evolutionary innovations in Antarctic brittle stars linked to glacial refugia

“…contrasting life histories, evolutionary innovation, glacial refugia, morphological innovation, population genetics sheets expanded and contracted throughout glacial-interglacial cycles (see Lau et al, 2020 for a review). Lastly, evolutionary innovations with novel biological changes linked to survival in Southern Ocean glacial refugia have also been observed.…”

Limits and Convergence properties of the Sequentially Markovian Coalescent

“…The demographic history (the variation of effective population size over time) is linked to environmental and demographic changes that existing and/or extinct species have experienced (population expansion, colonization of new habitats, past bottlenecks) (Bergstrom et al, 2020; Gaut et al, 2018; Palkopoulou, Lipson, et al, 2018). Current statistical tools to estimate the demographic history rely on genomic data (Schraiber and Akey, 2015) and these inferences are often linked to archaeological or climatic data, providing novel insights on the evolutionary history (Barroso et al, 2019; Fulgione et al, 2018; Lau et al, 2020; H Li and Durbin, 2011; Mattle-Greminger et al, 2018; Palkopoulou, Mallick, et al, 2015; Yew et al, 2018). From these analyses, evidence for migration events have been uncovered (Browning et al, 2018; H Li and Durbin, 2011), as have genomic consequences of human activities on other species (Choo et al, 2016).…”

Divergence time and species delimitation of microbivalves in the Southern Ocean: the case of Kidderia species

“…Furthermore, when a single specimen that differs from the others by one nucleotide substitution is found, GMYC tends to diverge in the presence of a low intraspecific divergence (Pentinsaari et al 2017 ; Luo et al 2018 ). The occurrence of multiple lineages in the Antarctic could be a consequence of a speciation process explained by repeated glacial–interglacial events that have left characteristic signatures of limited gene flow and the occurrence of multiple independent refuges, fragmented populations, and isolation, especially in brooders (Pearse et al 2009 ; Chown et al 2015 ; Riesgo et al 2015 ; Hayanich and Mahon 2018 ; Lau et al 2020 ).…”