Receding ice drove parallel expansions in Southern Ocean penguins

Abstract

Climate shifts are key drivers of ecosystem change. Despite the critical importance of Antarctica and the Southern Ocean for global climate, the extent of climate-driven ecological change in this region remains controversial. In particular, the biological effects of changing sea ice conditions are poorly understood. We hypothesize that rapid postglacial reductions in sea ice drove biological shifts across multiple widespread Southern Ocean species. We test for demographic shifts driven by climate events over recent millennia by analyzing population genomic datasets spanning 3 penguin genera (Eudyptes,Pygoscelis, andAptenodytes). Demographic analyses for multiple species (macaroni/royal, eastern rockhopper, Adélie, gentoo, king, and emperor) currently inhabiting southern coastlines affected by heavy sea ice conditions during the Last Glacial Maximum (LGM) yielded genetic signatures of near-simultaneous population expansions associated with postglacial warming. Populations of the ice-adapted emperor penguin are inferred to have expanded slightly earlier than those of species requiring ice-free terrain. These concerted high-latitude expansion events contrast with relatively stable or declining demographic histories inferred for 4 penguin species (northern rockhopper, western rockhopper, Fiordland crested, and Snares crested) that apparently persisted throughout the LGM in ice-free habitats. Limited genetic structure detected in all ice-affected species across the vast Southern Ocean may reflect both rapid postglacial colonization of subantarctic and Antarctic shores, in addition to recent genetic exchange among populations. Together, these analyses highlight dramatic, ecosystem-wide responses to past Southern Ocean climate change and suggest potential for further shifts as warming continues.

Update on the global abundance and distribution of breeding Gentoo Penguins (Pygoscelis papua)

“…To explore deglaciation as a possible mechanism for range expansion and colonization in Gentoo Penguins (Cole et al 2019), we analyzed high-resolution satellite imagery provided through Google Earth for eight of 14 recently colonized areas and compared it with digitized aerial photography taken in December, 1956 by the Falkland Islands and Dependencies Aerial Survey (Mott and Wiggins 1965).…”

“…Declines in the extent or concentration of winter sea ice might make these sites available for breeding and overwinter residency and explain the Gentoo Penguin's southern range expansion. Historically, deglaciation and terrestrial ice sheet retreat has led to the expansion and proliferation of Antarctic and sub-Antarctic penguin populations since the last glacial maximum (LaRue et al 2013;Clucas et al 2014;Younger et al 2015;Cole et al 2019). The WAP has continued to experience rapid thinning of its ice shelves and their tributaries since the 1990s, which in part is attributed to increases in upper ocean heat content (Pritchard et al 2012;Paulo et al 2015).…”

Genome-wide analyses reveal drivers of penguin diversification

“…The extent of ice and changes in the currents of the Southern Ocean during repeated glacial cycles likely played a significant role in the structuring and lineage diversification of seabird populations (14), including penguins (15,16). Population sizes of several penguin species contracted during glaciation and expanded during postglacial periods (17). Sharp changes in these effective population sizes suggest that the diversification of penguins has been sensitive to climate shifts.…”

Rapid reassembly of an intertidal community following prehistoric disturbance

“…community-level) demographic and/or evolutionary biogeographic shifts (e.g. Bunnefeldet al 2018;Cole et al 2019). Such analyses can potentially bridge the gap between community dynamics and microevolutionary processes, enhancing our understanding of community responses to rapid environmental change (Johnson and Stinchcombe 2007;Stone et al 2012;Cavender-Bares et al 2016).…”