This new pre-print of "Rapid radiation of Southern Ocean shags in response to receding sea ice" by Nic Rawlence, Hamish Spencer et al (University of Otago) sheds new light on the dispersal and evolution of the blue-eyed shags in the Southern Ocean and New Zealand:
Aim: Understanding how wild populations respond to climatic shifts is a fundamental goal of biological research in a fast-changing world. The Southern Ocean represents a fascinating system for assessing large-scale climate-driven biological change, as it contains extremely isolated island groups within a predominantly westerly, circumpolar wind and current system. The blue-eyed shags (Leucocarbo spp.) represent a paradoxical Southern Ocean seabird radiation; a circumpolar distribution implies strong dispersal capacity yet their speciose nature suggests local adaptation and isolation. Here we use genetic tools in an attempt to resolve this paradox.
Location Southern Ocean.
Taxa 17 species and subspecies of blue-eyed shags (Leucocarbo spp.) across the geographical distribution of the genus.
Methods Here we use mitochondrial and nuclear sequence data to conduct the first global genetic analysis of this group using a temporal phylogenetic framework to test for rapid speciation.
Results Our analysis reveals remarkably shallow evolutionary histories among island-endemic lineages, consistent with a recent high-latitude circumpolar radiation. This rapid sub-Antarctic expansion contrasts with significantly deeper lineages detected in more temperate regions such as South America and New Zealand that may have acted as glacial refugia. The dynamic history of high-latitude expansions is further supported by ancestral demographic and biogeographic reconstructions.
Main conclusions The circumpolar distribution of blue-eyed shags, and their highly dynamic evolutionary history, potentially make Leucocarbo a strong sentinel of past and ongoing Southern Ocean ecosystem change given their sensitivity to climatic impacts.
Link: https://www.biorxiv.org/content/10.1101 ... gvuM3p8kKc
Discussion about the evolution, relationships, and naming of New Zealand birds
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- Michael Szabo
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