Abstract
Major climatic changes in the Pleistocene had significant effects on marine organisms and the environments in which they lived. The presence of divergent patterns of demographic history even among phylogenetically closely-related species sharing climatic changes raises questions as to the respective influence of species-specific traits on population structure. In this work we tested whether the lifestyle of Antarctic notothenioid benthic and pelagic fish species from the Southern Ocean influenced the concerted population response to Pleistocene climatic fluctuations. This was done by a comparative analysis of sequence variation at the cyt b and S7 loci in nine newly sequenced and four re-analysed species. We found that all species underwent more or less intensive changes in population size but we also found consistent differences between demographic histories of pelagic and benthic species. Contemporary pelagic populations are significantly more genetically diverse and bear traces of older demographic expansions than less diverse benthic species that show evidence of more recent population expansions. Our findings suggest that the lifestyles of different species have strong influences on their responses to the same environmental events. Our data, in conjunction with previous studies showing a constant diversification tempo of these species during the Pleistocene, support the hypothesis that Pleistocene glaciations had a smaller effect on pelagic species than on benthic species whose survival may have relied upon ephemeral refugia in shallow shelf waters. These findings suggest that the interaction between lifestyle and environmental changes should be considered in genetic analyses.
Highlights
Climate change has always been a feature of the natural world
In order to understand the processes that lead to diverse population genetic patterns among marine species, Hellberg [4] asked: “Do closely related species differ in inferred effective population size? What are life histories or ecological attributes of this variation?” In this study we have addressed both of Hellberg’s questions
The S7 dataset of Pagetopsis macropterus was excluded from all analyses
Summary
Climate change has always been a feature of the natural world. we can trace some of the physical effects of climate change, identifying the biological effects of past climatic change is complicated. Explanations for different responses among species to Pleistocene climate change have been proposed in comparative studies [2,3] general patterns of response are not always present. Studies tend to focus on the more accessible Northern Hemisphere than on the Southern This is especially important since diversity patterns are not symmetrical between the two hemispheres [6] with much higher levels of endemism within the Southern polar circle, suggesting that different mechanisms apply.
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