Polito Michael J.

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Polito
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Michael J.
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Author: Emslie, Steven D. ×

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  • Article
    A reversal of fortunes : climate change ‘winners’ and ‘losers’ in Antarctic Peninsula penguins
    (Nature Publishing Group, 2014-06-12) Clucas, Gemma V. ; Dunn, Michael J. ; Dyke, Gareth ; Emslie, Steven D. ; Levy, Hila ; Naveen, Ron ; Polito, Michael J. ; Pybus, Oliver G. ; Rogers, Alex D. ; Hart, Tom
    Climate change is a major threat to global biodiversity. Antarctic ecosystems are no exception. Investigating past species responses to climatic events can distinguish natural from anthropogenic impacts. Climate change produces ‘winners’, species that benefit from these events and ‘losers’, species that decline or become extinct. Using molecular techniques, we assess the demographic history and population structure of Pygoscelis penguins in the Scotia Arc related to climate warming after the Last Glacial Maximum (LGM). All three pygoscelid penguins responded positively to post-LGM warming by expanding from glacial refugia, with those breeding at higher latitudes expanding most. Northern (Pygoscelis papua papua) and Southern (Pygoscelis papua ellsworthii) gentoo sub-species likely diverged during the LGM. Comparing historical responses with the literature on current trends, we see Southern gentoo penguins are responding to current warming as they did during post-LGM warming, expanding their range southwards. Conversely, Adélie and chinstrap penguins are experiencing a ‘reversal of fortunes’ as they are now declining in the Antarctic Peninsula, the opposite of their response to post-LGM warming. This suggests current climate warming has decoupled historic population responses in the Antarctic Peninsula, favoring generalist gentoo penguins as climate change ‘winners’, while Adélie and chinstrap penguins have become climate change ‘losers’.
  • Preprint
    Responses of high-elevation herbaceous plant assemblages to low glacial CO2 concentrations revealed by fossil marmot (Marmota) teeth
    ( 2014-05) McLean, Bryan S. ; Ward, Joy K. ; Polito, Michael J. ; Emslie, Steven D.
    Atmospheric CO2 cycles of the Quaternary likely imposed major constraints on the physiology and growth of C3 plants worldwide. However, the measured record of this remains both geographically and taxonomically sparse. We present the first reconstruction of physiological responses in a late Quaternary high-elevation herbaceous plant community from the Southern Rocky Mountains, USA. We used a novel proxy – fossilized tooth enamel of yellow-bellied marmots (Marmota flaviventris) – which we developed using detailed isotopic analysis of modern individuals. Calculated carbon isotopic discrimination (Δ) of alpine plants was nearly 2‰ lower prior to the Last Glacial Maximum than at present, a response almost identical to nonherbaceous taxa from lower elevations. However, initial shifts in Δ aligned most closely with onset of the late Pleistocene bipolar temperature ‘see-saw’ rather than CO2 increase, indicating unique limitations on glacial-age high-elevation plants may have existed due to both low temperatures and low CO2. Further development of system-specific faunal proxies can help to clarify this and other plant- and ecosystem-level responses to past environmental change.