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Climate tracking by alpine insect distribution across a century: concentric retreats, small refugia and strong elevational shifts in bumblebees
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  • Paolo Biella,
  • Maurizio Cornalba,
  • Pierre Rasmont,
  • Johann Neumayer,
  • Maurizio Mei,
  • Mattia Brambilla
Paolo Biella
University of Milan-Bicocca

Corresponding Author:[email protected]

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Maurizio Cornalba
University of Pavia
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Pierre Rasmont
Universite de Mons
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Johann Neumayer
University of Milan-Bicocca
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Maurizio Mei
University of Rome La Sapienza
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Mattia Brambilla
University of Milan
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Abstract

Cold-adapted species endangered by global change are crucial cases for understanding range dynamics and its interface with conservation. In view of climate change and their sensitivity, Alpine insects should modify their distribution by reducing ranges, while being unable of sufficient displacements and mostly moving uphill. To test these hypotheses, we targeted four threatened, high-altitude bumblebees differing in subgenera and elevation ranges, and covering the main central and south European mountains. We performed species distribution models including climate and habitat, and we described elevation uphill and the year of change with broken-line regressions. Results indicate that climate change will cause severe future range contractions across large areas, more in the Apennines (80% - 85% ca) than the Alps and Pyrenees (24 - 56% ca), with mostly concentric retreats as future extents will nearly entirely be included in the present ones. Remarkably, since the ‘80s elevation uplift has started by about 325 - 535 m, a period coinciding with the beginning of the main warming, and will continue. The size and distribution of climate refugia will challenge conservation: they will be small and context specific (2-60% of current areas), but while in the Apennines and Pyrenees they will be nearly entirely within Protected Areas, only a third will be so for the Alps. Such impressive distribution changes demonstrates that cold-adapted bumblebees can accurately track climate change and be precise sentinels of it, and these results link with the investigated species being specialists with specific habitat requirements of temperature and glacier presence. Overall, the distribution of cold specialist bumblebees driven by climate change demonstrates that conservation should act upon the dynamic realities of species ranges because their range reduction, the impossibility of finding new areas and the movement uphill emerge as consistent patterns.