While we know that many species are rare, what largely remains a mystery, is why they are rare. But now University of Plymouth experts have made exciting discoveries that have unlocked some of the clues.
The work, conducted by a team led by the university’s David Bilton and published in the Journal of Animal Ecology, also helps us understand how rare and common species may respond to future climate change.
Piero Calosi, working with Bilton and Professor John Spicer, investigated tolerance to heat and cold in fourteen closely related species of European diving beetles, which vary dramatically in geographical range size, from species restricted to mountain systems in southern Europe to those found from the Mediterranean to northern Sweden.
The ability to tolerate temperature extremes was linked with the geographical range size of species, far more in fact than differences in relative dispersal ability. These beetles survived ice ages in southern Europe, moving north as the climate warmed around 12, 000 years ago. Present-day widespread species are those which have been able to retain their southern range boundaries, and expand north, something which requires relatively high tolerance to both heat and cold.
Species with narrower temperature tolerances are far more restricted, and it is these species which seem likely to be the most vulnerable to ongoing climatic changes.
As Calosi explains: “As well as having limited temperature tolerance, these species also have limited ability to adjust their tolerance windows as temperatures change. Given that climate warming may also lead to a reduction in the availability of suitable aquatic habitats in Mediterranean areas, such restricted species would appear to be doubly threatened in the future.”
This research, funded by the Leverhulme Trust, was published in the British Ecological Society’s Journal of Animal Ecology (in a paper entitled ' What determines a species’ geographical range’ Thermal biology and latitudinal range size relationships in European diving beetles (Coleoptera: Dytiscidae)' 2010 Journal of Animal Ecology, volume 79, pages 194–204).
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