Species gain and loss per degree Celsius

Abstract

With climate zones moving poleward, it is interesting to know how rapidly species are gained and lost along temperature gradients. For the Australian native vascular flora, observed climate envelopes for species distributions have here been calculated from data for occurrence at geographical locations. For each degree temperature increase along a continental temperature gradient, numbers of species crossing their cold boundary and hence added to the flora, and crossing their warm boundary and hence lost to the flora, were counted. These counts of gains and losses were expressed as percentages of the flora recorded as present at that temperature. We report results for the flora at > 700 mm rainfall pa along the Australian east coast, where higher rainfall is continuously distributed throughout the latitudinal range. Per °C mean annual temperature increase, 20 ± 11% (mean ± SD) of species were gained, and 14 ± 4% were lost, across the range 9–23°C. Many further questions arise. For example, which other continental floras might show faster or slower rates of species gain and loss along temperature gradients? Similarly, might species with particular traits show faster rates of turnover: for example, species with local dispersal such as those with diaspore morphologies adapted for ants, compared to those adapted for bird dispersal?