Department of Life Sciences, National Cheng Kung University, Taiwan (Republic of China)
Background/Question/Methods
Climate change has resulted in pervasive species redistribution to track thermal isotherm shifts across the planet, and such phenomenon is of particular concern in mountain ecosystems owning to the disproportional biodiversity. Mountaintop extirpation, range-shift gaps, and lowland biotic attrition, have been proposed as the major threats but empirical tests were sparse. Here we assessed the three mechanisms of climate vulnerability by re-analysis the changes in elevational extents of 734 terrestrial plant and animal species between historical (1849-1998) and contemporary times (2003-2017).
Results/Conclusions
Using Bayesian multivariate and univariate linear mixed models, we found that, mountaintop extirpation has been widely observed across taxonomic groups as species moving upwards; meanwhile, lowland and narrow-ranging species have significantly expanded their elevational extents upwards. As such, range-shift gaps may not be the pervasive threats; lowland biotic attrition is likely but also brought about strong community reorganization in the mountains. Importantly, the tropical species reduced the elevational range sizes more than their temperate counterpart. Species exhibited greater lower-limit contractions at lowlands in the tropics but at uplands in the temperate regions, which has seldom been reported before. Collectively, the thermal niches of temperate species increase in the lowland but decrease toward the uplands while thermal niches of tropical species being particularly diverse in the uplands. Our results modify the three mechanisms of vulnerability in that mountaintop extirpation was pervasive but likely threaten temperate species more; rage shift gaps may not be the major concern; the extend of reducing biodiversity at lowlands will be a balance between species’ elevational expansion and contraction.
