From past to future: the response of Troglohyphantes to climate change dynamics

Spider of the genus Troglohyphantes (Linyphiidae) are generally found in cool and humid places such as caves and other subterranean habitats with peculiar microclimatic conditions and low climatic variability. All species of Troglohyphantes show small distribution ranges, in some cases point-like. Given their poor dispersal ability, the narrow ecological requirements and the peculiarity of their distribution, they can be considered valuable species-models for biogeographical studies focusing on the effects of past and future climate changes. On the base of a 10-years field data, we generated a dataset comprising more than 350 localities in the Western Italian Alps. We generated a climatic profile for each locality and related it to presence/absence data of Troglohyphantes species via Ecological Niche Modeling (ENM), generating a current potential distribution of the genus in the study area. On the base of the model result, we estimated the probability surface of the genus Troglohyphantes in the past (Last Glacial Maximum, Pleistocene) and in the future, by projecting the present-day model into three different global warming scenarios predicted by the International Panel on Climate Change (IPCC). Given the colder climatic condition in the Pleistocene, the potential past distribution was found to be wider than today. The present model is congruent with the known distribution range in the Western Italian Alps, and predicts the most suitable conditions in cold mountainous areas. Moreover, the higher suitability corresponds to the limits of the Pleistocene glaciers, in areas that were devoid from ice. We hypothesize that several populations underwent local extinctions during Pleistocene and the range of distribution successively contracted in consequence of the temperature increase. Future forecasts based on different temperature scenarios shows a general trend of decline of suitable areas all over the study area. In light of our results, we discuss how temperature increase due to Global Warming may affect Troglohyphantes species causing potential local extinctions.