Determinants of species richness in generalist and specialist Mediterranean butterflies: the negative synergistic forces of climate and habitat change

Abstract

Although it is well established that butterfly richness is affected by climate and human factors (e.g. habitat disturbance and degradation) at different spatial scales, the drivers behind these changes vary greatly according to the geographical region and the ecology of the species concerned. It is essential that this variation be understood if trends in diversity are to be predicted with any degree of confidence under a scenario of global change. Here we examine patterns of butterfly species richness among groups differing in degree of habitat specialization, diet breadth and mobility in the north‐west Mediterranean Basin, a European hotspot for this taxon. We analyze a large number of butterfly communities and take into consideration the main potential drivers, that include climatic, geographic and resource variables, landscape structure and human environmental impact at different spatial scales. Our study shows that both climatic and anthropogenic factors play an important role in determining butterfly species richness in the north‐west Mediterranean Basin, but that their relative impact differs between specialist and generalist groups. At lower altitudes, water availability, a product of the interplay between temperature and rainfall, and negative effects of temperature appear as the most determinant factors. Maximum diversity was observed at mid‐altitudes, which reveals the importance from a conservation point of view of Mediterranean mountain ranges. The results suggest serious population declines in specialist species restricted to mountain areas as a result of climate warming in combination with habitat loss caused by the abandonment of grazing and mowing. They also suggest negative trends for generalist species due to an increase in aridity in combination with an increase in intensification of human land use in lowland areas. Such synergies are expected to lead to rapid declines in Mediterranean butterfly populations in the coming years, thereby posing a severe threat for the conservation of European biodiversity.

Beyond annual and seasonal averages: using temporal patterns of precipitation to predict butterfly richness across an elevational gradient

“…We find that biotic-abiotic relationships vary greatly across an elevational gradient, which is likely to be especially true for Mediterranean climates where water stress can play a large role in determining species richness (Stefanescu et al, 2004(Stefanescu et al, , 2011. At both the lower sites used in this study (Suisun and Gates), variables that describe temporal patterns of precipitation (e.g.…”

Novel communities from climate change

“…number of food plant species), which have experienced relatively greater advances in their phenology than generalist butterflies [34]. Interestingly, other components of global change, namely the degree of intensification of human land use and aridity, affect generalist butterflies more severely than does climate change, while specialized butterflies showed serious richness and population declines with increasing temperatures [35].…”

Impacts of Global Change on Mediterranean Forests and Their Services

“…Determining if these changes in distribution will be fast enough to cope with current climate change, or conversely if species and communities are acquiring climatic debts, is therefore crucial [94]. Ample evidence suggests that these distributional changes are ultimately influenced by microclimatic effects, behavioral buffering and genetic and epigenetic adaptations [95][96][97][98][99]. Biotic interactions can also strongly modify the species-specific capacity to disperse and thus should also be included for developing more robust models for predicting future species distributions [100].…”