Environmental controls on butterfly occurrence and species richness in Israel: The importance of temperature over rainfall.

Butterflies are considered important indicators representing the state of biodiversity and key ecosystem functions, but their use as bioindicators requires a better understanding of how their observed response is linked to environmental factors. Moreover, better understanding how butterfly faunas vary with climate and land cover may be useful to estimate the potential impacts of various drivers, including climate change, botanical succession, grazing, and afforestation. It is particularly important to establish which species of butterflies are sensitive to each environmental driver. The study took place in Israel, including the West Bank and Golan Heights. To develop a robust and systematic approach for identifying how butterfly faunas vary with the environment, we analyzed the occurrence of 73 species and the abundance of 24 species from Israeli Butterfly Monitoring Scheme (BMS-IL) data. We used regional generalized additive models to quantify butterfly abundance, and generalized linear latent variable models and generalized linear models to quantify the impact of temperature, rainfall, soil type, and habitat on individual species and on the species community. Species richness was higher for cooler transects, and also for hilly and mountainous transects in the Mediterranean region (rendzina and Terra rossa soils) compared with the coastal plain (Hamra soil) and semiarid northern Jordan Vale (loessial sierozem soil). Species occurrence was better explained by temperature (negative correlation) than precipitation, while for abundance the opposite pattern was found. Soil type and habitat were insignificant drivers of occurrence and abundance. Butterfly faunas responded very strongly to temperature, even when accounting for other environmental factors. We expect that some butterfly species will disappear from marginal sites with global warming, and a large proportion will become rarer as the region becomes increasingly arid.