Partial separation of climatic niche between two cryptic species of Leptidea (Lepidoptera: Pieridae) in the Alpine–Adriatic region

Abstract

Many cryptic species have been recently recognized in the European butterfly fauna, and climatic determinants have been investigated to explain the usually parapatric distribution of these species. Cryptic species of Leptidea, however, are often sympatric throughout Europe, with variable ecological interactions and segregation patterns. Focusing on the highly diverse landscape between the Alps and the Adriatic Sea, we evaluated the climatic and geomorphological correlates of the fine distribution of L. sinapis and L. juvernica, by means of discriminant analysis on 151 sites in a representative region. In addition to reliable records selected from collections and from the literature, we identified 104 specimens from 89 sites by analysing the morphometric variation of male and female genitalia and filtering for consistency between all alternative identification methods hitherto developed for this species complex. We found that L. sinapis is widespread from the coastal plain to the inner mountains, up to 1800 m above sea level (a.s.l.), whereas L. juvernica is restricted to the mountainous areas, inhabiting also the bottom of pre-alpine valleys, as low as 200 m a.s.l. Despite that the two species are often syntopic, L. juvernica is more frequent in areas with more intense rainfall and steeper slopes, whereas L. sinapis may occur in a broader range of conditions, also in warmer sites with a wider temperature range.