Ecological correlates of distribution change and range shift in butterflies

Abstract

1. In order to be effective custodians of biodiversity, one must understand what ecological characteristics predispose species to population decline, range contraction, and, eventually, to extinction. 2. The present paper analyses distribution change (area of occupancy) and range shift (extent and direction) of the threatened and non-threatened butterfly species in Finland, and identifies species-specific ecological characteristics promoting changes in distribution and range. 3. Overall, the range of butterflies has shifted along the climatic isotherms, suggesting that climate change has influenced species’ ranges. Interestingly, though, threatened species have moved very little and not to any consistent direction. 4. The most obvious pattern observed is that ecological specialisation, be it at larval or at adult stage, promotes distribution decline. The analysis further revealed that poor dispersal ability and large body size predispose species to distribution decline. 5. Species ecological traits influence their susceptibility to distribution change and range shift. Thus, as a result of climate change, biological communities may become over-represented by highly dispersive generalists. It is argued that with the kind of ecological information provided here, managers should become proactive and initiate the necessary measures for conservation of species when their populations are still viable instead of reacting only to the imminent extinction risk when it already may be too late.