Extreme weather affects colonization-extinction dynamics and the persistence of a threatened butterfly

1. Extreme weather events can be expected to increase in frequency in the future. Our knowledge on how this may affect species persistence is, however, very limited. For reliable projections of future persistence we need to understand how extreme weather affects species’ population dynamics.

2. We analysed the effect of extreme droughts on the host plant (Succisa pratensis), colonization-extinction dynamics, and future persistence of the threatened marsh fritillary (Euphydryas aurinia). Specifically, we studied a metapopulation inhabiting a network of 256 patches on Gotland (Sweden), where the summer of 2018 was the driest ever recorded. We analysed how the frequency and leaf size of host plants changed between 2017 and 2019, based on 6833 records in 0.5 m2 sample plots. Using turnover data on the butterfly from 2018 to 2019 we modelled local extinction and colonization probabilities. Moreover, we projected future population dynamics with an increasing frequency of extreme years unde...