Spatio-temporal responses of butterflies to global warming on a Mediterranean island over two decades

1. One very conspicuous sign that warming is affecting the ecology of butterflies are the phenological advances occurring in many species. Moreover, rising temperatures are having a notable impact – both negative and positive – on population abundances. To date, patterns have generally been analysed at species level without taking into account possible differences between populations, which, when they are noted, are mostly attributed to large-scale climate differences across a latitudinal gradient. 2. We use a long-term database (18 years) of butterflies from five sites of the island of Menorca (Balearic Islands, Spain) to investigate how phenology and population dynamics have been affected by climate warming during the past two decades. 3. Both species' phenology and abundance respond differently to warming at a local scale depending on the season. Rising temperatures in spring give rise to greater advancement of the phenology, whereas warming affects population abundance negatively in summer. Additional variability of responses among sites suggests that habitats are involved in the modulation of the aforementioned seasonal effect. 4. We discuss how the effects of temperature could be partially offset in more inland habitats such as forests or deep ravines, especially the latter which represent particularly fresh and humid environments. The positive effect of temperature on ravine populations during the summer suggests that butterflies disperse across habitats as a response to rising temperatures during the season. This dispersal behaviour as a response to warming could be especially important in island ecosystems where the possibilities of modifying altitudinal or latitudinal distributions are often severely limited.PC is funded by a PhD fellowship financed by the Govern de les Illes Balears (FPI-CAIB-2018). This work is framed within project GLC2017-88122-P financed by the Spanish Ministry of Science and Innovation to AT. The Catalan Butterfly Monitoring Scheme is funded by the Departament de Territori i Sostenibilitat de la Generalitat de Catalunya.Peer reviewe