The effect of temperature and habitat quality on abundance of the Glanville fritillary on the Isle of Wight: implications for conservation management in a warming climate

Abstract

Creating variation in microclimates through habitat management is often advocated as a way of ameliorating the impact of climate warming, although the effectiveness of microclimate management has rarely been studied. We compared temporal variation in habitat quality (the availability of suitably warm microclimates) and ambient air temperature on the abundance of a highly thermophilous species of butterfly, the Glanville fritillary Melitaea cinxia, at one site on the south coast of the Isle of Wight, UK, from 1997 to 2010. Ground temperatures beneath the various habitat successional stages were measured and compared, and the relationship between butterfly abundance and hostplant and weather variables was examined. Temporal variation in habitat quality was almost twice as strong as a predictor of butterfly abundance as ambient air temperature. We found no relationship between abundance and rainfall. Comparisons of ground temperatures beneath habitats showed that earlier successional stages were considerably warmer than later successional stages, and the distribution of Glanville fritillary larval ‘webs’ within plots was restricted to these warmer habitats. Hostplants selected for oviposition by gravid females were also considerably warmer than ambient temperature. The importance of habitat quality reinforces the notion that thermophilous insects would benefit from site management practices that create thermally diverse environments. Heterogeneous habitats provide refugia for species intolerant of climate change, as well as opportunities for range expansion.