The habitat preferences and phenology of a generalist butterfly species, Melanargia galathea (marbled white), at multiple spatial and temporal scales, within the British Isles

Abstract

The climate is undergoing unprecedented rates of change, altering species’ abundances, phenologies and distributions and providing a huge challenge to conservation biology. I look at the distribution of a generalist British butterfly, Melanargia galathea, at multiple temporal and spatial scales, to provide detailed knowledge on this species’ ecology useful for its conservation under a changing climate.
At a broad spatial scale I estimated demographic parameters for six generalist British butterflies. Carrying capacities differed between occupied habitats, with estimates varying from 7 (P. c-album; heathland/moorland) to 279 (P. tithonus; neutral grassland) butterflies per hectare per year. Average intrinsic growth rates in newly colonised sites varied from 0.26 (P. c-album) to 0.56 (P. tithonus). I suggest that these differences should be incorporated into species distribution models to increase the accuracy of predictions of future ranges.
Phenological asynchrony may occur when interacting species differ in the rate at which they respond to climate change. I show that some M.galathea individuals may be emerging before a key nectar source, Centaurea scabiosa is available. However, topographical diversity lengthened the flowering period of two key nectar species by up to 14 days and could therefore decrease the likelihood of phenological asynchrony.
The diverse microclimates provided by topographically heterogeneous sites may also affect M.galathea behaviour. Using scan samples and point counts I show that the abundance and behaviour of M.galathea differs between microhabitats, with a mean five minute point count of 0.18 butterflies in flat sheltered areas compared with 1.32 in flat exposed areas.
Effective monitoring methods are vital to accurately assess the success of conservation strategies and to estimate demographic parameters. I compared estimates of emergence and population sizes obtained from transect data and mark release recapture data and suggest that an inability to sex individuals during transects could cause bias.