Morphological and genetic variation in the speckled wood butterfly (Pararge aegeria L.) among differently fragmented landscapes

We compared morphological and genetic variation between populations of the speckled wood butterfly (Parage aegeria L.) from four landscapes differing in degree of fragmentation: a continuous woodland, a set of woodland fragments, another, more isolated set of woodlots and a highly fragmented area with very small woodland fragments and hedgerows scattered in an intensively used agricultural landscape. Male butterflies were collected, weighed and their wing features (size and colour) measured by means of an image analysis system. We used Polyacrylamide Gel Electrophoresis (PAGE) to investigate generic variation. The dearest morphological differences were found between the large, continuous woodland and the three other areas. Males of this woodland had a paler basal and distal forewing colour and larger yellow patches on the dorsal side of the forewing. Since these features are relevant to thermoregulation and anti-predation, this result suggests differences with respect to microclimate and predation between the study areas. Relative thorax size also increased with degree of fragmentation. Since the thorax contains the flight muscles, this result may relate to differences in patterns of mobility or different costs for the same mobility pattern. The genetic diversity of the butterflies of the large, continuous woodland was significantly higher than in the other study areas. There were also indications for genetic differentiation. Hence, this study may point at adaptive morphological variation in the speckled wood butterfly among differently fragmented landscapes.