Plant invasion alters movement behaviour in endangered butterflies but not their morphology or genetic variability

Abstract

Invasions of alien plants often result in biodiversity loss and may impact the biology of native species. However, the effects of biological invasions on the behavioural responses of native species have rarely been investigated. We studied how the alteration of habitat due to the invasion of alien goldenrod (Solidago spp) affects a native butterfly, the scarce large blue Phengaris teleius, which is a flagship species for grassland biodiversity conservation. To better understand immediate responses in flight behaviour (daily movements, resting, and dispersal) to a new habitat, we performed observations of experimentally translocated butterflies of two origins (invaded vs. non-invaded habitats) to four different environments: invaded habitat, non-invaded habitat, invaded matrix, non-invaded matrix. Moreover, we tested whether the level of invasion may be related to the variation in morphological traits associated with flight (wing size, body mass) and genetic variability. Flight behaviour was affected by the high goldenrod cover and the sex of the butterflies, regardless of the butterflies’ origin. In the habitat and matrix invaded by goldenrod, the butterflies tended to display dispersal behaviour more often compared to the non-invaded ones. Flight distances were longest in the matrix with goldenrod and resting time was longest in habitats invaded by goldenrod. Analysis of morphological traits as well as eight microsatellite loci did not reveal significant differences in morphology or genetic variation among the populations studied.