Effects of morphology, habitat and weather on the movement behaviour of range-expanding butterfly species
Dispersal capacity is an important trait enabling species to respond to climate change, particularly in fragmented landscapes, where individuals often need to move longer distances to colonise new areas. It is therefore crucial to understand species’ movement behaviour and how it is affected by environmental variables to plan effective conservation measures for a wide range of species. This thesis aimed to enhance the current understanding of the role of dispersal in enabling species to respond to global environmental change using seven species of butterflies. I identified that species and individuals with longer move bouts (step length) cross habitat boundaries more frequently. Because step length is relatively easy to measure for butterflies, it could potentially be used as a general proxy of species dispersal capacity at a landscape level. I also found a higher investment in morphological traits that enhance dispersal capacity for one out of three range-expanding species in newly colonised sites at the range margin. Differences in species dispersal capacity and habitat availability could explain why only one species showed increased investment in dispersal at the margin. Also, there was poor evidence of a relationship between movement and an associated morphological trait; wing length was not associated with increased mobility for two out of four species which suggests that increased dispersal ability may not always be linked to morphological changes during range expansion. Finally, an assessment of the relative importance of temperature, habitat quality and structure on the movements of two species within their habitats revealed no contribution of the habitat variables for one of the species, whilst temperature, habitat size, edge ratio and vegetation height significantly affected movements of the second species. Overall, this thesis highlights that responses to global environmental change are highly dependent on species and its interactions with the environment.
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