Energetic strategies modulate the distribution and abundance of butterflies Data sets

In our study, we hypothesized that species can allocate more energy towards dispersal and reproduction if they compensate their energetic costs by reducing mobility costs or increasing energy uptake or both. Furthermore, according to the central assumption of trait-based approaches, we predict that the effects of morphological traits on species’ distribution and abundance are not direct but mediated by components of the energy budget. <br>As proxies for the energetic strategies of butterfly species associated with the two main components of their energy budget, we first assessed wingbeat frequencies of 102 butterfly species based on high-speed camera footage and their nectar-foraging propensities by estimating the relative time species spent collecting nectar. We combined these data with information on the occupancy of species across Europe and Switzerland, population densities from Switzerland (i.e. regional distribution, local distribution and local abundance) and estimates of the average body size, colour darkness and wing size of species from standardised images. <br>To test whether species compensate an investment into body size and melanisation by reducing their mobility costs or increasing energy uptake as adults, we investigated the effects of interactions between morphological traits and components of the energy budget on the distribution and abundance of species using generalised least-squares models that included a Brownian correlation structure to account for the phylogenetic relatedness of species. <br>We tested our second hypothesis that the effects of morphological traits on the distribution and abundance of species are mediated by components of the energy budget and integrated the complex interdependencies of the considered morphological traits by fitting two different piecewise structural equation models. In the first model, we assumed that morphological traits directly affect the distribution and abundance of species, whereas in the second model we assumed indirect effects via mobility costs and energy uptake. All components of the structural equation models were controlled for species’ phylogenetic relatedness. In addition, we considered habitat availability (i.e. occupancy of larval host plants) as a potential constraint on the distribution of species.