Dealing with the heat and a changed prey composition: urban adaptation in the garden spider

Urbanisation leads to a strong homogenisation of biodiversity, as many species go extinct while few species are able to persist in cities across the world. This persistence is caused by tolerance or adaptations towards a.o. urban heating and altered resources. Orb web spiders are predators that experience strong changes in prey composition but also a performance reduction due to thermal stress. Changes in body colouration are an important adaptation to thermal conditions, but they are constrained by nutritional conditions. As city-life would select for paler colouration, reduced costs of producing pigments may provide an explanation for rescue under poor nutritional conditions in urban environments. The project will study the interplay between these two urban selection pressures in the garden spider. This will be achieved by an unprecedented survey of prey in a research platform in Flanders, combined with a quantification of body colouration across urban gradients in Europe. Targeted experiments will subsequently allow understanding of the adaptive value of these phenotypic changes, as well as the potential for genetic evolution.