Urbanisation drives inter- and intraspecific variation in flight-related morphological traits of aquatic insects at different landscape scales

Abstract

Urbanisation, as an unstoppable global phenomenon, has led to decreasing connectivity between habitats, which gives strong pressure on organisms. Current research has barely investigated urban effects on aquatic insect species traits. Here, we investigated how inter- and intraspecific variations of flight-related morphological traits change along an urban gradient in three species of Dytiscidae at different landscape scales. We collected specimens in 30 urban wetlands in Helsinki, Finland. We measured flight-related traits, including body length, pronotum length, elytron length, and the hind wing length and area. With linear models, we modelled how flight-related traits of the three species responded to the percentage of impermeable surfaces in buffers with nine different radii: 100, 200, 300, 400, 500, 600, 800, 1000 and 1200 m. Our results show that (a) Ilybius ater was not affected by urbanisation in traits, indicating that some species are good dispersers and pre-adapted to urbanisation. (b) The other two species, Acilius canaliculatus and Hydaticus seminiger, exhibited different patterns along the urban gradient, suggesting species utilise different strategies to cope with movement barriers in urban landscapes. (c) Species were affected by urbanisation at different scales, suggesting species have different ability to adjust morphological plasticity to endure movement barriers caused by urbanisation. This study reveals that urban land-use change can have complex effects on inter- and intraspecific variation of aquatic insects. We highlight that urban planning should consider at which scale target species can endure urbanisation, to create an effective network of urban ponds for aquatic biodiversity conservation.