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.

Large uncertainty in trait responses across insects among overall declines in a subtropical city

“…Insects are extremely diverse, both functionally and taxonomically, and have complex life histories (Schmitt & Burghardt, 2021), making it difficult to discover which traits determine if an insect species will be an urban exploiter or avoider. Determining the scale at which insect species and populations respond to urbanisation is a fundamental pursuit of the landscape ecology of insects (Betts et al 2019), and previous studies have demonstrated the spatial scale at which insects respond to urbanisation differs across taxonomic and functional groups (Chust et al, 2004;González-Césped et al, 2021;Liao & Lin, 2024). Our approach, which tested urbanisation effects on multiple insect orders at a uniform spatial scale, may have missed crucial interactions between traits and urbanisation operating at either smaller or larger spatial scales than examined.…”

Insect ecology and conservation in urban areas: An overview of knowledge and needs

“…Urban density may also select for dispersal-enhancing morphologies within populations or species assemblages, which has been proposed for flight-related traits of aquatic beetles (Liao & Lin, 2024), as well as body size of wild bees (Brasil et al, 2023) and macro moths (Merckx, Kaiser, & Van Dyck, 2018). These patterns, which are also considered a form of ecological filtering, may reflect changes in the costs and benefits of dispersal in urban environments (Ancillotto & Rocco, 2024;Jones & Leather, 2012), although they may also reflect traits of founder individuals in low-dispersal systems, and conclusions are largely uncertain (see also genetics section below) (Federico et al, 2024).…”

“…Lessons from metapopulation ecology and a better understanding of patch quality for specific taxa will be critical to raising urban insect diversity and conserving this as a stable ecosystem component (e.g., Azhar et al, 2024;Liao & Lin, 2024). There are pathways to understanding patch improvement, but above this, integrating connectivity and opportunity for insects in urban areas more broadly and by design will contribute further (e.g., Noël et al, 2024) as will translocations to restore extirpated diversity (e.g., Yagui et al, 2024).…”

“…This picture is, however, nuanced (e.g., Ancillotto & Rocco, 2024; Federico et al, 2024; Ombugadu et al, 2024) and although urban areas can detrimentally impact some insect taxa through the predominance of artificial environments, constrained habitats and disturbances, other taxa can adapt and thrive in the mosaic of semi‐natural and novel environments, management variation and abundant resources (Curry et al, 2024; Hill et al, 2024; Nunes et al, 2024; Plummer et al, 2024; Xu et al, 2024). Lessons from metapopulation ecology and a better understanding of patch quality for specific taxa will be critical to raising urban insect diversity and conserving this as a stable ecosystem component (e.g., Azhar et al, 2024; Liao & Lin, 2024). There are pathways to understanding patch improvement, but above this, integrating connectivity and opportunity for insects in urban areas more broadly and by design will contribute further (e.g., Noël et al, 2024) as will translocations to restore extirpated diversity (e.g., Yagui et al, 2024).…”