Spatial scale-dependent effects of urbanisation on phenotypic traits in a thermophilous grasshopper

• Published in: Behavioral ecology and sociobiology 2023-05, Vol.77 (5), p.54, Article 54
• Main Authors: Waterschoot, Béranger Olivier Gilles, Bataille, Gwennaël, Van Dyck, Hans
• Format: Article
• Language: English
• Subjects: Animal Ecology; Anthropogenic factors; Artificial environments; Behavioral Sciences; Biomedical and Life Sciences; Conspecifics; Divergence; Exploratory behavior; Frequency ranges; Functional morphology; Grasshoppers; Human influences; Impact analysis; Life Sciences; Local population; Metabolic rate; Microclimate; Morphology; Natural selection; Original Article; Orthoptera; Phenotypic plasticity; Phenotypic variations; Population studies; Populations; Predation; Size effects; Song; Urban areas; Urban environments; Urban populations; Urbanization; Zoology
• ISSN: 0340-5443; 1432-0762
• DOI: 10.1007/s00265-023-03325-7

Urban environments are characterised by different microclimates, ecological resources and habitat connectivity compared to nonurban environments. Hence, urban environments may affect phenotypic variation of local populations relative to populations in adjacent nonurban environments through different mechanisms (phenotypic plasticity, natural selection, phenotypic sorting). We analysed the effects of urbanisation on phenotypic traits in adults of the grasshopper Chorthippus brunneus at three spatial scales (0.5, 3, and 5 km). Traits included functional morphology, personality-related behaviours (i.e. boldness and exploration), metabolic rate and song parameters. Our experimental tests pointed to several lines of behavioural divergence between individuals of urban and nonurban populations. Grasshoppers of urban population origin were on average shyer and less explorative, but they were more rapid to reach the edges of an artificial environment deprived of any food or conspecifics compared to individuals of nonurban population origin. Songs of urban grasshoppers were characterised by a narrower frequency range than songs of nonurban grasshoppers. Their constitutive bursts of sound (echemes) were more spaced out than songs of nonurban conspecifics. Interestingly, we found more autotomized grasshoppers (i.e. self-amputated individuals) in the urban environment, and these individuals tended to be bolder, while also having more spaced echemes in comparison to uninjured conspecifics. We also demonstrate that the spatial scale at which urbanisation showed the most pronounced effects varied considerably for behavioural and song traits. The detectability and size effects of urbanisation on traits may vary with the spatial scale at which urbanisation is studied around focal populations or habitat patches. Our study motivates for a documented characterisation of the multiple and complex effects of urbanisation on functional phenotypic trait values at the intraspecific level. Significance statement We analysed the impact of urbanisation on multiple phenotypic traits of a thermophilous grasshopper species. We integrated information on morphology, physiology, behaviour and song characteristics, and we addressed the relationships of those traits with urbanisation at several spatial scales. Our study points at phenotypic differences between urban and nonurban environments, and we show that such relationships are spatial-scale dependent or sensitive. We provide evidence for