Wing shape patterns among urban, suburban, and rural populations of Ischnura elegans (Odonata: Coenagrionidae)

Abstract

Dragonflies and damselflies (the Odonata) are among the most efficient flying insects. However, fragmentation of the landscape can increase distance between habitats and affect costs of dispersal, thus shaping phenotypic patterns of flight-related traits, such as wing shape, wing loading and wing size. Urban landscapes are highly fragmented, which limits dispersal among aquatic habitats. Hence, strong selective pressures can act upon urban populations in favour of individuals with increased flight performance or may lead to the reduction in dispersal traits. Here, we explore differentiation in morphological flight-related traits among urban, suburban, and rural populations of the damselfly Ischnura elegans, which is one of the most abundant species in both urban and rural ponds in Europe. We sampled 20 sites across Leeds and Bradford, UK, in an urban-to-rural gradient from June to August 2014 and 2015 (N_males = 201, N_females = 119). We compared wing shape among different land use types using geometric morphometrics. Other wing properties analysed were wing aspect ratio, wing loading and wing centroid size. Unexpectedly, no significant effect of urban land use was found on wing shape. However, wing shape differed significantly between males and females. Additionally, females showed significantly larger wing centroid sizes (P < 0.001), increased wing loading (forewings: P = 0.007; hind wings: P = 0.002) and aspect ratio (P < 0.001) compared to males across all land use types. Possible mechanisms driving these results are further discussed.

Keywords: dragonfly, flight performance, geomorphometrics, city, aspect ratio, wing loading, wing size

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