Does range expansion modify trait covariation? A study of a northward expanding dragonfly

Abstract

The adaptive value of correlations among phenotypic traits depends on the prevailing environmental conditions. Differences in selection pressures during species range expansions may therefore shape phenotypic integration. In this study, we assessed variation in behavioral and morphological traits, as well as their covariations, in replicated southern and northern European populations of the northward expanding dragonfly Crocothemis erythraea. Larvae from northern populations were, on average, darker in color, and therefore, better camouflaged than larvae from southern populations. However, there was no difference in activity level. Darkness and activity were positively correlated in larvae from northern populations, whereas this trait covariation was missing in southern populations. These findings indicate the emergence of alternative strategies in time-limited northern populations, a higher activity level that required better camouflage through darker coloration, while less active larvae benefited from an energy-saving strategy by reducing the investment in costly traits, such as body darkness. We further found that larger larvae emerged into larger adults, with a higher investment in flight morphology. Our findings imply that phenotypic integration is associated with the northward range shift, potentially differentially shaping fitness consequences, and ecological interactions in southern versus northern populations.

Seasonal time constraints shape life history, physiology and behaviour independently, and decouple a behavioural syndrome in a damselfly

“…Future work on carry‐over effects of seasonal time constraints on the adult pace‐of‐life and fitness may further provide clues on the adaptive function of the decoupling of activity and boldness. Interestingly, the only study that compared trait integration among populations differing in experienced time constraints reported a stronger trait integration in the more time‐constrained populations (Raffard et al 2020). Studies that integrate plastic (within population) and evolutionary (among populations) responses to time constraints are needed to clarify this intriguing, contrasting pattern.…”

Current evidence of climate‐driven colour change in insects and its impact on sexual signals

“…Distributions across different latitudes can also relate to colour variation in insects (Raffard et al., 2020 ; Zheng et al., 2015 ). A study conducted on monarch caterpillars ( Danaus plexippus ) over a 650,000‐km 2 area in the USA and Canada showed comparatively less pigmentation at lower latitude or warmer locations than in individuals found at higher latitude or colder locations (Tseng et al., 2023 ).…”

“…Distributions across different latitudes can also relate to colour variation in insects (Raffard et al, 2020;Zheng et al, 2015).…”