Latitudinal patterns of phenology and age-specific thermal performance across six Coenagrion damselfly species (Odonata)
(English)Manuscript (preprint) (Other academic)
Using a combination of computer simulations and laboratory experiments we test if the thermal sensitivity of growth rates change during ontogeny and if variation in age-specific growth rates can be predicted based on the natural progression of average temperature or thermal variability in the field. Although annual fluctuations in temperature represent a key characteristic of temperate environments, very few studies of thermal performance have considered the ecological importance of the studied traits within a seasonal context. Instead, thermal performance is assumed to remain constant throughout ontogeny and reflect selection acting over the whole life cycle. Our laboratory experiment revealed that the slope of reaction norms of growth rates changed during ontogeny in five out of six species. In four species from Southern and Central Europe, reaction norms were steepest during early ontogeny, becoming less steep later in life (low-temperature acclimation). In one species from Northern Europe, no change in the slope of reaction norms occurred. In the other North European species, reaction norms became steeper during ontogeny (high-temperature acclimation). Because high-latitude species have a short flight season and inhabit a strongly seasonal environment, we had expected high-latitude species to show strong low-temperature acclimation responses. Instead, we found the reversed pattern: low-latitude species displayed strong low-temperature acclimation responses and high-latitude species displayed weak, or even reversed, acclimation responses to low temperatures. Therefore, we suggest that acclimation to low temperatures may be less beneficial and possibly more costly in habitats with rapid seasonal transitions in average temperature. We conclude that thermal performance traits are more dynamic than typically assumed and caution against using results from single ontogenetic stages to predict species’ responses to changing environmental conditions.
IdentifiersURN: urn:nbn:se:umu:diva-62272OAI: oai:DiVA.org:umu-62272DiVA: diva2:576934