Latitudinal and voltinism compensation shape thermal reaction norms for growth rate

Abstract

Latitudinal variation in thermal reaction norms of key fitness traits may inform about the response of populations to climate warming, yet their adaptive nature and evolutionary potential are poorly known. We assessed the contribution of quantitative genetic, neutral genetic and environmental effects to thermal reaction norms of growth rate for populations of the damselfly Ischnura elegans. Among populations, reaction norms differed primarily in elevation, suggesting that time constraints associated with shorter growth seasons in univoltine, high-latitude as well as multivoltine, low-latitude populations selected for faster growth rates. Phenotypic divergence among populations is consistent with selection rather than drift as Q ST was greater than F ST in all cases. Q ST estimates increased with experimental temperature and were influenced by genotype by environment interactions. Substantial additive genetic variation for growth rate in all populations suggests that evolution of trait means in different environments is not constrained. Heritability of growth rates was higher at high temperature, driven by increased genetic rather than environmental variance. While environment-specific nonadditive effects also may contribute to heritability differences among temperatures, maternal effects did not play a significant role (where these could be accounted for). Genotype by environment interactions strongly influenced the adaptive potential of populations, and our results suggest the potential for microevolution of thermal reaction norms in each of the studied populations. In summary, the observed latitudinal pattern in growth rates is adaptive and results from a combination of latitudinal and voltinism compensation. Combined with the evolutionary potential of thermal reaction norms, this may affect populations' ability to respond to future climate warming.

Combined effects of larval exposure to a heat wave and chlorpyrifos in northern and southern populations of the damselfly Ischnura elegans

“…In line with the higher numbers of generations per year at southern latitudes, southern larvae were growing faster than the northern larvae (Shama et al, 2011;Stoks et al, 2012). Yet, despite the higher frequency of heat waves at southern latitudes (Orlowski and Seneviratne, 2012), we found little indication of a higher ability to withstand a heat wave in southern larvae.…”

Evolutionary Ecology of Odonata: A Complex Life Cycle Perspective

“…In contrast, trait-mediated carry-over effects from the adult stage to offspring traits and fitness, i.e., maternal effects (67), are poorly documented in odonates. Studies that looked specifically at maternal effects on larval growth and development using a breeding design suggested them to be weak (103) or absent (88). However, parasite-mediated maternal effects have been demonstrated.…”

Rapid range expansion increases genetic differentiation while causing limited reduction in genetic diversity in a damselfly

“…The finding that the decrease in genetic diversity is rather subtle is indicative of a range expansion where edge populations are established from a high number of individuals and possibly multiple colonization waves. This is a realistic scenario in our case as the possible migration routes from different core regions and the high dispersal capability commonly observed in damselflies (Conrad et al, 1999;De Block et al, 2008;Shama et al, 2011) could allow for a high migration rate. Unfortunately, the general low genetic differentiation between our populations did not allow estimating migration rates between populations.…”

“…Both models with admixture and without admixture were used in the simulations. As dispersal can be expected to be high in damselfly species (Conrad et al, 1999;De Block et al, 2008;Shama et al, 2011), the former is considered more plausible. Correlated allele frequencies were assumed and the admixture model simulations were run with and without prior information on the population of the individuals.…”