Phosphoglucose isomerase genotype effects on life history depend on latitude and food stress

Abstract

Summary1.Phosphoglucose isomerase (Pgi) genotypes differ in life‐history traits and shifts in their frequencies are thought to contribute to latitudinal gradients in life history. Yet, it is unstudied whether the life‐history effects of Pgi are invariant across latitudes. Further, while genetic variation at the Pgi locus is thought to be maintained by genotype‐by‐environment interactions and by life‐history trade‐offs involving resource allocation, the effects of food stress on Pgi genotype effects are largely unstudied.2.We compared Pgi allozyme genotype effects on life history between northern and southern populations of the damselfly Ischnura elegans in a common garden experiment where we manipulated food stress.3.Pgi genotypes differed in larval development time and body mass, but neither in larval growth rates nor in adult life span.4.The effect of the Pgi genotype on larval development time differed between latitudes, suggesting interactions with the latitude‐specific genetic background and/or maternal effects. Pgi genotype effects on both development time and body mass were dependent on food stress and indicated a trade‐off between both fitness‐related traits associated with the Pgi gene.5.The newly identified interaction between the Pgi genotype and latitude, the poorly studied Pgi genotype‐by‐food stress interactions and the observed life‐history trade‐offs associated with the Pgi genotypes can all potentially contribute to maintaining genetic variation at the Pgi locus and to latitudinal patterns in life history. Both types of interactions may also explain the poorly understood differences in the Pgi genotype effects on life history among studies of the same species.