Phenotypic plasticity can either hinder or promote adaptation to novel environments. Recent studies that have quantified alignments between plasticity, genetic variation and divergence propose that such alignments may reflect constraints that bias future evolutionary trajectories. Here, we emphasize that such alignments may themselves be a result of natural selection and do not necessarily indicate constraints on adaptation. We estimated developmental plasticity and broad sense genetic covariance matrices (G) among damselfly populations situated along a latitudinal gradient in Europe. Damselflies were reared at photoperiod treatments that simulated the seasonal time constraints experienced at northern (strong constraints) and southern (relaxed constraints) latitudes. This allowed us to partition the effects of (1) latitude, (2) photoperiod and (3) environmental novelty on G and its putative alignment with adaptive plasticity and divergence. Environmental novelty and latitude did not affect G, but photoperiod did. Photoperiod increased evolvability in the direction of observed adaptive divergence and developmental plasticity when G was assessed under strong seasonal time constraints at northern (relative to southern) photoperiod. Since selection and adaptation under time constraints is well understood in Lestes damselflies, our results suggest that natural selection can shape the alignment between divergence, plasticity and evolvability.

In 2018, we collected eggs from L. sponsa females that had been sampled from three latitudes in Europe: northern Sweden (northern: 66°N; n=34 females), central Sweden (central: 59°N; n=36) and north-western Poland (southern: 54°N; n=38) on 1 August, 23-27 July and 8-14 August, and 29-30 July respectively.  Thereafter eggs were  hatched and larvae were reared as described in the article. We measured eight traits for 3-6 larvae from each clutch: larval development time between hatching and emergence, adult body mass at emergence, head width, thorax length, thorax width, abdomen length, tibia length (third leg on the right side) and wing length (posterior right wing). Exact landmarks, used to characterise the phenotype (see Supplementary Information 3), were measured from the first larvae that emerged from each clutch, with one clutch of eggs typically consisting of 50-100 eggs.