TtADAPTIVE PHNEOTYPIC plasticity of wild Capsicum annuum (Solanaceae) to variable environments of water-light availability

Abstract

Adaptive evolution enhances the fitness of populations via the natural selection of genetic variants. Phenotypic plasticity may also increase fitness but it can be neutral or even maladaptive. In natural environments, water and light are factors that generate plastic responses of plants. The purpose of this study was to analyze the adaptive phenotypic plasticity and the genetic differentiation of wild Capsicum annuum populations in northwest Mexico. 20 families from each population were subject to water-light treatments, assessing nine traits. Significant plastic responses as well as interaction of treatments by populations and treatments by families within populations were detected for almost all traits. Differences among and within populations had a genetic basis. Population trait means were not correlated to latitude. Phenotypic differentiation may be the result of different regimes of natural selection in each population (and non-clinal) or due to genetic drift. Variation in magnitude and patterns of multivariate norms of reaction was detected, pointing a potential to produce large phenotypic responses. Multivariate norms of reaction differentiated populations and treatments effects separately. Water and light drove patterns of multivariate responses, allowing to clarify the effect of each factor. Intensities of selection gradients of foliar traits were larger than vegetative traits. Magnitudes of selection differed among populations and treatments. Selection magnitudes decreased as resource availability increased and correlated negatively to population plasticity. Opposed patterns of linear selection suggested a trade-off between leaf area and specific leaf area. Results suggested that natural selection is relevant in the determination of phenotypic responses of wild Capsicum annuum in northwest Mexico.