Dependence of Lifetime Fitness on Gene-by-Environment Interaction: Effects of Soil Salinity on an Annual Legume

Abstract

Premise of research. Rapid environmental changes have raised questions about the capacity of plant populations to adapt to novel conditions. Salinity is increasing in both urban and rural areas because of irrigation and road deicing salt. While adaptation to salinity is found in some plant species, salt impairs plant fitness for the vast majority. Breeding to enhance adaptation to salinity has proved difficult, suggesting barriers to adaptation.Methodology. In this project, we assessed the capacity for adaptation to soil salinity. We planted an experimental population of Chamaecrista fasciculata (partridge pea, Fabaceae) in both roadside and greenhouse conditions. We assessed lifetime fitness as a composite of germination, survival, and the number of flowers or fruits produced. We estimated additive genetic variance for fitness in each greenhouse salinity treatment using aster models.Pivotal results. Significant additive genetic variance for fitness was detected in the control treatment in the greenhouse, in the low-salinity treatment in the greenhouse, and in the roadside experimental plot. Gene-by-environment interactions were also significant. This gene-by-environment interaction is caused by both differences in genetic variation among environments and a change in the ranks of the families. In the control and low-salinity treatments in the greenhouse experiment, the relative ranks of fitness among the paternal families visually demonstrate the gene-by-environment interaction.Conclusions. The findings of the roadside experiment demonstrate that this population has the potential to adapt to a salinized environment. This research found a gene-by-environment interaction that may alter the fitness of various families over small geographic scales, such as those found in a roadside. Reducing deicing salt usage may improve the health and quality of roadside ecosystems by enhancing the potential of some species to adapt.