Genotype-environment interaction and the maintenance of genetic variation: an empirical study of Lobelia inflata (Campanulaceae)

Genetic variation in natural populations often occurs at levels suggesting the action of processes such as frequency-dependent selection, heterozygote advantage, and variable selection. However, the maintenance of genetic variation in fitness-related traits remains incompletely explained.  Obligately self-fertilizing populations of Lobelia inflata(Campanulaceae L.) are characterized by high levels of genetic variation, strongly implying balancing selection.  L. inflataoffers an exceptional opportunity for an empirical test of genotype-environment interaction (GxE) as a variance-maintaining mechanism under fluctuating selection: L. inflatais monocarpic and reproduces only by seed, facilitating assessment of lifetime fitness; genome-wide homozygosity precludes some mechanisms of balancing selection, and microsatellites are, in effect, genotypic lineage markers. Here, we find support for the temporal GxE hypothesis using a manipulated space-for-time approach across four environments: a fie...