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Chromosomal inversions can play an important role in adaptation, but the mechanism of their action in many natural populations remains unclear. An inversion could suppress recombination between locally beneficial alleles, thereby preventing maladaptive reshuffling with less‐fit, migrant alleles. The recombination suppression hypothesis has gained much theoretical support but empirical tests are lacking. Here, we evaluated the evolutionary history and phenotypic effects of a chromosomal inversion which differentiates annual and perennial forms of Mimulus guttatus. We found that perennials likely possess the derived orientation of the inversion. In addition, this perennial orientation occurs in a second perennial species, M. decorus, where it is strongly associated with life history differences between co‐occurring M. decorus and annual M. guttatus. One prediction of the recombination suppression hypothesis is that loci contributing to local adaptation will predate the inversion. To test whether the loci influencing perenniality pre‐date this inversion, we mapped QTLs for life history traits that differ between annual M. guttatus and a more distantly related, collinear perennial species, M. tilingii. Consistent with the recombination suppression hypothesis, we found that this region is associated with life history in the absence of the inversion, and this association can be broken into at least two QTLs. However, the absolute phenotypic effect of the LG8 inversion region on life history is weaker in M. tilingii than in perennials which possess the inversion. Thus, while we find support for the recombination suppression hypothesis, the contribution of this inversion to life history divergence in this group is likely complex. [ABSTRACT FROM AUTHOR]

Germination is determined by the depth of primary dormancy and the dynamics of secondary dormancy induction. We assess how dark imbibition at cool temperatures influences primary dormancy breakage and secondary dormancy induction, and how the depth of primary dormancy influences secondary dormancy induction. We manipulated primary dormancy by maturing seeds at two temperatures ('pre-dispersal') known to induce different levels of primary dormancy, and by employing genotypes that differ in primary dormancy. To assess primary dormancy breakage and secondary dormancy induction, seeds of each genotype and maturation treatment were imbibed in the dark at one of four temperatures ('post-dispersal') for one of three durations. Germination proportions were recorded. Seed -maturation condition and genotype influenced the degree of primary dormancy breakage in response to dark stratification and in the optimal temperature for dormancy breakage. Secondary dormancy induction was strongest in cool-matured seeds and seeds stratified at warmer temperatures for longer durations. These effects were consistent across genotypes. Maturation temperature influenced the expression of genetic variation for primary but not secondary dormancy, which showed little genetic variation. Seed-maturation temperature influenced primary and secondary dormancy induction by dark imbibition, and it also influenced the expression of genetic variation for temperature-dependent dormancy breakage. Cool seed-maturation induced primary dormancy in a genotype-specific manner and enhanced secondary dormancy induction. Post-dispersal temperature also influenced primary dormancy breakage and secondary dormancy induction. The observed interactions between primary and secondary dormancy, and between pre- and post-dispersal temperature, are expected to influence life-history expression in nature. [ABSTRACT FROM AUTHOR]