The genetic architecture and evolution of life history divergence among perennials in the Mimulus guttatus species complex

Ecological divergence is a main source of trait divergence between closely
related species. Despite its importance in generating phenotypic
diversity, the genetic architecture of most ecologically relevant traits
is poorly understood. Differences in elevation can impose substantial
selection for phenotypic divergence of both complex, correlated suites of
traits (such as life history), as well as novel adaptations. Here, we use
the Mimulus guttatus species complex to assess if divergence in elevation
is accompanied by trait divergence in a group of closely related perennial
species, and determine the genetic architecture of this divergence. We
find that divergence in elevation is associated with differences in
multivariate quantitative life history traits, as well as a unique trait;
the production of rhizomes, which may play an important role in
overwintering survival. However, the extent of phenotypic divergence among
species depended on ontogeny, suggesting that species also diverged in
investment strategies across development. Lastly, we show that the genetic
architecture of life history divergence between two species is simple,
involving few mid to large effect Quantitative Trait Loci (QTLs), and that
the genetic architecture of the ability to produce rhizomes changes
through development, which has potential implications for hybrid fitness
in the wild.