The genetic architecture and evolution of life history divergence among perennials in theMimulus guttatusspecies complex

Abstract

Ecological divergence is a main source of trait differences between closely related species. Despite its importance in generating biodiversity, the genetic architecture of most ecologically relevant traits is poorly understood. In plants, 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 associated with 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 both differences in multivariate quantitative life history traits, as well as a unique trait; the production of belowground stolons, but the extent of phenotypic divergence among species depends on ontogeny. We show that the genetic architecture of this divergence between two perennial species is simple, involving few mid to large effect Quantitative Trait Loci (QTLs). Lastly, we discover that the genetic architecture of the ability to produce belowground stolons changes through development. In sum, perennials of the M. guttatus species complex exhibit substantial phenotypic divergence, which is associated with elevational differences, and is controlled by few genetic changes.

When good species have porous boundaries: weak reproductive isolation and extensive gene flow between Mimulus glaucescens and M. guttatus in northern California

“…Habitat associated with each species was modelled using 2512 georeferenced collection records from the Global Biodiversity Information Facility, which were filtered after download (GBIF; 2194 M. guttatus records: https://doi.org/10.15468/dl.ywy9s3 and 318 M. glaucescens: https://doi.org/10.15468/dl.r93avz; see Supplemental Methods and Results) and environmental data including primary and secondary geological substrates, elevation, and 19 bioclimatic variables (https://www.worldclim.org/), all standardized to a resolution of 2.5 minutes. Species distribution models were constructed using MaxEnt by sampling locations of collection records as well as 1000 randomly located background samples from across the geographic extent to create pseudo-absence data (Coughlan et al 2021). Models were computed separately for each species, and reproductive isolation was inferred based on the number of shared and unshared pixels in the map following equation RI 4C from Sobel and Chen (2014) (see Supplemental Methods and Results).…”

“…For the newly described whole-genome re-sequencing data, we followed protocols described elsewhere for sample preparation, sequencing, and preparation of VCF files (e.g. Coughlan et al 2020, Coughlan et al 2021; see Supplemental Methods for details).…”

Population genomic consequences of life‐history and mating system adaptation to a geothermal soil mosaic in yellow monkeyflowers

“…We investigate how life-history and mating system divergence influence population structure and individual genomic variation in yellow monkeyflowers across geothermal soil mosaic in Yellowstone National Park (YNP). The yellow monkeyflowers of the Mimulus guttatus species complex are a model system for understanding the evolutionary genetics of edaphic adaptation (Lee and Coop 2017;Selby and Willis 2018) and life history (Lowry and Willis 2010;Coughlan et al 2021), phenology (Friedman and Willis 2013;Fishman et al 2014;Kooyers et al 2019), and mating system (Fishman et al 2002) divergence, cre-ating a robust comparative framework. Across a latitudinal range from Alaska to Baja California, M. guttatus populations exhibit alternative annual and perennial ecotypes, with annuals found in ephemeral wet soils and perennials wherever soils remain saturated through the summer (Lowry and Willis 2010;Oneal et al 2014;Twyford and Friedman 2015;Peterson et al 2020).…”

“…The yellow monkeyflowers of the Mimulus guttatus species complex are a model system for understanding the evolutionary genetics of edaphic adaptation (Lee and Coop 2017; Selby and Willis 2018) and life history (Lowry and Willis 2010; Coughlan et al. 2021), phenology (Friedman and Willis 2013; Fishman et al. 2014; Kooyers et al.…”

Developmental evidence for parental conflict in driving Mimulus species barriers

“…Populations of M. caespitosa and M. tilingii occur exclusively at high elevations and appear to be mostly allopatric, with M. caespitosa restricted to Washington state and M. tilingii mostly known from alpine areas of Oregon and California. M. guttatus occupies a more diverse range in western North America, sometimes overlapping with populations of M. caespitosa and M. tilingii (Nesom, 2012; Coughlan et. al ., 2021).…”