Developing monkeyflowers as a system for evo-phys synthesis
It is widely assumed that physiological tradeoffs are among the primary causes of adaptive evolution. But there is surprisingly little evidence of divergent natural selection on physiological traits under natural conditions. To redress this gap, we need a system for integrative biology, one amenable to multiple empirical tools, including genetics and genomics, laboratory and greenhouse manipulations, natural history and field experiments. These tools are readily available in Mimulus (monkeyflowers). In collaboration with Amy Angert (UBC), I am using one species, Mimulus cardinalis, in particular to investigate the physiology of local adaptation to different environments. My ongoing work includes:
Latitudinal cline in growth and photosynthesis
In M. cardinalis, I found a latitudinal cline in leaf-level photosynthetic rates and whole-plant growth, along a ‘fast-slow’ continuum (Muir & Angert in prep.). Populations from Southern California germinate quicker, have higher photosynthetic rates, and grow faster. Based on life history theory, I hypothesize that a faster, ‘annualized’ life history is favored in environments with a higher frequency of dry years, as in Southern populations, because it is deleterious to invest much in belowground storage if drought may kill plants the following season.
Reciprocal transplant to test for local adaptation to climate
Northern garden: Middle Fork Feather River, Plumas County, California
Southern Garden: King Creek, San Diego County, California
Genetics of adaptation: QTL mapping physiological traits underlying adaptation
I am also collaborating with Lila Fishman (Montana) to identify loci underlying physiological differences between Southern and Northern populations of M. cardinalis.
Scaling up: connecting adaptation and diversification in monkeyflowers using herbarium specimens
This is a group project looking at the connection between adaptation to climate, traits, and diversification rates in the genus Mimulus as a whole. So far, we have found significant variation in diversification rates, indicating that some clades of monkeyflowers may speciation faster. Next we are testing whether diversification is linked to rates of adaptation and trait divergence. We are measuring key ecological traits using herbarium specimens.