Evolutionary mechanisms influencing the spread of hybridization: genomics, fitness and dispersal

Science Center Objects

Invasive species and hybridization (reproduction between different species or subspecies) – among the most serious threats to native species and biodiversity – provide some of the richest opportunities for “natural experiments” in evolutionary biology. New genomic technologies, combined with long-term hybridization studies in natural populations, provide exciting opportunities to advance our understanding of evolutionary mechanisms that influence hybridization, adaptation, and the spread of invasive species. Rates of hybridization and species invasion are increasing as a result of environmental change and introductions of nonnative species. However, interpreting the evolutionary and ecological significance of hybridization remains a conservation challenge. 

Native westslope cutthroat trout swim in the north fork of the Flathead River in northwestern Montana. This region is recognized as a range-wide stronghold for genetically pure westslope cutthroat trout. However, rainbow trout invasion and hybridization threatens these populations. 
Image courtesy of Jonny Armstrong.

All 12 remaining subspecies of native cutthroat trout are threatened by hybridization with introduced rainbow trout in western North America. This is particularly true for westslope cutthroat trout, where widespread introgression with non-native rainbow trout has created hybrid swarms over extensive geographical areas, providing an excellent system for investigating the genomic and fitness effects of hybridization in wild populations. The goal of this research project is to understand how genetic and evolutionary processes influence fitness, introgressive hybridization, and the spread of nonnative (invasive) alleles in different environments. To achieve this goal, this research project combines genomics, field studies, lab experiments, and extensive computer simulations to: (1) test if hybridization reduces fitness in a consistent way in different environments; (2) test the "spatial sorting" hypothesis, which predicts that some hybrids will have novel phenotypes with increased dispersal propensity, accelerating the spread of hybridization; and (3) identify loci associated with fitness and dispersal in hybrids.


Funding: National Science Foundation, USGS, and Montana Fish, Wildlife and Parks


Collaborators: University of Montana (Drs. Gordon Luikart, Fred Allendorf, and Winsor Lowe), USGS (Dr. Ryan Kovach), and Montana Fish, Wildlife and Parks (Matthew Boyer).