Research

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Current projects in the Galloway lab focus on the evolution of plant reproduction and the early stages of speciation. While many of our projects use Campanula americana (American bellflower) as a study system, we use a variety of taxa depending on the question addressed. We combine molecular genetic analysis, quantitative genetics, and ecological genetics in both lab/greenhouse and field studies in our work.

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One set of projects addresses range-wide patterns of variation in mating system and reproductive biology in C. americana. The ability to self if pollinators aren’t around is greater in northern and western populations. In contrast to the typical explanation, lack of pollinators doesn’t appear to drive the evolution of selfing. Instead, we’ve found that the northern movement of plants after the last glaciation may have favored individuals that could self as it gave them a colonization advantage. We are developing projects to test this directly. In addition, we are exploring range-wide patterns in pollen color and its association with abiotic and biotic selective agents, as well as how both efficient and inefficient pollinators may drive the evolution of floral traits. 

A second set of projects explores incipient speciation. We found substantial reproductive isolation between C. americana populations, with up to 90% reduction in fitness of between-population crosses relative to those within populations! Reproductive isolation is largely limited to crosses between clades and is due to incompatibility between chloroplast and nuclear genes. Interestingly, the chloroplast genome evolves fairly rapidly in C. americana and, in contrast with most other taxa, chloroplasts may be inherited maternally, paternally or from both parents. C. americana is an autotetraploid and polyploidy has been implicated in changing the rate of reproductive isolation. Finally, we are investigating whether reproductive isolation is enhanced or reduced at contact zones between incompatible populations with the goal of understanding the earliest stages of speciation.

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