Research Focus
My lab builds on my experiences in evolutionary ecology and host-microbiome interactions. I aim to understand how the internal and external environment selects for outcrossing (sex among two individuals) versus self-fertilization. I am interested in both abiotic (temperature, salinity, pH) and biotic (sex ratio, genetic diversity, parasite pressure) factors.
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I use two animal systems to explore my research questions. In the lab, I use the nematode Caenorhabditis elegans. In the field, I am studying the mangrove rivulus fish, Kryptolebias marmoratus, one of only two vertebrates known to self-fertilize. While in the field, I also aim to document the ecology of this amazing fish.
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See below for past and current research projects.
Mangrove rivulus research
Like many fish that live in salt water, individual mangrove rivulus can change sex. Some self-fertilizing hermaphrodites change sex to obligately outcrossing males. There are not any females. With sex change, the exterior body of the fish changes as well. Individuals lose the ocellus (spot) at the base of their tail and change color from brown-ish gray to orange.
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To better identify when individuals had in fact changed sex to male, we needed to verify that the changes we see on the outside correspond to the sex change happening on the inside.
Unlike other fish that change sex to increase their reproductive fitness, we found that sex change in the mangrove rivulus offers a significant survival advantage. Those individuals that changed sex to male survived better in a variety of salinity and tidal treatments compared to those individuals that remained hermaphrodites.
Mating strategy can have serious implications on fitness. I am interested in how outcrossing versus selfing (and thus genome heterozygosity) affects both survival and reproductive fitness. We found that an increase of heterozygosity correlates with a decrease in fecundity in two stressful environments (high salinity and tidal).
Different lineages of the mangrove rivulus have varying propensities to change sex. Individuals of some lineages never change sex. In other lineages, up to 70% of the individuals change sex.
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We wanted to know how this "sex change propensity" correlated with different measures of self-compatibility; fecundity, proportion of eggs that are self-fertilized, and the hatch success of those self-fertilized eggs. We found a significant negative relationship among sex change propensity and all three measures of self-compatibility.
Mate selection often correlates with reproductive fitness. In a hilarious experiment to test whether male rivulus showed a preference among hermaphrodite siblings of different ages, we found that males did not show any preference at all, and mostly just spazzed out in the behavior arena.
C. elegans Research
One factor that may impact mating strategy is the food resource availability. We tested this hypothesis and found that C. elegans nematodes do outcross at a higher rate when in low food environments.
It has been documented that parasite pressure does select for outcrossing in C. elegans (Morran et al. 2011). However, these experiments used only one parasitic bacteria type. In an ongoing project, we are documenting fitness in environments of increasing microbiome complexity. The goal is to also perform experimental evolution with these microbiome communities to document how the nematode mating strategy evolves in complex microbiome communities.