Seasonal adaptation and plasticity in the sea slug Alderia willowi

For my NSF postdoctoral fellowship I am studying the relationship between plasticity and seasonal adaptation in the sea slug Alderia willowi using a combination of population genetics, physiology assays, and quantitative genetics experiments. This research takes place at UC Davis in the Bay Lab and at UC Berkeley in the Williams Lab.

The habitat of A. willowi (mudflads at dusk).

Gene by environment interactions and selection for egg size in Alderia willowi

The sacoglossan sea slug Alderia willowi, exhibits striking life-history plasticity. Egg size is bimodal in A. willowi resulting in either a few-large larvae that settle and metamorphose into juveniles several days after being laid, or many-small larvae that spend weeks in the water column feeding and growing. The frequency of egg-mass type shifts seasonally. In my dissertation I showed that egg-mass type is a GXE interaction in A. willowi, with some families exhibiting greater plasticity than others. Egg size can be selected upon significantly increasing the proportion of lecithotrophic egg masses in three generations. Salinity appears to be an important cue for egg-mass type and may also be a selective agent. These experiments show that egg-mass type in A. willowi is heritable and likely controlled by many alleles, some of which are environmentally sensitive.

Genome-wide association test for egg size in Alderia willowi

In my dissertation, I used an evolve and resequence approach to identify the genomic response to selection for increased proportions of lecithotrophy in two environments (low and high salinity) in the poecilogonous sea slug Alderia willowi. I found an association between 10 loci across 8 scaffolds clearly illustrating the polygenic nature of developmental mode in A. willowi. Three of these loci responded to selection significantly and independently of the salinity environment

Convergent evolution of developmental mode in sacoglossan sea slugs

Phenotypic convergence is common but whether phenotypic convergence is due to genetic convergence varies considerably. In the sacoglossan sea slug system, I conducted the I present the first test of genetic convergence for developmental mode between species that exhibit intraspecific variation in developmental mode (poecilogony). I found a significant signal of positive selection in each poecilogonous branch. This shows that scans of positive selection can reveal genetic convergence for developmental mode, but that these signals are not equally shared across all species.

Self-fertilization coupled with greater fecundity in a nemertean worm

Paper here


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