Project: Barriers to cross-shelf coral connectivity in the Florida Keys

NSF Award Abstract:

Coral reefs in the Florida Keys are in severe decline, which is the most prominent along the offshore reef tract while many nearshore reefs retain high coral cover. Why then coral larvae produced from surviving nearshore patches do not recolonize offshore reefs? The investigators hypothesize that such cross-shelf migrants do not survive in the new habitat due to genetic specialization for different environmental conditions, specific to their reef of origin. This project will analyze genetic diversity of coral populations to quantify the severity of this barrier in three common coral species. This will be the first study to assess the strength of ecological barriers to coral dispersal across the seascape, which will fill an important knowledge gap that currently precludes informed assessment of threats to Florida reefs and development of accurate models to forecast their future. The project includes a variety of broader impact activities. Public outreach: This project is very well poised to raise public awareness of ongoing biodiversity loss. The investigators regularly give public lectures at diverse Austin venues, such as Science Under the Stars, Science in the Pub, and Nerd Nite. The progress of the project will be followed by press releases, materials on the University of Texas public outreach web page Know and in The Daily Texan. K-12 outreach: Two interns from Crockett High School and will be involved in the research. Graduate education: The project will be the main PhD theme for one full-time graduate student. Undergraduate education: The primary investigator regularly employs undergraduates. In this project they will participate in field experiments and sample processing, and later assigned individual sub-projects. Promotion of rapid data sharing: All sequencing data will be made available for unconditional use prior to publication. Specifically, the investigators will rapidly share new coral genome data, as well as data on genome-wide variation in coral populations.

The project consists of four parts, each of which is designed to demonstrate the action of divergent selection among nearshore and offshore reefs and to obtain quantitative estimate of its demographic impact. (1) To look for genomic signatures of ongoing selection between inshore and offshore habitats. The research team will perform genome-wide genotyping in three coral species representing alternative life histories and replicate the nearshore-offshore population comparison along the Florida Reef Tract. (2) To confirm continuous action of selection by comparing the extent of inshore-offshore divergence among juveniles and adults. Juveniles are presumed to have experienced local selection for shorter time and hence should show less cross-shelf divergence at the candidate loci. (3) To demonstrate association of genotypes at the candidate loci with local fitness by quantifying in situ growth and survival of genotyped juveniles. This part as well as part 2 is expected to provide quantitative estimates of the strength of selection against cross-shelf immigrants. (4) To verify the obtained estimates by simulating genome evolution under divergent selection and confirming that the proposed selection scenario is compatible with the observed genomic signatures.