Meeting Abstract
Many broadly-dispersing marine taxa are species rich, show genetic heterogeneity on small spatial scales, and are locally adapted to various environmental conditions. How such genetic subdivisions can emerge despite apparent lack of barriers to genetic exchange continues to be the major paradox of evolution in the sea. One understudied process potentially contributing to genetic structuring in marine populations is variation in larval recruitment. Here, we report an unusual recruitment pattern in the broadcast-spawning coral species Acropora hyacinthus on Yap Island, Micronesia. Reduced representation genotyping of 281 individuals on this isolated reef system demonstrated island-wide panmixia but also a genetically divergent group of juveniles at one out of the four sites sampled, showing elevated inbreeding and familial relatedness, including two pairs of siblings. Notably, adult corals as well as the majority of juveniles at the same site belong to the panmictic gene pool, suggesting that representatives of the inbred lineage co-recruited from elsewhere and are at least partially reproductively isolated from the rest of the island population. Reproductive isolation is further supported by finding several distinct genomic regions of greatly reduced genetic diversity in the inbred lineage, encompassing genes involved in sperm-egg recognition and fertilization that may serve as reproductive barrier loci. We propose that co-recruitment of genetic relatives via cohesive dispersal, a process that was previously unrecognized in marine invertebrates with planktonic larval phase, can generate familial genetic structure on the background of general panmixia and might be important for the emergence of genetically distinct locally adapted ectomorphs and sympatric, cryptic species.
