UCB Moorea Class: Biology and Geomorphology of Tropical Islands

Natural and anthropogenic disturbances are changing coral reef systems at local and global scales. In Mo’orea, French Polynesia, it is unsure whether a Pocilloporid-and Poritid-dominant reef represents either a transitional, recovering community or a new, stable community (Pratchett 2010). Understanding the species-specific associations between coral-symbionts and their coral hosts will provide a more precise look at how symbionts contribute to their relationship. To better understand this mutualism, this study combined field surveys with phylogenetic analyses to examine the species-specific association between Trapezia crabs and their Pocillopora coral hosts and ask more broadly if there is an association between environmental variables and a morphological phylogeny of Trapezia. There was a significant association between certain species of Trapezia and Pocillopora (Likelihood ratio, x²=84.49, df=16, p=<0.0001*), whereT. rufopunctata was found most frequently withP. edyouxi (80.75%) andT. serenei onP. meandrina (63.4%) andP. verrucosa (37.50%). Discriminant analyses support that differences between crab communities are largely attributed to the morphological features (coral size and branching depth) of coral hosts. Field observations paired with a morphological phylogeny support a trend where similar sized corals were found to be associated with more closely related crab species. Understanding the degree of species-specific associations allows us to better grasp how coral communities and their symbionts will change with natural and anthropogenic episodic changes