Merging Approaches to Explore Connectivity in the Anemonefish, Amphiprion bicinctus, along the Saudi Arabian Coast of the Red Sea

Abstract

The field of marine population connectivity is receiving growing attention from ecologists worldwide. The degree to which metapopulations are connected via larval dispersal has vital ramifications for demographic and evolutionary dynamics and largely determines the way we manage threatened coastal ecosystems. Here we addressed different questions relating to connectivity by integrating direct and indirect genetic approaches over different spatial and ecological scales in a coral reef fish in the Red Sea. We developed 35 novel microsatellite loci for our study organism the two-band anemonefish Amphiprion bicinctus (Rüppel 1830), which served as the basis of the following approaches. First, we collected nearly one thousand samples of A. bicinctus from 19 locations across 1500 km along the Saudi Arabian coast to infer population genetic structure. Genetic variability along the northern and central coast was weak, but showed a significant break at approximately 20°N. Implementing a model of isolation by environment with chlorophyll-a concentrations and geographic distance as predictors we were able to explain over 90% of the genetic variability in the data (R2 = 0.92). For the second approach we sampled 311 (c. 99%) putative parents and 172 juveniles at an isolated reef, Quita al Girsh (QG), to estimate self-recruitment using genetic parentage analysis. Additionally we collected 176 juveniles at surrounding locations to estimate larval dispersal from QG and ran a biophysical dispersal model of the system with real5 time climatological forcing. In concordance with model predictions, we found a complete lack (c. 0.5%) of self-recruitment over two sampling periods within our study system, thus presenting the first empirical evidence for a largely open reef fish population. Lastly, to conceptualize different hypotheses regarding the underlying processes and mechanisms of self-recruitment versus long-distance dispersal in marine organisms with pelagic larval stages, I introduce and discuss the concept of “origin effects”, providing the theoretical background to some of the questions that have arisen during this research. Overall, this thesis has generated significant new insights into the patterns of coral reef fish connectivity, specifically for the Red Sea, where such information has previously been scarce.