| Summary: | 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.
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