| Understanding the spatial scales over which populations of coral reef fishes are connected is important for elucidating the evolutionary mechanisms generating biodiversity. Describing connectivity also is vital for setting conservation priorities to protect that biodiversity. Direct observation of migration between populations is nearly impossible for species, like reef fish, with pelagic larvae; however, genetic connectivity can serve as a surrogate for population connectivity. This thesis compares patterns of genetic connectivity of several coral reef fishes over multiple spatial scales.;On the finest scale, among the islands of Fiji, there is widespread genetic homogenization within most, but not all, of the species I examined. On the next highest spatial scale (between Fiji and the rest of Melanesia), I demonstrated regional endemism within five species of fishes based on both molecular and morphological evidence. Expanding further, I investigated two of those species (Amphiprion melanopus and Pomacentrus moluccensis : Pomacentridae) whose ranges are entirely within Melanesia and Indonesia. At this scale there is evidence for restricted gene flow across the Indo-West Pacific archipelago, ultimately leading to the evolution of unique haplotypes found only in peripheral populations. Finally, at the largest spatial scales, I used the widely distributed species Halichoeres hortulanus (Labridae) to investigate gene flow across the Indian and Pacific oceans and discovered significant barriers to gene flow between these oceans occurring across the Indonesian archipelago.;Taken as a whole, this dissertation demonstrates that despite having pelagic larvae and the ability to distribute genes over broad geographic differences, some coral reef fish populations are geographically structured, but the magnitude of that structure depends on the spatial scale considered. These data have two major conservation implications. The first is that we have underestimated the alpha biodiversity in the Indo-Pacific region, as several putatively widespread monospecific taxa are actually assemblages of geographically restricted taxa. Secondly, within archipelagos there is sufficient gene flow to homogenize populations and thus providing the maximum functional unit for conservation priority setting. However as the spatial scale increases, barriers to gene flow may necessitate parallel development of twin networks flanking the biogeographic barrier. |
