Olfactory homing and dispersal of coral reef fishes in the Great Barrier Reef, Australia

Dispersal of plants and animals from their site of origin is a fundamental process that profoundly impacts the biogeography, ecology and evolution of life on earth.;The purpose of this thesis is to examine the effect of life history, behavior and sensory biology on dispersal in coral reef fishes. We used genetic markers to analyze dispersal patterns in two species of damselfish both within reef groups separated between 4-23 km and between reef groups separated by 125 km. Acanthochromis polyacanthus is a species without a pelagic larval dispersal phase and Pomacentrus coelestis is a species with a pelagic larval period of 16-26 days. A. polyacanthus showed limited dispersal between all reefs with a strong correlation between genetic and geographic distance. A. polyacanthus broods consisted of full siblings and even as adults some related individuals remained together. There was no evidence for inbreeding. Sex-biased dispersal and/or assortative mating may contribute to maintaining genetic diversity. P. coelestis showed no genetic differences within reef groups, but showed a small, statistically significant difference between reef groups.;Pomacentrus coelestis and Ostorhinchus doederleini , a cardinalfish with limited gene flow within a reef group, prefer the odor of their settlement reef over neighboring reefs. We found in both species that exposure to water from another reef over a period of 5 days did not change odor preference to a new odor. This result shows that olfactory preferences are stable over time. Olfactory imprinting before leaving the home reef would result in a stable preference that would allow larvae to recognize the odor halo around the natal reef throughout the larval period. To determine the sensitive period of olfactory imprinting in a reef fish we tested the olfactory preference for the host anemone in the damselfish Amphiprion melanopus after exposure to an anemone for different periods of time before and after hatching. The sensitive period for olfactory imprinting is the hour and a half surrounding hatching. These experiments demonstrate that olfactory preferences formed through olfactory imprinting at hatching combined with a reef fish's behavior and life history influence its dispersal capability.