The processes that drive speciation in the marine environment are a constant source of debate among evolutionary biologists. Geographic isolation is considered the primary evolutionary force, where species evolve in allopatry due to physical barriers which act to isolate populations. Coral reefs however, represent a challenge to this understanding. They contain the most diverse vertebrate communities in the world despite existing in a medium where physical barriers are rare. Many coral reef fish also co-exist with closely related taxa which they are known to hybridise with in the wild. The presence of viable hybrids demonstrates a lack of reproductive barriers among many coral reef fishes. So how does diversity originate and how is it maintained in these high gene flow environments? Genetic and genomic evidence suggest that natural selection can lead to speciation in the absence of physical barriers. This study proposes to use genomic scans to investigate the role of natural selection in the maintenance of diversity among two groups of hybridising species. Contemporary patterns of selection will also be compared among populations to understand the interplay between geographic isolation and localised selection.
Sam completed his BSc. (Hons.) in Marine Science at Curtin University where he studied hybrid reef fish at Cocos (Keeling) Islands and Christmas Island in the Indian Ocean. He then worked as a research intern at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia. This time, studying colour polymorphism in coral reef fish and joining expeditions to the remote Phoenix Islands Protected Area in the Central Pacific. Upon returning home, Sam spent a memorable year living in a shack in Shark Bay, Western Australia. He worked as an Aquarist, Curator and Dive Master in the world heritage site and after spending a little too long away from civilization he decided he was ready to do a PhD. Sam is studying the role of natural selection and hybridisation in the evolution of coral trout (Plectropomus) and pygmy angelfish (Centropyge). His research focuses on the Coral Sea where he will combine genetic and ecological tools to study these species.