A pattern of dolphins: the seascape genetics of island populations in protected and uprotected habitats of Oceania
"Teirake! Teirake! (Arise! Arise!)... They come, they come!.. Our friends from the west... They come!.. Let us go down and greet them." The cry of the ‘dreamer’ for the traditional ‘calling of dolphins’ in the Gilbert Islands, Republic of Kiribati, from a first-hand account by Sir Arthur Grimble, A Pattern of Islands, London, John Murray, 1952.
Long-lived, highly mobile top predators, such as dolphins, pose particular challenges to the design and implementation of marine protected areas (MPAs). Researchers are still working to answer questions regarding the appropriate scale of a reserve required to ensure stability of local communities of these species and the proximity of reserves required to provide resilience and connectivity. The islands of Oceania, extending from Melanesia in the west to far Polynesia in the east, represent the world’s most extensive habitat for isolated island (insular) populations of dolphins. Available information from several species in this vast region suggests that each forms a complex metapopulation, or group of spatially separated populations of the same species which interact at some level. It also appears that there are relatively isolated local populations connected by long-term or episodic gene flow.
To understand the potential role of MPAs for these insular populations of dolphins, a comprehensive description of ‘seascape genetics’ is needed. Seascape genetics use samples collected from local communities in habitats chosen to represent connectivity or isolation on a scale from 10s to 1,000s of kilometres. Across Oceania, there is the potential to collect genetic samples in areas where dolphins are protected and where they have been exposed to local hunting or other sources of anthropogenic or human-induced mortality (e.g., accidental death in fishing gear). Scott Baker’s Pew Fellowship project pursues a large-scale study in the western Pacific to gather data on the genetic diversity and relatedness of dolphin populations. With the advent of next generation genetic sequencing technology, he and his colleagues have the potential to greatly enhance the resolution of conventional markers for measuring genetic diversity and differentiation. Where available, independent information on local abundance will be used to predict the types of habitats the dolphins prefer.
Together, descriptions of seascape genetics and the models of habitat preference should provide important data for estimating the distribution, abundance and metapopulation structure of dolphins throughout Oceania. From an understanding of this ‘pattern of dolphins’, Baker’s research will provide a scientific basis to assess the adequacy of existing MPAs for conserving local populations of dolphins and to inform the design of new MPAs intended to help protect top predators.