Here are the results of our latest study investigating the global genetic structure and demographic history of populations of blacktip reef sharks (C. melanopterus) throughout its Indo-Pacific range investigated from more than 1000 samples!
Vignaud TM, Mourier J, Maynard JA, Leblois R, Spaet J, Clua E, Neglia V, Planes S (Accepted) Blacktip reef sharks, Carcharhinus melanopterus, have high genetic structure and varying demographic histories in their Indo-Pacific range. Molecular Ecology. Doi : 10.1111/mec.12936
Figure: Genetic structure diagram produced by the DAPC analysis – each vertical bar represents an individual, and each color represents the probability of belonging to one of the
genetic clusters (top). Sampling locations are shown on the bottom in the Indian and Pacific oceans (left) and in French Polynesia (right).
For free-swimming marine species like sharks, only population genetics and demographic history analyses can be used to assess population health/status since baseline population numbers are usually unknown. We investigated the population genetics of blacktip reef sharks, Carcharhinus melanopterus; one of the most abundant reef-associated sharks and the apex predator of many shallow water reefs of the Indian and Pacific Oceans. Our sampling includes 4 widely separated locations in the Indo-Pacific and 11 islands in French Polynesia with different levels of coastal development. 14 microsatellite loci were analysed for samples from all locations and 2 mitochondrial DNA fragments, the control region and cytochrome b, were examined for 10 locations. For microsatellites, genetic diversity is higher for the locations in the large open systems of the Red Sea and Australia than for the fragmented habitat of the smaller islands of French Polynesia. Strong significant structure was found for distant locations with FST values as high as ~0.3, and a smaller but still significant structure is found within French Polynesia. Both mitochondrial genes show only a few mutations across the sequences with a dominant shared haplotype in French Polynesia and New Caledonia suggesting a common lineage different to that of East Australia. Demographic history analyses indicate population expansions in the Red Sea and Australia that may coincide with sea level changes after climatic events. Expansions and flat signals are indicated for French Polynesia as well as a significant recent bottleneck for Moorea, the most human-impacted lagoon of the locations in French Polynesia.