Abstract
Despite the unique nature of endemic species, their origin and population history remain poorly studied. We investigated the population history of 28 coral reef fish species, close related, from the Gambier and Marquesas Islands, from five families, with range size varying from widespread to small-range endemic. We analyzed both mitochondrial and nuclear sequence data using neutrality test and Bayesian analysis (EBSP and ABC). We found evidence for demographic expansions for most species (24 of 28), irrespective of range size, reproduction strategy or archipelago. The timing of the expansions varied greatly among species, from 8,000 to 2,000,000 years ago. The typical hypothesis for reef fish that links population expansions to the Last Glacial Maximum fit for 14 of the 24 demographic expansions. We propose two evolutionary processes that could lead to expansions older than the LGM: (a) we are retrieving the signature of an old colonization process for widespread, large-range endemic and paleoendemic species or (b) speciation; the expansion reflects the birth of the species for neoendemic species. We show for the first time that the demographic histories of endemic and widespread reef fish are not distinctly different and suggest that a number of processes drive endemism.
Highlights
Despite the unique nature of endemic species, their origin and population history remain poorly studied
Of the four factors used as predictors of haplotype and nucleotide diversity for the 4 genes, the only significant predictors were archipelago for nucleotide diversity of the Gonadotropin-Releasing Hormone (GnRH) intron (W = 82, p-value < 0.05; higher values for Gambier Islands) and families for the S7 intron (H4 = 10.2945, p-value < 0.05; with higher values for Serranidae and lower for Chaetodontidae)
Considering the 24 species displaying population expansion, we found the EBSP (TEBSP) that varied by a factor of 26 for the mitochondrial marker and 250 for the nuclear marker
Summary
Despite the unique nature of endemic species, their origin and population history remain poorly studied. Even if actual patterns of distribution of coral reef fish species are well depicted, the evolution and processes underlying the establishment and maintenance of endemic species remains unclear Despite their unique nature and their potentially higher risk of extinction, the origin and population history of endemic species is poorly studied. Large parts of continental shelves were exposed during low sea level, altering shallow water habitat and likely reducing coral reef area[12,13,14] These dramatic changes to the environment influence the demographic history of populations, leaving a footprint in the pattern of genetic diversity[15] that will vary depending on the range extent of the species (i.e., how much of the global species was affected by the event). We expect to see major differences in the demographic histories of endemic and widespread species
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