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, 2 (7), 1592-604

Historic Hybridization and Introgression Between Two Iconic Australian Anemonefish and Contemporary Patterns of Population Connectivity

Historic Hybridization and Introgression Between Two Iconic Australian Anemonefish and Contemporary Patterns of Population Connectivity

M H van der Meer et al. Ecol Evol.


Endemic species on islands are considered at risk of extinction for several reasons, including limited dispersal abilities, small population sizes, and low genetic diversity. We used mitochondrial DNA (D-Loop) and 17 microsatellite loci to explore the evolutionary relationship between an endemic anemonefish, Amphiprion mccullochi (restricted to isolated locations in subtropical eastern Australia) and its more widespread sister species, A. akindynos. A mitochondrial DNA (mtDNA) phylogram showed reciprocal monophyly was lacking for the two species, with two supported groups, each containing representatives of both species, but no shared haplotypes and up to 12 species, but not location-specific management units (MUs). Population genetic analyses suggested evolutionary connectivity among samples of each species (mtDNA), while ecological connectivity was only evident among populations of the endemic, A. mccullochi. This suggests higher dispersal between endemic anemonefish populations at both evolutionary and ecological timeframes, despite separation by hundreds of kilometers. The complex mtDNA structure results from historical hybridization and introgression in the evolutionary past of these species, validated by msat analyses (NEWHYBRIDS, STRUCTURE, and DAPC). Both species had high genetic diversities (mtDNA h > 0.90, π = 4.0%; msat genetic diversity, gd > 0.670). While high gd and connectivity reduce extinction risk, identifying and protecting populations implicated in generating reticulate structure among these species should be a conservation priority.

Keywords: Amphiprion; Great Barrier Reef; Lord Howe Island; coral reef fish; endemism; extinction risk; isolated islands.


Figure 1
Figure 1
(A) An outgroup rooted phylogram of D loop sequences from 50 Amphiprion mccullochi individuals from Middleton Reef and Lord Howe Island and 44 A. akindynos individuals from Lizard and One Tree Islands on the Great Barrier Reef. Amphiprion clarkii was specified as the outgroup species. This represents the best ML tree from 10 individual runs in GARLI. Asterisks identify individuals of A. akindynos that fall outside a clade. Numbers on branches indicate support for each clade, BEAST, MB, ML, and MP. (B) Haplotype minimum spanning tree (MST) with number of substitutions between haplotypes indicated on connectors. Different shading represents each of the four locations as shown on the key to the figure.
Figure 2
Figure 2
Separation of Amphiprion mccullochi and A. akindynos based on various analyses of msat loci: (A) NEWHYBRID analysis showing pure (gray) and F1 hybrid (black) status, (B) STRUCTURE cluster analysis, and (C) Scatterplots of the discriminant analysis of principal components (DAPC) of msat data for two A. mccullochi and two A. akindynos populations using geographic sample site as priors for genetic clusters. Populations are named and individual genotypes appear as dots surrounded by 95% inertia ellipses. Eigenvalues show the amount of genetic information contained in each successive principal component with X and Y axes constituting the first two principal components, respectively.

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