Allopatric divergence and speciation in coral reef fish: the three spot Dascyllus, Dascyllus trimaculatus

Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California 95060, USA.
Evolution (Impact Factor: 4.61). 12/2009; 64(5):1218-30. DOI: 10.1111/j.1558-5646.2009.00917.x
Source: PubMed


Long pelagic larval phases and the absence of physical barriers impede rapid speciation and contrast the high diversity observed in marine ecosystems such as coral reefs. In this study, we used the three-spot dascyllus (Dascyllus trimaculatus) species complex to evaluate speciation modes at the spatial scale of the Indo-Pacific. The complex includes four recognized species and four main color morphs that differ in distribution. Previous studies of the group using mitochondrial DNA revealed a noncongruence between color morphs and genetic groupings; with two of the color morphs grouped together and one color morph separated into three clades. Using extensive geographic sampling of 563 individuals and a combination of mitochondrial DNA sequences and 13 nuclear microsatellites, we defined population/species boundaries and inferred different speciation modes. The complex is composed of seven genetically distinct entities, some of which are distinct morphologically. Despite extensive dispersal abilities and an apparent lack of barriers, observed genetic partitions are consistent with allopatric speciation. However, ecological pressure, assortative mating, and sexual selection, were likely important during periods of geographical isolation. This study therefore suggests that primarily historical factors later followed by ecological factors caused divergence and speciation in this group of coral reef fish.

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Available from: Giacomo Bernardi
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    • "The study found substantial population structure overall for both marker types (Φ ST = 0.096, P < 0.0001; mean D est = 0.17; F ST = 0.015, P < 0.0001), confirming expectations derived from genetic population structuring seen in other anemonefish (A. ocellaris, Nelson et al. 2000; Timm et al. 2012) and other reef-dwelling species with a pelagic larval phase (e.g., Bay et al. 2004; DeBoer et al. 2008; Leray et al. 2010; reviewed in Carpenter et al. 2011). Demersal egg development (Riginos et al. 2011), a relatively short PLD (18 days) (Wellington and Victor 1989), site attachment of adult fishes (Fautin and Allen 1997), and high rates of self-recruitment (Madduppa et al. 2014) are all expected to contribute to the observed structure and highlight the vulnerability of this and similar species from a conservation standpoint. "
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    ABSTRACT: To enhance the understanding of larval dispersal in marine organisms, species with a sedentary adult stage and a pelagic larval phase of known duration constitute ideal candidates, because inferences can be made about the role of larval dispersal in population connectivity. Members of the immensely diverse marine fauna of the Indo-Malay Archipelago are of particular importance in this respect, as biodiversity conservation is becoming a large concern in this region. In this study, the genetic population structure of the pink anemonefish, Amphiprion perideraion, is analyzed by applying 10 microsatellite loci as well as sequences of the mitochondrial control region to also allow for a direct comparison of marker-derived results. Both marker systems detected a strong overall genetic structure (ΦST = 0.096, P < 0.0001; mean Dest = 0.17; FST = 0.015, P < 0.0001) and best supported regional groupings (ΦCT = 0.199 P < 0.0001; FCT = 0.018, P < 0.001) that suggested a differentiation of the Java Sea population from the rest of the archipelago. Differentiation of a New Guinea group was confirmed by both markers, but disagreed over the affinity of populations from west New Guinea. Mitochondrial data suggest higher connectivity among populations with fewer signals of regional substructure than microsatellite data. Considering the homogenizing effect of only a few migrants per generation on genetic differentiation between populations, marker-specific results have important implications for conservation efforts concerning this and similar species.
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    • "During low sealevel episodes in the Quaternary, the Sunda shelf (i.e. the south-eastern extension of the continental shelf of South-east Asia, including the Malay Peninsula, Sumatra, Borneo, Java, Madura, and Bali) repeatedly formed a broad land bridge protruding from Southeast Asia towards the Sahul shelf (i.e. the northwestern extension of the Australian continent, which includes most of the Timor Sea), thus restricting the exchange of marine fauna between the western Pacific and the Indian Ocean (Randall, 1998; Briggs, 1999; Voris, 2000). This potentially caused genetic differentiation and, in some cases, eventually led to allopatric speciation on either side of the Sunda and Sahul shelves (Gaither et al., 2010; Leray et al., 2010; Gaither et al., 2011a; Gaither & Rocha, 2013). The positive correlation between divergence time and the degree of geographical overlap in sister species of Indo-West Pacific reef fishes (Quenouille et al., 2011) is further indirect evidence for allopatric speciation. "
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