Molecular phylogenetic evidence for the evolution of specialization in anemonefishes

Abstract

Anemonefishes (genera: Amphiprion and Premnas; family Pomacentridae) are a group of 28 species of coral reef fishes that are found in obligate symbiosis with large tropical sea anemones. A phylogenetic hypothesis based on morphological analyses of this group suggests that the ancestral anemonefish was a generalist with similar morphology to other pomacentrids, and that it gave rise to other anemonefish species that were more specialized for living with particular species of host anemones. To test this hypothesis we constructed a molecular phylogeny for the anemonefishes by sequencing 1140 base pairs of the cytochrome b gene and 522 base pairs of the 16S rRNA gene for six species of anemonefishes (representatives of all subgenera and species complexes) and two other pomacentrid species. Three methods of phylogenetic analysis all strongly supported the conclusion that anemonefishes are a monophyletic group. The molecular phylogeny differs from the tree based on morphological data in that the two species of specialized anemonefishes (Premnas biaculeatus and Amphiprion ocellaris) were assigned to a basal position within the clade, and the extreme host generalist (Amphiprion clarkii) to a more derived position. Thus, the initial anemonefish ancestors were probably host specialists and subsequent speciation events led to a combination of generalist and specialist groups. Further phylogenetic studies of additional anemonefish species are required to substantiate this hypothesis.

Molecular systematics of the damselfishes (Teleostei: Pomacentridae): Bayesian phylogenetic analyses of mitochondrial and nuclear DNA sequences

“…Overall, the family Pomacentridae appears relatively bereft of phylogenetically informative morphological characters (Emery, 1973;Fitzpatrick, 1992;Gluckmann and Vandewalle, 1998), which is not surprising given that the high species diversity in the family is associated with a relatively small number of general body plans. Molecular systematic investigation of the family is increasing in importance, but most studies to date have focused on congeneric relationships (Dascyllus: Bernardi and Crane, 1999;McCafferty et al, 2002; Amphiprion + Premnas: Elhott et al, 1999;Abudefduf. Bermingham et al, submitted;and Stegastes: Lessios et al, in prep.).…”

Host preference and habitat segregation among Red Sea anemonefish: effects of sea anemone traits and fish life stages

“…As members of the A. clarkii complex of anemonefishes (Allen 1972), A. bicinctus also may be highly mobile and thus able to migrate easily to Entacmaea quadricolor if space becomes available after growing large enough in Heteractis crispa. This habitat-switch strategy is used by coral gobies (Dirnwöber & Herler 2007), but contrasts with that of less mobile anemonefishes such as A. percula (not in the A. clarkii complex; Elliott et al 1999), in which conspecifics settle into adult habitats and form queues of juveniles leading to the inheritance of a breeding position (Buston 2004). (2) A second possible cause of lower mobility by juvenile than adult A. bicinctus may be aggression by adults, which oust smaller fish that attempt to migrate to an anemone, and prevent them from remaining in preferred anemones.…”

“…Anemonefishes comprise 28 species of damselfishes that engage in obligate shelter symbioses with 10 species of sea anemones on Indo-Pacific coral reefs (Elliott et al 1999). They are protandrous and form social groups with rigid size-based hierarchies in each host anemone: the terminal female is largest in size and dominant, her mate is second in size and rank, and any other individuals are smaller subadults or juveniles (e.g.…”

Phylogenetic analysis of anemone fishes of the Persian Gulf using mtDNA sequences

“…There is only one report about anemone fish populations using genetic and morphological variations among them (Bell et al, 1982). A molecular research on anemone fishes has been carried out for their ability to be a symbiotant of different sea anemones (Elliott et al, 1999). A similar study is carried out with more anemone fish species to survey their unusual life style (Santini and Polacco, 2006).…”

“…The molecular studies on anemone fishes are scarce all over the world. These studies are mainly focused on taxonomy and evo- lution of the anemone fishes based on phylogenetic analysis of nuclear and mtDNA (Elliott et al, 1999;Tang, 2001;Jang-Liaw et al, 2002;Quenouille et al, 2004;Santini and Polacco, 2006;Mabuchi ea al., 2007). There is only one report about anemone fish populations using genetic and morphological variations among them (Bell et al, 1982).…”