Dataset Information

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.

SUBMITTER: Elliott JK

PROVIDER: S-EPMC1689819 | biostudies-other | 1999 Apr

REPOSITORIES: biostudies-other

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Molecular phylogenetic evidence for the evolution of specialization in anemonefishes.

Elliott J K JK Lougheed S C SC Bateman B B McPhee L K LK Boag P T PT

Proceedings. Biological sciences 19990401 1420

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 tes ...[more]

PMID: 10331288

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Project description:BackgroundGlutamine synthetase (GS) is essential for ammonium assimilation and the biosynthesis of glutamine. The three GS gene families (GSI, GSII, and GSIII) are represented in both prokaryotic and eukaryotic organisms. In this study, we examined the evolutionary relationship of GSII from eubacterial and eukaryotic lineages and present robust phylogenetic evidence that GSII was transferred from gamma-Proteobacteria (Eubacteria) to the Chloroplastida.ResultsGSII sequences were isolated from four species of green algae (Trebouxiophyceae), and additional green algal (Chlorophyceae and Prasinophytae) and streptophyte (Charales, Desmidiales, Bryophyta, Marchantiophyta, Lycopodiophyta and Tracheophyta) sequences were obtained from public databases. In Bayesian and maximum likelihood analyses, eubacterial (GSIIB) and eukaryotic (GSIIE) GSII sequences formed distinct clades. Both GSIIB and GSIIE were found in chlorophytes and early-diverging streptophytes. The GSIIB enzymes from these groups formed a well-supported sister clade with the gamma-Proteobacteria, providing evidence that GSIIB in the Chloroplastida arose by horizontal gene transfer (HGT). Bayesian relaxed molecular clock analyses suggest that GSIIB and GSIIE coexisted for an extended period of time but it is unclear whether the proposed HGT happened prior to or after the divergence of the primary endosymbiotic lineages (the Archaeplastida). However, GSIIB genes have not been identified in glaucophytes or red algae, favoring the hypothesis that GSIIB was gained after the divergence of the primary endosymbiotic lineages. Duplicate copies of the GSIIB gene were present in Chlamydomonas reinhardtii, Volvox carteri f. nagariensis, and Physcomitrella patens. Both GSIIB proteins in C. reinhardtii and V. carteri f. nagariensis had N-terminal transit sequences, indicating they are targeted to the chloroplast or mitochondrion. In contrast, GSIIB proteins of P. patens lacked transit sequences, suggesting a cytosolic function. GSIIB sequences were absent in vascular plants where the duplication of GSIIE replaced the function of GSIIB.ConclusionsPhylogenetic evidence suggests GSIIB in Chloroplastida evolved by HGT, possibly after the divergence of the primary endosymbiotic lineages. Thus while multiple GS isoenzymes are common among members of the Chloroplastida, the isoenzymes may have evolved via different evolutionary processes. The acquisition of essential enzymes by HGT may provide rapid changes in biochemical capacity and therefore be favored by natural selection.

Project description:Biotic specialization holds information about the assembly, evolution, and stability of biological communities. Partner availabilities can play an important role in enabling species interactions, where uneven partner availabilities can bias estimates of biotic specialization when using phylogenetic diversity indices. It is therefore important to account for partner availability when characterizing biotic specialization using phylogenies. We developed an index, phylogenetic structure of specialization (PSS), that avoids bias from uneven partner availabilities by uncoupling the null models for interaction frequency and phylogenetic distance. We incorporate the deviation between observed and random interaction frequencies as weights into the calculation of partner phylogenetic α-diversity. To calculate the PSS index, we then compare observed partner phylogenetic α-diversity to a null distribution generated by randomizing phylogenetic distances among the same number of partners. PSS quantifies the phylogenetic structure (i.e., clustered, overdispersed, or random) of the partners of a focal species. We show with simulations that the PSS index is not correlated with network properties, which allows comparisons across multiple systems. We also implemented PSS on empirical networks of host-parasite, avian seed-dispersal, lichenized fungi-cyanobacteria, and hummingbird pollination interactions. Across these systems, a large proportion of taxa interact with phylogenetically random partners according to PSS, sometimes to a larger extent than detected with an existing method that does not account for partner availability. We also found that many taxa interact with phylogenetically clustered partners, while taxa with overdispersed partners were rare. We argue that species with phylogenetically overdispersed partners have often been misinterpreted as generalists when they should be considered specialists. Our results highlight the important role of randomness in shaping interaction networks, even in highly intimate symbioses, and provide a much-needed quantitative framework to assess the role that evolutionary history and symbiotic specialization play in shaping patterns of biodiversity. PSS is available as an R package at https://github.com/cjpardodelahoz/pss.

Dataset Information

Molecular phylogenetic evidence for the evolution of specialization in anemonefishes.

Publications

Molecular phylogenetic evidence for the evolution of specialization in anemonefishes.

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