Nuclear gene-inferred phylogenies resolve the relationships of the enigmatic Pygmy Sunfishes, Elassoma (Teleostei: Percomorpha)

Elassoma, the Pygmy Sunfishes, has long proven difficult to classify among the more than 15,000 species of percomorph fishes. Hypotheses dating to the 19th Century include Elassoma in Centrarchidae or in the monogeneric Elassomatidae, and more recent phylogenetic hypotheses have classified Elassoma in Smegmamorpha that also contained Synbranchiformes, Mugiliformes, Gasterosteiformes, and Atherinomorpha. No published phylogenetic analysis of morphological or molecular data has supported the monophyly of Smegmamorpha, or a consistent resolution of Elassoma relationships. In this study, we investigated the phylogenetic relationships of Elassoma and test the monophyly of Smegmamorpha with a nucleotide dataset comprising 10 protein-coding nuclear genes sampled from 65 percomorph species. Maximum likelihood analyses of each individual gene and the concatenated 10 genes all result in strong support for a clade composed of Elassoma and Centrarchidae, and no analysis supports monophyly of Smegmamorpha. Based on these results, a rank-free phylogenetic definition of Centrarchidae is presented that includes Elassoma, and the continued recognition of Smegmamorpha is discouraged. We discuss the implications of these phylogenetic analyses for relationships of several other percomorph lineages, including Kyphosidae, Terapontidae, Kuhliidae, Cheilodactylidae, Percichthyidae, Howellidae, Enoplosidae, Sinipercidae, and Cirrhitidae.

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► We investigated the phylogenetic affinity of Elassoma and monophyly of Smegmamorpha.
► Analysis of the 10 gene dataset supports monophyly of traditional Centrarchidae Elassoma, and expanded Centrarchidae that includes Elassoma.
► Smegmamorpha is not monophyletic in the nuclear gene-inferred phylogeny.
► Nine of the ten genes resolve a monophyletic Centrarchidae that includes Elassoma.
► The taxonomy of Centrarchidae is revised to include Elassoma.