Phylogenetic relationships among the clownfish-hosting sea anemones

The clownfish-sea anemone symbiosis is an icon of Info-Pacific coral reef communities. While the systematics and evolution of the ~30 species of clownfish have been heavily studied, the clownfish-hosting sea anemones are poorly represented in phylogenetic studies of sea anemones and their placement within the sea anemone phylogeny remains broadly unknown. Currently there are 10 morphologically described clownfish-hosting sea anemones within five anemone genera. These include Entacmaea, Heteractis, Stichodactyla, Cryptodendrum, and Macrodactyla- all within the superfamily Actinioidea. Unlike their clownfish symbionts, these do not form a monophyletic clade, but 7/10 species belong to the family Stichodactylidae (including the genera Heteractis & Stichodactyla). Our study investigates the phylogenetic placement of 9/10 clownfish hosts in what is, to date, the largest sea anemone phylogenetic dataset. We also test whether the family Stichodactylidae and each of the 5 genera of clownfish-hosting sea anemones are monophyletic. Finally, we examine branch lengths of each clownfish-hosting lineage in our newly developed phylogeny and discuss the evolutionary implications of the clownfish symbiosis on the diversification of anemone hosts in this evolutionarily young symbiosis. This project was completed with contributions from Ben Titus from the American Museum of Natural History Department of Invertebrate Zoology.