Phylogenetics, systematics and biogeography of deep-sea Pennatulacea (Anthozoa: Octocorallia): evidence from molecules and morphology

Despite its extreme environmental conditions, the deep sea harbours a unique and<br/>species-rich fauna of mostly unknown age and phylogeny. Pennatulids (Anthozoa:<br/>Octocorallia) are a group whose taxonomy and phylogenetic relationships remain poorly<br/>known and little studied, in spite of their abundance and ecological importance in softbottom<br/>communities. Phylogenetic analysis of a combination of partial ND2 and msh1<br/>sequences produced well-supported phylogenetic relationships for representative deepsea<br/>(and shallow-water) pennatulids at familial, generic and specific taxonomic levels.<br/>Generally, molecular data were congruent with current classification and previous<br/>phylogenetic reconstructions of the O. Pennatulacea based on morphology.<br/>Discrepancies were evident concerning the finer details for some families and genera: this<br/>can be attributable to the high frequency of homoplasy in pennatulids where reversals in<br/>evolution have led to taxa that possess apomorphic character states that are analogous<br/>with plesiomorphic traits. Genetic analysis gave strong support that highly-derived taxa<br/>occur in both shallow and deep water and that many may have differentiated and<br/>dispersed from the deep sea to the shallows. The Renillidae, which is considered one of<br/>the most primitive shallow-water families, evolved recently from deep-water ancestors.<br/>Conversely, the bathyal Anthoptilidae was the most primitive of families, and although<br/>more evidence is required, pennatulids as a group may have originated in deep water.<br/>The systematics of the exclusively deep-sea genus Umbellula, which contains fortytwo<br/>species, remains unclear despite the repeated attempts of revision. Incorporating<br/>new morphological and distributional data from the examination of recently collected<br/>material, together with type specimens, genetic analysis, and a critical study of the<br/>literature, fifteen Umbellula species are here considered valid, including three new to<br/>science. Eight species lack sclerites in the autozooids, U. magniflora, U. encrinus, U.<br/>antarctica, U. carpenteri and Umbellula sp.1 n. sp. (quadrangular axes), and U. huxleyi and<br/>U. pellucida (round axes); and seven possess autozooid sclerites, U. thomsoni and U.<br/>hemigymna (quadrangular axes), and U. monocephalus, U. aciculifera, U. durissima,<br/>Umbellula sp.2 n. sp. and Umbellula sp.3 n. sp. (round axes).<br/>Biogeographic data and genetic evidence supported the hypothesis that species of<br/>Umbellula differentiated in the Indo-Pacific. Many radiated southwards to the Antarctic<br/>and later north into the Atlantic, E Pacific, Indian and Arctic oceans, occupying bathyal<br/>and abyssal depths. Other, older species that evolved via a separate evolutionary<br/>pathway, may have originated in the Indo-Pacific, and dispersed to the Subantarctic (U.<br/>sp.2 n. sp.) or Indian and Atlantic oceans (U. monocephalus). Further, morphological<br/>examination of Umbellula showed it adapted to the oligotrophic conditions of the deep<br/>sea by reducing the number but increasing the size of the autozooids, and in doing so,<br/>enlarged the food-catchment area; abyssal species have done so even more extremely.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2008

Author dc:creator

• Dolan, Emily