Reconciling genealogical and morphological species in a worldwide study of the Family Hydractiniidae (Cnidaria, Hydrozoa)
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The Hydractiniidae are a family of globally distributed marine hydrozoans (class Hydrozoa, phylum Cnidaria). Despite being one of the most well-studied families of the Hydrozoa, their genus and species-level taxonomy is unsettled and disputed. The taxonomic difficulties of the Hydractiniidae are due to many inadequate species descriptions, a paucity of available morphological characters, many cryptic species, and the often-extreme plasticity seen when colonies of the same species are found at different stages of growth or different environmental conditions. This confusion over species identity is especially important because some species of the family Hydractiniidae are well-established model organisms for a wide array of studies ranging from gene expression to developmental biology and colony growth. Here we report the species-level implications of 226 mitochondrial large ribosomal subunit (16S) rDNA sequences from around the world and 52 nuclear DNA sequences (Elongation Factor 1α) with the intent to reconcile described morphospecies with genealogical lineages. Our data show that Podocoryna carnea and P. exigua are distinct and geographically disjunct species, P. borealis is paraphyletic with respect to Podocoryna sp. from South Africa and P. bella from New Zealand. Podocoryna australis, from New Zealand form a distinct monophyletic group. Podocoryna from New England, New York and Florida all fall into a distinct monophyletic group (P. americana) and fail to support the existence of a distinct, P. selena in the Gulf of Mexico. Hydractinia pruvoti is the only species within the Podocoryna clade without fully formed medusae. We identify a Clava clade closely related to other algae dwelling Hydractiniidae. Our data do not recover Stylactaria inabai from Japan as a distinct species from S. misakiensis, and S. carcinicola as distinct from H. epiconcha. Also, 10 colonies identified as S. carcinicola fall into a distantly related clade that is close to the American S. hooperi. Finally, we identify Janaria mirabilis as the sister group to the H. echinata species complex and clarify the relationships between the H. echinata, H. symbiopollicaris, H. polyclina, H. symbiolongicarpus and H. [GM]. © 2009 The Norwegian Academy of Science and Letters.
author list (cited authors)
Miglietta, M. P., Schuchert, P., & Cunningham, C. W.