30.6 Friday, Jan. 4 Evolution of recent squids (Cephalopoda:Decapodiformes) inferrred from molecular data LINDGREN, AR; Ohio State University email@example.com
Cephalopods are an enigmatic group of mollusc consisting of squid, cuttlefish, and octopus which inhabit an array of marine ecosystems. The squid, or Decapodiformes, are of particular interest from an evolutionary standpoint due to their ecological similarity to fishes, and their possession of unique morphological features. For example, squid have modified appendages, complex eyes and other sensory structures that are used to detect and capture prey in a variety of environments. Difficulties in observing and collecting squid, particularly those living in the midwater, have led to a paucity of biological information for most lineages. Previous phylogenetic studies of squid using genetic and morphological data yielded contradictory or inconsistent relationships, perhaps due to a lack of specimens or rapid rates of evolution across lineages. The present research employed molecular data from 5 genes (18S, Histone H3, 28S, COI, 16S) to generate a phylogeny of ordinal and family-level relationships for Decapodiformes. The inclusion of new data and intermediate taxa yielded well-supported and consistent topologies and recovered all higher-level groups (Sepiolida, Sepiida, Spirulida, Myopsida, Bathyteuthoida and Oegopsida) as monophyletic. The monophyly of these lineages is particularly important as key innovations in evolution, such as the timing in appearance of the internalized pen and a cornea, can now be pinpointed. Family-level relationships were also recovered with high degrees of support. For example, Enoploteuthidae and Ommastrephidae were found to be sister and at the base of the oegopsid clade, implying that many key features of midwater squids appeared early in the lineage. This is the most comprehensive analysis of Decapodiformes to date, and provides interesting implications regarding evolution, adaptation and radiation.