M.S. Marine Biology
Antedonidae (Crinoidea: Comatulida) is the largest of extant crinoid families; it currently includes ~155 accepted species in 50 genera and accounts for ~23% of extant crinoid species (~29% of feather stars) and 27% of genera. Molecular phylogenies have returned the family as polyphyletic, with several clades scattered among non-antedonid sister groups (Hemery 2011, Hemery et al. 2013, Rouse et al. in prep.). Traditional morphological characteristics are thus inadequate for reconstructing relationships among taxa. SEM imaging was used in an effort to discover new diagnostic features that will support the molecular data, focusing on skeletal ossicles within the calyx, specifically the radial ossicles, as they are least likely to be affected by their hydrodynamic environment. Geometric morphometric analysis and landmark software were used to systematically compare equivalent skeletal parts among antedonid and non-antedonid sister taxa to identify likely homologies and homoplasies. Principal Component Analysis (PCA/BGPCA) and Procrustes ANOVAs were used for visualizing and testing variances within and between taxonomic and molecular groups. Linear Discriminant Analysis (LDA) was used with leave-one-out cross validation (LOOCV) to identify any misclassifications based on morphological similarities. UPGMA Hierarchical clustering models using both Procrustes and Mahalanobis distances were produced for comparison, and inter-landmark measurements were compared between species in search for possible intra-radial character states. Results yielded significant variation of radial morphology within the family Antedonidae with significant effects by depth range, taxonomic classification, and phylogenetic forces. All species with a radial height to width (H:W) ratio <1.0 were restricted to the shallower depths (0-200m) and notable morphological similarities were seen within both molecular clades and taxonomic subfamilies (Antedoninae and Thysanometrinae excepted). Regional affects were seen within the subfamily Antedoninae, as the Atlantic antedonines differed significantly from the Pacific antedonines, both in overall radial appearance and in H:W ratio. These results, with limited variation within molecular clades, give at least rudimentary support to recent molecular phylogenetics and promote further morphological studies of this nature that will strengthen our understanding of extant crinoid phylogeny (Bull et al. 1993, Littlewood et al. 1997, Hemery 2011, Rouse et al. 2013, Roux et al. 2013).
Brenna Hays. 2016. Can Skeletal Morphology Support New Molecular Phylogenies of Antedonidae (Crinoidea: Comatulida)?. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (424)
Available for download on Wednesday, August 30, 2017