The Society for Integrative and Comparative Biology Annual Meeting 2013
Date: 3-7 January 2013
Place: San Francisco, California, USA
PRESENTATIONS and ABTRACTS
1) Summers, M. M. and Rouse, G. W. 2013. Untangling the trees of obligate symbionts: myzostomes and echinoderms.
The obligate association of myzostome worms (Myzostomida) with echinoderms, in particular with crinoids, is an ideal system in which the evolution of symbiotic lifestyles and body plans can be investigated using phylogenetic inference.
An association that has persisted since before the Jurassic, the body plans of myzostomes vary considerably and are consistent with four prominent symbiotic lifestyles (free-living, gall-forming, cyst-forming, and internal) in which the myzostome steals food from or directly consumes the host. Those living freely are mainly disk-shaped and tend to “mimic” the host by adapting similar colors and/or appendages that resemble the host, traits which are lacking in those that live internally or form cysts and galls. This variety of life histories and dependence on an echinoderm host over long time-scales presents the opportunity to compare the evolutionary histories of myzostomes and their hosts, as well as investigate the evolution of character traits related to this symbiosis. In this study we combine new and previously published sequence and morphological data to present a systematic revision of Myzostomida and their echinoderm hosts, assess congruence between host and symbiont phylogenies, and infer possible evolutionary events leading to the current diversity of myzostome species, lifestyles, and body plans.
2) Mah, C. and Foltz, D. 2013. Biogeographic Insights from Molecular Phylogenetics of Pacific Northwest Sea Stars.
Recently molecular phylogenetic analyses of the Asteroidea have produced comprehensive and well-resolved trees for the Forcipulatacea and the Valvatacea, two of the most taxonomically diverse and ecologically important groups of asteroids. Although our work is broadly concerned with higher level phylogeny, we have focused on projects across a diversity of scales and herein we present highlights from our work that emphasize interests relevant to asteroid taxa on the west coast of North America. Analysis of the Asteriidae shows it is composed of multiple clades corresponding to specific geographic/climatic regions. The boreal clade suggests endemism for asteriids occurring on the west coast of N. America and adjoining regions, including familiar genera such as Pisaster and Leptasterias. Pycnopodia and the deep-sea Rathbunaster were supported as sister taxa which presents at least 2 different hypotheses of relationship. The goniasterid Hippasteria includes 15 nominal species and is widely distributed in cold-water settings throughout the Atlantic, Pacific and southern Indian Ocean. In order to assess relationships and genetic structure, we sampled populations from throughout the world. Partial sequences for a mitochondrial gene (COI) and a nuclear gene (ATPS) were obtained for approximately 150 specimens. Our results showed little ongoing genetic exchange between trans-Arctic populations. Only 1 of 31 COI haplotypes and 4 of 16 ATPS haplotypes were shared among two or more ocean regions (N. Pacific, S. Pacific and N. Atlantic) despite sampling between 50-100 sequences per region. The widespread H. phrygiana identified from Atlantic, New Zealand, and Kerguelen Island populations and H. spinosa from the N. Pacific were all supported as one widely distributed global lineage, which has recently diversified.