Abstract
Vertebrates share several distinct morphological characters with three invertebrate groups, lancelets, tunicates and hemichordates. Tunicates, lancelets and vertebrates are a monophyletic group, the chordates, which share five morphological characters: a notochord, a dorsal neural tube, an endostyle, a muscular, post-anal tail and pharyngeal gill slits. Hemichordates share some of these chordate features, the pharyngeal gill slits, an endostyle and a post-anal tail, and were thought to contain a notochord homolog, the stomochord, and a dorsal neural tube in the neck region. Developmental genetics and genomics have allowed re-examination of the question of chordate origins, comparing developmental gene expression in embryos of different phyla has allowed insights into the molecular mechanisms underlying morphological changes. Genomics has allowed insight into the phylogenetic relationships of the chordates and their invertebrate relatives, and comparison of the shared genetic pathways in related embryos. Recent evidence from the speaker’s lab has shown that the chordate ancestor was likely a benthic worm, with a mouth and pharyngeal gill slits, supported by cartilaginous gill bars. It is possible that the deuterostome ancestor was actually a chordate and that notochord was lost in the ambulacrarian ancestor, with echinoderms losing all of the chordate features. The speaker is using phylogenies, genomes, and developmental characters to test these contrasting hypotheses.
About the speaker
Prof Billie Swalla received her MS in Zoology and PhD in Biology from the University of lowa in 1983 and 1988 respectively. She then joined the University of Texas at Austin as a Post-Doctoral Fellow in 1988 and moved to University of California at Davis as an Assistant Research Development Biologist in 1991. After that, she joined Vanderbilt University as the Assistant Professor in Biology in 1994 and Pennsylvania State University as the Assistant Professor in Biology in 1997. She entered University of Washington as the Assistant Professor of Zoology in 1999 and then became the Associate Professor of Biology in 2001. She is now a Professor of Biology and the Director of Friday Harbor Laboratories at University of Washington.
Prof Swalla is a leading scholar on the evolution and development of Chordates. Her research interests are molecular analysis of invertebrate evolution and development, evolution of the chordate body plan and phylogeny of hemichordates and tunicates. She has served on the Editorial Boards of Evolution & Development and Molecular and Developmental Evolution since 1999 and 2005 respectively. She has also been the Associate Editor of Molecular Biology and Evolution since 2002.
Prof Swalla has been a strong supporter for diversity in STEM and promoting science literacy. She received the University of Washington Undergraduate Research Mentor Award in 2012 and College of Environment Commitment to Diversity Award in 2015.
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