Harilaos Lessios
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Harilaos Lessios

My research focuses on molecular evolution and speciation in marine invertebrates. Currently, I am working with Lytechinus williamsi, a small (ca 2 cm in diameter) sea urchin found in some locations of the Caribbean. It lives on coral reefs, which are often found close to Thalassia beds. In these beds there is another, more common, species, L. variegatus, which, according to mitochondrial and nuclear phylogenies, is its sister species. The two species hybridize somewhat, but there must be an isolating barrier preventing wholesale genetic exchange. The reproductive cycles of the two species overlap, and their gametes are completely compatible with each other. Bindin, a gamete recognition molecule, is reciprocally monophyletic, but there are only four amino acid differences. Hybrid larvae survive and metamorphose into perfectly viable adult sea urchins, which can readily back-cross to either species. It is, therefore, highly likely that the isolating barrier is the product of many small differences in either gametic recognition or developmental molecules. Such differences could be detected in the transcriptome of the two species. The transcriptome of L. variegatus has already been published and partially annotated;however we currently lack the transcriptome of L. williamsi.

Suggested Reading
  • Zigler, K. S. and Lessios, H. A. 2004. Speciation on the coasts of the new world: Phylogeography and the evolution of bindin in the sea urchin genusLytechinus. Evolution. 58:1225-1241

  • McCartney, M. A. and Lessios, H. A. 2004. Adaptive evolution of sperm bindintracks egg incompatibility in neotropical sea urchins of the genus Echinometra. Molecular Biology and Evolution. 21:732-745

  • McCartney, M. A. and Lessios, H. A. 2002. Quantitative analysis of gametic incompatibility between closely related species of neotropical sea urchins. Biological Bulletin. 202:166-181