Transcriptome of Lytechinus williamsi to determine reproductive barriers against L. ariegatus.
Lytechinus williamsi is a small (ca 3 cm in diameter) sea urchin found in some locations of the Caribbean. It lives on coral reefs close to Thalassia beds. In these beds is found L. variegatus a more common species, 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. I would like to determine the transcriptome of L. williamsi. This would involve purification of mtDNA from both somatic and reproductive tissues of this species, determination of differences from that of L. variegatus and annotation of regions that show clear differences.
Representative and Recent Publications
- 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 genus Lytechinus. Evolution. 58:1225-1241
- McCartney, M. A. and Lessios, H. A. 2004. Adaptive evolution of sperm bindin tracks 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