Northwest Fisheries Science Center

Display All Information

Document Type: Journal Article
Center: NWFSC
Document ID: 1092
Title: Adaptive Divergence in the Thyroid Hormone Signaling Pathway in the Stickleback Radiation
Author: Jun Kitano, S. C. Lema, J. A. Luckenbach, Seiichi Mori, Yui Kawagishi, Makoto Kusakabe, P. Swanson, C. L. Peichel
Publication Year: 2010
Journal: Current Biology
Volume: 20
Pages: 2124-2130
DOI: 10.1016/j.cub.2010.10.050
Abstract: During adaptive radiations, animals colonize diverse environments, which requires adaptation in multiple phenotypic traits [1]. Because hormones mediate the dynamic regulation of suites of phenotypic traits [24], evolutionary changes in hormonal signaling pathways might contribute to adaptation to new environments. Here we report changes in the thyroid hormone signaling pathway in stream-resident ecotypes of threespine stickleback fish (Gasterosteus aculeatus), which have repeatedly evolved from ancestral marine ecotypes [58]. Stream-resident fish exhibit a lower plasma concentration of thyroid hormone and a lower metabolic rate, which is likely adaptive for permanent residency in small streams. The thyroid-stimulating hormone-b2 (TSHb2) gene exhibited significantly lower mRNA expression in pituitary glands of stream-resident sticklebacks relative to marine sticklebacks. Some of the difference in TSHb2 transcript levels can be explained by cis-regulatory differences at the TSHb2 gene locus. Consistent with these expression differences, a strong signature of divergent natural selection was found at the TSHb2 genomic locus. By contrast, there were no differences between the marine and stream-resident ecotypes in mRNA levels or genomic sequence in the paralogous TSHb1 gene. Our data indicate that evolutionary changes in hormonal signaling have played an important role in the postglacial adaptive radiation of sticklebacks.