Daniel Rubinoff1 and Patrick Schmitz
-Author Affiliations
Department of Plant and Environmental Protection Sciences, University of Hawaii, Honolulu, HI 96822
Edited by May R. Berenbaum, University of Illinois at Urbana–Champaign, Urbana, IL, and approved February 10, 2010 (received for review November 2, 2009)
Abstract
Insects are the most diverse form of life on the planet, dominating both terrestrial and freshwater ecosystems, yet no species has a life stage able to breath, feed, and develop either continually submerged or without access to water. Such truly amphibious insects are unrecorded. In mountain streams across the Hawaiian Islands, some caterpillars in the endemic moth genus Hyposmocoma are truly amphibious. These larvae can breathe and feed indefinitely both above and below the water's surface and can mature completely submerged or dry. Remarkably, a molecular phylogeny based on 2,243 bp from both nuclear (elongation factor 1α and carbomoylphosphate synthase) and mitochondrial (cytochrome oxidase I) genes representing 216 individuals and 89 species of Hyposmocoma reveals that this amphibious lifestyle is an example of parallel evolution and has arisen from strictly terrestrial clades at least three separate times in the genus starting more than 6 million years ago, before the current high islands existed. No other terrestrial genus of animals has sponsored so many independent aquatic invasions, and no other insects are able to remain active indefinitely above and below water. Why and how Hyposmocoma, an overwhelmingly terrestrial group, repeatedly evolved unprecedented aquatic species is unclear, although there are many other evolutionary anomalies across the Hawaiian archipelago. The uniqueness of the community assemblages of Hawaii's isolated biota is likely critical in generating such evolutionary novelty because this amphibious ecology is unknown anywhere else.
evolution Hyposmocoma molecular clock phylogeography amphibious
Footnotes
1To whom correspondence should be addressed. E-mail:rubinoff@hawaii.edu.
Author contributions: D.R. designed research; D.R. and P.S. performed research; D.R. and P.S. contributed new reagents/analytic tools; D.R. and P.S. analyzed data; and D.R. and P.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. GU560194–GU560727).
This article contains supporting information online at www.pnas.org/cgi/content/full/0912501107/DCSupplemental.
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