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The Hawaiian amphibious caterpillar guild: new species of Hyposmocoma (Lepidoptera: Cosmopterigidae) confirm distinct aquatic invasions and complex speciation patterns




Although aquatic caterpillars are a globally rare lifestyle, we have found them in multiple, independent lineages of the endemic moth genus Hyposmocoma across all of the Hawaiian Islands with flowing water. We formally describe 11 new species of Hyposmocoma that belong to four different larval case types: cone, bugle, medium burrito, and large burrito: Hyposmocoma kahamanoasp. nov. from Oahu Island, Hyposmocoma kamakou sp. nov. from Molokai Island, Hyposmocoma kahaiaosp. nov., Hyposmocoma waihohonusp. nov., and Hyposmocoma moopalikeasp. nov. from Maui Island, andHyposmocoma aumakuawaisp. nov.,Hyposmocoma eepawaisp. nov., Hyposmocoma ipowainuisp. nov., Hyposmocoma kawaikoisp. nov., Hyposmocoma uhauiolesp. nov., and Hyposmocoma wailuasp. nov. from Kauai Island. We also illustrate and describe in detail the aquatic case-bearing larva of Hyposmocoma kahamanoa. Despite having similar ecologies as algae and lichen grazers at and below the water line of streams, prior research indicates that species with each case type constitute an independent lineage, with terrestrial sister taxa, and therefore the different groups of species bearing unique case types each represent an independent aquatic invasion. The case-bearing larvae often occur sympatrically, and on Kauai even species with similar case-types occur together, suggesting complex patterns of speciation and either past periods of isolation or sympatric speciation. Phylogenetic analysis of 2243 base pairs from two nuclear and one mitochondrial gene for 18 species confirm that each species is endemic to a single volcano, and that morphological divergence within case-types has not been dramatic. Diversification has been complex, and superficially similar case type lineages are not all monophyletic. Kauai, the oldest but smallest of the major high islands, supports more species in the aquatic guild than any other island, thus island age, rather than size, may be important in generating diversity in this group.

© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162, 15–42.