Classification, Distribution, and Phylogeny of North American (North of Mexico) Species of Gyrinus Muller (Coleoptera: Gyrinidae)

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The species of Gyrinus Müller from North America (North of Mexico) are revised; 40 species are assigned to Gyrinus. Gyrinus rugosus is described as new from California. Separate keys are provided for males and females. Information is provided about type specimens and taxonomic notes, sexual dimorphism, habitat information, and Nearctic distribution. Five new synonyms are recognized: G. frosti Fall and G. floridensis Ochs are junior synonyms of G. gibber LeConte, G. hatchi Wallis is junior synonym of G. ventralis Kirby, G. punctellus Ochs is junior synonym of G. bifarius Fall, and G. instabilis Fall is junior synonym of G. aeratus Stephens. Lectotypes are designated for: G. pectoralis LeConte, G. minutus Fabricius, G. rockinghamensis LeConte, G. confinis LeConte, G. dichrous LeConte, G. maculiventris LeConte, G. aquiris LeConte, and G. ventralis Kirby. A neotype is designated for each of G. parcus Say, G. analis Say, G. obtusus Say. G. limbatus Say is listed as a nomen inquirendum.

The occurrence of G. marinus Gyllenhal and G. aeratus Stephens in the Nearctic region is verified. In the eastern half of North America, the most speciose region is in the northeast United States; in western North America it is in British Columbia. The phylogenetic position of Gyrinus in Gyrinidae is investigated by using characters in Hatch (1925), Ochs (1926-27), Balfour-Browne (1950), Brinck (1955), and Larsén (1966), with Spanglerogyrus Folkerts (Spanglerogyinae) as the outgroup. Most data indicate that, within Gyrininae, Orectochilini is the sister clade to Gyrinini and Enhydrini. A phylogenetic hypothesis for Nearctic species of Gyrinus is also constructed; this phylogenetic analysis is highly polychotomous but four groups are suggested. Monophyly of these groups is primarily established by abdominal coloration and aedeagal structure. Two subgroups based on leg and tarsal claw coloration are proposed within the third and fourth clades.

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