Revision of the Nearctic Liodessus affinis (Say 1823) species group (Coleoptera: Dytiscidae, Hydroporinae, Bidessini)

Abstract

AbstractNorth American members of the Liodessus affinis (Say 1823) species complex are revised. The species group comprises four species. Two new species are described: L. noviaffinis (type locality: Gainesville Forest Insect Lab, Alachua Co., Florida) and L. saratogae (type locality: Saratoga Springs, San Bernardino County, California). Liodessus obscurellus (LeConte 1852), formerly considered a junior subjective synonym of L. affinis, is given specific status. The following synonymies are established: L. affinis microreticulatus (Hatch 1928), L. charlottii (Clark 1862), L. emilianus (Clark 1862), L. erythrostomus (Mannerheim 1852), L. macularis (LeConte 1852), and L. nigrinus (Casey 1884) = L. obscurellus. All of these names were previously treated as junior subjective synonyms of L. affinis. Also, L. youngi (Larson & Roughley 1990) = L. abjectus (Sharp 1882). Lectotypes are designated for L. abjectus, L. charlottii, L. erythrostomus, L. emilianus, L. macularis, L. nigrinus, and L. obscurellus. A neotype is designated for L. affinis. Liodessus nanus (Aubé 1838) is considered a species name of uncertain status, but is probably a subjective synonym of L. affinis. A key is provided for the nine known species of North American Liodessus Guignot. The genus Liodessus is diagnosed, and its taxonomic history and questionable status as a natural group are discussed. The L. affinis complex is diagnosed, and its taxonomic history and natural history are discussed. Male genitalia are the only consistently useful structures known for differentiating species in the L. affinis complex. Females are not distinguishable based on currently known morphological features but may be identified using geographic information. Characters used previously, including coloration, punctation and general shape are too variable within and between species to be useful for species diagnosis or delimitation. For each species in the complex the following are provided: a bibliography of the species, discussion of type specimens, taxonomic history and synonymy, diagnosis, variation, etymology (for new species), geographic relationships, natural history, and geographic distribution. Distribution maps and illustrations of important structural features are provided for all species of the complex. For other Nearctic species of Liodessus the following are provided: a brief bibliography of the species, diagnosis, distribution, remarks about bionomics and/or taxonomy, and illustrations of important structural features.