New insight into the systematics of the willowsia complex (collembola: Entomobryidae)

Abstract

The three closely related genera Willowsia Shoebotham 1917 with 22 species, Janetschekbrya Yosii 1971 with 2 species and Americabrya Mari-Mutt & Palacios-Vargas 1987 with 3 species (the “Willowsia complex”) are examined in the light of a phylogenetic analysis and a re-evaluation of their original differential characters. A hypothesis based on 56 morphological characters is proposed for 15 Willowsia species and Americabrya arida Christiansen & Bellinger 1980. With Drepanosira hussi Neuherz 1976 as outgroup, three major clades are recovered: the species Willowsia samarkandica, a clade with 4 species, and a large clade with 10 species and Americabrya arida in a terminal position. Conversely, if Americabrya is used as outgroup with the Willowsia species as ingroup, all Willowsia including W. samarkandica constitute a monophyletic clade. Biogeographically, we show that the Willowsia complex exhibits a remarkable distribution pattern. Beside four species of Willowsia largely distributed across continents, all species of the complex are restricted to two areas: the Neotropics, with the three species of Americabrya and the Willowsia species closest to this genus (W. mexicana); and the temperate and subtropical region of Asia, with all other species of Willowsia and the two species of Janetschekbrya. Using characters of scale morphology, the genera Americabrya, Janetschekbrya and Willowsia are redefined. Four types of scale morphology are disclosed in the genus Willowsia. The strong similarities between the scales of W. mexicana and those of Americabrya on one hand, and between those of Janetschekbrya and the chaetae of the unscaled genus Himalanura on the other hand, suggest that Willowsia in its current definition is probably paraphyletic. A key to the 27 recognizable species of the Willowsia complex is provided. W. samarkandica is redescribed. Complements to descriptions, mostly dorsal chaetotaxy, are given for W. buski, W. japonica, W. nigromaculata and W. platani. Three species new to science are described: W. yiningensissp. nov., W. quisp. nov. and W. potapovisp. nov. Two species are synonymized: W. kahlertaesyn. nov. of W. japonica, and W. mesothoraxasyn. nov. of W. jacobsoni. Three species considered as Willowsia in the literature are placed as incertae sedis because data on the presence of scales on dentes are unavailable. Two species are removed from Willowsia and assigned to Lepidosira for having scales on dentes. © 2011 Taylor & Francis Group, LLC.