The genera Boiruna and Clelia (serpentes: pseudoboini) in Paraguay and Argentina

Abstract

Snakes of the pseudoboine genera Clelia, which is probably polyphyletic, and Boiruna are distributed from southern Argentina, southern Brazil, and Uruguay northwards into central México. Six members occur in Paraguay and Argentina: B. maculata, Clelia bicolor, C. clelia, C. plumbea, C. quimi, and C. rustica. Historically, there has been taxonomic confusion among the larger species (B. maculata, C. clelia, C. plumbea, and C. rustica) and between the small species (C. bicolor and C. quimi). All of the species except C. rustica have distinct ontogenetic color changes. Species can be distinguished on the bases of size, color, hemipenial spines, and loreal, supralabial, and ventral scale counts. Much of the morphological evolutionary differentiation in Boiruna and Clelia seems to have taken place in the snout region, as evidenced by the differing proportions of the scales of the loreal region. Boiruna maculata has the widest ecological amplitude. It is broadly distributed in most vegetation types north of the 38th parallel in central Argentina, being absent only from the deltaic sediments of Buenos Aires Province, Argentina and the broad valleys and rolling hills of eastern Paraguay. Clelia bicolor is most common in the Paraguay and Paraná river valleys, with a few records from the Andean foothills in northern Argentina. Clelia clelia is distributed along the Río Paraguay and the lower Paraná, and is also found throughout much of eastern Paraguay. Clelia plumbea is apparently parapatric with C. clelia along the Río Paraná in southeastern Paraguay and Misiones Province, Argentina. The ranges of C. quimi to the east and C. bicolor in the west about in this same region without apparent overlap. There are no vouchered records of Clelia rustica from Paraguay. In Argentina, it is a species of temperate climates; north of the 30th parallel, it occurs in the Andean foothills and the wet forests of Misiones Province. Southwards, it is widely distributed to beyond the 40th parallel.