Systematics and Distribution of the Mexican and Central American Stream Frogs Related to Eleutherodactylus rugulosus

Abstract

The ubiquitous Mexican and Central American stream frogs allied to Eleutherodactylus rugulosus form a confusing spectrum of distinctive to subtly different populations. The condition of the male secondary sexual features: presence or absence of vocal slits and presence or absence of nuptial pads on the thumb, combined with the geographically consistent color (white, pale yellow, gold, orange, red or chestnut) of the venter of adults in life, provide the key to untangling the species problem in this group. For purposes of analysis the populations were grouped by the male secondary sexual features and compared in detail on the basis of 15 other characters of morphology and coloration. Twelve species are recognized within the rugulosus group, and may be placed in four series based on the presence (+) or absence (-) of vocal slits and nuptial pads in adult males. + +: Eleutherodactylus milesi of northern Honduras; E. merendonensis of northwestern Honduras; E. punctariolus of southern Costa Rica and western Panama; E. fleischmanni of Costa Rica; and E. escoces (sp. nov.) a bright red-bellied new species from the slopes (1100-2100 m) of Volcan Barba, Volcan Irazu and Volcan Turrialba of Costa Rica; +-: E. vocalis of northwestern Mexico; a new species, E. azueroensis (sp. nov.) from the Peninsula Azuero of western Panama; and E. taurus of the Golfo Dulce lowlands of southwestern Costa Rica and adjacent Panama; +: E. matudai from the Pacific slopes of extreme southern Mexico and adjacent Guatemala; and a new species, E. angelicus, from the Cordillera de Tilaran and Volcan Poas in Costa Rica; --: E. brocchi of Alta and Baja Verapaz, Guatemala; and the wideranging lowland and slope species known from Mexico to western Panama, E. rugulosus. The Atlantic versant Mexican populations of this species are distinctive and have been variously recognized as a subspecies of E. rugulosus or as a separate species by previous authors. The earliest name for this population is Hylodes berkenbuschii Peters and E. natator Taylor and E. vulcani Shannon and Werler are strict synonyms. The seemingly allopatrically isolated southern populations of E. rugulosus in eastern and southwestern Nicaragua, Costa Rica and Panama are slightly distinct from the main population system of E. rugulosus. The earliest name for the southern stock is Lithodytes ranoides Cope with Liohyla pittieri Guinther a strict synonym. Neither of these populations is recognized as separate from E. rugulosus. E. chiquito Lynch placed by its describer in the rugulosus group is a synonym of E. greggi of extreme southern Pacific slope Mexico and Guatemala, which is a member of the distantly related mexicanus group. Members of the rugulosus group fall into four geographic and ecologic distribution patterns: a) lowland and slope species, centered on the distribution of the wide-ranging E. rugulosus population system, with the allopatric E. vocalis on the northwest Mexican periphery, E. azueroensis on the southwest Panama periphery, the small population of E. merendonensis in northwestern Honduras and E. taurus occupying the Golfo Dulce lowlands of Costa Rica and western Panama, where E. rugulosus occurs only along the Pacific slope (600-1200 m) of the Talamanca-Chiriqui massif; b) E. brocchi and E. matudai in the highlands of southern Mexico and Guatemala; c) E. milesi in the uplands of