Relationships of the Frogs of the Genus Ceratophrys (Leptodactylidae) and their Bearing on Hypotheses of Pleistocene Forest Refugia in South America and Punctuated Equilibria

Lynch,J. D. (School of Life Sciences, The University of Nebraska, Lincoln, Nebraska 68588) 1982. Relationships of thefrogs of the genus Ceratophrys (Leptodactylidae) and their bearing on hypotheses of Pleistocene forest refugia in South America and punctuated equilibria. Syst. Zool. , 31:166-179. -Of the eight currently recognized species of Ceratophrys (aurita, calcarata, cornuta, cranwelli, ornata, pierottii, stolzmanni, and testudo) six are considered to be species. Ceratophrys testudo is considered a synonym of C. cornuta. The subfamily Ceratophryinae is argued to be monophyletic and is defined on the basis of two synapomorphies. The genus Ceratophrys (excluding C. pierottii) is monophyletic and is defined on the basis of three synapomorphies. Two subgenera are recognized within Ceratophrys. The subgenus Ceratophrys (one synapomorphy) includes C. aurita, C. cranwelli, and C. ornata where C. aurita and C. ornata are more closely interrelated. The subgenus Stombus (three synapomorphies) includes C. calcarata, C. cornuta, and C. stolzmanni where C. calcarata and C. cornuta are nearest relatives. Ceratophrys pierottii is hypothesized to be an intergeneric hybrid between Ceratophrys cranwelli and Lepidobatrachus llanensis. The least refuted hypothesis of relationships is inconsistent with the hypothesis that speciation amongst forest-dwelling species was mediated by Pleistocene contractions of forest into refugia. The northern species of Ceratophrys form a group fragmented in part by the Andes and the southern (and eastern) species form a second group fragmented ecologically but not physically. The widespread Amazonian species, C. cornuta, shows little evidence of having had its distribution fragmented by forest contractions. Ceratophrys cornuta is the most widely distributed species, is centrally distributed, and is by far the most apomorphous (measured in terms of autapomorphies). Such a combination is contrary to the expectations under the macroevolutionary hypothesis termed punctuated equilibria. [Cladistics; Ceratophrys; South America; Pleistocene forest refugia; punctuated equilibria; systematic relationship; hypothesis testing. ] The biota of South America is remarkably diverse reflecting the antiquity of the continent's isolation as well as its ecogeographic diversity. The Neotropics contain a very diverse anuran fauna. Some elements of that fauna are wholely restricted to rainforests, others are endemic to non-forest units, and yet others have species in both rainforests and non-forest environments (Lynch, 1979). An example of the latter is the leptodactylid frog genus Ceratophrys with three rainforest species (C. aurita in the Atlantic forests of Brazil and C. cornuta and C. testudo in the forests of the Amazon Basin) and five species in non-forest areas (C. calcarata in northern Colombia and Venezuela, C. cranwelli and C. pierottii in the Chaco, C. ornata in the grasslands of Argentina, and C. stolzmanni in the arid terrain around the Gulf of Guayaquil (Fig. 1). Ceratophrys and the Chacoan genus Lepidobatrachus make up the subfamily Ceratophryinae (Lynch, 1971). Two of the rainforest species (C. aurita and C. cornuta) have been considered closely related (Cochran and Goin, 1970; Lynch, 1979) and as such provide support for the refugia hypothesis of Haffer (1969, 1974, 1979) and indirectly for a relatively recent speciation event. The purposes of this study are two-fold: firstly, to discover the pattern of relationships within Ceratophrys and, secondly, to use these data