CHARACTER ASSESSMENT, GENUS LEVEL BOUNDARIES, AND PHYLOGENETIC ANALYSES OF THE FAMILY RHACOPHORIDAE:: A REVIEW AND PRESENT DAY STATUS

Abstract

The first comprehensive phylogenetic analysis of the family Rhacophoridae was conducted by Liem (1970) scoring 81 species for 36 morphological characters. Channing (1989), in a reanalysis of Liem’s study, produced a phylogenetic hypothesis different from that of Liem. We compared the two studies and produced a third phylogenetic hypothesis based on the same characters. We also present the synapomorphic characters from Liem that define the major clades and each genus within the family. Finally, we summarize intergeneric relationships within the family as hypothesized by other studies, and the family’s current status as it relates to other ranoid families. The family Rhacophoridae is comprised of over 200 species of Asian and African tree frogs that have been categorized into 10 genera and two subfamilies (Buergerinae and Rhacophorinae; Duellman, 1993). Buergerinae is a monotypic category that accommodates the relatively small genus Buergeria. The remaining genera, Aglyptodactylus, Boophis, Chirixalus, Chiromantis, Nyctixalus, Philautus, Polyp edates, Rhacophorus, and Theloderma, comprise Rhacophorinae (Channing, 1989). The family is part of the neobatrachian clade Ranoidea, which also includes the families Ranidae, Hyperoliidae, Dendrobatidae, Arthroleptidae, the genus Hemisus, and possibly the family Microhylidae. The Ranoidea clade is distinguished from other neobatrachians by the synapomorphic characters of completely fused epicoracoid cartilages, the medial end of the coracoid being wider than the lateral end, and the insertion of the semitendinosus tendon being dorsal to the m. (musculus) gracilis (Ford and Cannatella, 1993). Liem (1970) analyzed the family Rhacophoridae along with some representatives of the family Hyperoliidae to revise the systematics and possibly construct a phylogenetic hypothesis of relationships among these families' genera. Based on this study, distinguishing characteristics of Rhacophoridae have been proposed as being: the fusion of carpals and tarsals; only one slip of the m. extensor digitorum communis longus inserting on the distal portion of the fourth metatarsal; the outermost slip of the m. palmaris longus inserting on the proximolateral rim of the aponeurosis palmaris; the frontoparietal being trapezoidal; the terminal phalanx being bifurcate; and the presence of intercalary elements (if hyperoliids are not sister to rhacophorids, otherwise they share this characteristic; Channing, 1989; Ford and Cannatella, 1993). Channing (1989), in a reanalysis of Liem's study and based on his set of characters, produced a cladogram in some respects similar to, but in many others different from Liem’s preferred tree (Liem, 1970; Figure 1). The similarities are that the Malagasy rhacophorid genera and the genus Buergeria have basal positions, and Aglyptodactylus is sister to Mantidactylus. But, none of the remaining sister group relationships are common between the two topologies (e.g., Nyctixalus is sister to Theloderma in Channing’s tree, but is sister to Chirixalus in Liem’s tree) and Buergeria, not the (Mantidactylus, Aglyptodactylus) clade, is the most basal lineage. Based on this cladogram Channing proposed, as did Duellman and Trueb (1986), that rhacophorids and hyperoliids are sister groups, but he also moved the subfamily Mantellinae from Ranidae to Rhacophoridae because Mantidactylus (a mantelline ranid) and Aglyptodactylus (a rhacophorid) shared nine synapomorphies and were nested within the rhacophorid clade. The other mantelline genera Mantella and Laurentomantis were also moved to the family Rhacophoridae in his study (though no representatives of these genera were examined). Channing (1989) also proposed that the monotypic subfamily Buergeriinae be erected to accommodate the genus Buergeria, based not on any unique characters for this genus per se, but on its basal position in his tree (Figure 2). Finally, Channing indicated that the subfamily Rhacophorinae (which in Frost [1985] includes the genera Aglyptodactylus, Boophis, Buergeria, Chirixalus, Chiromantis, Nyctixalus, Polyp edates, Rhacophorus, and Theloderma) is paraphyletic because in his reconstructed phylogenetic tree the genus Philautus, though considered the one genus of the subfamily Philautinae (Dubois, 1981; Frost, 1985), is nested well within the Rhacophorinae subfamily and is sister to Chiromantis (Figure 2), and because Aglyptodactylus forms a clade with Mantidactylus, as previously mentioned. Also, his most parsimonious trees support either Polypedates or the (Theloderma, Nyctixalus) clade being sister to the (Chirixalus, Chiromantis, Philautus, Rhacophorus ) clade, and within this clade, Rhacophorus is either sister to Chirixalus or the (Philautus, Chiromantis) clade. As part of a larger project, we have re-analyzed the data set of Liem (1970) and its modification by Channing (1989) in an attempt to understand how different phylogenetic conclusions can result from the same characters, and to determine whether these characters are phylogenetically and taxonomically important in delimiting genera within this family. In other words, does each genus comprise a monophyletic group that can be separated from other genera by synapomorphic characters, based on the data set presented by Liem (1970)? We consider this important because the assignment of a species (particularly in Asia) before his study was based on the presence or absence of vomerine teeth, with species that contain vomerine teeth assigned to the genus Rhacophorus and those that lack vomerine teeth assigned to the genus Philautus (Inger, 1954, 1966; Taylor, 1962; Berry, 1975; Dutta and ManamendraArachchi, 1996). Yet, since the resurrection of the genera Buergeria, Chirixalus, and Polypedates (Liem, 1970), this method of species assignment appears to have been inadequate, resulting in numerous reassignments (Table 1).