| The phylogenetic placement of the neotropical Dendrobatidae (poison-dart frogs) among all other anurans remains controversial, because of differing views concerning the identity of its sister group. The dendrobatids are hypothesized to be derived from within either the Leptodactylidae or the Ranidae, which belong to the superfamilies Bufonoidea and Ranoidea, respectively. An extensive phylogenetic analysis was undertaken to investigate neobatrachian relationships, and to address specifically the placement of the dendrobatid family. The study included 41 species representing 38 genera and 14 families of anurans, and was based on 124 osteological characters.; The phylogeny resulting from this analysis showed several neobatrachian taxa to be paraphyletic: (1) "Bufonoidea" with respect to the Microhylidae and Ranoidea; (2) "Leptodactylidae" with respect to Bufonidae, Hylidae, Myobatrachidae, Microhylidae, and Ranoidea; and (3) "Ranidae" with respect to the Rhacophoridae, Arthroleptidae, and Dendrobatidae. Several interesting sister-group relationships include: Arthroleptidae to Dendrobatidae; Microhylidae to Ranoidea; and Mantellinae to Rhacophoridae. The dendrobatid-arthroleptid-"ranid" relationship is an important framework for biogeographic discussion of anurans because of the collateral African and South American distributions of these groups. In conclusion, the Dendrobatidae should be included in the superfamily Ranoidea based on this analysis.; In addition, this study provided a case-in-point for the examination of complex characters, through the empirical analysis of the pectoral girdle. These data support that decisions regarding functional or structural dependence should not, and need not, be made a priori. Historical interdependence or independence can be verified by the occurrence of the character states of the individual elements as inferred from a phylogenetic hypothesis. When the individual elements of a complex functional character, such as the anuran pectoral girdle, were coded a priori as independent characters in a phylogenetic analysis, the interrelationship of characters was verified at two levels: (1) congruence among the individual elements of the pectoral girdle; and (2) congruence between these elements and non-girdle characters. This analysis empirically supports that individual elements can be inferred for their historical interdependence as part of a complex character. Furthermore, the historical information from phylogenetic studies can help to provide biological definitions based on homologous morphology and not analogous functions. |
