Autor: Albert Levan

One of the major problems encountered when attempting to provide a comprehensive overview of amphibian cytogenetics is the choice of a suitable taxonomy. Substantial changes to the higher taxonomies continue to occur at a relatively rapid rate, although they have varying levels of acceptance. A comparison of Dowling & Duellman?s (1974) radical reappraisal of the Anura, when compared to the currently aecepted version edited by Frost (1985), shows considerable flexibility at the familial and sub-familial levels, and major discrepancies in taxonomic affiliations at all levels. Much of the variation in higher taxonomic nomenclature appears to have been strongly influenced by geographic criteria. For example, Savage (1973) argued that the Australian hylid frogs should be relegated to a separate famin called the Pelodryadidae, on largely geographic grounds. Although this step has not gained universal acceptance, Frost (1985) did give these animals subfamilial status. Similarly, Dowling & Duellman (1974) argued that the primitive North American frog Ascapbus truei should be given familial status and placed it in the monotypic famin Ascaphidae. However, Frost (1985) included Ascapbus with three endemic New Zealand species in the Leiopelmatidae, a decision which in the past has been most difficult to justify on geographic grounds. In other cases, such as the Arthroleptidae and Hemisiidae, specialized groups of animals have been elevated to familial status from subfamilial rank because they form a unique and morphologically distinctive assemblage. Such reclassifications have been made possible by the significant taxonomic input being made in these taxa. That is, the additional species which had been described provided systematists with a broad perspective on the range of variation within a higher taxa, and they can therefore more precisely define its limits. The magnitude of the taxonomic changes can be seen in the following two examples. Dowling & Duellman (1974) when discussing the largely African Hyperoliidae considered the then known group to be comprised of 14 genera with 63 species. Twelve years later Frost (1985) recognized 14 genera and 219 species. Similarly, the South American poison arrow frogs of the Dendrobatidae comprised three genera and 60 species (sensu Dowling & Duellman, 1974), whereas, Frost (1985) considered four genera and 116 species. In both examples, these substantial changes to the number of species are a product of the increased taxonomic effort in regions where such studies have in the past been neglected, namely Africa and South America.