HOW MANY TIMES HAS TERRESTRIAL BREEDING EVOLVED IN ANURAN AMPHIBIANS?

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Abstract
Aspects of the breeding biology of anurans have been used as generic criteria in a number of families and, in some instances, species may not be adequately classified without knowledge of their breeding biology. Terrestrial breeding has been used as justification for recognizing advanced genera or species, however, there is little available evidence that this mode of reproduction is either derived or advanced. It is becoming increasingly apparent that some species may have phylogenetic affinities which are independent of their present continental distribution. The possibility exists that terrestrial breeding may have been well established in early anurans and that it is maintained in varying diverse genera of most anuran families. Common ancestry would be a reasonable explanation for the evolution of terrestrial development in so many genera. Genetic selection involving physiological, embryological, and behavioural parameters of terrestrial breeders must surely be more involved than could be adequately explained by remarkable convergence. Perhaps some of the taxonomically valid characters, such as the architecture of the pectoral girdle, are more pliable and could conceivably be the result of minor genetic alteration. Terrestrially breeding anurans have variable karyotypes including variable numbers of chromosomes and the presence of telocentric pairs. Most aquatic breeders have conservative karyotypes which consist mostly of metacentric and submetacentric chromosomes. Speciation is assumed to be rapid among terrestrial breeders which may provide the basis for the evolution of major lineages of advanced frogs.