RAPID CHROMOSOME EVOLUTION IN JAMAICAN FROGS OF THE GENUS ELEUTHERODACTYLUS (LEPTODACTYLIDAE)

Chromosomes from all 17 species of native Jamaican Eleutherodactylus a s well as introduced E.johnstonei were subjected to computer-assisted analyses. Diploid chromosome numbers of 24, 26, 28, 30 and 32 were fou nd and no two species had identical karyotypes. Karyotypic data were s uperimposed on a phylogeny derived from allozyme and immunological dat a in order to assess karyotypic changes that occurred in lineages of J amaican Eleutheronactylus. Chromosome number changes have occurred at least nine times on the island and have involved both fission and fusi on mutational events. C-bands and the sites of secondary constrictions varied and provide very little phylogenetic information. In most inst ances, karyotypically determined interspecific evolutionary relationsh ips corresponded with the molecular data. The combination of karyologi cal analyses and molecular data clarified lineages which involved conv ergent chromosome numbers or extremely divergent karyotypes. Karyotypi c changes in Jamaican Eleutherodactylus are best explained by chromoso me fission, fusion, translocations and inversions which arose in isola ted demes and have been fixed through inbreeding and genetic drift. Ra tes of karyotypic evolution among Jamaican Eleutherodactylus are much faster than previous published rates for frogs. Karyotypic evolution a ppears to be dictated by behavioural factors and effective population sizes irrespective of taxonomic groupings.