Phenetic Relationships Among Populations of Podarcis sicula and P. melisellensis (Sauria: Lacertidae) from Islands in the Adriatic Sea

Abstract

Island populations (31) of P. sicula and P. melisellensis from Yugoslavia were examined to determine phenetic similarities based on means of 15 characters. Both cluster analysis and multidimensional scaling (MDS) revealed the following patterns of variation: the 2 spp. formed distinct groups; within each species, OTU [operational taxonomic unit] from northern and southern islands grouped separately; and within P. melisellensis, OTU from small islands tended to resemble other small island OTU from geographically close islands. These patterns may contradict similarities implied by previous subspecific designations based largely on color and pattern differences. Genetic drift, gene flow and selection are evaluated as explanations for observed phenetic patterns. Drift may be highly unlikely as a major force determining regional, large island and small island similarities among OTU. Channel depths and estimates of the rate of net increase in sea level suggest that the northern islands are younger than the southern islands, supporting the idea that gene flow has been restricted among the southern islands and between the 2 regions for a longer time than among the northern islands. Combined with differences in selection regimes, the recency of gene flow may have been important in determining north-south phenetic similarities. Populations on small islands are exposed to qualitatively different selection regimes than those on large islands. The closer similarity of northern, small island OTU to large island OTU suggests that the northern OTU have not responded to small island selection regimes to the same extent that southern island OTU have.