Genetic differentiation reflects geological history in the Azorean land snail, Leptaxis azorica

The land snail Leptaxis azorica , endemic on the Azores, was subjected to an electrophoretic (allozymes) and morphometric (genital tract) analysis. Genetic distances suggest the presence of four distinct lineages and are compatible with colonisation proceeding from the eastern, older islands (Santa Maria and São Miguel) to the west (Flores and Corvo). On São Miguel, genetic and morphometric differentiation is concordant with the separate colonisation of two islands that gave rise to the current island 50 000 years ago. The maximum time available for differentiation in isolation (0.55 million years) suggests a high rate of allozyme change between the two lineages on São Miguel. This may be related to population isolation and bottlenecks caused by human and volcanic activity on São Miguel in relatively recent times. This is more prominent in the eastern region where populations are also characterised by reduced genetic variation (loss of alleles and heterozygosity) compared to populations elsewhere.