Patterns of gene flow and genetic structure in cave-dwelling crickets of the Tuscan endemic, Dolichopoda schiavazzii (Orthoptera, Rhaphidophoridae)

Dolichopoda schiavazzii is a cave cricket species endemic to Tuscany, Italy. This species inhabits natural limestone caves and also man-made hypogean environments. Dolichopoda schiavazzii can colonize new environments both passively and actively. This species shows a metapopulational structure depending on both the cave's external bioclimatic conditions and the geographical distance. This paper reports data on 26 allozyme loci in nine populations of D. s. schiavazzii and in one of D. s. caprai, investigates their genetic structuring and provides measures of gene flow between them at different geographical scales. Some loci showed heterozygote deficiencies, probably owing to the Wahlund effect, caused by the mixing of individuals belonging to two different cohorts. Genetic subdivision is high, particularly among populations inhabiting caves located on the Tyrrhenian coast. The mean F-ST (theta estimator) across populations was 0.34. An analysis of the gene flow levels, carried out by comparing pairwise Nm values, indicates that the number of migrants drops as the geographical distance increases, suggesting the actual occurrence of gene flow only between geographically close populations in an inner area of Tuscany where the occurrence of mesophilous woods might favour migration between caves. The general picture, however, is one of a substantial lack of gene flow, even if a significant trend of isolation by distance is found, probably reflecting historical gene flow.