Genetic differentiation and detection of cryptic species in the genusLepismachilis(Insecta: Microcoryphia) from the Western Mediterranean region

Abstract

Different species of the bristletail genusLepismachiliswere collected in 14 localities in Italy and Spain and an allozyme electrophoretic survey was carried out to estimate the degree of genetic variability and differentiation at intra- and interspecific levels. Four morphological species were initially identified (L. osellai,L. y-signata,L. affinis,L. targionii), but the electrophoretic analysis demonstrated the presence of two additional species among the individuals ofL. targionii(Lepismachilissp1 and sp2). The validity of these species and their differentiation fromL. targioniiwere demonstrated by the fixation of alternative allelic patterns at several loci (7 inLepismachilissp1 and 8 inLepismachilissp2), coupled with fixed, previously undetected, morphological differences. In addition,Lepismachilissp2 was sympatric withL. targioniiin three collecting sites, where the fixation of alternative allelic patterns unequivocally demonstrated reproductive isolation. Genetic variability did not seem to be correlated with local ecological factors, and differences between species should rather be explained by different historical factors. Low levels of gene flow, estimated with two different indirect methods, were observed inL. targioniiandL. y-signata, and were due to high levels of structuring among populations. Genetic differentiation among conspecific populations was not correlated to their geographical arrangement and the presence of loci fixed for different alleles among them suggested that stochastic factors (such as genetic drift) may have played a role in determining genetic differentiation of geographically isolated populations. Genetic divergence values indicated that the six species are well differentiated and allozyme profiles were diagnostic for all of them. On the other hand, allozyme data did not provide adequate information to resolve evolutionary relationships among the species, nor did they confirm the validity of the two subgenera (LepismachilisandBerlesilis) in which the genusLepismachilisis traditionally divided.