Geographic variation in relict populations: genetics and phenotype of bush-cricket Pholidoptera frivaldskyi (Orthoptera) in Carpathians

A decreasing population size is often causing species extinction, however, relict species persisting in small-sized populations counter this. We analysed spatial genetic variation and past changes in population size at the maternally-inherited mitochondrial DNA level to clarify the origin of all recently known isolated populations of Pholidoptera frivaldskyi occurring in the range of Carpathian Mountains. Along with that we analysed also morphological variation as some phenotypic traits can retain useful information on population genetic structure. We found a relatively low genetic diversity within isolated populations as 778 bp COI gene sequences revealed only 13 unique haplotypes (n = 173 individuals from 10 populations). The spatial analysis of molecular variance identified three geographically homogenous genetic clusters (one in Slovakia and two in Romania) with a high level of differentiation among them, suggesting restricted gene flow, whilst Bayesian skyline simulation reconstructed a negative demographic change through evolutionary time. Inferred genetic pattern clearly coincides with differences in males' colour phenotype as the extent of pigmentation on the lateral pronotum varied significantly among genetic lineages. We suggest that geographical variation in the species populations has relict-like character and their isolated occurrence is not a result of recent introduction events. Identification of 'evolutionary units' may help in the conservation and management of this rare insect species.