The Grasshopper Paradigm in damselflies: evidence for phalanx-like postglacial recolonization of Europe from a Balkan refugium in Platycnemis pennipes Pallas (Odonata: Zygoptera: Platycnemidae)

Abstract

We explore haplotype diversity, phylogeography and phylogenetic relationships of the damselfly Platycnemis pennipes in Europe based on 618 bp DNA from the mitochondrial gene COI. A haplotype network analysis shows that the species is divided into two haplotype groups. One is restricted to the Italian Peninsula, while the other is found from the Black Sea region across eastern and central Europe to Scandinavia, England, and southwestern France. This pattern is recovered in a Bayesian phylogenetic analysis. Genetic distance (K2P) between the two groups is approximately 1.5%, while within-group variation is an order of magnitude lower. An analysis of the molecular variance (AMOVA) shows that variation between the two groups account for more than 96% of the total variation within the dataset, adding to the evidence that they have been isolated for a considerable amount of time. The pattern we find is similar to the so-called Grasshopper Paradigm in European phylogeography, where a species has recolonized Europe after the last glaciation from a glacial refugium in the southeast, while other refugial populations in the Iberian and Italian peninsulas have remained isolated to this day. In P. pennipes there is only an isolated refugial population in Italy as the species does not have current populations in the Iberian Peninsula. By comparing the genetic distance between the two groups to a previously published divergence time analysis of European Odonata we estimate that they have likely been isolated since the onset of the Saale Glaciation ca 400 ky ago.