Assessment of the genetic diversity in populations of Philaenus spumarius collected from different areas

The spittlebug Philaenus spumarius is a widespread species in Europe, recently attentioned because of its relevant role in spreading the plant pathogenic bacterium Xylella fastidiosa (Xf), a new emerging pathogen threatening the landscape and several crops in southern European countries. Being the main species associated with the epidemic spread of this bacterium currently decimating olive trees in the Apulia region (southern Italy), molecular investigations have been carried out to characterise the populations occurring in the so-called Xylella-demarcated areas of Apulia versus those present in other regions currently free from X. fastidiosa. Analysis also included specimens received from Montenegro and Tunisia. Three DNA markers were used, the mitochondrial genes COI and cytochrome b and the nuclear gene EF1-?, to amplify and sequence DNA fragments from a total of 60 specimens. Mitochondrial sequence analysis showed that all Italian specimens belong to the south-west clade (which includes the Mediterranean basin and western Europe) and, in particular, the majority of the Apulian specimens and those collected in Montenegro belong to the eastern Mediterranean subgroup, whereas the specimens collected in other regions of Italy belong to the western Mediterranean subgroup. Conversely, the Tunisian specimens fell in the eastern group (Anatolia/Caucasus). Similar genetic relationships were retrieved from the analysis of the EF1-? gene. The data herein obtained, while confirming that the population of P. spumarius responsible for the epidemic spread of Xf in Apulia belong to a single phylogenetic group, integrate the large dataset of biological and ecological information collected from the studies intensified on this species in the last few years.