Description of Calling, Courtship and Mating Behaviour of Six Species of the Genus Zyginidia (Auchenorrhyncha: Cicadellidae).

The vibrational communication and mating behaviour of the graminicolous leafhoppers Zyginidia pullula, Z. ribauti, Z. scutellaris, Z. serpentina, Z. sohrab, and Z. biroi were investigated to explain why the first five species hybridize. Z. biroi was used as a control species. All species behaved in the same way and no significant statistical differences were detected with regard to male calls, while female calls and the male courtship song differed in Z. biroi, thus showing that a specific pre-mating isolation mechanism was used by the latter species and the first five ones lacked such a mechanism. In addition, Z. sohrab is missing in Italy, while the other species live allopatrically in Italy, with the only exceptions being Z. serpentina and Z. biroi, which live in Sicily and are often found in sympatry, and Z. scutellaris and Z. biroi, which live in Sardinia. All these species can be distinguished by means of male genital appendages; however, Z. biroi is longer and has a different body colour. The existence of natural hybrids of Z. pullula, Z. ribauti, and Z. scutellaris in the Italian peninsula and their hybridization in the laboratory with Z. serpentina and Z. sohrab require the investigation of possible post-mating reproductive barriers before re-considering their systematic validity.

Unravelling the Wolbachia evolutionary role: the reprogramming of the host genomic imprinting.

Environmental factors can induce significant epigenetic changes that may also be inherited by future generations. The maternally inherited symbiont of arthropods Wolbachia pipientis is an excellent candidate as an 'environmental' factor promoting trans-generational epigenetic changes: by establishing intimate relationships with germ-line cells, epigenetic effects of Wolbachia symbiosis would be manifested as a 'maternal effect', in which infection of the mother modulates the offspring phenotype. In the leafhopper Zyginidia pullula, Wolbachia feminizes genetic males, leaving them as intersexes. With the exception of male chitinous structures that are present in the last abdominal segment, feminized males display phenotypic features that are typical of females. These include ovaries that range from a typical histological architecture to an altered structure. Methylation-sensitive random amplification of polymorphic DNA profiles show that they possess a female genomic imprint. On the other hand, some rare feminized males bear testes instead of ovaries. These specimens possess a Wolbachia density approximately four orders of magnitude lower than feminized males with ovaries and maintain a male genome-methylation pattern. Our results indicate that Wolbachia infection disrupts male imprinting, which dramatically influences the expression of genes involved in sex differentiation and development, and the alteration occurs only if Wolbachia exceeds a density threshold. Thus, a new Wolbachia's role as an environmental evolutionary force, inducing epigenetic trans-generational changes, should now be considered.