Psyllid communication: acoustic diversity, mate recognition and phylogenetic signal

Acoustic signals play an important role in mate selection and speciation in diverse groups of insects. We report reciprocal acoustic mate signalling, often as highly synchronised duetting, for several species of psyllid (Hemiptera:Psylloidea). We reveal that considerable acoustic diversity is present in Australian psyllids belonging to the family Triozidae. The acoustic signals are species and gender specific. Our acoustic analysis and observations suggest that acoustic signals are important in both species recognition and mate selection in psyllids. We found a significant level of phylogenetic signal in the acoustic data when we compared divergence in genetic data (obtained from mitochondrial DNA sequences of the small subunit rRNA) with divergence in acoustic signals in two groups of Australian psyllids. Phylogenetic reconstruction based on DNA sequence data supports the monophyly of the Eucalyptus-feeding genus Schedotrioza Tuthill & Taylor, 1955, whereas a diverse but little known group on Casuarinaceae hosts appears to be paraphyletic. These two psyllid groups also differ in amounts of geographical and ecological sympatry. We found a significant positive correlation between acoustic distance and genetic distance using pairwise comparisons for all taxa, but the trends within the two groups differ due to a negative association between acoustic and genetic divergence among the sympatric taxa. Phylogenetic information in acoustic data may be greatest in recently speciating and allopatric groups because of increased acoustic divergence in sympatric taxa and greater acoustic convergence in more distantly related species. Additional keywords: acoustic communication, Allocasuarina, Casuarinaceae, Eucalyptus, Psylloidea, speciation, substrate vibration, Triozidae.