Mitochondrial DNA variation and the evolutionary history of the Mediterranean species ofCicadaL. (Hemiptera, Cicadoidea)

Checklist and provisional atlas of singing cicadas (Hemiptera: Cicadidae) of Bulgaria, based on bioacoustics

Background

The singing cicadas (Hemiptera: Cicadidae) of Bulgaria were poorly known. There are published records for 14 species: Cicadaorni, Lyristesplebejus, Cicadatraatra, Cicadatrahyalina, Cicadatrapersica, Cicadettamontana, Cicadettamediterranea, Dimissalnadimissa, Oligoglenatibialis, Tympanistalnagastrica, Pagiphoraannulata, Saticulacoriaria, Tibicinahaematodes and Tibicinasteveni.

New information

Two species from this list were doubtful in the beginning of our study, since Tympanistalnagastrica is distributed in central and southern Portugal and Saticulacoriaria is a north African species.

We checked three major institutional collections housed in Sofia, Bulgaria: the National Museum of Natural History (SOFM), the Institute of Zoology (ZISB) and the Biology Faculty of Sofia University "St. Kliment Ohridski" (BFUS). We confirmed 11 of the species mentioned in literature, except Cicadettamediterranea and found two additional species: Cicadatraplatyptera and Cicadettamacedonica (the specimens in BFUS were bioacoustically confirmed).

Based on this knowledge, we further investigated the singing cicadas of Bulgaria with the use of morphological and bioacoustic methods in the years 2008, 2009, 2010, 2012, 2016, 2018 and 2019. We were not able to confirm the presence of Cicadatrapersica and Cicadettamediterranea, but found three additional species: Cicadettabrevipennis s. lat., Cicadettacantilatrix and Tettigettulapygmea. Using the bioacoustic methods, we also detected unknown singing patterns, which could belong to three or four additional taxa, which need to be described.

The Bulgarian fauna of singing cicadas at the moment consists of 16 confirmed and 3-4 potential species.

Genetic divergence, population differentiation and phylogeography of the cicada Subpsaltria yangi based on molecular and acoustic data: an example of the early stage of speciation?

Background

Geographical isolation combined with historical climatic fluctuations have been identified as two major factors that contribute to the formation of new species. On the other hand, biotic factors such as competition and predation are also able to drive the evolution and diversification of organisms. To determine whether geographical barriers contributed to population divergence or speciation in the rare endemic cicada Subpsaltria yangi the population differentiation, genetic structure and phylogeography of the species were investigated in the Loess Plateau and adjacent areas of northwestern China by analysing mitochondrial and nuclear DNA and comparing the calling song structure of 161 male individuals.

Results

The results reveal a low level of genetic differentiation and relatively simple phylogeographic structure for this species, but two independent clades corresponding to geographically isolated populations were recognised. Genetic and geographical distances were significantly correlated among lineages. Results of divergence-time estimation are consistent with a scenario of isolation due to glacial refugia and interglacial climate oscillation in northwestern China. Significant genetic divergence was found between the population occurring in the Helan Mountains and other populations, and recent population expansion has occurred in the Helan Mountains and/or adjacent areas. This population is also significantly different in calling song structure from other populations.

Conclusions

Geographical barriers (i.e., the deserts and semi-deserts surrounding the Helan Mountains), possibly coupled with related ecological differences, may have driven population divergence and allopatric speciation. This provides a possible example of incipient speciation in Cicadidae, improves understanding of population differentiation, acoustic signal diversification and phylogeographic relationships of this rare cicada species of conservation concern, and informs future studies on population differentiation, speciation and phylogeography of other insects with a high degree of endemism in the Helan Mountains and adjacent areas.

Electronic supplementary material

The online version of this article (10.1186/s12862-018-1317-8) contains supplementary material, which is available to authorized users.