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?

Abstract

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

De novo comparative transcriptome analysis of a rare cicada, with identification of candidate genes related to adaptation to a novel host plant and drier habitats

“…3a). This is in line with the genetic differentiation among populations of S. yangi based on mitochondrial ( COI + COII + Cytb + A6A8 ) genes, where the mean Fst among the three comparisons, ‘HL vs HC’, ‘HL vs FX’ and ‘HC vs FX’ was 0.0735, 0.0676 and 0.0121, respectively [8]. This suggests that differential gene expression in the midgut among these populations is closely associated with genetic variations of related populations.…”

“…In this case, the DEGs detected in the midgut of S. yangi might be initially beneficial in the process of host shift in this species, which may subsequently evolve in a long-term feeding on a new host plant (viz., E. lepidosperma ). A previous study indicated that the HL population has evolved into a distinct independent lineage according to the analysis of population differentiation based on both molecular data and males’ calling song structure [8]. The deserts or semi-deserts surrounding the Helan Mountains were previously shown as a major dispersal and climatic barrier for gene flow of related animals [74].…”

“…This rare species had been known to be distributed in the Loess Plateau and adjacent areas in Shaanxi Province and the Helan (hereafter HL) Mountains, Ningxia Hui Nationality Autonomous Region [4, 5, 7]. During the field investigations of S. yangi since 2011, a few more populations were discovered from the Loess Plateau and adjacent areas in Shaanxi, Shanxi and Gansu provinces [8]. We found that most populations of S. yangi occurring in the Loess Plateau and adjacent areas specialize on the sour jujube Ziziphus jujuba Mill.…”

“…spinosa is available (see Results). Genetic evidence and acoustic analysis of the calling song of males significantly indicate that the HL population is genetically differentiated from other populations of S. yangi , which provide a possible example of incipient speciation in insects [8]. This, coupled with the fact that Z. jujuba var.…”

The East Asian Winter Monsoon Acts as a Major Selective Factor in the Intraspecific Differentiation of Drought-Tolerant Nitraria tangutorum in Northwest China

“…Higher degrees of genetic variation were found in both East-A ( H T = 0.843) and East-B ( H T = 0.930) lineages than in the West lineage ( H T = 0.375) ( Table 2 ), further demonstrating that population divergence in N. tangutorum originated in the eastern groups. Taken together, these data suggest that genetic variation is a major driver of population differentiation [ 40 , 41 , 42 ].…”