Search

Background: Although the importance of host plant chemistry in plant-insect interactions is widely recognized, our understanding about the genetic basis underlying the relationship between changes in midgut proteins and adaptation of plant-feeding insects to novel host plants and habitats is very limited. To address this knowledge gap, the transcriptional profiles of midguts among three populations of the cicada Subpsaltria yangi Chen were compared. Among which, the Hancheng (HC) and Fengxiang (FX) populations occurring in the Loess Plateau feed on Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chow, while the population occurring in a much drier habitat in the Helan (HL) Mountains is locally specialized on a chemically divergent plant, Ephedra lepidosperma C. Y. Cheng., Results: Based on comparative analysis, 1826 (HL vs HC) differentially expressed genes (DEGs) and 723 DEGs (HL vs FX) were identified between the populations utilizing different host plants, including 20, 36, 2, 5 and 2 genes related to digestion, detoxification, oxidation-reduction, stress response and water-deprivation response, respectively, and 35 genes presumably associated with osmoregulation. However, only 183 DEGs were identified between the HC and FX populations, including two genes related to detoxification, two genes related to stress response, and one gene presumably associated with osmoregulation. These results suggest that the weakest expression differences were between the populations utilizing the same host plant and occurring in the closest habitats, which may help explain the metabolic mechanism of adaptation in S. yangi populations to novel host plants and new niches., Conclusions: The observed differences in gene expression among S. yangi populations are consistent with the hypothesis that the host plant shift and habitat adaptation in the HL population was facilitated by differential regulation of genes related to digestion, detoxification, oxidation-reduction, stress response, water-deprivation response and osmoregulation. The results may inform future studies on the molecular mechanisms underlying the relationship between changes in midgut proteins and adaptation of herbivorous insects to novel host plants and new niches.

Construction and demolition (C&D) waste is a novel, widespread environmental stress that negatively affects environment, organisms and ecosystem. Yet effects of cumulative consequences of C&D waste on the fitness and community structure of most underground insects remain unclear. With relatively sessile life underground lasting several years, cicadas can be an important aspect in forest nutrient cycles. Whether cicada nymphs are easily affected by C&D waste, and whether they have evolved any adaptations to cope with the adverse environments merit exploration. Here, we investigated the biodiversity, community structure, population dynamics and morphology of cicada nymphs in both uncontaminated and contaminated habitats by C&D waste in Guanzhong Plain, China since 2011. In total, 1,573 cicada nymphs were collected from 2011 to 2015, including 62 malformed nymphs. The malformed nymphs can be divided into three types: physically damaged individuals (still alive) (3.2%), fungus-infected individuals (dead) (64.5%), and bacterium-infected individuals (dead) (32.3%). The proportion of malformed nymphs increased year by year in the habitats contaminated by C&D waste. In the uncontaminated habitats, although no significant differences of population density among the investigated years were observed, yet there was a distinct increasing trend of population of Meimuna mongolica, whereas populations of both Cryptotympana atrata and Platypleura kaempferi distinctly decreased. This indicates that M. mongolica is possibly evolving into the most dominant species in the ecological niche when it competes with other sympatric species, but more researches are needed to establish whether there is a shift in the species composition of cicadas. In the habitats contaminated by C&D waste, a higher ratio of malformed individuals and a decline of population of both M. mongolica and C. atrata were revealed; P. kaempferi was not found in the contaminated habitats, indicating a weaker resistance of this species against C&D waste. The negative responses of cicada nymphs to C&D waste have significant implications for the habitat destruction. Cicada nymphs may be suitable bioindicators for underground-habitat-quality monitoring, as merits further research to reveal the association between the magnitude of C&D waste contamination with the fitness and population dynamics of cicada nymphs., Competing Interests: The authors have declared that no competing interests exist.

The functions of female song found in a few cicadas have rarely been studied. In the cicada Subpsaltria yangi we investigated the acoustic behaviour and signal structure of songs produced by females, the phonotaxis of males, and mate choice, as well as the selective pressure imposed on this species by predators. Pair-formation in S. yangi occurs when males signal, females respond, then males move to signaling females, which is opposite to that in most other cicadas where females move to calling males. Females only mate once and are sexually unreceptive after copulation. Most males mate once, but ~25% mate multiply. Females display little direct evidence of mate preference or choice of males, and all mate encounters led to a successful mating. Only males are attacked by a robber fly, Philonicus albiceps, while flying to females. This imposes strong selection on males - only males who can evade predators mate. Males are also attracted to human simulations of female calls. This behaviour exposes the mating system to impacts from anthropogenic noise systems which could disrupt mating activity of this species. Our results improve the understanding of mate choice/competition in cicadas, and are valuable for future studies of the evolution of sound communication in the Cicadoidea.