Phenological Asynchrony Is Associated With Diapause Program and Heat Shock Protein Expression in Three Grasshopper Species in the Inner Mongolian Steppe

Phenological asynchrony is a common and important natural phenomenon that affects interspecific interaction, resource allocation, species survival, and range shift in sympatric species. However, the underpinnings for regulating phenological asynchrony at physiological and molecular levels remains less explored. We investigated the seasonal pattern of emergence period and abundance in three dominant grasshopper species, namely, Dasyhipus barbipes, Oedalus asiaticus, and Chorthippus dubius, which occur sympatrically in the Inner Mongolian steppe. The three grasshopper species decoupled their population occurrence phenology that occurred in a growing season between May and September and diverged into early, middle, and late seasonal species. We also examined the association of embryonic diapause and heat shock protein (Hsp) expression with phenological asynchrony in the three species. The species developed different embryonic diapause programs, i.e., obligate diapause, facultative diapause, and non-diapause, to control the timing of egg hatching and seasonality of population occurrence. The diapausing eggs exhibited significantly enhanced supercooling capacity compared with pre- and post-diapausing eggs. Gene expression analysis in the developmental process revealed that three Hsps, e.g., Hsp20.6, Hsp40, and Hsp90, were significantly upregulated in diapause state relative to that in pre- and post-diapause states; expression of these genes seems to be associated with the diapause program regulation. This study provides a possible mechanistic explanation for phenological differentiation among sympatric species in a typical steppe habitat and establishes a potential linkage among phenological asynchrony, diapause, and Hsp gene expression. The findings will facilitate our prediction of population dynamics and pest management.

Relationships between plant community productivity and diversity vary with trampling disturbance in an Inner-Mongolian steppe

The relationship between diversity and productivity of plant communities is an important issue in grassland restoration. However, the degree to which this relationship varies during the restoration stage after trampling disturbance is not clear. Here, we conducted a five-year study in a steppe after 4-year trampling to detect restoration patterns of plant community and investigate variation in diversity-productivity relationships. Our results showed that community cover, abundance, height, and productivity recovered quickly after the trampling disturbance ceased. However, the recovery of diversity was slower than biomass in the steppe. In addition, grass, annual, and biennial recovery was more rapidly than the recovery of forbs in the steppe. Moreover, following the restoration process, the positive correlation between productivity and diversity was decoupled, and a negative correlation between productivity and diversity developed. Our finding provides the key evidence for the asynchronous relation between productivity and diversity, and reveals that grass restored more rapidly than forbs in plant community restoration after disturbance. This study indicates that the trade-off between plant community structure and function can vary with the restoration process, and implicates that future modeling and experimental studies should focus on the different responses of productivity and diversity in plant community restoration.