Aristolochia mimics stink bugs to repel vertebrate herbivores via TRPA1 activation.

Mimicry is the phenomenon in which one species (the mimic) closely resembles another (the model), enhancing its own fitness by deceiving a third party into interacting with it as if it were the model. In plants, mimicry is used primarily to gain fitness by withholding rewards from mutualists or deterring herbivores cost-effectively. While extensive work has been documented on putative defence mimicry, limited investigation has been conducted in the field of chemical mimicry. In this study, we used field experiments, chemical analyses, behavioural assays, and electrophysiology, to test the hypothesis that the birthwort Aristolochia delavayi employs chemical mimicry by releasing leaf scent that closely resembles stink bug defensive compounds and repels vertebrate herbivores. We show that A. delavayi leaf scent is chemically and functionally similar to the generalized defensive volatiles of stink bugs and that the scent effectively deters vertebrate herbivores, likely through the activation of TRPA1 channels via (E)-2-alkenal compounds. This study provides an unequivocal example of chemical mimicry in plants, revealing intricate dynamics between plants and vertebrate herbivores. Our study underscores the potency of chemical volatiles in countering vertebrate herbivory, urging further research to uncover their potentially underestimated importance.

Genetic diversity and structure of the endemic and endangered species Aristolochia delavayi growing along the Jinsha River.

The traditional medicinal plant, and endangered species Aristolochia delavayi (Aristolochiaceae) is an endemic species in China and occurs in the warm and dry areas along the Jinsha river. It is also a specific host of the larvae of Byasa daemonius, a vulnerable butterfly. In this study, 15 pairs of polymorphic microsatellite primers of A. delavayi were designed and screened based on the Simple Sequence Repeats (SSR) loci found by using the results of genome skimming. Based on these 15 SSR markers, the genetic diversity and structure of 193 individuals from ten natural populations were analyzed in detail. In comparison to other endemic and endangered plants in the region, the population of A. delavayi possess a relatively high genetic diversity (He = 0.550, I = 1.112). AMOVA analysis showed that 68.4% of the total genetic diversity was within populations and 31.6% of the variation occurred among populations. There was a significant genetic differentiation among natural populations of A. delavayi detectable, with low gene flow (Nm = 0.591). This might be attributed to geographical barriers and limited seed dispersal. To test the isolation by distance (IBD), we performed Mantel test, which showed a significant correlation between the geographic and genetic distances. In order to cope with the possible biases caused by IBD, we additionally performed Bayesian genetic cluster analyses and principal coordinate analysis (PCoA). The final cluster analysis revealed three groups with distinct geographical distribution. Habitat fragmentation and limited gene flow between these populations may be the main reasons for the current genetic structure. For conservation of this species, we suggest to divide its populations into three protection management units, with subsequent focus on the Yongsheng and Luquan populations which experienced a genetic bottleneck event in the past.

Reinstatement of the Chinese endemic species Styrax zhejiangensis.

Styrax zhejiangensis has been treated as a synonym of S. macrocarpus. Examination of herbarium specimens and observation of wild living plants demonstrates that S. zhejiangensis is a distinct species and is clearly distinguishable from S. macrocarpus through its flowering phenology in which leaves and flowers open simultaneously, its smaller corolla lobes and filaments, and its white-stellate-pubescent seeds. On this basis, we reinstate S. zhejiangensis as an accepted species. Photographic images and a distribution map of the two species are provided. A lectotype of S. zhejiangensis is also designated.