https://doi.org/10.1038/s41396-023-01488-9
In the intricate world of nature，finding and judging a suitable mate is pivotal for reproduction in many animals. Sex pheromones are widely used by insects as a reproductive isolating mechanism to attract conspecifics and repel heterospecifics. Closely related species usually have similar sex pheromones that may only differ in the ratio of the different chemical components. However, the differentiation mechanism of sex pheromones in closely related species is still unclear.
In order to understand the mechanism, we use Bactrocera dorsalis and Bactrocera cucurbitae as the study model to investigate how the male-borne sex pheromones are different. The results demonstrated that both 2,3,5-trimethylpyrazine(TMP) and 2,3,5,6-tetramethylpyrazine (TTMP) were sex pheromones produced by rectal Bacillus using glucose and threonine (or glycine) in the two flies. However, the TMP/TTMP ratios were reversed, indicating sex pheromone specificity in the two flies (Fig 1).
Through a series of experiments, we have shown that this specificity is not related to the difference in rectal Bacillus or the rectal glucose. Different amino acid levels determined the preference of rectal Bacillus to produce TMP or TTMP.
Modifications of sex pheromones are thought to represent a rapid means for altering mate recognition abilities during the evolution of new species. Our results provide insights into how interspecific sexual barriers arise. Our results may indicate a mode of evolution whereby rapid changes in chemical composition occur during speciation events, and greater divergence gradually occurs subsequently.