Table_2_Dispersal From Natal Patch Correlates With the Volatility of Female Sex Pheromones in Parasitoid Wasps.XLSX

Chemical communication via pheromones is considered the oldest and most widespread form of communication in nature. However, the way that the enormous diversity of species-specific pheromones evolved is still of debate. One possible process driving pheromone evolution is the mate-finding and dispersal behavior, as long-distance mate-finding requires highly volatile compounds. In contrast, less volatile compounds might be sufficient attractants in species that search for mates within proximity. In the parasitoid wasp genus Leptopilina, the composition of species-specific sex pheromones ranges from highly volatile iridoid compounds through combinations of iridoids with low volatile cuticular hydrocarbons (CHCs) to only CHCs. To study the selective forces shaping the composition of sex pheromones in Leptopilina, we examined the dispersal behavior, i.e., the proportion of male and female wasps dispersing after emergence, in four species with known sex pheromone compositions. If males and females disperse immediately, long-range mate attraction might become necessary, favoring volatile iridoids over CHCs. If mating occurs directly on the host patch, short-range mate attraction by low volatile CHCs might suffice. Our analyses have revealed that the dispersal behavior of Leptopilina males and females after emergence does indeed differ between species with differently volatile sex pheromones. Specifically, males of species with iridoid sex pheromones start to disperse immediately before their females’ emergence, whereas males of species with CHC sex pheromones delay dispersal until their conspecific females emerge. While the differences in female dispersal behavior turned out to be species-specific, differences in male dispersal correlated with the volatility of female-produced sex pheromones of each species. This study significantly contributes to our understanding of the evolution of sex pheromones by differences in dispersal behavior.

信息素介导的化学通讯被认为是自然界中最古老且分布最广泛的通讯形式。然而，物种特异性信息素的巨大多样性是如何演化而来的，这一问题至今仍存在争议。驱动信息素演化的一个潜在过程与求偶定位和扩散行为相关：长距离求偶定位需要高挥发性化合物；而对于在近距离范围内寻找配偶的物种而言，低挥发性化合物或许足以作为引诱剂。在寄生蜂刻腹小蜂属（Leptopilina）中，物种特异性性信息素的组成跨度极大，从高挥发性的环烯醚萜类化合物，到环烯醚萜与低挥发性表皮碳氢化合物（CHCs）的混合物，再到仅由表皮碳氢化合物组成的性信息素。为探究塑造刻腹小蜂属物种性信息素组成的选择压力，我们针对4种已明确性信息素组成的刻腹小蜂，研究了其羽化后的扩散行为——即雌雄蜂的扩散比例。若雌雄蜂在羽化后立即扩散，则需要长距离求偶定位，此时相较于表皮碳氢化合物，挥发性环烯醚萜类化合物会更受青睐；若交配直接发生在寄主斑块上，则依靠低挥发性表皮碳氢化合物实现的近距离求偶定位便已足够。我们的分析显示，刻腹小蜂属物种羽化后的雌雄扩散行为，确实与性信息素挥发性存在差异的类群之间存在差异。具体而言，分泌环烯醚萜类性信息素的物种，其雄蜂会在雌蜂羽化前就开始扩散；而仅分泌表皮碳氢化合物性信息素的物种，其雄蜂会延迟扩散，直至同种雌蜂羽化后才开始活动。尽管雌蜂的扩散行为差异呈现出物种特异性，但雄蜂的扩散差异则与各物种雌蜂分泌的性信息素挥发性密切相关。本研究极大地推动了我们对扩散行为差异驱动性信息素演化这一过程的理解。