Geographic variation in floral scent reinforces local pollinator attraction in the fig-fig wasp mutualism.

backgroundVolatile organic compounds (VOCs) emitted during floral receptivity are crucial for attracting pollinators, especially in brood-site pollination systems. Geographic variation in floral scent can alter host recognition cues, potentially shaping pollinator behavior in obligate mutualisms such as the fig–fig wasp system. Understanding whether and how such variation affects pollinator responses is essential for assessing the stability of these interactions. Here, we investigated geographic variation in floral scent and pollinator responses in Ficus hispida, a dioecious species widely distributed in tropical Asia.Using dynamic headspace sampling and GC-MS, we characterized receptive fig VOCs from populations in South China, Southwest China, and South Thailand. Behavioral assays tested the responses of Ceratosolen marchali wasps from the South China Botanical Garden (SCBG) and Xishuangbanna Tropical Botanical Garden (XTBG) to local versus non-local fig odors.

resultsScent profiles differed significantly among regions, forming three distinct clusters. Although C. marchali was present at both sites, Y-tube experiments revealed that wasps responded only to odors from their local population.

conclusionsThis local scent specificity may reinforce population-level mutualisms and restrict long-distance pollinator movement. While such divergence could promote reproductive isolation among closely related wasp lineages, the mechanisms allowing cryptic species to coexist on the same host remain unclear. Overall, our results highlight the key role of chemical cues in shaping plant–pollinator interactions across different populations.