The reproductive biology of the cassava genus (Manihot, Euphorbiaceae) remains unknown, despite its relevance to humanity. Here, we investigated the pollination system of two cassava wild relatives concerning the filtering of visitors in unisexual flowers, the specialization–generalization degree, and verified the dependency on pollinators for seed production. We studied two monoecious species M. violacea and M. oligantha on floral traits differences and visitors during flowering periods in natural conditions. For specialization–generalization degree analysis, we grouped pollinators into functional groups. We performed hand pollination treatments to verify the mating system. About half of floral visitors visited a floral type exclusively. The sexually dimorphic floral display contributed to filtering abundant pollinators, whereas nectar traits acted as attractant filter. In addition to polysaccharides, a remarkable presence of alkaloids and terpenes was observed in the nectary tissue of both male and female flowers. The species exhibited specialization associated with distinct functional groups, M. violacea with bees and M. oligantha with flies. The two Manihot species presented self-compatibility and depend on pollinators to produce seeds and the threatened species M. oligantha manifested pollen limitation. Our findings evidence conspicuous filtering of visitors and consequently, a specialized pollination system emerged for the two Manihot species despite the apparent generalist flowers. The reproductive success relying on groups of abundant pollinators suggests a threatening scenario to cassava wild relatives due to the worldwide decline of insect abundance.

木薯属（Manihot，大戟科）的生殖生物学尽管与人类有关，但仍未知。在这里，我们研究了两个木薯野生近缘植物的授粉系统，涉及到单性花朵中访客的过滤，专业化-泛化程度，并验证了种子生产对传粉媒介的依赖性。我们研究了两种单性物种M. violacea和M. oligantha自然条件下花期性状的差异和花期的访客。为了进行专业化-广义化程度分析，我们将授粉媒介分为功能组。我们进行了人工授粉处理，以验证交配系统。大约一半的花卉访客专门访问了花卉类型。有性的两性花饰有助于过滤丰富的授粉媒介，而花蜜性状起到引诱剂过滤作用。除多糖外，在雄花和雌花的蜜腺组织中均观察到生物碱和萜烯的显着存在。该物种表现出与不同功能组相关的专业化，紫罗兰M. laclacea与蜜蜂，而M. oligantha与苍蝇。两个玛尼霍特的物种表现出自我相容性，并依赖传粉媒介产生种子，而濒危物种M. oligantha表现出花粉限制。我们的发现证明了访客的明显过滤，因此，尽管有明显的通才花，但这两个Manihot物种仍出现了专门的授粉系统。依靠大量授粉媒介的繁殖成功表明，由于全世界昆虫数量的减少，对木薯野生近缘种构成了威胁。