Faculty of Philosophy, Sciences and Literature of Ribeirão Preto, Department of Biology, Laboratory of Molecular Biology and Systematics of Plants, University of São Paulo, Ribeirão Preto, Brazil.
Plant Biol (Stuttg). 2024 Dec;26(7):1185-1192. doi: 10.1111/plb.13726. Epub 2024 Oct 5.
Flowering plants are essentially sessile organisms that disperse their genes through pollination, expanding their areas of occurrence through seed dispersal. In orchids, seed dispersal is commonly mediated by air currents. Conversely, members of several genera have evolved seeds adapted to endozoochory. This is the case for Vanilla, the most economically important genus in the orchid family. The role of indehiscent fruits in the attraction and rewarding of Vanilla seed dispersers was investigated based on field observations, analysis of fragrances, reward substances, and investigation of seed viability through the digestive tract. Indehiscent Vanilla fruits are consumed exclusively by herbivores, i.e. agoutis. Besides providing nutritional rewards, the fruits are rich in polyphenols that are unpalatable to omnivores. The most dominant compound in fruits is attractive only to agoutis. This is the first study showing synzoochory in Orchidaceae and specificity of seed dispersal in orchids. Indehiscent fruits may have evolved early in Neotropical Vanilla in response to selection pressures mediated by large herbivores as the genus emerged ca. 34 Mya in South America, concomitantly with megafauna diversification in the Oligocene. Extinction of the megafauna during the Pleistocene has left agoutis as inheritors of seed dispersal in species with large fleshy fruits. Apart from the effects on omnivores, this study shows that indehiscent fruits of V. chamissonis are consumed exclusively by agoutis, providing the first evidence of target mutualism in orchid seed dispersal.
开花植物本质上是固着生物，它们通过授粉来传播基因，通过种子散布来扩大其发生范围。在兰花中，种子散布通常由气流介导。相反，几个属的成员已经进化出适应内生动物传播的种子。这就是兰科植物中最重要的经济属——香荚兰的情况。基于野外观察、香气分析、奖励物质分析以及通过消化道调查种子活力，研究了不开裂果实对香草种子传播者的吸引力和奖励作用。不开裂的香草果实仅被食草动物（即食蚁兽）消耗。除了提供营养奖励外，果实还富含多酚，对杂食动物来说是不可口的。果实中最主要的化合物只对食蚁兽有吸引力。这是第一项表明在兰科植物中存在 synzoochory 以及兰花中种子传播具有特异性的研究。不开裂的果实可能在 Neotropical Vanilla 中早期进化，以响应由大型草食动物介导的选择压力，因为该属大约在 3400 万年前在南美洲出现，与上新世的大型动物多样化同时发生。更新世大型动物的灭绝使食蚁兽成为具有大肉质果实的物种中种子传播的继承者。除了对杂食动物的影响外，这项研究表明，V. chamissonis 的不开裂果实仅被食蚁兽消耗，为兰花种子传播中的目标共生提供了第一个证据。
