The Chemical Ecology of Lemur Seed Dispersal

许多热带被子植物依靠食果动物来传播种子，并进化出肉质果实来吸引它们。虽然水果特性在多大程度上受其主要种子传播载体施加的选择压力的影响仍然存在争议，但一些研究已经证明，水果的颜色、气味或大小等特征可能是对食果性动物取食行为的反应而进化的。因此，研究表明，蝙蝠散布的无花果中的水果气味可能是一种适应，其功能是吸引食果蝙蝠，促进种子传播。灵长类在许多热带系统的食果性动物群落中占有相当大的份额，是许多植物物种的重要种子传播者。近年来，人们越来越清楚地看到，它们具有很高的嗅觉能力，这在水果选择阶段特别有用。因此，以灵长类为主要传播媒介的水果可能已经进化为通过嗅觉线索，即水果气味来表明它们的成熟度。这一假说在最近完成的一个由DFG资助的项目中得到了初步支持，该项目发现，在四个新热带肉质水果物种中，只有分散在灵长类动物中的物种在成熟时会发出强烈的、富含化合物的独特气味，这些气味让蜘蛛猴能够区分成熟和未成熟的水果。拟议的项目将建立在这些初步结果的基础上，并试图建立这样的假设，即水果气味是对灵长类种子传播的适应，即它已经进化为调节被子植物和传播种子的灵长类之间的交流。该项目将在马达加斯加进行，这是一个生物多样性的热点地区，当地的灵长类狐猴是脊椎动物种子传播的主要媒介。与大多数其他古热带灵长类动物相比，狐猴的颜色辨别能力较低，因此被认为强烈依赖嗅觉，因此它们是检验这一假设的理想模型系统。该项目将提出四个主要问题：(Q1)水果气味是否调解了狐猴和其种子被散布的植物之间的沟通？(Q2)有证据表明水果气味已经进化来实现这一功能吗？(Q3)狐猴可以从它们的气味中推断出哪些关于水果质量的信息？(问题4)是否有证据表明狐猴的嗅觉系统已经对水果的气味做出了反应？为了回答这些问题，这个跨学科的项目将应用化学生态学、行为生态学、植物学、遗传学和微生物学的方法，与所有这些领域的专家合作。综上所述，回答这些问题可能会开始确定狐猴和植物是否以及如何经历了一种化学协同进化，在这种进化中，水果气味和狐猴嗅觉共同进化，调节了它们之间的互惠互动。

Many tropical angiosperms rely on frugivores for seed dispersal and evolved fleshy fruits to attract them. While it is still arguable to what extent fruit characteristics are malleable to selection pressures exerted by their main seed-dispersal vectors, several studies have demonstrated that traits such as fruit color, scent or size may have evolved in response to frugivore feeding behavior. Consequently, it has been shown that fruit odor in bat-dispersed figs may be an adaptation whose function is to attract frugivorous bats and promote seed dispersal. Primates constitute a significant share of the community of frugivores in many tropical systems and are important seed dispersers of many plant species. In recent years, it has become increasingly clear that they possess high olfactory capacities which are especially useful in the fruit selection phase. Thus, it is possible that fruits whose main dispersal vector is primates have evolved to signal their ripeness through olfactory cues, i.e. fruit odor. This hypothesis has received preliminary support in a recently completed DFG-funded project, which found that among four Neotropical fleshy fruit species, only primate-dispersed species emit strong, compound-rich and unique odors at ripeness and that these odors allow spider monkeys to discriminate between ripe and unripe fruits. The proposed project will build upon these preliminary results and attempt to establish the hypothesis that fruit odor is an adaptation to primate seed dispersal, i.e. that it has evolved to mediate the communication between angiosperms and primate which disperse their seeds. The project will take place in Madagascar, a biodiversity hotspot in which lemurs, the local primates, are the main vertebrate seed-dispersal vector. Lemurs possess lower color discrimination abilities than most other Paleotropical primates and are presumed to strongly rely on olfaction, thus making them an ideal model system to test the hypothesis. The project will ask four major questions: (Q1) Does fruit odor mediate the communication between lemurs and plants whose seeds they disperse? (Q2) Is there evidence that fruit odor has evolved to fulfill this function? (Q3) What information regarding fruit quality can lemurs infer from their odor? (Q4) Is there evidence that the lemur olfactory system has evolved in response to the odors of fruits? To answer these questions, this interdisciplinary project will apply methods from chemical ecology, behavioral ecology, botany, genetics and microbiology, in collaboration with experts in all of these fields. Taken together, answering these questions may begin establishing whether and how lemurs and plants have gone through a chemical coevolution in which fruit odor and lemur olfaction coevolved to mediate the mutualistic interaction between them.