Abstract：
AbstractPollination and seed dispersal mutualisms are critical for biodiversity and ecosystem services yet face mounting threats from anthropogenic perturbations that cause their populations to decline. Characterizing the dynamics of these mutualisms when populations are at low density is important to anticipate consequences of these perturbations. We developed simple population dynamic models detailed enough to distinguish different mechanisms by which plant populations benefit from animal pollination or seed dispersal. We modeled benefits as functions of foraging rate by animals on plant rewards and specified whether they affected plant seed set, germination, or negative density dependence during recruitment. We found that pollination and seed dispersal mutualisms are stable at high density but exhibit different dynamics at low density, depending on plant carrying capacity, animal foraging efficiency, and whether populations are obligate on their partners for persistence. Under certain conditions, all mutualisms experience destabilizing thresholds in which one population declines because its partner is too rare. Plants additionally experience Allee effects when obligate on pollinators. Finally, pollination mutualisms can exhibit bistable coexistence at low or high density when plants are facultative on pollinators. Insights from our models can inform conservation efforts, as mutualist populations continue to decline globally.
摘要：
授粉和种子传播相互关系对于生物多样性和生态系统服务至关重要，但由于人为扰动而面临越来越大的威胁，导致其种群数量下降。当种群处于低密度时，表征这些相互作用的动力学对于预测这些扰动的后果很重要。我们开发了简单的种群动态模型，该模型足够详细，可以区分植物种群从动物授粉或种子传播中受益的不同机制。我们将益处建模为动物对植物奖励的觅食率的函数，并指定它们是否影响植物种子集，发芽,或招募期间的负密度依赖性。我们发现，授粉和种子传播的相互关系在高密度下是稳定的，但在低密度下表现出不同的动力学，根据植物的承载能力，动物觅食效率，以及人口是否对他们的伴侣有持久的义务。在一定条件下,所有的相互关系都经历了不稳定的门槛，在这个门槛中，一个人口因为其伴侣太罕见而下降。当植物对传粉者专一时，植物还会经历Allee效应。最后,当植物在授粉媒介上兼性时，授粉互体可以在低密度或高密度下表现出双稳态共存。我们模型的见解可以为保护工作提供信息，随着全球共同主义者的人口继续下降。
