Am Nat. 2022 Aug;200(2):202-216. doi: 10.1086/720204. Epub 2022 Jun 13.
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互惠互利对生物多样性和生态系统服务至关重要，但它们正面临着人为干扰的威胁，这些干扰导致它们的种群数量下降。当种群密度较低时，描述这些互惠互利关系的动态对于预测这些干扰的后果非常重要。我们开发了简单的种群动态模型，这些模型足够详细，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。我们将收益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的种子结实、发芽或在招募期间的负密度依赖性。我们发现，授粉和种子传播互惠互利在高密度下是稳定的，但在低密度下表现出不同的动态，这取决于植物的承载能力、动物的觅食效率以及种群是否必须依赖其伙伴才能生存。在某些条件下，所有的互惠互利关系都会经历一个不稳定的阈值，其中一个种群因为其伙伴过于稀少而减少。当植物必须依赖传粉者时，植物还会经历阿利效应。最后，当植物对传粉者具有兼性时，授粉互惠互利关系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，因为全球范围内的互惠互利关系种群仍在继续减少。
