Committee on Evolutionary Biology, University of Chicago, Chicago, Illinois, USA.
Ecol Lett. 2022 Jun;25(6):1458-1470. doi: 10.1111/ele.14014. Epub 2022 Apr 26.
Janzen-Connell effects (JCEs), specialised predation of seeds and seedlings near conspecific trees, are hypothesised to maintain species richness. While previous studies show JCEs can maintain high richness relative to neutral communities, recent theoretical work indicates JCEs may weakly inhibit competitive exclusion when species exhibit interspecific fitness variation. However, recent models make somewhat restrictive assumptions about the functional form of specialised predation-that JCEs occur at a fixed rate when offspring are within a fixed distance of a conspecific tree. Using a theoretical model, I show that the functional form of JCEs largely impacts their ability to maintain coexistence. If predation pressure increases additively with adult tree density and decays exponentially with distance, JCEs maintain considerably higher species richness than predicted by recent models. Loosely parameterising the model with data from a Panamanian tree community, I elucidate the conditions under which JCEs are capable of maintaining high species richness.
简森-康奈尔效应（JCEs）是指在同种树木附近对种子和幼苗的专门捕食，这种现象被认为可以维持物种丰富度。虽然之前的研究表明，与中性群落相比，JCE 可以维持较高的丰富度，但最近的理论工作表明，当物种表现出种间适应度差异时，JCE 可能会弱抑制竞争排斥。然而，最近的模型对专门捕食的功能形式做出了一些限制假设，即当后代在与同种树木的固定距离内时，JCEs 以固定的速率发生。利用一个理论模型，我表明 JCEs 的功能形式在很大程度上影响了它们维持共存的能力。如果捕食压力随成年树木密度呈累加性增加，并随距离呈指数衰减，那么 JCEs 维持的物种丰富度将远高于最近模型的预测。通过使用来自巴拿马树木群落的数据对模型进行松散参数化，我阐明了 JCEs 能够维持高物种丰富度的条件。
