The densities of a species and its specialist enemies are expected to covary, giving rare species an advantage that may promote species coexistence. This hypothesis has been particularly applied to tree species coexistence, and theoretical work has investigated how the spatial scale of dispersal and degree of enemy specialization influence coexistence outcomes. A simplifying assumption of this modeling work is that enemies are ubiquitous and host individuals always colonized. Yet recent studies have suggested that this assumption may not be justified in natural systems. Here we build a multispecies spatial model in which both the host species and enemy species are demographically dynamic. Exploring a range of spatial scales of enemy dispersal and seed dispersal, we find that the lag between seedling recruitment and colonization by enemies generally results in reduced species richness compared with models assuming ubiquitous enemies. This result depends on the spatial dynamics of enemy dispersal, and holds whether or not species diversity is supported by migration from outside the study area, as is often assumed in community ecology models. In light of our findings, we suggest that a full understanding of how enemies promote species coexistence must account for the colonization dynamics of enemies.

物种及其专门敌人的密度预计会发生变化，从而使稀有物种具有可以促进物种共存的优势。该假设特别适用于树种共存，并且理论工作已经研究了扩散的空间规模和敌人专业化程度如何影响共存结果。此建模工作的一个简化假设是，敌人无处不在，并且宿主总是被殖民。然而，最近的研究表明，这种假设在自然系统中可能不成立。在这里，我们建立了一个多物种空间模型，其中宿主物种和敌人物种在人口统计学上都是动态的。探索敌人散布和种子散布的一系列空间尺度，我们发现，与假定无处不在的敌人的模型相比，敌人招募幼苗和定植之间的时滞通常会导致物种丰富度降低。该结果取决于敌人扩散的空间动态，并决定物种多样性是否受到研究区域外部迁移的支持，这在社区生态模型中通常是假设的。根据我们的发现，我们建议对敌人如何促进物种共存的全面理解必须考虑到敌人的定居动态。