Ontogenetic diversity buffers communities against consequences of species loss

Biodiversity can be measured at multiple organizational scales. While traditional studies have focused at taxonomic diversity, recent studies have emphasized the ecological importance of diversity within populations. However, it is unclear how these different scales of diversity interact to determine the consequence of species loss. Here we asked how predator diversity and presence of ontogenetic diversity within predator populations influences community structure. Ontogenetic diversity arises from shifts in the traits and ecology of individuals during ontogeny and it is one of the biggest sources of intraspecific diversity. However, whether it dampens or strengthens the negative consequences of with species loss is poorly understood. To study this interaction of species diversity and ontogenetic diversity, we experimentally manipulated predator species diversity and diversity of developmental stages within focal predator species and analyzed their joint effect on predator and prey survival, biomass, and prey community structure in experimental pond systems. While individual effects of ontogenetic diversity were often species-specific, losing predator species from the community often had a much smaller or no effect on prey survival, biomass, or community structure when all predator populations had high ontogenetic diversity. Thus, ontogenetic diversity within populations buffered against some of the consequences of biodiversity loss at higher organizational levels. Because the experiment controlled mean per capita size and biomass across structured vs. unstructured populations, this pattern was not driven by differences in biomass of predators. Instead, results suggest that effects were driven by changes in the functional roles and indirect interactions across and within species. This indicates that even if all environmental conditions are similar, differences in the intrinsic structure of populations can modify the consequences of biodiversity loss. Together, these results revealed the importance of ontogenetic diversity within species for strengthening the resilience of natural communities to consequences of biodiversity loss and emphasize the need to integrate biodiversity patterns across organizational scales.

生物多样性（biodiversity）可在多个组织尺度（organizational scales）下进行度量。传统研究多聚焦于分类多样性（taxonomic diversity），而近期研究则强调种群内多样性的生态重要性。然而，目前尚不清楚这些不同尺度的多样性如何相互作用，以决定物种丧失所带来的后果。
本研究旨在探究捕食者物种多样性，以及捕食者种群内个体发育多样性（ontogenetic diversity）如何影响群落结构。个体发育多样性源于个体在个体发育过程中性状与生态特征的转变，是种内多样性的主要来源之一。但目前学界对其是会缓解还是加剧物种丧失的负面后果仍知之甚少。
为研究物种多样性与个体发育多样性的这一交互作用，我们在实验池塘系统中，通过操控焦点捕食者物种的捕食者物种多样性与发育阶段多样性，分析二者对捕食者与猎物的存活率、生物量，以及猎物群落结构的联合效应。
尽管个体发育多样性的单独效应通常具有物种特异性，但当所有捕食者种群均具备较高的个体发育多样性时，群落中丧失捕食者物种往往对猎物存活率、生物量或群落结构的影响大幅减弱，甚至无显著影响。因此，种群内的个体发育多样性可缓冲更高组织层级上生物多样性丧失带来的部分后果。
由于本实验控制了结构化与非结构化捕食者种群的平均个体大小与生物量，该现象并非由捕食者生物量的差异所驱动。相反，研究结果表明，其效应源于物种内部及物种间功能角色（functional roles）与间接相互作用（indirect interactions）的改变。这意味着，即便所有环境条件均保持一致，种群内在结构的差异仍可改变生物多样性丧失的后果。
综上，本研究结果揭示了物种种内个体发育多样性对于增强自然群落应对生物多样性丧失后果的恢复力（resilience）的重要性，并强调需要整合不同组织层级的生物多样性格局开展研究。