Realized trophic niche driven by apparent competition: an example with marsupials

According to apparent competition theory, the co-occurrence of two species that share the same predators appears to affect each other's population growth and abundance. However, due to habitat loss and over-hunting, top predators are being made rare worldwide. Considering that apparent competitors share similar resources, we would expect the absence of top predators to reflect in changes on prey realized trophic niches. To test our hypothesis, we developed a model to predict the abundance ratio of apparent competitor species based on changes in their realized trophic niches. We tested our model against field data on the Neotropical marsupials Didelphis aurita and Metachirus nudicaudatus. Our results revealed that D. aurita and M. nudicaudatus are two species under apparent competition and their realized trophic niche and diet overlap change according to the presence of top predators. The model was able to predict the actual relative abundances of D. aurita and M. nudicaudatus in the thr...

根据表观竞争理论（apparent competition theory），共享同一捕食者的两个物种种群同域共存时，会彼此影响对方的种群增长与种群丰度。然而受栖息地丧失与过度狩猎影响，全球范围内的顶级捕食者种群正日渐稀少。鉴于表观竞争的物种共享相似资源，我们可推测：顶级捕食者的缺失会反映在猎物实际营养生态位（realized trophic niche）的变化中。为验证这一假说，我们构建了模型，基于表观竞争物种的实际营养生态位变化来预测其种群丰度比。我们以新热带有袋类（Neotropical marsupials）白耳负鼠（Didelphis aurita）与裸尾负鼠（Metachirus nudicaudatus）的野外数据对该模型进行了检验。研究结果显示，D. aurita与M. nudicaudatus这两个物种正处于表观竞争关系中，其实际营养生态位与饮食重叠度会随顶级捕食者的存在与否发生改变。该模型能够准确预测D. aurita与M. nudicaudatus的实际相对丰度，相关研究内容暂未完全呈现