Estevo César Augusto, Nagy-Reis Mariana Baldy, Nichols James D
Independent Researcher, Paulínia, São Paulo, Brazil.
Department of Animal Biology, University of Campinas, Campinas, São Paulo, Brazil.
PLoS One. 2017 Jul 26;12(7):e0179489. doi: 10.1371/journal.pone.0179489. eCollection 2017.
Disentangling the role of competition in regulating the distribution of sympatric species can be difficult because species can have different habitat preferences or time use that introduce non-random patterns that are not related to interspecific interactions. We adopted a multi-step approach to systematically incorporate habitat preferences while investigating the co-occurrence of two presumed competitors, morphologically similar, and closely related ground-dwelling birds: the brown tinamou (Crypturellus obsoletus) and the tataupa tinamou (C. tataupa). First, we used single-species occupancy models to identify the main landscape characteristics affecting site occupancy, while accounting for detection probability. We then used these factors to control for the effect of habitat while investigating species co-occurrence. In addition, we investigated species present-time partitioning by measuring the degree of overlap in their activity time. Both species were strictly diurnal and their activity time highly overlapped (i.e., the species are not present-time partitioning). The distribution of the two species varied across the landscape, and they seemed to occupy opposite portions of the study area, but co-occurrence models and species interaction factors suggested that the tinamous have independent occupancy and detection. In addition, co-occurrence models that accounted for habitat performed better than models without habitat covariates. The observed co-occurrence pattern is more likely related to habitat preferences, wherein species segregated by elevation. These results provide evidence that habitat characteristics can play a bigger role than interspecific interactions in regulating co-existence of some species. Therefore, exploring habitat preferences while analyzing co-occurrence patterns is essential, in addition to being a feasible approach to achieve more accurate estimation of parameters reflecting species interactions. Occupancy models can be a valuable tool in such modeling.
理清竞争在调节同域物种分布中的作用可能很困难，因为物种可能有不同的栖息地偏好或时间利用方式，从而引入与种间相互作用无关的非随机模式。我们采用了多步骤方法，在研究两种假定的竞争者（形态相似且亲缘关系密切的地栖鸟类：褐穴小雉和塔陶穴小雉）的共存时，系统地纳入栖息地偏好。首先，我们使用单物种占有率模型来识别影响位点占有率的主要景观特征，同时考虑检测概率。然后，在研究物种共存时，我们使用这些因素来控制栖息地的影响。此外，我们通过测量它们活动时间的重叠程度来研究物种的时间划分。两种物种都严格日行性，且它们的活动时间高度重叠（即这两个物种不存在时间划分）。这两个物种的分布在整个景观中各不相同，它们似乎占据了研究区域的相对部分，但共存模型和物种相互作用因素表明，穴小雉有独立的占有率和检测率。此外，考虑了栖息地的共存模型比没有栖息地协变量的模型表现更好。观察到的共存模式更可能与栖息地偏好有关，其中物种按海拔高度分隔。这些结果提供了证据，表明在调节某些物种的共存方面，栖息地特征可能比种间相互作用发挥更大的作用。因此，在分析共存模式时探索栖息地偏好至关重要，这也是实现更准确估计反映物种相互作用参数的可行方法。占有率模型在这种建模中可能是一个有价值的工具。
