Instituto de Biologia, Universidade Federal de Uberlândia, C.P. 593, 38400-902 Uberlândia MG, Brazil.
J Anim Ecol. 2011 Mar;80(2):352-60. doi: 10.1111/j.1365-2656.2010.01779.x. Epub 2010 Nov 30.
1. Arboreal ants are both diverse and ecologically dominant in the tropics. Such ecologically important groups are likely to be particularly useful in ongoing empirical efforts to understand the processes that regulate species diversity and coexistence. 2. Our study addresses how access to tree-based resources and the diversity of pre-existing nesting cavities affect species diversity and coexistence in tropical arboreal ant assemblages. We focus on assemblage-level responses to these variables at local scales. We first surveyed arboreal ant diversity across three naturally occurring levels of canopy connectivity and a gradient of tree size. We then conducted whole-tree experimental manipulations of canopy connectivity and the diversity of cavity entrance sizes. All work was conducted in the Brazilian savanna or 'cerrado'. 3. Our survey suggested that species richness was equivalent among levels of connectivity. However, there was a consistent trend of lower species density with low canopy connectivity. This was confirmed at the scale of individual trees, with low-connectivity trees having significantly fewer species across all tree sizes. Our experiment demonstrated directly that low canopy connectivity results in significantly fewer species coexisting per tree. 4. A diverse array of cavity entrance sizes did not significantly increase overall species per tree. Nevertheless, cavity diversity did significantly increase the species using new cavities on each tree, the species per tree unique to new cavities, total species using new cavities, and total cavity use. The populations of occupied cavities were consistent with newly founded colonies and new nests of established colonies from other trees. Cavity diversity thus appears to greatly affect new colony founding and colony growth. 5. These results contribute strong evidence that greater resource access and greater cavity diversity have positive effects on species coexistence in local arboreal ant assemblages. More generally, these positive effects are broadly consistent with niche differentiation promoting local species coexistence in diverse arboreal ant assemblages. The contributions of this study to the understanding of the processes of species coexistence are discussed, along with the potential of the focal system for future work on this issue.
树栖蚂蚁在热带地区具有多样性和生态优势。这些在生态上非常重要的群体，可能在当前理解调节物种多样性和共存的过程的经验研究中特别有用。
我们的研究探讨了获取基于树木的资源和预先存在的巢穴腔室多样性如何影响热带树栖蚂蚁组合的物种多样性和共存。我们专注于局部尺度上这些变量对组合层面的响应。我们首先在三个自然发生的树冠连通性水平和树木大小梯度上调查了树栖蚂蚁的多样性。然后，我们对树冠连通性和腔室入口大小的多样性进行了全树实验处理。所有工作都在巴西草原或“塞拉多”进行。
我们的调查表明，连通性水平之间的物种丰富度相当。然而，随着树冠连通性的降低，物种密度呈现出一致的下降趋势。这在单棵树的尺度上得到了证实，低连通性的树木在所有树木大小上的物种数量明显较少。我们的实验直接证明，低树冠连通性导致每棵树共存的物种数量明显减少。
各种腔室入口大小并没有显著增加每棵树上的总物种数。尽管如此，腔室多样性确实显著增加了每棵树上使用新腔室的物种数量、每棵树上特有的新腔室物种数量、使用新腔室的总物种数量和总腔室使用量。被占用腔室的种群与新建立的殖民地和来自其他树木的已建立殖民地的新巢穴一致。腔室多样性因此似乎极大地影响了新殖民地的建立和殖民地的生长。
这些结果有力地证明了更大的资源获取和更大的腔室多样性对本地树栖蚂蚁组合中物种共存具有积极影响。更一般地说，这些积极影响与生态位分化促进多样化的树栖蚂蚁组合中的本地物种共存是一致的。本文讨论了这项研究对理解物种共存过程的贡献，以及该焦点系统在未来这一问题研究中的潜力。
