Data from: Patch size drives colonization by aquatic insects, with minor priority effects of a cohabitant

Patch size is one of the most important factors affecting the distribution and abundance of species, and recent research has shown that patch size is an important niche dimension affecting community structure in aquatic insects. Building on this result, we examined the impact of patch size in conjunction with presence of larval anurans on colonization by aquatic insects. Hyla chrysoscelis (Cope's gray treefrog) larvae are abundant and early colonists in fishless lentic habitats, and these larvae can fill multiple ecological roles. By establishing larvae in mesocosms prior to colonization, we were able to assess if H. chrysoscelis larvae have priority effects on aquatic insect assemblages. We conducted a series of three experiments in naturally-colonized experimental landscapes to test whether (1) H. chrysoscelis larval density affects insect colonization, (2) variation in patch size affects insect colonization, and (3) the presence and larval density of H. chrysoscelis shifts colonization of insects between patches of different size. Larval density independently had almost no effect on colonization, while patch size had species-specific effects consistent with prior work. When larvae and patch size were tested in conjunction, patch size had numerous, often strong, species-specific effects on colonization; larval density had effects largely limited to the assemblages of colonizing beetles and water bugs, with few effects on individual species. Higher larval densities in large mesocosms shifted some insect colonization to smaller patches, resulting in higher beta diversity among small patches in proximity to high density large mesocosms. This indicates establishing H. chrysoscelis larvae prior to insect colonization can likely create priority effects that slightly shape insect communities. Our results support the importance of patch size in studying species abundances and distributions, and also indicate that colonization order plays an important role in determining the communities found within habitat patches.

生境斑块大小是影响物种分布与多度的核心因子之一，近期研究表明，斑块大小亦是影响水生昆虫群落结构的关键生态位维度。基于上述研究结论，我们探究了斑块大小结合无尾类幼体存在与否对水生昆虫定殖过程的影响。北美灰树蛙（Hyla chrysoscelis，Cope's gray treefrog）幼体在无鱼静水生境中种群丰富且为早期定殖者，该类幼体可承担多种生态功能。通过在水生昆虫定殖前于中型实验生态系统（mesocosms）中接入该树蛙幼体，我们得以评估北美灰树蛙幼体是否会对水生昆虫群落组合（assemblages）产生优先效应（priority effects）。我们在自然定殖的实验景观中开展了三组系列实验，以验证以下三个假说：1）北美灰树蛙幼体密度是否会影响昆虫定殖；2）斑块大小的差异是否会影响昆虫定殖；3）北美灰树蛙的存在及其幼体密度是否会改变不同大小斑块间的昆虫定殖格局。单独考量幼体密度时，其几乎不对定殖过程产生影响，而斑块大小则会对不同昆虫类群产生特异性影响，这与既往研究结果一致。当同时考量幼体密度与斑块大小两个因素时，斑块大小对昆虫定殖产生了诸多且往往较强的类群特异性影响；而幼体密度的影响则主要局限于定殖的甲虫与水生蝽类的群落组合，对单个物种的影响极少。大型中型实验生态系统中较高的幼体密度会将部分昆虫的定殖位点转移至小型斑块，使得邻近高密度大型生态系统的小型斑块间的β多样性（beta diversity）升高。这表明在水生昆虫定殖前接入北美灰树蛙幼体，大概率会产生优先效应，进而小幅塑造水生昆虫群落结构。本研究结果证实了斑块大小在物种分布与多度研究中的重要性，同时也表明定殖顺序在决定生境斑块内群落组成方面发挥着关键作用。