Department of Zoology, University of British Columbia , Vancouver , Canada.
PeerJ. 2013 Jul 9;1:e100. doi: 10.7717/peerj.100. Print 2013.
Ecological processes that determine the abundance of species within ecological communities vary across space and time. These scale-dependent processes are especially important when they affect key members of a community, such as ecosystem engineers that create shelter and food resources for other species. Yet, few studies have examined the suite of processes that shape the abundance of ecosystem engineers. Here, we evaluated the relative influence of temporal variation, local processes, and latitude on the abundance of an engineering insect-a rosette-galling midge, Rhopalomyia solidaginis (Diptera: Cecidomyiidae). Over a period of 3-5 years, we studied the density and size of galls across a suite of local experiments that manipulated genetic variation, soil nutrient availability, and the removal of other insects from the host plant, Solidago altissima (tall goldenrod). We also surveyed gall density within a single growing season across a 2,300 km latitudinal transect of goldenrod populations in the eastern United States. At the local scale, we found that host-plant genotypic variation was the best predictor of rosette gall density and size within a single year. We found that the removal of other insect herbivores resulted in an increase in gall density and size. The amendment of soil nutrients for four years had no effect on gall density, but galls were smaller in carbon-added plots compared to control and nitrogen additions. Finally, we observed that gall density varied several fold across years. At the biogeographic scale, we observed that the density of rosette gallers peaked at mid-latitudes. Using meta-analytic approaches, we found that the effect size of time, followed by host-plant genetic variation and latitude were the best predictors of gall density. Taken together, our study provides a unique comparison of multiple factors across different spatial and temporal scales that govern engineering insect herbivore density.
生态过程决定了生态群落中物种的丰度，这些过程在空间和时间上是不同的。当这些过程影响到群落中的关键成员时，如为其他物种创造庇护所和食物资源的生态工程师，这些尺度依赖的过程就显得尤为重要。然而，很少有研究探讨过影响生态工程师丰度的一系列过程。在这里，我们评估了时间变化、局部过程和纬度对一种工程昆虫——一种罗萨塔叶瘿蚊（Rhopalomyia solidaginis）（双翅目：瘿蚊科）丰度的相对影响。在 3-5 年的时间里，我们研究了一系列局部实验中罗萨塔叶瘿蚊密度和虫瘿大小的变化，这些实验操纵了遗传变异、土壤养分供应以及从宿主植物（紫菀）上移除其他昆虫。我们还在整个生长季节内调查了美国东部 2300 公里长的紫菀种群中单一纬度的虫瘿密度。在局部尺度上，我们发现宿主植物基因型变异是单一年份罗萨塔叶瘿蚊密度和大小的最佳预测因子。我们发现，移除其他昆虫食草动物会导致虫瘿密度和大小增加。四年来对土壤养分的改良对虫瘿密度没有影响，但与对照和氮添加相比，添加碳的地块中的虫瘿较小。最后，我们观察到虫瘿密度在几年内变化了数倍。在生物地理尺度上，我们观察到罗萨塔叶瘿蚊的密度在中纬度达到峰值。使用荟萃分析方法，我们发现时间的效应大小，其次是宿主植物遗传变异和纬度，是虫瘿密度的最佳预测因子。总的来说，我们的研究提供了一个独特的比较，即在不同的时空尺度上，多种因素共同作用，决定了工程昆虫食草动物的密度。
