Department of Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, Am Hubland 97074, Würzburg, Germany.
Friedrich Schiller University Jena, Institute of Ecology and Evolution, Dornburger Strasse 159, 07743, Jena, Germany.
Ecology. 2021 Dec;102(12):e03521. doi: 10.1002/ecy.3521. Epub 2021 Sep 21.
Patterns of insect diversity along elevational gradients are well described in ecology. However, it remains little tested how variation in the quantity, quality, and diversity of food resources influence these patterns. Here we analyzed the direct and indirect effects of climate, food quantity (estimated by net primary productivity), quality (variation in the specific leaf area index, leaf nitrogen to phosphorus and leaf carbon to nitrogen ratio), and food diversity (diversity of leaf traits) on the species richness of phytophagous beetles along the broad elevation and land use gradients of Mt. Kilimanjaro, Tanzania. We sampled beetles at 65 study sites located in both natural and anthropogenic habitats, ranging from 866 to 4,550 m asl. We used path analysis to unravel the direct and indirect effects of predictor variables on species richness. In total, 3,154 phytophagous beetles representing 19 families and 304 morphospecies were collected. We found that the species richness of phytophagous beetles was bimodally distributed along the elevation gradient with peaks at the lowest (˜866 m asl) and upper mid-elevations (˜3,200 m asl) and sharply declined at higher elevations. Path analysis revealed temperature- and climate-driven changes in primary productivity and leaf trait diversity to be the best predictors of changes in the species richness of phytophagous beetles. Species richness increased with increases in mean annual temperature, primary productivity, and with increases in the diversity of leaf traits of local ecosystems. Our study demonstrates that, apart from temperature, the quantity and diversity of food resources play a major role in shaping diversity gradients of phytophagous insects. Drivers of global change, leading to a change of leaf traits and causing reductions in plant diversity and productivity, may consequently reduce the diversity of herbivore assemblages.
沿海拔梯度的昆虫多样性模式在生态学中已有很好的描述。然而，食物资源数量、质量和多样性的变化如何影响这些模式，这方面仍有待验证。在这里，我们分析了气候、食物数量（通过净初级生产力估计）、质量（比叶面积指数、叶片氮磷比和叶片碳氮比的变化）以及食物多样性（叶性状多样性）对坦桑尼亚乞力马扎罗山广阔海拔和土地利用梯度上植食性甲虫物种丰富度的直接和间接影响。我们在 65 个研究点采集了甲虫样本，这些研究点位于自然和人为生境中，海拔范围从 866 米到 4550 米。我们使用路径分析来揭示预测变量对物种丰富度的直接和间接影响。总共收集到了 3154 只植食性甲虫，代表 19 个科和 304 个形态种。我们发现，植食性甲虫的物种丰富度沿海拔梯度呈双峰分布，在最低（约 866 米）和中上海拔（约 3200 米）处出现峰值，在更高海拔处急剧下降。路径分析显示，初级生产力和叶性状多样性的温度和气候驱动变化是植食性甲虫物种丰富度变化的最佳预测因子。物种丰富度随年均温度、初级生产力和当地生态系统叶性状多样性的增加而增加。我们的研究表明，除了温度之外，食物资源的数量和多样性在塑造植食性昆虫多样性梯度方面起着主要作用。导致叶性状变化、减少植物多样性和生产力的全球变化驱动因素可能会降低食草动物组合的多样性。
