Data from: Insects on plants: explaining the paradox of low diversity within specialist herbivore guilds

Classical niche theory explains the coexistence of species through their exploitation of different resources. Assemblages of herbivores coexisting on a particular plant species are thus expected to be dominated by species from host-specific guilds with narrow, coexistence-facilitating niches, rather than by species from generalist guilds. Exactly the opposite pattern is observed for folivores feeding on trees in New Guinea. The least specialized mobile chewers were most species-rich, followed by the moderately specialized semi-concealed and exposed chewers. The highly specialized miners and mesophyll suckers were the least species-rich guilds. The Poisson distribution of herbivore species richness among plant species in specialized guilds and the absence of a negative correlation between species richness in different guilds on the same plant species suggest that these guilds are not saturated with species. We show that herbivore assemblages are enriched with generalists because they are more completely sampled from regional species pools. The herbivore diversity increases as a power function of plant diversity, and the rate of increase is inversely related to their host-specificity. The relative species diversity among guilds is thus scale-dependent, as the importance of specialized guilds increases with plant diversity. Specialized insect guilds may therefore comprise a larger component of overall diversity in the tropics (where they are also poorly known taxonomically) than in the temperate zone, which has lower plant diversity.

经典生态位理论（Classical niche theory）通过物种对不同资源的差异化利用，阐释了物种共存的机制。因此，栖息于某一特定植物物种上的植食动物群落（herbivore assemblages），理论上应被具有狭窄且促进物种共存的生态位的宿主特异性功能群（host-specific guilds）所主导，而非广食性功能群（generalist guilds）。
然而取食新几内亚（New Guinea）树木的食叶动物（folivores）却呈现出完全相反的格局：取食广度最低的活动性蛀食者（mobile chewers）物种丰富度最高，其次为取食中度特化的半隐蔽与裸露蛀食者（semi-concealed and exposed chewers）；高度特化的潜叶虫（miners）与叶肉吮吸者（mesophyll suckers）所属功能群的物种丰富度则最低。
针对特化功能群的分析显示，植食动物物种丰富度在不同植物物种间呈泊松分布（Poisson distribution），且同一植物物种上不同功能群的物种丰富度之间不存在负相关关系，这表明此类功能群并未达到物种饱和状态。
本研究表明，植食动物群落中广食性类群占比更高，是因为它们从区域物种种库（regional species pools）中得到了更全面的采样。
植食动物多样性随植物多样性呈幂函数（power function）增长，且增长速率与其宿主特异性呈负相关。
因此，不同功能群间的相对物种多样性具有尺度依赖性，因为特化功能群的重要性随植物多样性提升而增强。相较于植物多样性更低的温带地区，特化昆虫功能群在热带地区的整体物种多样性中占比更高（该区域的特化昆虫类群在分类学上尚未被充分研究）。