Fuller Chris L, Evans-White Michelle A, Entrekin Sally A
Biology Department, University of Central Arkansas, Conway, AR, USA.
Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA.
Oecologia. 2015 Mar;177(3):837-848. doi: 10.1007/s00442-014-3154-9. Epub 2014 Nov 27.
Consumer growth determines the quantity of nutrients transferred through food webs. The extent to which leaf composition and consumer physiology interact to constrain consumer production is not well understood. For example, detritivore growth, and thus material transfer, could change with detrital elemental composition. Detrital type and associated microbial biofilms can mediate the amount and rate of detritus consumed and used towards growth. Detritivore body stoichiometry or the threshold elemental ratio, the food ratio resulting in optimal growth, may predict taxon-specific growth response to stoichiometrically-altered detritus. Empirical measures of detritivore growth responses across a range of detrital stoichiometry are rare. We fed a common detritivore, Tipula abdominalis, maple or oak leaves that spanned a gradient of carbon:phosphorus (C:P) to examine how leaf identity and C:P interact to influence growth, consumption, assimilation efficiencies, and post-assimilatory processes. Tipula abdominalis growth and consumption varied with leaf type and stoichiometry. Individuals fed oak grew faster and ate more compared to individuals fed maple. Individuals fed maple grew faster and ate more as leaf C:P decreased. All individuals lost most of the material they assimilated through respiration and excretion regardless of leaf type or leaf stoichiometry. Consumption and growth rates of T. abdominalis increased with maple nutrient enrichment, but not oak, indicating leaf-specific nutrient enrichment affected leaf palatability. Slightly non-homeostatic T. abdominalis C:P was maintained by varied consumption, carbon assimilation, and P excretion. Our study underlines the importance of how detritivore consumption and post-assimilatory processing could influence whole-stream material storage and nutrient cycling in detrital-based ecosystems.
消费者的生长决定了通过食物网转移的营养物质的数量。叶片组成与消费者生理机能相互作用以限制消费者生产的程度尚未得到充分理解。例如，碎屑食性动物的生长以及由此产生的物质转移，可能会随着碎屑的元素组成而变化。碎屑类型和相关的微生物生物膜可以调节碎屑被消耗和用于生长的数量和速率。碎屑食性动物的身体化学计量或阈值元素比率（即导致最佳生长的食物比率）可能预测分类群对化学计量改变的碎屑的特定生长反应。关于碎屑食性动物在一系列碎屑化学计量范围内生长反应的实证研究很少。我们用跨越碳：磷（C:P）梯度的枫树叶或橡树叶喂养一种常见的碎屑食性动物——腹大蚊，以研究叶片种类和C:P如何相互作用来影响生长、消耗、同化效率和同化后过程。腹大蚊的生长和消耗随叶片类型和化学计量而变化。与喂食枫树叶的个体相比，喂食橡树叶的个体生长更快且食量更大。随着叶片C:P的降低，喂食枫树叶的个体生长更快且食量更大。无论叶片类型或叶片化学计量如何，所有个体通过呼吸和排泄失去了大部分同化的物质。腹大蚊的消耗和生长速率随着枫树叶营养物质的富集而增加，但橡树叶则不然，这表明特定于叶片的营养物质富集影响了叶片的适口性。腹大蚊的C:P通过不同的消耗、碳同化和磷排泄维持在略非稳态的水平。我们的研究强调了碎屑食性动物的消耗和同化后处理如何影响碎屑基生态系统中整个溪流的物质储存和养分循环的重要性。
