Odum School of Ecology, University of Georgia, Athens, Georgia, USA.
PLoS One. 2012;7(9):e45230. doi: 10.1371/journal.pone.0045230. Epub 2012 Sep 28.
The effect of consumers on their resources has been demonstrated in many systems but is often confounded by trophic interactions with other consumers. Consumers may also have behavioral and life history adaptations to each other and to co-occurring predators that may additionally modulate their particular roles in ecosystems. We experimentally excluded large consumers from tile periphyton, leaves and natural benthic substrata using submerged electrified frames in three stream reaches with overlapping consumer assemblages in Trinidad, West Indies. Concurrently, we assessed visits to (non-electrified) control frames by the three most common large consumers-primarily insectivorous killifish (Rivulus hartii), omnivorous guppies (Poecilia reticulata) and omnivorous crabs (Eudaniela garmani). Consumers caused the greatest decrease in final chlorophyll a biomass and accrual rates the most in the downstream reach containing all three focal consumers in the presence of fish predators. Consumers also caused the greatest increase in leaf decay rates in the upstream reach containing only killifish and crabs. In the downstream reach where guppies co-occur with predators, we found significantly lower benthic invertebrate biomass in control relative to exclosure treatments than the midstream reach where guppies occur in the absence of predators. These data suggest that differences in guppy foraging, potentially driven by differences in their life history phenotype, may affect ecosystem structure and processes as much as their presence or absence and that interactions among consumers may further mediate their effects in these stream ecosystems.
消费者对其资源的影响在许多系统中都得到了证实，但往往与其他消费者的营养相互作用相混淆。消费者也可能具有相互作用和共同出现的捕食者的行为和生活史适应性，这可能进一步调节它们在生态系统中的特定作用。我们在特立尼达的三个溪流中使用浸入式通电框架从周生藻类、叶片和天然底质基质中排除了大型消费者，这些溪流的消费者组合重叠。同时，我们评估了三种最常见的大型消费者（主要是食虫性的丽鱼（Rivulus hartii）、杂食性的孔雀鱼（Poecilia reticulata）和杂食性的螃蟹（Eudaniela garmani））对（非通电）对照框架的访问。在存在鱼类捕食者的情况下，消费者在包含所有三种焦点消费者的下游河段中导致最终叶绿素 a 生物量和积累率的最大减少。消费者还导致仅包含丽鱼和螃蟹的上游河段的叶片腐烂率增加最大。在与捕食者共存的下游河段，我们发现对照处理的底栖无脊椎动物生物量明显低于封闭处理，而在没有捕食者的中游河段，孔雀鱼的存在。这些数据表明，食鱼者觅食的差异，可能是由它们的生活史表型差异驱动的，可能与它们的存在与否一样，对生态系统结构和过程产生影响，并且消费者之间的相互作用可能进一步调节它们在这些溪流生态系统中的作用。
