Ellis Taylor D, Cushman J Hall
Department of Biology Sonoma State University Rohnert Park California.
Present address: Point Reyes National Seashore California.
Ecol Evol. 2018 Nov 11;8(23):12115-12125. doi: 10.1002/ece3.4670. eCollection 2018 Dec.
Multiple consumer species frequently co-occur in the same landscape and, through effects on surrounding environments, can interact in direct and indirect ways. These interactions can vary in occurrence and importance, and focusing on this variation is critical for understanding the dynamics of interactions among consumers. Large mammalian herbivores are important engineers of ecosystems worldwide, have substantial impacts on vegetation, and can indirectly affect small-mammal populations. However, the degree to which such indirect effects vary within the same system has received minimal attention. We used a 16-year-old exclosure experiment, stratified across a heterogeneous landscape, to evaluate the importance of context-dependent interactions between tule elk () and small mammals (deer mice [], meadow voles [], and harvest mice []) in a coastal grassland in California. Effects of elk on voles varied among habitats and seasons: In open grasslands, elk reduced vole numbers during fall 2013 but not summer 2014; in -dominated grasslands, elk reduced vole numbers during summer 2014 but not fall 2013; and in -dominated grasslands, elk had no effect on vole numbers in either season. Effects of elk on the two mice species also varied among habitats and seasons, but often in different ways from voles and each other. In fall 2013, elk decreased mice abundances in -dominated grasslands, but not in -dominated or open grasslands. In summer 2014, elk decreased the abundance of harvest mice consistently across habitat types. In contrast, elk increased deer-mice numbers in open grasslands but not other habitats. Within the same heterogenous study system, the influence of elk on small mammals was strongly context-dependent, varying among habitats, mammal species, and seasons. We hypothesize that such variability is common in nature and that failure to consider it may yield inaccurate findings and limit our understanding of interactions among co-occurring consumers.
多种消费性物种经常在同一景观中共存，并且通过对周围环境的影响，它们可以直接或间接地相互作用。这些相互作用在发生频率和重要性上可能会有所不同，关注这种变化对于理解消费性物种之间相互作用的动态至关重要。大型哺乳食草动物是全球生态系统的重要塑造者，对植被有重大影响，并可能间接影响小型哺乳动物种群。然而，在同一系统中这种间接影响的变化程度却很少受到关注。我们利用一个在异质景观中分层的、为期16年的围栏实验，来评估加利福尼亚沿海草原上， tule 麋鹿（）与小型哺乳动物（鹿鼠 []、草地田鼠 [] 和收获鼠 []）之间依赖环境的相互作用的重要性。麋鹿对田鼠的影响在不同栖息地和季节有所不同：在开阔草原上，麋鹿在2013年秋季减少了田鼠数量，但在2014年夏季没有；在以 为主的草原上，麋鹿在2014年夏季减少了田鼠数量，但在2013年秋季没有；而在以 为主的草原上，麋鹿在两个季节对田鼠数量均无影响。麋鹿对两种鼠类的影响在不同栖息地和季节也有所不同，但通常与对田鼠的影响方式不同，且两种鼠类之间也不同。在2013年秋季，麋鹿降低了以 为主的草原上鼠类的数量，但在以 为主的草原或开阔草原上没有。在2014年夏季，麋鹿在所有栖息地类型中均持续降低了收获鼠的数量。相比之下，麋鹿增加了开阔草原上鹿鼠的数量，但在其他栖息地没有。在同一异质研究系统中，麋鹿对小型哺乳动物的影响强烈依赖环境，在不同栖息地、哺乳动物物种和季节之间存在差异。我们推测这种变异性在自然界中很常见，不考虑它可能会得出不准确的结果，并限制我们对共存的消费性物种之间相互作用的理解。
