Moll Remington J, Jackson Patrick J, Wakeling Brian F, Lackey Carl W, Beckmann Jon P, Millspaugh Joshua J, Montgomery Robert A
Department of Natural Resources and the Environment, University of New Hampshire, 56 College Road, Durham, NH, 03824, USA.
Department of Fisheries and Wildlife, Michigan State University, 480 Wilson Road, Room 13 Natural Resources Building, East Lansing, MI, 48824, USA.
Oecologia. 2021 May;196(1):223-234. doi: 10.1007/s00442-021-04927-6. Epub 2021 May 1.
Apex predators can shape communities via cascading top-down effects, but the degree to which such effects depend on predator life history traits is largely unknown. Within carnivore guilds, complex hierarchies of dominance facilitate coexistence, whereby subordinate species avoid dominant counterparts by partitioning space, time, or both. We investigated whether a major life history trait (hibernation) in an apex carnivore (black bears Ursus americanus) mediated its top-down effects on the spatio-temporal dynamics of three sympatric mesocarnivore species (coyotes Canis latrans, bobcats Lynx rufus, and gray foxes Urocyon cinereoargenteus) across a 15,000 km landscape in the western USA. We compared top-down, bottom-up, and environmental effects on these mesocarnivores using an integrated modeling approach. Black bears exerted top-down effects that varied as a function of hibernation and were stronger than bottom-up or environmental impacts. High black bear activity in summer and fall appeared to buffer the most subordinate mesocarnivore (gray foxes) from competition with dominant mesocarnivores (coyotes and bobcats), which were in turn released by black bear hibernation in winter and early spring. The mesocarnivore responses occurred in space (i.e., altered occupancy and site visitation intensity) rather than time (i.e., diel activity patterns unaffected). These results suggest that the spatio-temporal dynamics of mesocarnivores in this system were principally shaped by a spatial predator cascade of interference competition mediated by black bear hibernation. Thus, certain life history traits of apex predators might facilitate coexistence among competing species over broad time scales, with complex implications for lower trophic levels.
顶级食肉动物可通过自上而下的级联效应塑造群落，但此类效应在多大程度上依赖于食肉动物的生活史特征，目前仍 largely unknown。在食肉动物群落中，复杂的优势等级制度促进了共存，即从属物种通过划分空间、时间或两者兼而有之来避开优势物种。我们调查了一种顶级食肉动物（美洲黑熊 Ursus americanus）的一个主要生活史特征（冬眠）是否介导了其对美国西部 15000 公里景观范围内三种同域中型食肉动物物种（郊狼 Canis latrans、短尾猫 Lynx rufus 和灰狐 Urocyon cinereoargenteus）时空动态的自上而下的影响。我们使用综合建模方法比较了对这些中型食肉动物的自上而下、自下而上和环境影响。黑熊产生的自上而下的影响随冬眠而变化，且比自下而上或环境影响更强。夏季和秋季黑熊的高活动量似乎缓冲了最从属的中型食肉动物（灰狐）与优势中型食肉动物（郊狼和短尾猫）的竞争，而郊狼和短尾猫又在冬季和早春因黑熊冬眠而得到释放。中型食肉动物的反应发生在空间上（即占用率和站点访问强度改变），而非时间上（即昼夜活动模式未受影响）。这些结果表明，该系统中中型食肉动物的时空动态主要由黑熊冬眠介导的干扰竞争的空间捕食者级联所塑造。因此，顶级食肉动物的某些生活史特征可能在广泛的时间尺度上促进竞争物种之间的共存，对较低营养级具有复杂的影响。
