Data from: Using predator-prey theory to predict outcomes of broad-scale experiments to reduce apparent competition

Apparent competition is an important process influencing many ecological communities. We used predator-prey theory to predict outcomes of ecosystem experiments aimed at mitigating apparent competition by reducing primary prey. Simulations predicted declines in secondary prey following reductions in primary prey because predators consumed more secondary prey until predator numbers responded to reduced prey densities. Losses were exacerbated by a higher carrying capacity of primary prey and a longer lag time of the predator’s numerical response, but a gradual reduction in primary prey was less detrimental to the secondary prey. We compared predictions against two field experiments where endangered woodland caribou (Rangifer tarandus caribou) were victims of apparent competition. First, when deer (Odocoileus sp.) declined suddenly following a severe winter, cougar (Puma concolor) declined with a 1–2-year lag, yet in the interim more caribou were killed by cougars, and caribou populations declined by 40%. Second, when moose (Alces alces) were gradually reduced using a management experiment, wolf (Canis lupus) populations declined but did not shift consumption to caribou, and the largest caribou subpopulation stabilized. The observed contrasting outcomes of sudden versus gradual declines in primary prey supported theoretical predictions. Combining theory with field studies clarified how to manage communities to mitigate endangerment caused by apparent competition that affects many taxa.

表观竞争（apparent competition）是影响诸多生态群落的关键生态过程。本研究依托捕食者-猎物理论，对旨在通过削减基础猎物以缓解表观竞争的生态系统实验结果开展预测。模拟结果表明，削减基础猎物后，次级猎种种群将出现下降：由于捕食者会更多地捕食次级猎物，直至其种群对猎物密度降低作出响应。基础猎物的承载量越高、捕食者的数量响应滞后时间越长，次级猎物的种群损失便会加剧；而逐步削减基础猎物则对次级猎物的负面影响更弱。

我们将理论预测结果与两项针对濒危林地驯鹿（*Rangifer tarandus caribou*）——其本身为表观竞争受害者的野外实验进行了比对。第一项实验中，鹿属（*Odocoileus* sp.）种群在遭遇严重冬季灾害后突然下降，美洲狮（*Puma concolor*）种群随之出现1~2年的滞后下降，但在此期间美洲狮对驯鹿的捕杀量上升，驯鹿种群降幅达40%。第二项实验通过管理手段逐步削减驼鹿（*Alces alces*）种群，灰狼（*Canis lupus*）种群虽出现下降，但并未转向捕食驯鹿，最大的驯鹿亚种群得以稳定。

野外实验中基础猎物种群突然下降与逐步下降所呈现的截然不同的结果，验证了理论预测。将理论模型与野外研究相结合，明确了如何通过群落管理来缓解因表观竞争导致的、对诸多类群均有影响的物种濒危问题。