McEwen Brendan L, Lichtenstein James L L, Fisher David N, Wright Colin M, Chism Greg T, Pinter-Wollman Noa, Pruitt Jonathan N
Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
Department of Ecology, Evolution & Marine Biology, University of California at Santa Barbara, Santa Barbara, CA 93106, USA.
Behav Ecol Sociobiol. 2020 Jan;74(1). doi: 10.1007/s00265-019-2781-x. Epub 2019 Dec 13.
Many animal societies are susceptible to mass mortality events and collapse. Elucidating how environmental pressures determine patterns of collapse is important for understanding how such societies function and evolve. Using the social spider , we investigated the environmental drivers of colony extinction along two precipitation gradients across southern Africa, using the Namib and Kalahari deserts versus wetter savanna habitats to the north and east. We deployed experimental colonies ( = 242) along two ~ 800-km transects and returned to assess colony success in the field after 2 months. Specifically, we noted colony extinction events after the 2-month duration and collected environmental data on the correlates of those extinction events (e.g., evidence of ant attacks, no. of prey captured). We found that colony extinction events at desert sites were more frequently associated with attacks by predatory ants as compared with savanna sites, while colony extinctions in wetter savannas sites were more tightly associated with fungal outbreaks. Our findings support the hypothesis that environments vary in the selection pressures that they impose on social organisms, which may explain why different social phenotypes are often favored in each habitat.
许多动物群体容易遭受大规模死亡事件并走向崩溃。阐明环境压力如何决定崩溃模式对于理解此类群体的功能和进化至关重要。我们以群居蜘蛛为研究对象，利用纳米比亚沙漠和卡拉哈里沙漠与北部和东部较湿润的稀树草原栖息地，沿着南部非洲的两个降水梯度调查了群体灭绝的环境驱动因素。我们沿着两条约800公里的样带部署了实验群体（共242个），并在两个月后返回实地评估群体的存活情况。具体而言，我们记录了两个月后的群体灭绝事件，并收集了与这些灭绝事件相关的环境数据（例如，蚂蚁攻击的证据、捕获的猎物数量）。我们发现，与稀树草原地点相比，沙漠地点的群体灭绝事件更频繁地与捕食性蚂蚁的攻击有关，而较湿润的稀树草原地点的群体灭绝则与真菌爆发联系更为紧密。我们的研究结果支持了这样一种假设，即不同环境对社会性生物施加的选择压力各不相同，这或许可以解释为什么每个栖息地往往都青睐不同的社会表型。
