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Top-down effects have primacy over bottom-up effects on the population dynamics of a flightless desert bird
Journal of Arid Environments ( IF 2.7 ) Pub Date : 2021-08-18 , DOI: 10.1016/j.jaridenv.2021.104611
Baptiste Wijas 1, 2 , Mike Letnic 1, 2
Affiliation  

In desert ecosystems, some argue that primary productivity controls vertebrate populations while others contend that predators' top-down effects are under-appreciated. While seldom used to explain population dynamics in desert environments, the exploitation ecosystems hypothesis (EEH) unites bottom-up and top-down processes by conceptualizing how the biomass of plants and consumers vary along spatial productivity gradients in the presence and absence of predators. Here, we test predictions from the EEH along temporal primary productivity gradients, by comparing abundances of an apex predator (dingo) and a large omnivorous flightless bird (emu) on either side of Australia's dingo-proof fence over a nine year period. Where dingo populations were not suppressed by humans, their abundance increased with rainfall in the previous 12 months but did not respond to rainfall where their populations were suppressed. Conversely, emu abundance increased in response to antecedent rainfall where dingoes were rare but showed a negligible response to rainfall where dingoes were common. Our results accord with the EEH by suggesting that dingoes' top-down effects can decouple the linkage between emu populations and primary productivity. More generally, our findings show that top-down effects can have primacy over bottom-up effects for both an apex predator and an omnivorous prey species.



中文翻译:

对于不会飞的沙漠鸟类的种群动态,自上而下的影响优于自下而上的影响

在沙漠生态系统中,一些人认为初级生产力控制着脊椎动物种群,而另一些人则认为捕食者自上而下的影响没有得到充分重视。虽然很少用于解释沙漠环境中的种群动态,但开发生态系统假说 (EEH) 将自下而上和自上而下的过程结合起来,通过概念化植物和消费者的生物量如何在捕食者存在和不存在的情况下沿着空间生产力梯度变化。在这里,我们通过比较澳大利亚防野狗围栏两侧的顶级捕食者(澳洲野狗)和大型杂食性不会飞的鸟类(鸸鹋)的丰度,来测试 EEH 沿时间初级生产力梯度的预测。在野狗种群没有被人类压制的地方,它们的丰度随着过去 12 个月的降雨而增加,但在其种群受到抑制的情况下对降雨没有反应。相反,鸸鹋丰度随着前次降雨而增加,其中野狗很少见,但对野狗常见的降雨的反应可以忽略不计。我们的结果与 EEH 一致,表明野狗的自上而下效应可以使鸸鹋种群与初级生产力之间的联系脱钩。更一般地说,我们的研究结果表明,对于顶级捕食者和杂食性猎物,自上而下的影响可能比自下而上的影响更为重要。我们的结果与 EEH 一致,表明野狗的自上而下效应可以使鸸鹋种群与初级生产力之间的联系脱钩。更一般地说,我们的研究结果表明,对于顶级捕食者和杂食性猎物,自上而下的影响可能比自下而上的影响更为重要。我们的结果与 EEH 一致,表明野狗的自上而下效应可以使鸸鹋种群与初级生产力之间的联系脱钩。更一般地说,我们的研究结果表明,对于顶级捕食者和杂食性猎物,自上而下的影响可能比自下而上的影响更为重要。

更新日期:2021-08-19
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