Kuang Jessica J, Chesson Peter
Department of Ecology and Evolution Biology, University of Arizona, Tucson, AZ 85721, United States.
Theor Popul Biol. 2010 Feb;77(1):56-70. doi: 10.1016/j.tpb.2009.11.002. Epub 2009 Nov 27.
We study frequency-dependent seed predation (FDP) in a model of competing annual plant species in a variable environment. The combination of a variable environment and competition leads to the storage-effect coexistence mechanism (SE), which is a leading hypothesis for coexistence of desert annual plants. However, seed predation in such systems demands attention to coexistence mechanisms associated with predation. FDP is one such mechanism, which promotes coexistence by shifting predation to more abundant plant species, facilitating the recovery of species perturbed to low density. When present together, FDP and SE interact, undermining each other's effects. Predation weakens competition, and therefore weakens mechanisms associated with competition: here SE. However, the direct effect of FDP in promoting coexistence can compensate or more than compensate for this weakening of SE. On the other hand, the environmental variation necessary for SE weakens FDP. With high survival of dormant seeds, SE can be strong enough to compensate, or overcompensate, for the decline in FDP, provided predation is not too strong. Although FDP and SE may simultaneously contribute to coexistence, their combined effect is less than the sum of their separate effects, and is often less than the effect of the stronger mechanism when present alone.
我们在一个可变环境中竞争一年生植物物种的模型中研究频率依赖型种子捕食（FDP）。可变环境与竞争的结合导致了存储效应共存机制（SE），这是沙漠一年生植物共存的一个主要假设。然而，此类系统中的种子捕食需要关注与捕食相关的共存机制。FDP就是这样一种机制，它通过将捕食转移到更丰富的植物物种上来促进共存，从而促进受到干扰而密度降低的物种的恢复。当FDP和SE同时存在时，它们会相互作用，削弱彼此的影响。捕食会削弱竞争，因此也会削弱与竞争相关的机制：这里指的是SE。然而，FDP在促进共存方面的直接作用可以补偿或超过补偿SE的这种削弱。另一方面，SE所需的环境变化会削弱FDP。如果休眠种子的存活率较高，那么只要捕食不太强烈，SE就可能强大到足以补偿或过度补偿FDP的下降。尽管FDP和SE可能同时有助于共存，但它们的综合作用小于它们各自单独作用的总和，而且通常小于单独存在时较强机制的作用。
