Mougi Akihiko, Nishimura Kinya
Graduate School of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan.
J Theor Biol. 2007 Sep 7;248(1):194-201. doi: 10.1016/j.jtbi.2007.04.005. Epub 2007 Apr 10.
Theoretical studies have shown a paradoxical destabilizing response of predator-prey ecosystems to enrichment, but there is the gap between the intuitive view of nature and this theoretical prediction. We studied a minimal predator-prey system (a two predator-two prey system) in which the paradox of enrichment pattern can vanish; the destabilization with enrichment is reversed, leading to stabilization (a decrease in the amplitude of oscillation of population densities). For resolution of the paradox, two conditions must be met: (1) the same prey species must be preferred as a dietary item by both predator species, creating the potential for high exploitative competition between the predator species, and (2), while both predators are assumed to select their diet in accordance with optimal diet utilization theory, one predator must be a specialist and the other a generalist. In this system, the presence of a less profitable prey species can cause the increase in population oscillation amplitudes associated with increasing enrichment to be suppressed via the optimal diet utilization of the generalist predator. The resulting stabilization is explained by the mitigating effect of the less profitable prey showing better population growth with increasing enrichment on the destabilization underlying the specialist predator and prey relation, thus resolving the paradox of enrichment.
理论研究表明，捕食者 - 猎物生态系统对资源增加会产生矛盾的不稳定反应，但自然界的直观观点与这一理论预测之间存在差距。我们研究了一个最小的捕食者 - 猎物系统（一个双捕食者 - 双猎物系统），在该系统中，资源增加模式的矛盾现象可能消失；随着资源增加而产生的不稳定状态会逆转，从而导致稳定（种群密度振荡幅度减小）。为了解决这一矛盾，必须满足两个条件：（1）两种捕食者物种都必须偏好同一种猎物作为食物来源，这就产生了捕食者物种之间高强度利用性竞争的可能性；（2）虽然假设两种捕食者都根据最优饮食利用理论来选择食物，但其中一种捕食者必须是特化物种，另一种是泛化物种。在这个系统中，一种获利较少的猎物物种的存在，可以通过泛化捕食者的最优饮食利用，抑制与资源增加相关的种群振荡幅度的增加。由此产生的稳定状态可以通过以下方式解释：获利较少的猎物随着资源增加而表现出更好的种群增长，这对特化捕食者与猎物关系中潜在的不稳定状态起到了缓解作用，从而解决了资源增加的矛盾。
