Kribs Christopher M, Mackey Crystal
Department of Mathematics, University of Texas at Arlington, USA.
Department of Mathematics, University of Texas at Arlington, USA.
J Theor Biol. 2022 Mar 21;537:110981. doi: 10.1016/j.jtbi.2021.110981. Epub 2021 Dec 14.
Different species of scavengers may compete for the same food in an ecosystem. This case study considers the competition between jackals and vultures in Etosha National Park in Namibia. While jackals are facultative scavengers, able to hunt for food if necessary, vultures are obligate scavengers wholly dependent on carcasses of animals like zebras for persistence. This competition may be further affected by outbreaks of infections such as anthrax, which temporarily increase the number of carcasses but lower the zebra population, acting in some ways as a third competitor. We use a dynamical system to model the interplay between competition dynamics and infection dynamics, and how it is affected by the nature of the competition: indirect (exploitative) or direct (interference). A bifurcation analysis using reproduction numbers shows how vultures' survival may depend on their direct competitive edge in reaching carcasses faster than jackals, and how the infection and the scavengers complicate each other's persistence. Vultures' interference causes a backward bifurcation which enables them to persist. One possible outcome is a "strange bedfellows" bistability in which anthrax and vultures persist only together, not apart, despite being competitors.
在一个生态系统中，不同种类的食腐动物可能会争夺同一种食物。本案例研究探讨了纳米比亚埃托沙国家公园中豺和秃鹫之间的竞争。豺是兼性食腐动物，必要时能够捕食，而秃鹫是专性食腐动物，完全依赖斑马等动物的尸体生存。这种竞争可能会受到炭疽等传染病爆发的进一步影响，炭疽会暂时增加尸体数量，但会减少斑马种群数量，在某种程度上起到了第三个竞争者的作用。我们使用一个动态系统来模拟竞争动态和感染动态之间的相互作用，以及它如何受到竞争性质的影响：间接（剥削性）或直接（干扰性）。使用繁殖数进行的分岔分析表明，秃鹫的生存可能取决于它们比豺更快到达尸体的直接竞争优势，以及感染和食腐动物如何使彼此的生存变得复杂。秃鹫的干扰导致向后分岔，使它们能够生存。一种可能的结果是“奇怪的伙伴”双稳态，即炭疽和秃鹫仅在共存时才能生存，尽管它们是竞争者，但不能单独生存。
