Committee on Evolutionary Biology, University of Chicago, 1101 East 57th Street, Chicago, IL 60637, USA.
Proc Biol Sci. 2010 Feb 22;277(1681):539-47. doi: 10.1098/rspb.2009.1564. Epub 2009 Oct 28.
What are the relative roles of mechanisms underlying plant responses in grassland communities invaded by both plants and mammals? What type of community can we expect in the future given current or novel conditions? We address these questions by comparing Markov chain community models among treatments from a field experiment on invasive species on Robinson Crusoe Island, Chile. Because of seed dispersal, grazing and disturbance, we predicted that the exotic European rabbit (Oryctolagus cuniculus) facilitates epizoochorous exotic plants (plants with seeds that stick to the skin an animal) at the expense of native plants. To test our hypothesis, we crossed rabbit exclosure treatments with disturbance treatments, and sampled the plant community in permanent plots over 3 years. We then estimated Markov chain model transition probabilities and found significant differences among treatments. As hypothesized, this modelling revealed that exotic plants survive better in disturbed areas, while natives prefer no rabbits or disturbance. Surprisingly, rabbits negatively affect epizoochorous plants. Markov chain dynamics indicate that an overall replacement of native plants by exotic plants is underway. Using a treatment-based approach to multi-species Markov chain models allowed us to examine the changes in the importance of mechanisms in response to experimental impacts on communities.
植物在受到植物和哺乳动物共同入侵的草原群落中所产生的反应机制的相对作用是什么？考虑到当前或新出现的条件，我们未来会迎来什么样的群落？我们通过比较智利鲁滨逊克鲁索岛上入侵物种的野外实验中不同处理方式的马尔可夫链群落模型来回答这些问题。由于种子传播、放牧和干扰的影响，我们预测外来的欧洲兔（Oryctolagus cuniculus）会以牺牲本地植物为代价，促进散布动物传播的外来植物（种子粘在动物皮毛上的植物）的生长。为了验证我们的假设，我们将兔围栏处理与干扰处理交叉进行，并在 3 年内对永久样地中的植物群落进行了采样。然后，我们估计了马尔可夫链模型的转移概率，并发现处理之间存在显著差异。正如假设的那样，该模型表明，外来植物在受干扰的地区更容易存活，而本地植物则不喜欢有兔子或干扰。令人惊讶的是，兔子对外来的散布动物传播植物有负面影响。马尔可夫链动态表明，本地植物正被外来植物整体取代。使用基于处理的多物种马尔可夫链模型方法，我们可以研究在对群落进行实验干扰时，机制的重要性变化情况。
