Institute of Life Sciences and Technologies, Daugavpils University, Parades Street 1A, Daugavpils, 5401, Latvia.
Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel.
Parasitol Res. 2021 Oct;120(10):3461-3474. doi: 10.1007/s00436-021-07303-8. Epub 2021 Sep 3.
We investigated factors affecting species composition and patterns of species associations in parasite communities of water frogs (Pelophylax esculentus complex), applying the distance-based redundancy analysis for component communities (assemblages harboured by host populations) and Markov random fields modelling for infracommunities (assemblages harboured by individual hosts), respectively. We asked (a) What are the relative effects of variation in environmental, land use (i.e., anthropogenic), and spatial factors on the variation in the species composition of component communities (i.e., in a locality)? and (b) What is the dominant pattern of species associations in infracommunities (in a host individual), and how do these associations vary along environmental and/or anthropogenic gradients? In component communities, the greatest portion of variation in helminth species composition was explained by the combined effects of space, anthropogenic pressure, and NDVI, with the pure effect of the spatial predictor being much stronger than the effects of the remaining predictors. In infracommunities, the probability of occurrence of some, but not all, helminth species depended on the occurrence of another species, with the numbers of negative and positive co-occurrences being equal. The strength and/or sign of associations of some species pairs were spatially stable, whereas interactions between other species pairs varied along the gradient of the amount of green vegetation, from negative to positive and vice versa. We conclude that the processes in parasite infracommunities and component communities in frogs are intertwined, with both bottom-up and top-down effects acting at different hierarchical scales.
我们分别应用基于距离的冗余分析（针对组成群落，即宿主种群所包含的群落）和马尔可夫随机场模型（针对亚群落，即个体宿主所包含的群落），研究了影响寄生虫群落物种组成和物种关联模式的因素，这些寄生虫群落为食用蛙（Pelophylax esculentus 复合体）。我们提出了以下两个问题：（a）环境、土地利用（即人为因素）和空间因素的变化对组成群落（即特定地点）的物种组成变化有哪些相对影响？（b）亚群落中物种关联的主要模式是什么，以及这些关联如何沿环境和/或人为梯度变化？在组成群落中，寄生虫物种组成变化的最大部分可归因于空间、人为压力和 NDVI 的综合影响，而空间预测因子的纯效应远强于其余预测因子的效应。在亚群落中，某些（但不是全部）寄生虫物种的出现概率取决于另一种物种的出现概率，负和正的共存数量相等。一些物种对之间的关联的强度和/或方向在空间上是稳定的，而其他物种对之间的相互作用则沿植被量的梯度从负相关变为正相关，反之亦然。我们得出的结论是，青蛙寄生虫亚群落和组成群落中的过程相互交织，存在自上而下和自下而上的影响，作用于不同的层次尺度。
