Parasites have been neglected from most biodiversity surveys even though they are an essential component of ecosystems and intimately associated with the free-living communities within them. Parasites with complex life cycles, such as digenean trematode flatworms, utilize at least two host species within an ecosystem for their development and transmission, taking advantage of species networks to complete their life cycles. Despite this knowledge, our understanding of the processes that contribute to parasite community assembly, and which limit their geographic distributions, are rudimentary, including the importance of host diversity. Utilizing recent advancements in the identification of cryptic trematode species through molecular barcoding, we examined patterns of community assembly involving 79 species in six Alberta lakes over three years. Specifically, we focused on spatiotemporal variation in trematode diversity within their snail first intermediate hosts (component communities), how this might relate to host diversity through the specificity of host-parasite relationships, and the role of certain environmental factors in structuring these communities. We found substantial natural fluctuations of trematode communities through space and time within these lakes. Trematode communities were diverse, showing an overall positive relationship with snail diversity, but were often dominated by a few common species. We found that ecoregion and lake trophic status were key predictors for the presence of these trematode species. Such information is key for understanding how biodiversity alterations may affect parasite community composition, as well as our ability to formulate predictive models, by considering how this could influence both species richness and evenness.

大多数寄生虫已被大多数生物多样性调查所忽略，尽管它们是生态系统的重要组成部分，并与其中的自由生活社区密切相关。具有复杂生命周期的寄生虫，例如第杰尼亚级吸虫扁虫，利用生态系统中的至少两个宿主物种进行发育和传播，并利用物种网络来完善其生命周期。尽管有这些知识，但我们对导致寄生虫群落聚集并限制其地理分布的过程的理解是基本的，包括宿主多样性的重要性。利用分子条形码技术在鉴定隐吸虫物种方面的最新进展，我们研究了三年来涉及六个艾伯塔省湖泊中79种物种的群落聚集模式。具体而言，我们关注蜗牛的第一个中间宿主（组成群落）内吸虫多样性的时空变化，这可能通过宿主-寄生虫关系的特异性与宿主多样性之间的关系以及某些环境因素在构造这些群落中的作用。我们发现在这些湖泊中，随着时间和空间的变化，吸虫的自然波动很大。吸虫的群落是多样的，与蜗牛的多样性总体上呈正相关，但通常以一些常见的物种为主。我们发现，生态区和湖泊的营养状态是这些吸虫物种存在的关键预测因子。这些信息对于了解生物多样性的变化如何影响寄生虫群落组成至关重要，