DISSERTATION RESEARCH: The effects of dendritic structure on parasite metacommunities in stream networks

生态群落由许多相互作用的物种组成，并提供从清洁水到授粉等有价值的生态系统服务。为了维持这些生态系统服务，重要的是要了解决定何时何地以及哪些物种一起发生的过程。扩散，或生物在景观上的移动，是确定在特定地点存在什么物种的重要过程；然而，对于不同类型的生物和不同的栖息地，扩散的重要性可能是不同的。迄今为止，大多数研究都集中在有明确边界的栖息地，如森林碎片或池塘。本研究的主要目的是探讨河流中野生寄生虫在群落结构中的扩散作用。该研究的第二个目标是开发方法，使用新的DNA测序技术来量化水样中寄生虫的丰度，从而有可能快速调查寄生虫群落并确定高感染和低感染区域。溪流和河流可能是病原体运动的重要渠道，这项研究将增加我们对淡水生态系统中传染病动态的理解，同时也为评估淡水寄生虫的分布和丰度提供新的方法。吸虫，也被称为吸虫或寄生扁虫，是软体动物和所有脊椎动物的专性内寄生虫。它们具有复杂的生命周期，需要多个寄主，并且由于寄主在不同的空间尺度上分散（例如，鱼与鸟），它们代表了一个有价值的系统，用于研究分散在当地群落结构中的作用。本研究将采用实地调查和分子分析来表征美国东南部多个河流网络内部和之间的吸虫丰度和多样性。从主干到上游，研究人员将量化每个河流网络中15个地点的第一中间宿主（蜗牛）的吸虫感染。蜗牛作为多种吸虫物种的第一中间寄主，整合了整个吸虫生命周期中宿主群落的信息。研究者假设：i)由于自由寄生寄生虫和受感染宿主在下游的持续移动，吸虫总体流行率和多样性将呈不断增加的下游梯度；ii)与鱼类宿主相比，哺乳动物或鸟类宿主的吸虫在流行度和多样性上的下游梯度不那么明显，因为宿主在整个景观中的流动性更大。通过关注一个不同的寄生虫群落，这些寄生虫都使用同一种蜗牛作为第一中间宿主，但在脊椎动物宿主的使用和传播潜力方面各不相同，本研究将为传播在构建当地群落中的重要性提供新的见解。

Ecological communities are composed of many interacting species and provide valuable ecosystem services ranging from clean water to pollination. To maintain these ecosystem services, it is important to understand the processes that determine where, when and which species occur together. Dispersal, or the movement of organisms across the landscape, is an important process in determining what species exist at a specific site; however, the importance of dispersal is likely to vary for different types of organisms and for different habitats. To date, most research examining the role of dispersal has focused on habitats with distinct boundaries, such as forest fragments or ponds. The primary goal of this research is to explore the role of dispersal in structuring communities of wildlife parasites live in streams. A second goal of the research is to develop methods to use new DNA sequencing technologies to quantify the abundance of parasites in water samples, making it possible to rapidly survey parasite communities and identify areas of high and low infection. Streams and rivers can be important channels for the movement of pathogens, and this research will increase our understanding of infectious disease dynamics in freshwater ecosystems while also contributing new methods for assessing the distribution and abundance of freshwater parasites. Trematodes, also known as flukes or parasitic flatworms, are obligate endoparasites of mollusks and all classes of vertebrates. They have complex life cycles requiring multiple hosts, and because the hosts disperse at different spatial scales (e.g., fish vs. birds), they represent a valuable system for examining the role of dispersal in local community structure. This research will employ field surveys and molecular analyses to characterize trematode abundance and diversity within and across multiple stream networks in the southeastern U.S. Proceeding from mainstem to headwaters, investigators will quantify trematode infection in first-intermediate hosts (snails) from 15 sites within each stream network. As the obligate first-intermediate hosts of multiple trematode species, snails integrate information on the entire community of hosts involved in trematode life cycles. Investigators hypothesize that: i) there will be an increasing downstream gradient of overall trematode prevalence and diversity due to the continuous movement of free-living parasite stages and infected hosts downstream; and ii) that trematodes with mammalian or avian hosts will have a less pronounced downstream gradient of prevalence and diversity than those with fish hosts, due to greater host mobility across the landscape. By focusing on a diverse community of parasites that all use the same snail species as a first-intermediate host but that vary in vertebrate host use and thus dispersal potential, this research will provide new insights into the importance of dispersal in structuring local communities.