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Abstract The relationship between infection prevalence and host age is informative because it can reveal processes underlying disease dynamics. Most prior work has assumed that age‐prevalence curves are shaped by infection rates, host immunity and/or infection‐induced mortality. Interactions between parasites within a host have largely been overlooked as a source of variation in age‐prevalence curves.We used field survey data and models to examine the role of interspecific interactions between parasites in shaping age‐prevalence curves. The empirical dataset included quantification of parasite infection prevalence for eight co‐occurring trematodes in over 15,000 snail hosts. We characterized age‐prevalence curves for each taxon, examined how they changed over space in relation to co‐occurring trematodes and tested whether the shape of the curves aligned with expectations for the frequencies of coinfections by two taxa in the same host. The models explored scenarios that included negative interspecific interactions between parasites, variation in the force‐of‐infection (FOI) and infection‐induced mortality that varied with host age, which were mechanisms hypothesized to be important in the empirical dataset.In the empirical dataset, four trematode parasites had monotonic increasing age‐prevalence curves and four had unimodal age‐prevalence curves. Some of the curves remained consistent in shape in relation to the prevalence of other potentially interacting trematodes, while some shifted from unimodal to monotonic increasing, suggesting release from negative interspecific interactions. The most common taxa with monotonic increasing curves had lower co‐infection frequencies than expected, suggesting they were competitively dominant. Taxa with unimodal curves had coinfection frequencies that were closer to those expected by chance.The model showed that negative interspecific interactions between parasites can cause a unimodal age‐prevalence curve in the subordinate taxon. Increases in the FOI and/or infection‐induced mortality of the dominant taxon cause shifts in the peak prevalence of the subordinate taxon to a younger host age. Infection‐induced mortality that increased with host age was the only scenario that caused a unimodal curve in the dominant taxon.Results indicated that negative interspecific interactions between parasites contributed to variation in the shape of age‐prevalence curves across parasite taxa and support the growing importance of incorporating interactions between parasites in explaining population‐level patterns of host infection over space and time. Read the freePlain Language Summaryfor this article on the Journal blog. 

Abstract Urbanization can influence local richness (alpha diversity) and community composition (beta diversity) in numerous ways. For instance, reduced connectivity and land cover change may lead to the loss of native specialist taxa, decreasing alpha diversity. Alternatively, if urbanization facilitates nonnative species introductions and generalist taxa, alpha diversity may remain unchanged or increase, while beta diversity could decline due to the homogenization of community structure. Wetlands and ponds provide critical ecosystem services and support diverse communities, making them important systems in which to understand the consequences of urbanization. To determine how urban development shapes pond community structure, we surveyed 68 ponds around Madison, Wisconsin, USA, which were classified as urban, greenspace, or rural based on surrounding land use. We evaluated how landscape and local pond factors were correlated with the alpha diversity of aquatic plants, macroinvertebrates, and aquatic vertebrates. We also analyzed whether surrounding land use was associated with changes in community composition and the presence of specific taxa. We found a 23% decrease in mean richness (alpha diversity) from rural to urban pond sites and a 15% decrease from rural to greenspace pond sites. Among landscape factors, adjacent developed land, mowed lawn cover, and greater distances to other waterbodies were negatively correlated with observed pond richness. Among pond level factors, habitat complexity was associated with increased richness, while nonnative fishes were associated with decreased richness. Beta diversity was relatively high for all ponds due to turnover in composition between sites. Urban ponds supported more nonnative species, lacked a subset of native species found in rural ponds, and had slightly higher beta diversity than greenspace and rural ponds. Our results suggest that integrating ponds into connected greenspaces, maintaining riparian vegetation, preventing nonnative fish introductions, and promoting habitat complexity may mitigate the negative effects of urbanization on aquatic richness. While ponds are small in size and rarely incorporated into urban conservation planning, the high beta diversity of distinct pond communities emphasizes their importance for supporting urban biodiversity. 

Abstract Ecosystems across the United States are changing in complex and surprising ways. Ongoing demand for critical ecosystem services requires an understanding of the populations and communities in these ecosystems in the future. This paper represents a synthesis effort of the U.S. National Science Foundation‐funded Long‐Term Ecological Research (LTER) network addressing the core research area of “populations and communities.” The objective of this effort was to show the importance of long‐term data collection and experiments for addressing the hardest questions in scientific ecology that have significant implications for environmental policy and management. Each LTER site developed at least one compelling case study about what their site could look like in 50–100 yr as human and environmental drivers influencing specific ecosystems change. As the case studies were prepared, five themes emerged, and the studies were grouped into papers in this LTER Futures Special Feature addressing state change, connectivity, resilience, time lags, and cascading effects. This paper addresses the “connectivity” theme and has examples from the Phoenix (urban), Niwot Ridge (alpine tundra), McMurdo Dry Valleys (polar desert), Plum Island (coastal), Santa Barbara Coastal (coastal), and Jornada (arid grassland and shrubland) sites. Connectivity has multiple dimensions, ranging from multi‐scalar interactions in space to complex interactions over time that govern the transport of materials and the distribution and movement of organisms. The case studies presented here range widely, showing how land‐use legacies interact with climate to alter the structure and function of arid ecosystems and flows of resources and organisms in Antarctic polar desert, alpine, urban, and coastal marine ecosystems. Long‐term ecological research demonstrates that connectivity can, in some circumstances, sustain valuable ecosystem functions, such as the persistence of foundation species and their associated biodiversity or, it can be an agent of state change, as when it increases wind and water erosion. Increased connectivity due to warming can also lead to species range expansions or contractions and the introduction of undesirable species. Continued long‐term studies are essential for addressing the complexities of connectivity. The diversity of ecosystems within the LTER network is a strong platform for these studies.