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Ecological interactions among hosts are critical to consider when predicting disease dynamics. Most theory predicts that intraguild predation (IGP) and cannibalism negatively impact parasite populations, but this is based primarily on assumptions of simple or single‐host life cycles. Here we investigate the effects of cannibalism in a size‐structured host population on two digenean trematodes that have complex, multihost life cycles. A high incidence of cannibalism among paratenic hosts produced higher parasite infection loads and abundance, whereas cannibalism among obligate hosts reduced parasite abundances. We attributed this difference to trophic transmission aggregating parasites in larger, potentially fitter hosts and also to transmission among paratenic hosts via cannibalism. Moreover, we found evidence of indirect competitive interactions between parasites that can also increase infections at small scales. Our results show there are multiple mechanisms through which high cannibalism environments can benefit parasites that use paratenic hosts and trophic transfer to complete their life cycles. [ABSTRACT FROM AUTHOR]

Warming has broad and often nonlinear impacts on organismal physiology and traits, allowing it to impact species interactions like predation through a variety of pathways that may be difficult to predict. Predictions are commonly based on short‐term experiments and models, and these studies often yield conflicting results depending on the environmental context, spatiotemporal scale, and the predator and prey species considered. Thus, the accuracy of predicted changes in interaction strength, and their importance to the broader ecosystems they take place in, remain unclear. Here, we attempted to link one such set of predictions generated using theory, modeling, and controlled experiments to patterns in the natural abundance of prey across a broad thermal gradient. To do so, we first predicted how warming would impact a stage‐structured predator–prey interaction in riverine rock pools between Pantala spp. dragonfly nymph predators and Aedes atropalpus mosquito larval prey. We then described temperature variation across a set of hundreds of riverine rock pools (n = 775) and leveraged this natural gradient to look for evidence for or against our model's predictions. Our model's predictions suggested that warming should weaken predator control of mosquito larval prey by accelerating their development and shrinking the window of time during which aquatic dragonfly nymphs could consume them. This was consistent with data collected in rock pool ecosystems, where the negative effects of dragonfly nymph predators on mosquito larval abundance were weaker in warmer pools. Our findings provide additional evidence to substantiate our model‐derived predictions while emphasizing the importance of assessing similar predictions using natural gradients of temperature whenever possible. [ABSTRACT FROM AUTHOR]

This study presents a GIS-based database framework used to assess aggregate terrestrial habitat impacts from multiple highway construction projects in California, USA. Transportation planners need such impact assessment tools to effectively address additive biological mitigation obligations. Such assessments can reduce costly delays due to protracted environmental review. This project incorporated the best available statewide natural resource data into early project planning and preliminary environmental assessments for single and multiple highway construction projects, and provides an assessment of the 10-year state-wide mitigation obligations for the California Department of Transportation. Incorporation of these assessments will facilitate early and more strategic identification of mitigation opportunities, for single-project and regional mitigation efforts. The data architecture format uses eight spatial scales: six nested watersheds, counties, and transportation planning districts, which were intersected. This resulted in 8058 map planning units statewide, which were used to summarize all subsequent analyses. Range maps and georeferenced locations of federally and state-listed plants and animals and a 55-class landcover map were spatially intersected with the planning units and the buffered spatial footprint of 967 funded projects. Projected impacts were summarized and output to the database. Queries written in the database can sum expected impacts and provide summaries by individual construction project, or by watershed, county, transportation district or highway. The data architecture allows easy incorporation of new information and results in a tool usable without GIS by a wide variety of agency biologists and planners. The data architecture format would be useful for other types of regional planning.

The introduction and spread of non‐native species restructure native ecosystems and can be particularly impactful when invaders are ecosystem engineers or habitat‐forming species. In coastal, estuarine, and marine systems, submerged aquatic vegetation (SAV), like macroalgae and seagrasses, form key habitats for nekton, serving as nurseries, foraging grounds, and reproduction sites. If non‐native ecosystem engineers can provide sufficient structure and/or resources, they may exert a neutral or positive effect on organisms occupying higher trophic positions. As such, we hypothesized that nekton response to non‐native SAV species may be neutral or positive. We performed a quantitative meta‐analysis to quantify impacts of non‐native SAV on native crabs, fishes, and shrimps. We extracted data from 35 studies and evaluated 11 response metrics related to facilitation (e.g., habitat use and foraging), restricting our analysis to studies that compared at least one of these metrics in nekton from co‐occurring native and non‐native SAV habitats in marine, coastal, or estuarine systems. We found that nekton abundance, species richness, and biomass were the most assessed metrics of nekton performance. Our pooled data revealed differential results among response metrics, with nekton growth and reproduction enhanced in non‐native habitats and species richness enhanced in a native setting. The mean effect sizes for all other nekton response metrics, including abundance, had 95% CIs that overlapped zero, indicating no difference in response between native and non‐native SAV. For many endpoints, limited sample sizes prevented robust inferences, but they also highlighted areas where more research is needed in future studies. Non‐native species have the potential to restructure the systems they invade. Our results lend support to the relative trophic position hypothesis, indicating that non‐native habitat formers may facilitate native organisms in higher trophic levels. We identify research gaps that may guide future studies and allow for a more comprehensive understanding of responses to non‐native ecosystem engineers. [ABSTRACT FROM AUTHOR]

Networks have become a central concept in the policy and public management literature; however, theoretical development is hindered by a lack of attention to the empirical properties of network measurement methods. This paper compares three survey-based methods for measuring organizational networks: the roster, the free-recall name generator, and a hybrid name generator that combines these two classic approaches. Results indicate that the roster and free-recall name generator methods both suffer from important limitations. The roster method tends to measure many linkages among a limited set of network actors, whereas the name generator tends to measure fewer linkages among a larger set of network actors. Using survey data on policy networks within California regional planning processes (N = 752), we find that the hybrid method strikes an effective balance between these techniques. The hybrid approach performs well in terms of identifying a large number of network actors and interconnections between them. Although no survey-based measurement technique is perfect, this study suggests that the hybrid name generator is an excellent alternative for the measurement of complex networks with large or shifting boundaries that encompass a diverse set of actors. (Contains 8 footnotes, 4 tables, and 2 figures.)

A classroom activity to introduce students to the intrinsic and economic values of biodiversity.

Consider a data set of vector-valued observations that consists of noisy inliers, which are explained well by a low-dimensional subspace, along with some number of outliers. This work describes a convex optimization problem, called reaper, that can reliably fit a low-dimensional model to this type of data. This approach parameterizes linear subspaces using orthogonal projectors and uses a relaxation of the set of orthogonal projectors to reach the convex formulation. The paper provides an efficient algorithm for solving the reaper problem, and it documents numerical experiments that confirm that reaper can dependably find linear structure in synthetic and natural data. In addition, when the inliers lie near a low-dimensional subspace, there is a rigorous theory that describes when reaper can approximate this subspace., Author(s): Gilad Lerman[sup.1] , Michael B. McCoy[sup.2] , Joel A. Tropp[sup.3] , Teng Zhang[sup.4] Author Affiliations: (1) Department of Mathematics, University of Minnesota, 127 Vincent Hall, 206 Church St SE, [...]