16Increasing evidence indicates that parasites play an important role within many systems as prey 17 for higher trophic levels. Predation on parasites can decrease their numbers and may affect host 18 infection rates. Cercariae, a free-living infectious stage of trematode parasites, are abundant in 19 freshwater systems and are directly consumed by a number of freshwater predators. However, 20 few studies have tested whether predators exhibit a preference for cercariae when alternative 21 prey are available or how these preferences vary across predator body sizes. We assessed 22 whether dragonfly larvae, top predators in freshwater systems without fish, foraged preferentially 23 when presented with two prey types, cercariae and zooplankton, and whether foraging 24 preferences changed across predator body size. Body size of larval dragonfly predators was 25 found to be significantly, and negatively, related to the fraction of cercariae in the diet. Larger 26 bodied dragonfly larvae shifted their diet choice from cercariae to zooplankton. Changes in 27 foraging selectivity as body size increases across a predator's ontogeny can alter the strength of 28 predator-prey interactions. Further investigation into size-selective foraging on parasites may 29 provide new insights into the effects of predation on parasite abundance and transmission in 30 natural systems.31 32

Pastureland currently occupies 26% of Earth's ice-free land surface. As the global human population continues to increase and developing countries consume more proteinrich diets, the amount of land devoted to livestock grazing will only continue to rise. To mitigate the loss of global biodiversity as a consequence of the ever-expanding amount of land converted from native habitat into pastureland for livestock grazing, an understanding of how livestock impact wildlife is critical. While previous reviews have examined the impact of livestock on a wide variety of taxa, there have been no reviews examining how global livestock grazing affects amphibians. We conducted both an empirical study in south-central Florida examining the impact of cattle on amphibian communities and a quantitative literature review of similar studies on five continents. Our empirical study analyzed amphibian community responses to cattle as both a binary (presence/absence) variable, and as a continuous variable based on cow pie density. Across all analyses, we were unable to find any evidence that cattle affected the amphibian community at our study site. The literature review returned 46 papers that met our criteria for inclusion. Of these studies, 15 found positive effects of livestock on amphibians, 21 found neutral/mixed effects, and 10 found negative effects. Our quantitative analysis of these data indicates that amphibian species that historically occurred in closedcanopy habitats are generally negatively affected by livestock presence. In contrast, opencanopy amphibians are likely to experience positive effects from the presence of livestock, and these positive effects are most likely to occur in locations with cooler climates and/or greater precipitation seasonality. Collectively, our empirical work and literature review demonstrate that under the correct conditions well-managed rangelands are able to support diverse assemblages of amphibians. These rangeland ecosystems may play a critical role in protecting future amphibian biodiversity by serving as an "off-reserve" system to supplement the biodiversity conserved within traditional protected areas.

Globally endangered ecosystems, such as ephemeral wetlands, are often critical habitat for multiple interacting imperilled species. To conserve this biodiversity, managers must consider both species‐specific resource requirements and mechanisms for endangered species coexistence under variable habitat conditions. We examined communities native to California playa pools, ephemeral wetlands that have declined by >90% from their historic extent. Specifically, we describe the diet of a federally Threatened amphibian (Ambystoma californiense), and characterise interactions between this amphibian and two federally Endangered macrocrustaceans (Branchinecta conservatio and Lepidurus packardi) across three rain years to understand how these imperilled species coexist. We examined the dietary preferences of A. californiense larvae, metamorphs, juveniles, and breeding adults, and determined how prey electivity by larval A. californiense differs between natural playa pools and human‐modified stock ponds. Within playa pools, both breeding adult and larval A. californiense preyed extensively on L. packardi, whereas fully terrestrial juveniles had relatively empty stomachs. We provide evidence for size‐moderated optimal foraging by larval A. californiense, and show that larval prey differed dramatically between playa pools and stock ponds. Additionally, an ontogenetic progression from smaller to larger prey gave the relatively large, endangered macrocrustaceans an early‐season temporal refuge, during which they reached maturity in all three rain years. Consistent with complex life cycle theory, our results suggest that ephemeral wetland habitat offers abundant food resources for A. californiense relative to terrestrial habitat. Our findings also suggest that diet flexibility facilitates the persistence of this imperilled amphibian in human‐modified stock ponds. Temporal offsets in prey maturation rates and ontogenetic shifts in predator diets are likely to facilitate coexistence among the focal endangered species. We highlight the importance of accounting for spatial and temporal variation in interspecific interactions when predicting the effects of environmental change on biodiversity, particularly in highly threatened ecosystems.

We tested a potential new tool for marking Odonata larvae internally, evaluating the retention rates of injected coded-wire tags (CWT) and the effects of these tags on larval performance. Two species of dragonfly larvae (Epitheca canis McLachlan (Odonata: Corduliidae) and Leucorrhinia intacta Hagen (Odonata: Libellulidae)) were injected with CWT. Tag loss rates were assayed over experimental periods of 22 and 60 days, respectively for the two species. To assess whether tagging had negative effects on larvae, mortality, and growth of tagged larvae were compared to untagged larvae held in the same conditions. Tag retention rates were high (92–100%) and CWT were easily retrieved from preserved larvae via dissection, permitting most tagged larvae to be individually identified. There was 100% survival in larvae injected with CWT and tags do not appear to impair growth. The high retention and retrieval rates of this marking approach combined with no increase in mortality associated with tagging suggest that CWT are a useful means of individually labelling a large number of Odonata larvae in a time-efficient manner.

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