We tested the hypotheses that potential egg predators, crayfish Procambarus nigrocinctus and dytiscid Cybister sp. larvae, would accelerate the timing of hatching and that a larval predator, dragonfly naiad Anax junius, would delay hatching in the southern leopard frog (Rana sphenocephala). We also tested the hypothesis that differences in response would be proportional to predator lethality. Our results indicate that our hypotheses were partially supported. The presence of an efficient egg predator (crayfish) induces hatching faster than a less efficient predator (dytiscid larvae). However, the presence of a larval predator (naiads) did not delay hatching. Eggs that developed in the presence of egg predators produced hatchlings that were shorter (total length) than those reared in the presence of larval predators or those reared in the absence of predators. We suggest that earlier hatching times should decrease vulnerability to egg predators but result in shorter hatchlings.

Divergent natural selection drives a considerable amount of the phenotypic and genetic variation observed in natural populations. For example, variation in the predator community can generate conflicting selection on behavioral, life-history, morphological, and performance traits. Differences in predator regime can subsequently increase phenotypic and genetic variations in the population and result in the evolution of reproductive barriers (ecological speciation) or phenotypic plasticity. We evaluated morphology and swimming performance in field collected Bronze Frog larvae (Lithobates clamitans) in ponds dominated by predatory fish and those dominated by invertebrate predators. Based on previous experimental findings, we hypothesized that tadpoles from fish-dominated ponds would have small bodies, long tails, and large tail muscles and that these features would facilitate fast-start speed. We also expected to see increased tail fin depth (i.e., the tail-lure morphology) in tadpoles from invertebrate-dominated ponds. Our results support our expectations with respect to morphology in affecting swimming performance of tadpoles in fish-dominated ponds. Furthermore, it is likely that divergent natural selection is playing a role in the diversification on morphology and locomotor performance in this system.

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Chinese tallow (Triadica sebifera (L.) Small) is an aggressive invasive tree species that can be abundant in parts of its non-native range. This tree species has the capability of producing monocultures, by outcompeting native trees, which can be in or near wetlands that are utilized by breeding amphibians. Existing research suggests that leaf litter from invasive Chinese tallow reduces survival in larval anurans. The purpose of this study was to determine the effects of Chinese tallow leaf litter on anuran eggs. We exposed eggs of the Southern Leopard Frog (Lithobates sphenocephalus (Cope, 1886)) at various stages of development to different concentrations of Chinese tallow leaf litter to determine survival. Eggs in the earliest stages of development that we exposed to tallow leaf litter died, regardless of concentration; however, some more-developed eggs exposed to tallow leaf litter did hatch. We determined that the greater the concentration of tallow leaf litter, the lower the dissolved oxygen and pH levels we observed. We suggest that changes in these water-quality parameters are the cause of the observed mortality of anuran eggs in our experiments. Eggs exposed to water containing tallow leaf litter with dissolved oxygen <1.59 mg/L and a pH <5.29 did not survive to hatching.Résumé : Le suif végétal de Chine (Triadica sebifera (L.) Small) est une essence d'arbre envahissante agressive qui peut localement être abondante hors de son aire de répartition naturelle. Cette essence est capable de produire des monocultures en délogeant des essences indigènes pouvant se trouver dans des zones humides ou à proximité et que des amphibiens utilisent pour la reproduction. Les travaux existants suggèrent qu'une couverture de feuilles mortes de suif végétal de Chine réduit la survie de larves d'anoures. Le but de l'étude consiste à déterminer les effets des feuilles mortes de suif végétal sur les oeufs d'anoures. Nous avons exposé des oeufs de grenouille léopard du Sud (Lithobates sphenocephalus (Cope, 1886)) à différents stades de leur développement à différentes concentrations de feuilles de suif végétal dans la couverture de feuilles mortes afin de déterminer leur taux de survie. Les oeufs exposés aux stades les plus précoces de leur développement à des feuilles mortes de suif végétal sont morts, peu importe la concentration de ces dernières, alors que certains oeufs à des stades plus avancés ont éclos. Nous avons déterminé que plus la concentration de feuilles mortes de suif végétal dans la couverture était grande, plus les teneurs d'oxygène dissous et le pH étaient faibles. Nous suggérons que les modifications de ces paramètres de qualité de l'eau sont à l'origine de la mortalité observée parmi les oeufs d'anoures dans nos expériences. Les oeufs exposés à de l'eau contenant des feuilles mortes de suif végétal et présentant des teneurs d'oxygène dissous <1,59 mg/L et un pH <5,29 n'ont pas survécu jusqu'à l'éclosion.

In road construction projects across the United States, erosion control methods (e.g., erosion control blankets [ECBs]), are mandated to stimulate seedbed regeneration and prevent soil loss. Previous reports have suggested that snakes are vulnerable to entanglement in ECBs. We conducted a literature review, field surveys, and an entanglement experiment to examine what factors increase a snake's risk of ECB entanglement. Our literature review produced reports of 175 reptiles entangled in mesh products, 89.1% of which were snakes, with 43.6% of snake entanglements occurring in erosion control products. During our field surveys, we found 10 entangled snakes (n = 2 alive; n = 8 dead). From our experiment, we found that ECBs that contain fixed‐intersection, small‐diameter mesh consisting of polypropylene were significantly more likely to entangle snakes compared with ECBs with larger diameter polypropylene mesh or ECBs that have woven mesh made of natural fibers. Snake body size was also associated with entanglement; for every 1‐mm increase in body circumference, the probability of entanglement increased 4%. These results can help construct a predictive framework to determine those species and individuals that are most vulnerable to entanglement. © 2019 The Wildlife Society.

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AbstractThe assembly of local communities is likely to reflect the effects of local environmental factors associated with filters that act at larger spatial scales. Dissecting these multiscale effects remains a timely challenge that is particularly important for host-associated microbiomes. We investigated the relative roles of local selection (due to host species identity) and regional effects (due to water body identity) on the community structure of bacteria in the gut of tadpoles from three biogeographic areas and used graph theory and metanetwork approaches to explore and illustrate the distribution of bacteria across different ponds. The pond of origin, which represents a regional species pool of bacteria, was in general more important in shaping the gut microbiome of tadpoles than host species identity. The resulting metanetworks are modular and indicate relatively few species of bacteria occurring in more than one pond. Thus, each pond represents a relatively distinct species pool of bacteria available for community assembly of the tadpole microbiomes. Our findings indicate that microbiome community assembly in amphibian larvae, as in many other communities, is a multiscale process with important regional effects that constrain how local (i.e. host-dependent) filters act to influence microbiome community composition.