We describe a new frog, Pristimantis mutabilis sp. nov., from the Andes of Ecuador. Individuals of the new species are remarkable for their ability to change skin texture from tuberculate to almost smooth in a few minutes, being the first documented amphibian species to show such dramatic phenotypic plasticity. The new taxon is assigned to the P. myersi group. It differs from other members of its group by body size (adult males 17.2-17.4 mm; adult females 20.9-23.2 mm), arboreal habitat, and red flash coloration in females. We document three call types for the new species, which differ through their number of notes and amplitude peaks. The three types are pulsed calls that share a dominant frequency of 3186.9-3445.3 Hz. Surprisingly, we also document similar skin texture plasticity in species (P. sobetes) from a different species group, suggesting that this ability might be more common than previously thought. The discovery of these variable species poses challenges to amphibian taxonomists and field biologists, who have traditionally used skin texture and presence/absence of tubercles as important discrete traits in diagnosing and identifying species. Reciprocal monophyly and genetic distances also support the validity of the new species, as it has distances of 15.1-16.3% (12S) and 16.4-18.6% (16S) from the most similar species, Pristimantis verecundus. Additionally, each of the two known populations of Pristimantis mutabilis are reciprocally monophyletic and exhibit a high genetic distance between them (5.0-6.5%). This pattern is best explained by the presence of a dry valley (Guayllabamba River) that seems to be acting as a dispersal barrier. Scenario 1: double origin Scenario 2: single origin P. buckleyi (KU 217836 P. sp. "mashpi" (MZUTI 635) P. surdus (KU 177847) P. hectus (UVC 15843) P. cf. verecundus (QCAZ 12410) P. cf. curtipes (KU 217869 P. sobetes (MZUTI 447) P. thymelensis (TNHC-GDC 14370) P. jubatus (UVC 15919) P. jubatus (UVC 15903) P. hectus (UVC 15943) P. sp. "mashpi" (MZUTI 634) P. ocreatus (KU 208508) P. verecundus (MZUTI 539) P. eriphus (QCAZ 32705) P. gentryi (KU 218109) P. cf. curtipes (KU 217871) P. sp. "mashpi" (MZUTI 633) P. sobetes (MZUTI 471) P. sobetes (MZUTI 542) P. truebae (KU 218013) P. sobetes (MZUTI 446) P. mutabilis (MZUTI 2190) P. sobetes (MZUTI 432) P. pyrrhomerus (KU 218030) P. mutabilis (MZUTI 910) P. supernatis (WED 52961) P. sobetes (MZUTI 442) P. jubatus (UVC 15917) P. eriphus (JJM 210) P. mutabilis (MZUTI 909) P. sp. "mashpi" (MZUTI 636) P. surdus (JDL 8862) P. mutabilis (MZUTI 911) P. devillei (JDL 9416 P. vertebralis (KU 177972 P. mutabilis (MZUTI 912) P. cf. thymelensis (QCAZ 16428) P. jubatus (UVC 15911) P. celator (KU 177684) P. thymalopsoides (KU 177861) P. thymelensis (KU 202519) P. verecundus (MZUTI 540) P. leoni (KU 218227) P. verecundus (MZUTI 2114) P. verecundus (MZUTI 541) P. hectus (UVC 15942) P. jubatus (UVC 15920) P. quinquagesimus (KU 179374) P. sobetes (MZUTI 439) P. mutabilis (MZUTI 2191) P. duellmani (WED 53050) P. sobetes (MZUTI 558) P. devillei (KU 2179...

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Road salt runoff has potentially large effects on wetland communities, but is typically investigated in short-term laboratory trials. The authors investigated effects of road salt contamination on wood frogs (Rana sylvatica) by combining a field survey with 2 separate experiments. The field survey tested whether wood frog larval traits were associated with road salt contamination in natural wetlands. As conductivity increased, wood frog larvae were less abundant, but those found were larger. In the first experiment of the present study, the authors raised larvae in outdoor artificial ponds under 4 salt concentrations and measured larval vital rates, algal biomass, and zooplankton abundance. Salt significantly increased larval growth, algal biomass, and decreased zooplankton abundance. In the second experiment, the authors raised larvae to metamorphosis in the presence and absence of salt contamination and followed resulting juvenile frogs in terrestrial pens at high and low densities. Exposure to road salt as larvae caused juvenile frogs to have greater mortality in low-density terrestrial environments, possibly because of altered energy allocation, changes in behavior, or reduced immune defenses. The present study suggests that low concentrations of road salt can have positive effects on larval growth yet negative effects on juvenile survival. These results emphasize the importance of testing for effects of contaminants acting through food webs and across multiple life stages as well as the potential for population-level consequences in natural environments.

Recent global declines, extirpations and extinctions of wildlife caused by newly emergent diseases highlight the need to improve our knowledge of common environmental factors that affect the strength of immune defense traits. To achieve this goal, we examined the influence of acidification and shading of the larval environment on amphibian skin-associated innate immune defense traits, pre and post-metamorphosis, across two populations of American Bullfrogs (Rana catesbeiana), a species known for its wide-ranging environmental tolerance and introduced global distribution. We assessed treatment effects on 1) skin-associated microbial communities and 2) post-metamorphic antimicrobial peptide (AMP) production and 3) AMP bioactivity against the fungal pathogen Batrachochytrium dendrobatidis (Bd). While habitat acidification did not affect survival, time to metamorphosis or juvenile mass, we found that a change in average pH from 7 to 6 caused a significant shift in the larval skin microbial community, an effect which disappeared after metamorphosis. Additionally, we found shifts in skin-associated microbial communities across life stages suggesting they are affected by the physiological or ecological changes associated with amphibian metamorphosis. Moreover, we found that post-metamorphic AMP production and bioactivity were significantly affected by the interactions between pH and shade treatments and interactive effects differed across populations. In contrast, there were no significant interactions between treatments on post-metamorphic microbial community structure suggesting that variation in AMPs did not affect microbial community structure within our study. Our findings indicate that commonly encountered variation in the larval environment (i.e. pond pH and degree of shading) can have both immediate and long-term effects on the amphibian innate immune defense traits. Our work suggests that the susceptibility of amphibians to emerging diseases could be related to variability in the larval environment and calls for research into the relative influence of potentially less benign anthropogenic environmental changes on innate immune defense traits.

Disease-associated mortality is a leading cause of amphibian declines and extinctions worldwide. Understanding the influence of land-management practices, like herbicide use, on amphibian immune defense traits could guide changes to improve conservation outcomes. Amphibians are partially protected from pathogens by two skin-associated immune defense traits: bacterial communities inhabiting their skin, and antimicrobial peptides secreted by the skin. Utilizing the Blanchard's Cricket Frog (Acris blanchardi), a declining North American amphibian species, as our model, we manipulated Rodeoe aquatic herbicide concentration and the life stage at which Rodeo exposure occurred. We assessed juvenile survival, time to metamorphosis, juvenile mass, and skinassociated immune defense traits. We found a 37% decrease in survival of larvae exposed to 2.5 mg a.e. L-1 (acid equivalent) compared to controls despite that this commercial herbicide formulation does not contain an added surfactant. Surviving larvae exposed to 2.5 mg a.e. L-1 Rodeo had structurally different larval skin bacterial communities compared to controls. Larval Rodeo exposure did not carry over to postmetamorphic traits (juvenile mass, juvenile skin bacterial community, juvenile natural peptide secretions). Rodeo treatments did not affect time to metamorphosis or juvenile survival. Rodeo concentration had marginally significant effects on juvenile mass and the juvenile skin bacterial community. This study suggests glyphosate-based herbicide use may indirectly contribute to disease-related amphibian declines by altering the skin bacterial community that can provide pathogen resistance. Improving our knowledge of the influence of herbicide use on amphibians across life stages provides an opportunity for changes to application strategies to protect amphibian health or at minimum, lessen negative effects of the practice.