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The use of pesticides is important for growing crops and protecting human health by reducing the prevalence of targeted pest species. However, less attention is given to the potential unintended effects on nontarget species, including taxonomic groups that are of current conservation concern. One issue raised in recent years is the potential for pesticides to become more lethal in the presence of predatory cues, a phenomenon observed thus far only in the laboratory. A second issue is whether pesticides can induce unintended trait changes in nontarget species, particularly trait changes that might mimic adaptive responses to natural environmental stressors. Using outdoor mesocosms, I created simple wetland communities containing leaf litter, algae, zooplankton, and three species of tadpoles (wood frogs [ Rana sylvatica or Lithobates sylvaticus ], leopard frogs [ R. pipiens or L. pipiens ], and American toads [ Bufo americanus or Anaxyrus americanus ]). I exposed the communities to a factorial combination of environmentally relevant herbicide concentrations (0, 1, 2, or 3 mg acid equivalents [a.e.]/L of Roundup Original MAX) crossed with three predator-cue treatments (no predators, adult newts [ Notophthalmus viridescens ], or larval dragonflies [ Anax junius ]). Without predator cues, mortality rates from Roundup were consistent with past studies. Combined with cues from the most risky predator (i.e., dragonflies), Roundup became less lethal (in direct contrast to past laboratory studies). This reduction in mortality was likely caused by the herbicide stratifying in the water column and predator cues scaring the tadpoles down to the benthos where herbicide concentrations were lower. Even more striking was the discovery that Roundup induced morphological changes in the tadpoles. In wood frog and leopard frog tadpoles, Roundup induced relatively deeper tails in the same direction and of the same magnitude as the adaptive changes induced by dragonfly cues. To my knowledge, this is the first study to show that a pesticide can induce morphological changes in a vertebrate. Moreover, the data suggest that the herbicide might be activating the tadpoles' developmental pathways used for antipredator responses. Collectively, these discoveries suggest that the world's most widely applied herbicide may have much further-reaching effects on nontarget species than previous considered.

Carryover effects occur when experiences early in life affect an individual's performance at a later stage. Many studies have shown carryover effects to be important for future performance. However, it is currently unclear whether variation in later environments could overwhelm factors from an earlier life stage. We were interested in whether similar patterns would emerge under the same experimental design with similar taxa. To examine this, we implemented a four-way factorial experimental design with different forestry practices on three species of anurans (each examined in different years) in the aquatic larval environment and terrestrial juvenile environment in outdoor mesocosms in central Missouri, USA. Using Cormack-Jolly-Seber mark-recapture models implemented in program MARK, we investigated whether one environment or both environments best predicted terrestrial juvenile survival. We found only limited evidence of carryover effects for one of three species in one time period. These were the effects of time to metamorphosis and body condition at metamorphosis predicting leopard frog ( Lithobates sphenocephalus ) survival. However, both effects were counterintuitive and/or very weak. For wood frogs ( L. sylvaticus ), all of the variables predicting survival had confidence intervals that included zero, but very low survival may have limited our ability to estimate parameters. The terrestrial environment was important for predicting survival in both American toads ( Anaxyrus americanus ) and southern leopard frogs. The partial harvest forest tended to increase survival relative to control forest and early-successional forest in American toads. Alternately, early-successional forest with downed wood removed increased survival for leopard frogs, but this treatment was no different from control forest for American toads. Previous studies have shown negative effects of recent clearcuts on terrestrial amphibians. It appears that vegetative regrowth after just a few years can mitigate these initial negative effects. Our study shows that variation in later environments probably can overwhelm variation from earlier environments. However, previous evidence of carryover effects suggests that more research is needed to predict when carryover effects are likely to occur.

Artificial light at night (ALAN) affects over 20% of the earth's surface and is estimated to increase 6% per year. Most studies of ALAN have focused on a single mechanism or life stage. We tested for indirect and direct ALAN effects that occurred by altering American toads' (Anaxyrus americanus) ecological interactions or by altering toad development and growth, respectively. We conducted an experiment over two life stages using outdoor mesocosms and indoor terraria. In the first phase, the presence of ALAN reduced metamorphic duration and periphyton biomass. The effects of ALAN appeared to be mediated through direct effects on toad development, and we found no evidence for indirect effects of ALAN acting through altered ecological interactions or colonization. In the second phase, post-metamorphic toad growth was reduced by 15% in the ALAN treatment. Juvenile-stage ALAN also affected toad activity: in natural light, toads retreated into leaf litter at night whereas ALAN toads did not change behaviour. Carry-over effects of ALAN were also present; juvenile toads that had been exposed to larval ALAN exhibited marginally increased activity. In this time frame and system, our experiments suggested ALAN's effects act primarily through direct effects, rather than indirect effects, and can persist across life stages.

Summary While most frogs maximize jump distance as an escape behaviour, toads have traded jump distance for endurance with a strategy of hopping repeatedly. This strategy has enabled toads to expand across the continents as one of the most diverse groups of anurans. Multiple studies have revealed physiological endurance adaptations for sustained hopping in toads, however, the kinematics of their sequential hopping behaviour, per se, has not been studied. We compared kinematics and forces of single hops and multiple hopping sequences and quantified field performance of hopping behaviours in free ranging toads of three species and discovered a novel aspect of locomotion adaptation that adds another facet to their exceptional terrestrial locomotor abilities. We found that bouts of repeated hopping are actually a series of bounding strides where toads rotate on their hands and then land on their extended their feet and jump again without stopping. In addition, free‐ranging toads appear to use bounding locomotion more frequently than single hops. Bounding in toads has the advantage of maintaining velocity and producing longer jump distances. In comparison to single hops, cyclic bounding steps reduce energy expenditure and appear to provide limb loading dynamics better suited for potential cycling of elastic energy from stride to stride than would be possible with repeated single hops. This is the first case of the common use of a bounding gait outside of mammals. Bounding adds a key terrestrial locomotor trait to the toad's phenotype that may help explain their history of global expansion and the challenges to modern faunas as introduced toads rapidly invade new ecosystems today. Lay Summary

Documenting changes in the distribution and abundance of a given taxon requires historical data. In the absence of long-term monitoring data collected throughout the range of a taxon, conservation biologists often rely on preserved museum specimens to determine the past or present, putative geographic distribution. Distributional data for the Houston Toad ( Anaxyrus houstonensis ) has consistently been confounded by similarities with a sympatric congener, the Dwarf American Toad ( A. americanus charlesmithi ), both in monitoring data derived from chorusing surveys, and in historical data via museum specimens. In this case, misidentification can have unintended impacts on conservation efforts, where the Houston Toad is federally endangered, and the Dwarf American Toad is of least concern. Previously published reports have compared these two taxon on the basis of their male advertisement call and morphological appearance, often with the goal of using these characters to substantiate their taxonomic status prior to the advent of DNA sequencing technology. However, numerous studies report findings that contradict one another, and no consensus on the true differences or similarities can be drawn. Here, we use contemporary recordings of wild populations of each taxon to test for quantifiable differences in male advertisement call. Additionally, we quantitatively examine a subset of vouchered museum specimens representing each taxon to test previously reported differentiating morphometric characters used to distinguish among other Bufonids of East-Central Texas, USA. Finally, we assemble and qualitatively evaluate a database of photographs representing catalogued museum vouchers for each taxon to determine if their previously documented historic ranges may be larger than are currently accepted. Our findings reveal quantifiable differences between two allopatric congeners with respect to their male advertisement call, whereas we found similarities among their detailed morphology. Additionally, we report on the existence of additional, historically overlooked, museum records for the Houston Toad in the context of its putative historic range, and discuss errors associated with the curation of these specimens whose identity and nomenclature have not been consistent through time. These results bookend decades of disagreement regarding the morphology, voice, and historic distribution of these taxa, and alert practitioners of conservation efforts for the Houston Toad to previously unreported locations of occurrence.

The aim of this study was to evaluate the acute lethality and chronic sublethal effects of lithium (Li) on Rhinella arenarum tadpoles as model organisms. First a 96 h toxicity assay was performed by exposing tadpoles to Li concentrations from 44.08 to 412.5 mg L[sup.−1] to estimate the mortality, and lethal and sublethal effects. Another bioassay was carried out by exposing tadpoles to two environmentally relevant Li concentrations (2.5 and 20 mg L[sup.−1] ) for one and two weeks. The sublethal effects of Li on tadpoles were evaluated by analyzing biochemical, genotoxic, and physiological biomarkers. The mortality in Li-exposed tadpoles increased over time. The median lethal concentration (LC[sub.50] ) ranged from 319.52 (281.21–363.05) mg L[sup.−1] at 48 h to 66.92 (52.76–84.89) mg L[sup.−1] at 96 h. Exposure to Li at 2.5 and 20 mg L[sup.−1] induced alterations in enzymes related to detoxification, antioxidant, and hepatic mechanisms, endocrine disruption of thyroid hormones, genotoxicity, and effects on the physiology of the heart and gastrointestinal systems. Tadpoles exposed to the highest concentration in the chronic bioassay (20 mg L[sup.−1] Li), which is the concentration commonly recorded in Li mining sites, showed significant mortality after one week of exposure. These results warn about the high ecotoxicological risk of Li as a contaminant of emerging concern for amphibians.

Predation and competition can induce important density- and trait-mediated effects on species, with implications for community stability. However, interactions of these factors with parasitism remain understudied. Here we investigate interactions among competition, predation and parasitism by crossing tadpole density ( Bufo americanus ), presence of a caged predator ( Notophthalmus viridescens ), and Echinostoma trivolvis trematodes, experimentally partitioning their effects on tadpole exposure and susceptibility to infection. Predation did not affect E. trivolvis infection but accelerated tadpole development and growth, and decreased activity. The presence of E. trivolvis caused the opposite effects on these three responses and reduced tadpole survival. High conspecific density reduced tadpole survival, growth, and development, and increased tadpole activity. Effects of predation and parasitism on activity were only evident at low tadpole density. High-density mesocosms also had twice the number of E. trivolvis infections as low-density mesocosms, despite a lack of evidence for stress-induced immunomodulation. Instead, this effect was explained by high density delaying tadpole development, which increased both the duration of exposure to cercariae and susceptibility to infection, because tadpoles spent more time in highly susceptible early stages. These results highlight the importance of accounting for trait-mediated effects, host plasticity, and exposure vs. susceptibility in parasite ecology.

Although amphibians use human-created habitats in urban landscapes, few studies have investigated the quality of these habitats. To assess habitat quality of stormwater management ponds and adjacent urban uplands for wood frogs (Lithobates sylvaticus) and American toads (Anaxyrus americanus), we compared life history characteristics between populations breeding across an urbanization gradient. Specifically, we compared body size, ages of breeding adults, and female reproductive investment among urban, suburban, and rural populations in Baltimore County, Maryland, USA. Although there was variation in age at maturity among populations, ages of breeding adults did not differ among urban, suburban, and rural areas. Maternal body size strongly influenced reproductive investment in both species, but relationships did not vary among urban, suburban, and rural populations. Adult wood frogs and American toads from more urbanized landscapes were significantly smaller at age than conspecifics from rural landscapes; the magnitude of differences was similar across adult age classes. Our results suggest that in the urban and rural landscapes that we studied, adult habitats are similar in quality, but either larval or juvenile habitats may be of lower quality in urban areas.

The persistence of pond-breeding amphibians in highly fragmented landscapes may be constrained by the need for connectivity between aquatic breeding sites and suitable terrestrial habitat, an example of landscape complementation. Although migratory ability determines the spatial scale at which landscape complementation operates, the factors influencing migratory success of amphibians, especially of juveniles, are poorly understood. This study is the first to investigate whether juvenile amphibians possess any innate, long-distance orientation mechanisms that might improve their chances of locating suitable terrestrial habitat. I conducted experimental releases of spotted salamanders (Ambystoma maculatum) and American toads (Bufo americanus) from 18 artificial pools in replicate pastures at distances of 5-50 m from the nearest forest edges. Using circular drift fences with pitfall traps, I captured, individually marked, and released metamorphosed salamanders (n = 323) and toads (n = 203) leaving each pool. Salamanders exhibited nonrandom orientation at nine pools, but at only one was the mean movement direction consistent with the direction to the nearest forest edge. Emigrating salamanders probably responded to microtopographic or other distinct features of each pool, rather than to distant cues. Migratory success was determined by recaptures of marked juveniles at drift fences along the forest edges. I used logistic regression to model probability of recapture and evaluated alternative models using an information-theoretic approach. Migratory success of both species was primarily a function of distance to nearest forest. Of salamanders and toads released from 50-m pools, <15% reached the forest, suggesting that few juvenile amphibians would be able to migrate greater distances across pastures. Breeding sites lacking connectivity to suitable terrestrial habitat may be population sinks due to high mortality of juveniles during emigration. Additional research is needed to determine appropriate threshold distances between breeding sites and terrestrial habitat, as well as the potential effectiveness of movement corridors for migrating amphibians.

The mechanisms regulating sexual behaviours in female vertebrates are still poorly understood, mainly because in most species sexual displays in females are more subtle and less frequent than displays in males. In a sex-role reversed population of a teleost fish, the peacock blenny Salaria pavo, an external fertilizer, females are the courting sex and their sexual displays are conspicuous and unambiguous. We took advantage of this to investigate the role of ovarian-synthesized hormones in the induction of sexual displays in females. In particular, the effects of the sex steroids oestradiol (E2) and testosterone (T) and of the prostaglandin F2α (PGF2α) were tested. Females were ovariectomized and their sexual behaviour tested 7 days (sex steroids and PGF2α) and 14 days (sex steroids) after ovariectomy by presenting females to an established nesting male. Ovariectomy reduced the expression of sexual behaviours, although a significant proportion of females still courted the male 14 days after the ovary removal. Administration of PGF2α to ovariectomized females recovered the frequency of approaches to the male's nest and of courtship displays towards the nesting male. However, E2 also had a positive effect on sexual behaviour, particularly on the frequency of approaches to the male's nest. T administration failed to recover sexual behaviours in ovariectomized females. These results suggest that the increase in E2 levels postulated to occur during the breeding season facilitates female mate-searching and assessment behaviours, whereas PGF2α acts as a short-latency endogenous signal informing the brain that oocytes are mature and ready to be spawned. In the light of these results, the classical view for female fishes, that sex steroids maintain sexual behaviour in internal fertilizers and that prostaglandins activate spawning behaviours in external fertilizers, needs to be reviewed.