Poison Frog Research Articles

Tap dancing frogs: Posterior toe tapping and feeding in Dendrobates tinctorius

AbstractAnimals have myriad adaptations to help them hunt and feed in the most efficient and effective manner. One mysterious behavior related to hunting and feeding is the posterior toe tapping behavior of some frogs. Biologists and hobbyists alike have long noticed this behavior, but there is little empirical data to explain its causes and consequences. To test the hypothesis that tapping is related to feeding and modulated by environmental context, we conducted a series of related experiments in the Dyeing poison frog, Dendrobates tinctorius. We first confirmed that tap rate was higher during feeding as has been observed in other species. Interestingly, this effect was heightened in the presence of a conspecific. We next asked whether frogs tapped less under conditions when prey were visible, but inaccessible. Finally, we asked whether D. tinctorius adjusted tap rate based on substrate characteristics and whether prey capture success was higher when tapping. In addition to confirming an association between tapping and feeding, our work demonstrates modulation of toe tapping based on social context, prey accessibility, and substrate characteristics. Based on our findings, we suggest that tapping could act to induce prey movement and thereby facilitate prey detection and capture by frogs.

Under pressure: evidence for selection on color-related genes in poison frogs of the genus Ranitomeya

Aposematic organisms rely on their bright conspicuous coloration to communicate to potential predators that they are toxic and unpalatable. These aposematic phenotypes are strongly tied to survival and therefore make excellent opportunities to investigate the genetic underpinning of coloration. The genus Ranitomeya includes phenotypically diverse members of Neotropical aposematic poison frogs native to South America. Significant progress has been made in elucidating the molecular mechanisms responsible for aposematic coloration in poison frogs, which have paved the way for future studies to test hypotheses of the evolution of coloration across aposematic vertebrates. However, very little is known about whether these color related genes are under positive selection. We assembled transcriptomes from publicly available data reads sets for 9 different color morphs of poison frogs in the Ranitomeya genus that display bright conspicuous coloration (four morphs of R. imitator, two morphs of R. variabilis, two morphs of R. fantastica, one morph of R. summersi) to identify protein-coding genes responsible for color production that are under positive selection. Our results show that there are multiple genes under strong positive selection that are predicted to play roles in melanin synthesis (dct, tyrp1, irf4), iridophore development (fhl1), keratin metabolism (ovol1), pteridine synthesis (prps1, xdh), and carotenoid metabolism (adh1b, aldh2). The identification of positive selection affecting candidate color-pattern genes is consistent with the possibility that these genes mediate (in part) the molecular evolution of coloration. This may be attributed to aposematic phenotypes being directly tied to survival and reproduction in poison frogs.

Prospects for pharmacological screening of oral detoxification drugs with differentiation of targeted pathologies in animal husbandry

In the modern livestock sector, the domestic industry of the North-West region, cases of poisoning of animals on farms and large complexes are increasingly occurring. This is primarily due to the intensive use of various synthetic modulators, growth stimulants, fertilizers in the agronomic industry and the excessive use of antibiotics, hormones and other veterinary drugs in animal husbandry.Pharmacological screening of oral detoxification agents with differentiation of target pathologies is a promising direction in the development of domestic animal husbandry. A reasonable choice of sorbents in each individual case of poisoning allows you to quickly achieve a therapeutic effect, reduce the toxic load on the animal’s body, which further ensures sustainable productivity and high quality products. This work highlights the results of some studies on the functional activity of the most common enterosorbents in relation to toxins of various natures.Based on the results of the study, it was noted that with an increase in pH from 2.0 (rennet model) to 7.5 (analogue of the distal small intestine), a release of part of the indicator substance from the pores of the sorbent (desorption) is observed, which reduces its absolute sorption effect [5] . The lowest desorption value was shown by atoxyl (8.5%) and phytopos (9.0%). That is why these drugs are the most effective oral detoxification agents for toxins with a molecular weight close to methylene blue.The maximum adsorption effect for various poisonings in animals can be achieved by using sorbing agents that are highly selective for a particular toxin. Research on the choice of oral detoxification agents with differentiation of target pathologies significantly expands the database on existing sorbents, makes it possible to prevent and treat poisonings of various types more effectively, and provides opportunities for the combined use of various adsorbent substances.

Extensive evaluation of a new LC-MS-MS method to quantify monofluoroacetate toxin in the kidney.

Monofluoroacetate is a highly lethal toxin that causes death by inhibiting cellular adenosine triphosphate (ATP) production. The heart and brain are the primary target organs. Acute death is attributed to cardiac fibrillation and/or convulsions. Although it occurs naturally in some plants, a major source of animal intoxication is access to sodium monofluoroacetate (NaMFA) pesticide, which continues to be a concern in the USA and around the world despite restricted use in some countries including the USA. There are also concerns about misuse of this pesticide for malicious poisoning. Currently, a tissue-based diagnostic method for NaMFA intoxication in animals is lacking. There is a critical need by the veterinary diagnostic community for a simple, sensitive and reliable tissue-based diagnostic test to confirm NaMFA poisoning in animals. We have developed and extensively evaluated a sensitive novel liquid chromatography combined with tandem mass spectrometry method suitable for this purpose. The limits of detection and limits of quantitation are 1.7 and 5.0 ng/g, respectively. The accuracy and precision met or exceeded expectations. The method performance was verified using the incurred kidney obtained from animal diagnostic cases. This novel kidney-based method is now available for clinical use and can help with diagnostic purposes, including detecting potential issues related to animal foods.

Do aposematic species have larger range sizes? A case study with neotropical poison frogs

AbstractAimAposematic animals, i.e., those that are defended and warn potential predators through signals, are suggested to have resource‐gathering advantages against non‐aposematic ones. We here explore this in a biogeographic framework expecting that aposematic species are better dispersers, which translates into larger geographic range size.LocationSouth America.TaxonPoison frogs (Amphibia; Aromobatidae and Dendrobatidae).MethodsWe use 43 toxic and 26 non‐toxic poison frog species from the lowlands only as representatives of aposematic and non‐aposematic study organisms, respectively. Realised and potential geographic ranges are calculated using minimum convex polygon and species distribution modelling methods, respectively. Accounting for species body size and phylogeny, we test if both range and aposematism are correlated using linear mixed‐effects models.ResultsAposematic and non‐aposematic species neither differ in realised nor in potential geographic range size. There was no effect on body size.Main ConclusionsThe role of aposematism is not yet as clear as suggested and determinants of poison frog range sizes are multifaceted. A more integrative approach is needed using the information on behaviour, predation risk, and reproductive biology to assess the role of aposematism on observed species distributions. Such data are not yet available for most species, neither poison frogs nor other aposematic animals.

Autophagic-lysosomal damage induced by swainsonine is protected by trehalose through activation of TFEB-regulated pathway in renal tubular epithelial cells

Swainsonine (SW) is the main toxic component of locoweed. Previous studies have shown that kidney damage is an early pathologic change in locoweed poisoning in animals. Trehalose induces autophagy and alleviates lysosomal damage, while its protective effect and mechanism against the toxic injury induced by SW is not clear. Based on the published literature, we hypothesize that transcription factor EB(TFEB) -regulated is targeted by SW and activating TFEB by trehalose would reverse the toxic effects. In this study, we investigate the mechanism of protective effects of trehalose using renal tubular epithelial cells. The results showed that SW induced an increase in the expression level of microtubule-associated protein light chain 3-II and p62 proteins and a decrease in the expression level of ATPase H+ transporting V1 Subunit A, Cathepsin B, Cathepsin D, lysosome-associated membrane protein 2 and TFEB proteins in renal tubular epithelial cells in a time and dose-dependent manner suggesting TFEB-regulated lysosomal pathway is adversely affected by SW. Conversely, treatment with trehalose, a known activator of TFEB promote TFEB nuclear translocation suggesting that TFEB plays an important role in protection against SW toxicity. We demonstrated in lysosome staining that SW reduced the number of lysosomes and increased the luminal pH, while trehalose could counteract these SW-induced effects. In summary, our results demonstrated for the first time that trehalose could alleviate the autophagy degradation disorder and lysosomal damage induced by SW. Our results provide an interesting method for reversion of SW-induced toxicity in farm animals and furthermore, activation of TFEB by trehalose suggesting novel mechanism of treating lysosomal storage diseases.

Developments in the study of poison frog evolutionary ecology I: social interactions, life history and habitat use across space and ontogeny

Developments in the study of poison frog evolutionary ecology I: social interactions, life history and habitat use across space and ontogeny

Integrating ecological niche modeling and rates of evolution to model geographic regions of mimetic color pattern selection

Geographic variation in natural selection derived from biotic sources is an important driver of trait evolution. The evolution of Müllerian mimicry is governed by dual biotic forces of frequency-dependent predator selection and densities of prey populations consisting of conspecifics or congeners. Difficulties in quantifying these biotic forces can lead to difficulties in delimiting and studying phenomena such as mimicry evolution. We explore the spatial distribution of morphotypes and identify areas of high mimetic selection using a novel combination of methods to generate maps of mimetic phenotype prevalence in Ranitomeya poison frogs, a group of frogs characterized by great phenotypic variation and multiple putative Müllerian mimic pairs. We categorized representative populations of all species into four major recurring color patterns observed in Ranitomeya: striped, spotted, redhead, and banded morphs. We calculated rates of phenotypic evolution for each of the 4 morphs separately and generated ecological niche models (ENMs) for all species. We then split our species-level ENMs on the basis of intraspecific variation in color pattern categorization, and weighted ENM layers by relative evolutionary rate to produce mimicry maps. Our phenotypic evolutionary rate analyses identified multiple significant shifts in rates of evolution for the spotted, redhead, and banded phenotypes. Our mimicry maps successfully identify all suspected and known areas of Müllerian mimicry selection in Ranitomeya from the literature and show geographic areas with a gradient of suitability for Müllerian mimicry surrounding mimic hotspots. This approach offers an effective hypothesis generation method for studying traits that are tied to geography by explicitly connecting evolutionary patterns of traits to trends in their geographic distribution, particularly in situations where there are unknowns about drivers of trait evolution.

Do sexes differ in consistent individual differences and behavioural syndrome in an aposematic poison frog?

AbstractThere is a burgeoning interest in studying consistent individual differences in animal behaviour. Most studies consider mainly males, but sexes are subject to distinct selection pressures that may drive differences in life history and therefore lead to differences in a variety of behaviours. Here, we used Oophaga pumilio, a poison frog with sex differences in life‐history strategies (e.g., sex bias in space use and parental care), to explore whether sexes differ or share personality characteristics like behavioural consistency and behavioural syndromes. Based on the natural history of this species, we predicted sex differences in behavioural consistency in exploration but not in boldness, and a correlation between these behavioural traits. We found no sex differences in behavioural consistency in boldness and exploration, although, we observed a tendency of higher consistency in males than females in boldness. When pooling all individuals, we found a higher consistency in boldness than exploration, suggesting the presence of a bold personality in general. We observed a positive between‐individual correlation of boldness and exploration in both sexes indicating the presence of a behavioural syndrome. Our data suggest that selective mechanisms shaping individual behaviour act equally on both sexes in this poison frog.

Deep divergences among inconspicuously colored clades of Epipedobates poison frogs

Poison frogs (Dendrobatidae) are famous for their aposematic species, having a combination of diverse color patterns and defensive skin toxins, yet most species in this family are inconspicuously colored and considered non-aposematic. Epipedobates is among the youngest genus-level clades of Dendrobatidae that includes both aposematic and inconspicuous species. Using Sanger-sequenced mitochondrial and nuclear markers, we demonstrate deep genetic divergences among inconspicuous species of Epipedobates but relatively shallow genetic divergences among conspicuous species. Our phylogenetic analysis includes broad geographic sampling of the inconspicuous lineages typically identified as E. boulengeri and E. espinosai, which reveals two putative new species, one in west-central Colombia (E. sp. 1) and the other in north-central Ecuador (E. aff. espinosai). We conclude that E. darwinwallacei is a junior subjective synonym of E. espinosai. We also clarify the geographic distributions of inconspicuous Epipedobates species including the widespread E. boulengeri. We provide a qualitative assessment of the phenotypic diversity in each nominal species, with a focus on the color and pattern of inconspicuous species. We conclude that Epipedobates contains eight known valid species, six of which are inconspicuous. A relaxed molecular clock analysis suggests that the most recent common ancestor of Epipedobates is ∼11.1 million years old, which nearly doubles previous estimates. Last, genetic information points to a center of species diversity in the Chocó at the southwestern border of Colombia with Ecuador. A Spanish translation of this text is available in the supplementary materials.

Se Alleviated Pb-Caused Neurotoxicity in Chickens: SPS2-GPx1-GSH-IL-2/IL-17-NO Pathway, Selenoprotein Suppression, Oxidative Stress, and Inflammatory Injury.

Lead (Pb), a heavy metal environmental pollutant, poses a threat to the health of humans and birds. Inflammation is one of the most common pathological phenomena in the case of illness and poisoning. However, the underlying mechanisms of inflammation remain unclear. The cerebellum and the thalamus are important parts of the nervous system. To date, there have been no reports of Pb inducing inflammation in animal cerebellums or thalami. Selenium (Se) can relieve Pb poisoning. Therefore, we aimed to explore the mechanism by which Se alleviates Pb toxicity to the cerebellums and thalami of chickens by establishing a chicken Pb or/and Se treatment model. Our results demonstrated that exposure to Pb caused inflammatory damage in cerebellums and thalami, evidenced by the characteristics of inflammation, the decrease in anti-inflammatory factors (interleukin (IL)-2 and interferon-γ (INF-γ)), and the increase in pro-inflammatory factors (IL-4, IL-6, IL-12β, IL-17, and nitric oxide (NO)). Moreover, we found that the IL-2/IL-17-NO pathway took part in Pb-caused inflammatory injury. The above findings were reversed by the supplementation of dietary Se, meaning that Se relieved inflammatory damage caused by Pb via the IL-2/IL-17-NO pathway. In addition, an up-regulated oxidative index malondialdehyde (MDA) and two down-regulated antioxidant indices (glutathione (GSH) and total antioxidant capacity (TAC)) were recorded after the chickens received Pb stimulation, indicating that excess Pb caused an oxidant/antioxidant imbalance and oxidative stress, and the oxidative stress mediated inflammatory damage via the GSH-IL-2 axis. Interestingly, exposure to Pb inhibited four glutathione peroxidase (GPx) family members (GPx1, GPx2, GPx3, and GPx4), three deiodinase (Dio) family members (Dio1, Dio2, and Dio3), and fifteen other selenoproteins (selenophosphate synthetase 2 (SPS2), selenoprotein (Sel)H, SelI, SelK, SelM, SelO, SelP1, SelPb, SelS, SelT, SelU, and selenoprotein (Sep)n1, Sepw1, Sepx1, and Sep15), suggesting that Pb reduced antioxidant capacity and resulted in oxidative stress involving the SPS2-GPx1-GSH pathway. Se supplementation, as expected, reversed the changes mentioned above, indicating that Se supplementation improved antioxidant capacity and mitigated oxidative stress in chickens. For the first time, we discovered that the SPS2-GPx1-GSH-IL-2/IL-17-NO pathway is involved in the complex inflammatory damage mechanism caused by Pb in chickens. In conclusion, this study demonstrated that Se relieved Pb-induced oxidative stress and inflammatory damage via the SPS2-GPx1-GSH-IL-2/IL-17-NO pathway in the chicken nervous system. This study offers novel insights into environmental pollutant-caused animal poisoning and provides a novel theoretical basis for the detoxification effect of Se against oxidative stress and inflammation caused by toxic pollutants.

Effect of chronic intake of cadmium chloride on the transcriptional activity of metallothionein and zinc transporter genes

Introduction. Cadmium chloride is an inorganic compound containing cadmium, a heavy metal that is one of the active environmental pollutants today. Damage to organs in experimental animals due to cadmium poisoning is similar to that in humans. In this work, the activity of metallothionein and zinc transporters genes was studied in a chronic model of cadmium-induced poisoning in experimental animals.
 Materials and methods. The experiment was carried out using seventy two individuals of white inbred rats of both sexes, the average weight of which was 215 g. Animals from four groups were injected with a solution of cadmium chloride in four different doses, respectively, individuals of the fifth group, the control group, received an equimolar volume of pure water. The objects of the study were the kidneys and livers of rats, removed after the animals were withdrawn from the experiment. Next, the activity of the Mt1A, Mt2A, Mt3A, Zip1 and Znt1 genes was analyzed in organ samples using real-time PCR.
 Results. Significant increases in the expression multiplicity of Mt1A, Mt2A and Mt3A metallothionein genes in the kidneys at different doses of the toxicant were revealed. In liver samples, a decrease in the expression of the Mt2A gene was found in the experimental group exposed to cadmium chloride at a dose 
 of 0.1 mg/kg (p<0.05). For the Znt1 gene in rat liver tissue, there was a statistically significant decrease in expression at a dose of 0.001 mg/kg (p<0.05) 
 and, conversely, an increase at doses of 0.1 and 1 mg/kg (p<0.05) compared to the control group. Analysis of the level of transcripts of the Zip1 gene in the kidneys and liver after 6 months of inoculation with the toxicant in the presented doses did not reveal statistically significant differences between the groups.
 Limitations. Laboratory animals of the only biological species were used for the experiment. Four doses of the cadmium salt alone were evaluated.
 Conclusion. The results obtained allow concluding that the level of expression of the Mt1A, Mt2A and Mt3A genes in the kidneys can play the role of a diagnostic marker in chronic poisoning with the toxicant under study.

Body condition and diet of the dyeing poison frog Dendrobates tinctorius (Cuvier 1797) (Amphibia: Dendrobatidae) from the eastern Brazilian Amazonia

The present study adds new data on the natural history of Dendrobatestinctorius. We conducted our fieldwork during the rainy season of the years2018 and 2019 in two protected areas (Parque Natural Municipal do Cancão–PNMC and Reserva Extrativista Beija-Flor Brilho de Fogo–REBFBF) in the state of Amapá, Brazil. Through active visual searches we sampled 22 individuals of D. tinctorius, of which 10 were countedfor the population of PNMC and 12 for the population of REBFBF. We calculatedthe Body Condition Index (BCI) for all individuals and, for dietary data, each frog’s stomach was flushed. Females from the REBFBF were larger than males whencompared to the PNMC population. BCI of females from the REBFBF showed higher values than males. Gravid females of both populations showed higher BCI. Retrievedstomachs revealed a total of 290 prey items divided into four main taxonomiccategories of Arthropods. The Index of Relative Importance revealed that antsof the genus Solenopsis were the majority of the diet, and mites represented only 4.86%. The niche breadth for both populations was narrow, indicating a specialist diet, as expected for the species. Our study evidences the importance of integration between BCI and dietary aspects.

Bright Colors: Eat Me at Your Own Risk

Some poisonous animals use bright coloration to protect themselves from other animals that want to eat them. These bright colors are also called warning colors. Frogs, snakes, butterflies, skunks, and more all use warning coloration. But how do the animals get their bright colors and toxic poisons? Warning colors can be passed down to certain animals from their parents, and other animals get them from the foods they eat. Just because some animals have bright colors does not always mean they are toxic. Some animals, also known as mimics, copy the colors of toxic animals so they can protect themselves from being eaten. We will explore how poisonous animals show their true colors, and how non-poisonous animals that display the same signals can also be protected from predators. You may notice similar connections between color and warning signals all around you!

Pesticide Contamination Levels in the Stomach Contents of Wild Raccoons (Procyon lotor) and Masked Palm Civets (Paguma larvata) in Japan.

Pesticides, which are vital for agriculture, pose a significant threat to wildlife in transformed Japanese landscapes. Despite global reports of pesticide poisoning in animals, limited studies have examined current wildlife exposure in croplands or metropolitan areas in the region. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS), our study aimed to assess the contamination status of 368 commonly used pesticides. The stomach contents of raccoons living in croplands contained 13 pesticides, including six herbicides and 11 fungicides. Neonicotinoid insecticides, some fungicides, and previously banned insecticides (benzene hexachloride and dichlofenthion) were most frequently detected and found at the highest concentrations, suggesting direct soil-plant transfer and direct consumption by crop-eating species. In masked palm civets living in metropolitan areas, four insecticides and six fungicides were detected, indicating urban wildlife exposure from raided dustbins, urban gardens, and lumber from houses. Although the maximum measured concentrations of all pesticides were lower than the acceptable daily intake for humans, it remains unclear whether these concentrations may have toxic or adverse health effects on the species evaluated in these transformed landscapes. Our study is the first to examine recent pesticide exposures in wild mammals in Japan. Application of the method we developed will lay the foundation for the examination of pesticides in other wildlife species to assist conservation management efforts in the region. Environ Toxicol Chem 2024;43:943-951. © 2024 SETAC.

Divergent Nine-Step Syntheses of Perhydrohistrionicotoxin Analogs and Their Inhibition Activity Toward Chicken α4β2-Neuronal Nicotinic Acetylcholine Receptors.

Histrionicotoxin (HTX) alkaloids, which are isolated from Colombian poison dart frogs, are analgesic neurotoxins that modulate nicotinic acetylcholine receptors (nAChRs) as antagonists. Perhydrohistrionicotoxin (pHTX) is the potent synthetic analogue of HTX and possesses a 1-azaspiro[5.5]undecane skeleton common to the HTX family. Here, we show for the first time the divergent nine-step synthesis of pHTX and its three stereoisomers from the known aldehyde through a one-step construction of the 1-azaspiro[5.5]undecane framework from a linear amino ynone substrate. Surprisingly, some pHTX diastereomers exhibited antagonistic activities on the chicken α4β2-neuronal nAChRs that were more potent than pHTX.

Clinico-Pathological Alterations and Therapeutic Management of Thiram Poisoning in Cattle

As there is very scarce literature on fungicide poisoning in livestock animals and in view of reporting fungicide poisoning in cattle in the study area, the present study was conducted to study the clinico-pathology of thiram poisoning in cattle and to standardize the therapeutic regime for the poisoning cases. Clinical cases suspected for Thiram poisoning on the basis of confirm evidence from animal owner were subjected to clinical examination, hematology and therapeutic management. Cases died of severe poisoning were subjected to post-mortem examination. A total of 17 cattle suspected for Thiram poisoning on the basis of history and evidence showed clinical signs of sudden onset of anorexia, salivation, shivering, teeth grinding, restlessness, prolonged sitting, tympany, colic, dyspnea and constipation or diarrhea in few cases. Significant increase in heart rate and respiration rate was observed while hematological analysis showed non-significant changes compared to healthy counterparts. Post-mortem and histopathological examination of cattle died of thiram poisoning showed mild hepatocellular degeneration, tubular necrosis in kidneys with focal infiltrates while marked edema and congestion was evident in lung tissues. The ailing cattle were treated with fluid therapy, anti-inflammatory drugs, vitamin B complex, atropine sulphate, antihistaminics along with laxative and prebiotics-probiotics showed good response to treatment with complete clinical recovery in 4-5 days of treatment. Being there is no specific antidote, the cases of fungicide like Thiram poisoning could be managed with symptomatic treatment and regular clinical assessment of the severity of the poisoning.

Evidence for individual vocal recognition in a pair-bonding poison frog, Ranitomeya imitator.

Individually distinctive vocalizations are widespread in nature, although the ability of receivers to discriminate these signals has only been explored through limited taxonomic and social lenses. Here, we asked whether anuran advertisement calls, typically studied for their role in territory defense and mate attraction, facilitate recognition and preferential association with partners in a pair-bonding poison frog (Ranitomeya imitator). Combining no- and two-stimulus choice playback experiments, we evaluated behavioral responses of females to male acoustic stimuli. Virgin females oriented to and approached speakers broadcasting male calls independent of caller identity, implying that females are generally attracted to male acoustic stimuli outside the context of a pair bond. When pair-bonded females were presented with calls of a mate and a stranger, they showed significant preference for calls of their mate. Moreover, behavioral responses varied with breeding status: females with eggs were faster to approach stimuli than females that were pair bonded but did not currently have eggs. Our study suggests a potential role for individual vocal recognition in the formation and maintenance of pair bonds in a poison frog and raises new questions about how acoustic signals are perceived in the context of monogamy and biparental care.

Thermal limits along tropical elevational gradients: Poison frog tadpoles show plasticity but maintain divergence across elevation

Temperature is arguably one of the most critical environmental factors impacting organisms at molecular, organismal, and ecological levels. Temperature variation across elevation may cause divergent selection in physiological critical thermal limits (CTMAX and CTMIN). Generally, high elevation populations are predicted to withstand lower environmental temperatures than low elevation populations. Organisms can also exhibit phenotypic plasticity when temperature varies, although theory and empirical evidence suggest that tropical ectotherms have relatively limited ability to acclimate. To study the effect of temperature variation along elevational transects on thermal limits, we measured CTMAX and CTMIN of 934 tadpoles of a poison frog species, Epipedobates anthonyi, along two elevational gradients (200–1700 m asl) in southwestern Ecuador to investigate their thermal tolerance across elevation. We also tested if tadpoles could plastically shift their critical thermal limits in response to exposure to different temperatures representing the range of temperatures they experience in nature (20 °C, 24 °C, and 28 °C). Overall, we found that CTMAX did not change across elevation. In contrast, CTMIN was lower at higher elevations, suggesting that elevational variation in temperature influences this thermal trait. Moreover, all populations shifted their CTMAX and CTMIN according to treatment temperatures, demonstrating an acclimation response. Overall, trends in CTMIN among high, mid, and low elevation populations were maintained despite plastic responses to treatment temperature. These results demonstrate that, for tadpoles of E. anthonyi across tropical elevational gradients, temperature acts as a selective force for CTMIN, even when populations show acclimation abilities in both, CTMAX and CTMIN. Our findings advance our understanding on how environmental variation affects organisms’ evolutionary trajectories and their abilities to persist in a changing climate in a tropical biodiversity hotspot.

Little evidence for color- or size-based mating preferences by male strawberry poison frogs (Oophaga pumilio)

While there are many studies documenting female mating preferences across taxa, male mate choice remains relatively understudied. Male mate choice often develops when there is variation in female quality and thus the fitness benefits of mating with particular females. Specifically, males tend to prefer females with traits that confer direct fitness benefits such as large body size, which may be linked with high fecundity. Prior work has shown that females of the strawberry poison frog, Oophaga pumilio, prefer males bearing certain coloration (most often the female’s own color), and that this preference can be learned through maternal imprinting. Females have been shown to prefer larger males as well. Here we test whether similar mate preferences for color and size exist in males of this species using two-way choice tests on captive bred male O. pumilio. In each test focal males were placed in an arena with two stimulus females: either both of the same size but differing in color, or both of the same color but differing in size. We found only weak evidence for behavioral biases toward particular colors and no evidence for biases toward larger females, suggesting that males of O. pumilio do not predictably choose mates based on these female traits. Despite several aspects of their natural history that suggest males have reasons to be choosy, our findings suggest that the cost of mate rejection may outweigh any fitness benefits derived from being selective of mates. Studies of additional populations, ideally conducted on wild individuals, are needed to better understand the range of conditions under which males may exhibit mate choice and the types of traits on which they base these choices.Significance statementTo fully understand the fitness landscapes and evolutionary trajectories that result from sexual selection, we need to understand when and how the mate preferences of the two sexes act and interact. While female mate choice has been widely studied, male mate choice remains poorly understood. To help bridge this gap, we studied male mate preferences in the strawberry poison frog Oophaga pumilio, a small brightly colored frog for which female preferences for male color and size have been well-documented. We found no evidence that male O. pumilio exhibit mate preferences based on female size and little evidence for male mate preferences based on female color. This is surprising given that larger females are often more fecund, male O. pumilio are known to exhibit color-based behavioral biases in the context of male-male competition, and both sexes provide parental care.