Amphibian News!

Decemeber 4, 2023: The advent of genome-scale data has brought a new appreciation for the importance of hybridization and introgression in the evolutionary history of many organisms, including amphibians. These reticulate evolutionary histories can be challenging to reconstruct and may lead to discordance among inferences made from molecular and morphological datasets. Pierson et al. (2023) gathered genome-wide single nucleotide polymorphism (SNP) data from the Two-lined salamander (Eurycea bislineata) species complex—a group of widespread and abundant lungless salamanders. This study used a variety of phylogenomic methods to demonstrate that hybridization and introgression are responsible for the conflicting results of previous studies and may have resulted from a complicated history of river drainage reorganization in the region. The results highlight the inadequacy of the current taxonomy for fully describing species boundaries in the E. bislineata species complex and provide a more robust phylogenetic framework for future systematic studies. (Todd Pierson)

November 27, 2023: Amphibians are famous (or perhaps infamous) for their outsized genomes. Indeed, some salamanders have genomes up to 120 billion base pairs (120 GB) and, for comparison, the human genome is only 3 GB. Because large genomes are challenging to sequence, scientists have been slow to generate high-resolution genomes for amphibians. Recently Ovchinnikov et al. (2023) provided the second and third published high-resolution genomes for caecilians, specifically for Geotrypetes seraphini and Microcaecilia unicolor. By comparing the newly sequenced genomes with the first published caecilian genome (Rhinatrema bivittatum) and other vertebrate species, they made a number of interesting discoveries and observations. For example, the large genomes of caecilians are, not surprisingly, chock full of repeat sequences, which is typical of other taxa with extra-large genomes. However, whereas supersized salamander genomes are dominated by long terminal repeat (LTR) elements, those of caecilians are dominated by long interspersed elements (LINES), indicating that while both caecilians and salamanders have large genomes because of transposal elements (TEs) “gone wild”, this is not the result of failure to control a specific type of TE. Another finding is that the caecilian genomes have a large number of novel gene families (at least 1150) enriched for functions in olfaction and chemical signaling likely tied to their unique chemosensory tentacles as primary olfactory organs. Finally, the authors could find no evidence in caecilians of a developmental gene enhancer called ZRS that regulates the famous limb morphogenesis gene “Sonic Hedgehog”. Notably, snakes have been shown to have a mutant form of ZRS that, when inserted into mice, results in a limbless serpentized phenotype. The complete absence of the ZRS enhancer in caecilians implicates this gene in the convergent evolution of limblessness in caecilians and snakes. (JAM)

November 20, 2023: The largest known frog —even bigger than the extinct frog Beelzebufo from Madagascar— is the Goliath Frog, Conraua goliath, found only in Cameroon and mainland Equatorial Guinea. Though it has long been known that local people hunt this species, there has been little quantitative study of local knowledge and use of Goliath Frogs. Tasse Taboue and colleagues (2023) provide data from interviews of over 200 people from 11 ethnic groups as well as observations of frog hunters to document practices and inform conservation management. They document that in some communities hunting Goliath Frogs is a traditional and celebrated rite of men who hunt frogs for local consumption. Hunters prefer to hunt the largest individuals (typically females), and usually do so with fishing nets or spears. Most frogs are eaten locally, but some are sold to others in the community or to travelers, including for export to other countries. Though Goliath Frogs are formally protected by the Cameroonian government, their collection, hunting, and export remain common, and the relevant government ministry appears to not be tracking exportation. (DBlackburn)

November 13, 2023: The European Common frog (Rana temporaria) is an explosive breeding species, meaning that hundreds of individuals gather in early spring for a short period of time to breed. Females in these dense breeding aggregations are susceptible to losing their lives during the scramble by males to gain access to the rarer females. A study by Dittrich and Rödel (2023) shows that females are not as passive as previously thought. They display mate avoidance behaviours that include rotating (attempting to roll out the male's grip), calling (imitating the male's release call), and tonic immobility (formerly called death feigning). Tonic immobility is rarely observed in the context of mating, but is better known in predator-prey interactions, indicating high levels of stress in females during the mating season. Smaller and therefore younger females were more likely to exhibit all of these behaviours. This suggests that experience and learning may play a role in this system of sexual conflict. (Carolin Dittrich)

November 6, 2023: Australia is generally considered hot, dry, and flat, making it an apparently inhospitable place for frogs. Despite this, more than 250 species call the continent home, ranging from enormous green tree frogs, to tiny brown burrowing frogs. But where did Australia’s frogs come from and when did they get there? A study by Brennan et al. (2023) provides insight into the origins of Australia’s frogs, giving age estimates to the three major frog groups found on the continent (Myobatrachoids, Pelodryadidae treefrogs, Asterophryinae microhylids) and establishing their closest relatives. This new Australian frog tree-of-life highlights the amazing adaptive potential of frogs. This includes fully aquatic and burrowing "treefrogs", and the wonderful and bizarre turtle frog Myobatrachus gouldii. In retracing the history of Australia's frogs, they find that the oldest groups such as myobatrachids, limnodynastids, and pelodryadids likely originated from Gondwana before the separation of the Australian continent. In comparison, the youngest group (microhylids) likely immigrated to Australia from New Guinea just over 10 million years ago. Finally, they provide evidence from biogeographic modelling that Australia's tree frogs arrived via dispersal from South America through Antarctica, challenging previous hypotheses regarding long distance overwater dispersal. (Written by Ian Brennan)

October 30, 2023: Measurements of organismal maximum heat tolerance, such as critical thermal maximum (CTmax), are often used to partly assess a species’ vulnerability to warming temperatures. However, the usefulness of CTmax for vulnerability assessments has been questioned, with two major concerns. First, these assessments assume that experimental measurements of CTmax are transferable to a natural setting. The second major concern is the perception there is insufficient variation in CTmax among populations and species for CTmax to evolve in response to increasing temperatures. Recently, Cicchino and colleagues (2023) addressed these concerns by testing the assumption that CTmax estimates are related to heat stress tolerance (mortality) in natural conditions among populations of the Rocky Mountain Tailed Frog (Ascaphus montanus). They found that CTmax was strongly related to mortality from thermal stress in temperatures mimicking natural conditions among populations, demonstrating the relevance of experimental estimates of CTmax. They also showed that relatively small differences in CTmax can have large impacts on mortality from thermal stress. This result emphasizes the potential for observed existing variation in CTmax to play a role in mediating the consequences of warming temperatures. Overall, their results provide compelling evidence that experimental measurements of CTmax can be used in assessments of vulnerability to warming temperatures. (Amanda Cicchino)

October 23, 2023: Introducing the Amphibian Genomics Consortium– genomics for amphibian research and conservation. The Amphibian Genomics Consortium (AGC) was launched this February (2023) to advance research on amphibian ecology, evolution, and conservation by facilitating the genomic study of amphibians. Amphibians, with their challenging super-sized genomes, have been the subject of relatively few genomic sequencing efforts compared to other vertebrates, and the AGC aims to remedy this by promoting collaborative, interdisciplinary research that brings together amphibian researchers from around the world. Notably, the AGC includes researchers at all career stages and with diverse expertise. The AGC aims to complement and build upon the efforts of existing genomics consortia by supporting amphibian-focused sequencing projects and other types of genome-driven research and applications. The consortium will generate genomics resources, provide computational tools, technical guidelines, and support students and early-career researchers. Presently, the AGC has over 200 members from 36 countries, a monthly virtual seminar series, and an active communication channel. If you would like to join the AGC, complete the questionnaire on their website (membership is free). We are proud to include the AGC as one of our partners.

October 16, 2023: East Asian frogs seemingly withstand the deadly chytrid fungus, Batrachochytrium dendrobatidis (Bd), and host immune genes such as MHC (major histocompatibility complex) may play a role. Lau et al. (2023) established transcriptomic data from a range of Japanese frogs and characterized MHC genes to explore this relationship. They discovered a shared MHC class II 'supertype' (grouping functional properties) that may be important for disease resistance. This supertype is shared among all investigated Japanese and Korean species, which diverged millions of years ago. Preliminary MHC binding prediction analyses also suggested that this supertype has relatively high overall peptide binding ability (both Bd and non-Bd peptides). Their research contributes to uncovering how frogs combat Bd. (Quintin Lau)

October 9, 2023: Large-scale phylogenies have become indispensable for many ecological, evolutionary, and conservation studies in amphibians. However, in frogs, the widely used supermatrix trees are based on relatively few genes and are quite different from recent phylogenomic trees (those based on many genes), both in relationships among families and in ages of major clades. A new study (Portik et al. 2023) has generated the largest frog phylogeny to date. This phylogeny includes 5,242 anuran species, a 71% increase in sampling relative to the previously largest supermatrix study. The new supermatrix phylogeny also incorporates hundreds of genes from phylogenomic studies, and more than twice as many fossil calibration points (for divergence dating) as the largest supermatrix study. This new phylogeny more closely resembles recent phylogenomic trees in terms of relationships among families and divergence dates. For example, the ages estimated in the new tree for some of the largest frog clades (Neobatrachia, Hyloidea, and Ranoidea) are within 20 million years of those from these phylogenomic studies, but are 56–91 million years younger than those from the previous largest supermatrix study. This new phylogeny should offer an improved estimate for use in future comparative and systematic studies. The new tree and a set of 100 bootstrapped time-calibrated trees are available here. The authors are grateful to all the researchers who published the sequence data that underlie their study. (John Wiens)

October 2, 2023: Available now! Women in Herpetology: 50 Stories from Around the World unveils the inspiring journeys of 50 women from 50 countries and regions who have dedicated their lives to the study of amphibians and reptiles. This groundbreaking book showcases the determination, passion, and love for these creatures that drive these women while aiming to inspire future generations of women in herpetology. The book is led by The Global Women in Herpetology project, founded by Dr. Sinlan Poo from Taiwan, Dr. Itzue Caviedes-Solis from Mexico, and Dr. Umilaela Arifin from Indonesia. All profits from Women in Herpetology will be used to establish a scholarship for students in underrepresented regions to attend international herpetological conferences to present their research. "We aim to give our first scholarships to students to attend the World Congress of Herpetology in 2024", says Dr. Arifin. "We strongly believe that every voice counts and every story matters. The road has been bumpy and our careers and lives have moments of pain and challenges. But in the midst of it all, we have also found joy," says Dr. Caviedes-Solis. Dr. Poo adds, "We came together thanks to our love for amphibians and reptiles. We hope that people can flip through the pages and immerse themselves in the rich and diverse landscapes the authors are describing and the remarkable illustrations these artists have created." Purchase the book here.

Women in Herpetology is a compilation of captivating stories from herpetologists working in diverse fields such as conservation, biodiversity, ecotoxicology, and education. It highlights their unique challenges, including limited resources and mentorship opportunities, as well as the joys and rewards they have found through their work. The book also features stunning illustrations by seventeen talented artists from around the world.

September 25, 2023: Do caecilians face selective pressure from elapid snake predators? A study by Mancuso et al (2023) searched for clues in neurotoxin fighting systems in 37 caecilian species, representing all currently known families of caecilians in the Americas, Africa, and Asia, and the Seychelles. Three types of caecilian resistance neurotoxins were identified. The study demonstrated that resistance to alpha-neurotoxins convergently evolved at least fifteen times across the caecilian tree (three times in Africa, seven times in the Americas, and five times in Asia). In addition, several species were shown to possess multiple resistance modifications acting synergistically, thus they concluded that caecilians must have undergone at least 20 separate events involving the origin of toxin resistance. In contrast, resistance in non-caecilian amphibians was found to have arisen only five separate times. Together, the mutations underlying resistance in caecilians constitute a robust signature of positive selection, which strongly correlates with elapid presence through both space (sympatry with caecilian-eating elapids) and time (Cenozoic radiation of elapids). This study demonstrates the extent of convergent evolution that can be expected when a single widespread predatory adaptation triggers parallel evolutionary arms races at a global scale. (VV)

September 18, 2023: Tadpoles, the aquatic larvae of frogs, seem very simple when viewed from above, with large heads and wriggling tails. When viewed from below and up-close on the other hand, it is obvious just how bizarre and alien tadpoles really are. Their small size has limited our understanding of tadpoles as there are practical difficulties to understanding how they interact with their environment and ecosystem. Annibale et al. (2023) argue that, with recent advancements in, and increased access to, slow-motion macro videography, it is now possible to start understanding the alien lives of tadpoles. One way to do this is called “autecology”, the study of individuals via close observation with a goal of understanding an organism wholistically in the contexts of their biotic and abiotic environments. The authors suggest beginning with certain groups of tadpoles, including suctorial, stream-specialists (e.g., see photo of Heleophryne purcelli). Doing so, they argue, will allow us to ask and answer new questions surrounding tadpole evolution and community ecology. The authors also suggest that these methods are not exclusive to tadpoles, but could be more broadly applied across many small, fast-moving animals. (Jackson R. Phillips)

September 11, 2023: The U.S. Fish and Wildlife Service (USFWS) announced that it will provide US Federal Endangered Species Act (ESA) protections to many Foothill Yellow-legged frog populations including ESA endangered status for distinct population segments (DPS) in the South Sierra Nevada mountains, and the South Coast of California. The USFWS also granted threatened status for the populations in the North Feather River and Central California Coast. The ESA is a federal law enacted in the United States in 1973 to protect and recover species at risk of extinction and to promote the conservation of ecosystems and habitats necessary for the survival of those species. The Foothill Yellow-legged frog, named for its yellow belly and undersides of its rear legs, ranges from Oregon state to southern California, and is considered an ecological “sentinel” species serving as an important indicator for the ecological health of communities. While wide-ranging, the amphibian faces multiple threats, including altered waterflows from dams and diversions; competition with and predation by non-native species such as American bullfrogs (Rana catesbeiana) and crayfish (Pacifastacus leniusculus); disease (e.g., chytridiomycosis); precipitation and temperature changes related to climate change; high-severity wildfires; water-related recreation; and habitat conversion and degradation. This is a positive step to address the critical declines of a wide-ranging frog. (VV)

September 4, 2023: Many poison dart frog species (Dendrobatidae) conduct toe-tapping behavior, the quick up-and-down movement of the hind legs´ middle toes. Observational reports suggest interactions with prey animals and/or conspecifics triggering this behavior. Schulte and König (2023) systematically tested the influence of big and small prey animals (crickets and fruit flies), as well as conspecific playback calls on toe-tapping behavior in the green-and-black poison frog (Dendrobates auratus). The experiments revealed that playback calls had no influence on the toe-tapping frequencies. Though, both prey species triggered toe-tapping in the frogs, no matter if the prey animals were small or big. Furthermore, the toe-tapping behavior was positively correlated to feeding events. Juvenile frogs, however, were excluded from the analyses. Even though they also showed toe-tapping behaviors, they tapped much less frequently than adult frogs. (Lisa Schulte)

August 28, 2023: The Chernobyl nuclear power plant catastrophe occurred over 30 years ago and researchers are now gaining a better understanding of the long-term effects of nuclear exposure to wildlife. Recently, Car et al. (2023) surveyed populations of Hyla orientalis both within and outside of the Chernobyl Exclusion Zone to assess the population structure, genetic diversity, and individual gene expression. They found that frogs inside the exclusion zone had decreased body conditions, and smaller population sizes despite ongoing migration from low to high contaminated sites. Furthermore, populations within the exclusion zone had a unique transcriptome signature and more termination mutations in their energy metabolism pathways than those outside of the exclusion zone. While these results are correlative, they suggest either a relationship with radiation exposure and highlight the need for more research into the causal relationship of radiation exposure and long-term deleterious effects in wildlife. (AChang)

August 21, 2023: Many animals have the ability to change their appearance to better match their backgrounds and become cryptic. Some, like the octopus, can do this very quickly by expanding or contracting different colored pigments in their skin. Others, like the snowshoe hare, change their coloration from one season to the next, by increasing or decreasing the amounts of pigments in their skin or fur. This second type of color changes tends to be a little slower, but probably is more common in the animal kingdom, including in amphibians. Liedtke et al (2023) explore the extent to which Western Spadefoot Toad tadpoles (Pelobates cultripes) can change their color in response to different backgrounds. They find that in a matter of days, these tadpoles can become completely dark or light, tracking the brightness of their environment. The tadpoles can adjust their pigmentation depending on just how bright their background is, and even reverse this color change completely. For a tadpole that lives in temporally changing ponds across the Iberian Peninsula, this is a useful trick to hide from visual predators. Color change in these tadpoles is achieved through changes in the production of eumelanin, a dark pigment commonly found in vertebrate skin. Interestingly, changes in pigmentation also are associated with changes in body shape and may have physiological consequences on the organism’s oxidative stress levels. The hormones and mechanisms that are involved in this environmentally induced color change may, therefore, be intertwined with other physiological processes, an exciting prospect for future studies. (Christoph Liedtke)

August 14, 2023: Amphibians are found across a wide range of elevations, from sea level to above 5,000 meters, exposing them to a wide range of climates. The climate variability hypothesis predicts that organisms exposed to more temperate variation will be able to function across a wider range of temperatures. Bovo et al. (2023) tested the thermal tolerances of five species of frogs that are distributed across mountains in Brazil's Atlantic Rainforest in a variety of microhabitats, including Boana faber, Dendropsophus minutus, Leptodactylus latrans, Physalaemus cuvieri, and Rhinella icterica. They found differences among species in temperature tolerance, but did not always find that broader temperature variation at increasing elevations correlated with broader temperature tolerance. In addition, they did not find a consistent difference in water loss or water uptake across altitude or climates. Overall, they did not find strong support for the climate variability hypothesis or for elevation shaping these physiological traits. (MWomack)

August 7, 2023: No one likes mosquitos, or the diseases they transmit, but there is a positive link between their abundance and human-caused landscape alterations. Conversely, while amphibian density has been shown to have a negative relationship on mosquitos density, amphibians also are negatively impacted by human modifications to their habitat. Perrin et al. (2023) examined the interaction of these relationships with a survey of 77 anthropized ponds in western Switzerland. While their methods were indirect, their structural equation models and path analyses point to ponds with amphibians having reduced abundance and diversity of mosquitoes, likely through limiting competition and predation by amphibians. Their analysis also found that ponds were more likely to have amphibians if they were deeper and older, as mosquitos often colonize new ponds immediately while it takes a few years for their predators to do so. The authors argue that removing wetlands to reduce mosquito populations is counterproductive as it impacts mosquito predators more than mosquitos, and they encourage the development of more measures to protect amphibians. (AChang)

July 31, 2023: Previous studies on frogs and salamanders suggest a limited correlation between parental care and the transmission of microbiome from parent directly to the offspring, or vertical microbiome transmission. However, caecilians— among the most poorly known of terrestrial vertebrates and the most elusive amphibians— have not been investigated in this context. The oviparous, direct-developing caecilians present a unique opportunity for studying parent-offspring interactions because they exhibit elaborate forms of parental care. Juveniles both feed on the skin of the mother and, at least in some species, imbibe a fluid from her cloaca, both quite likely leading to vertical bacterial transmission. Kouete et al. (2023) studied the microbiomes of Herpele squalostoma, an oviparous, direct developing caecilian from Central Africa that engages in parental care through skin-feeding. Using 16S rRNA metabarcoding. they found that juveniles shared an important proportion of their skin and gut microbiome with the skin and gut of mothers, including high similarities with the mothers' skin. In addition, nitrogen stable isotope (15N) values of juvenile skin were approximately three times higher than that of the mothers, indicating a higher trophic position for juveniles due to skin-feeding. (Marcel Kouete)

July 24, 2023: As the most imperiled vertebrate class, amphibians face a slew of threats. Because amphibians use their skin for respiration and the regulation of ions, but have a higher potential for evaporative water loss, climate change, which is expected to bring higher average temperatures and unpredictable rainfall, is a particular risk. Rollins-Smith and Le Sage (2023) reviewed the current literature on the effects of heat stress and desiccation on amphibian immunity. While responses are varied, the overarching result from studies indicate that heat stress and desiccation can suppress the innate and lymphocyte-mediated responses by stimulating the hypothalamus pituitary-interrenal axis. Additionally, elevated temperatures can reduce the microbial communities of both the skin and gut, causing decreased immunity to pathogens and reduced nutrient uptake. These effects are particularly striking in larvae, resulting in the loss of recruitment. While these results are alarming, more studies are needed to understand how amphibians adapt to climate change, especially in understudied clades, such as salamanders, and underrepresented geographic regions. (AChang)

July 17, 2023: Herpetology, the study of amphibians and reptiles, has been a male-dominated field with most of its history rooted in Western-centric scientific tradition while many biodiversity hotspots of amphibian diversity occurring outside of the US and Europe. To bring some light to less visible herpetologists, Drs. Umilaela Arifin, Itzue Wendolin Caviedes Solis, and Sinlan Poo initiated the Global Women in Herpetology Project, first establishing an international registry of women scientists to facilitate networking, support, and visibility. Already, it represents 50 countries and regions with women at all stages of their career, from students to professionals. Their passion extended to a recently released book that beautifully illustrates the fieldwork, challenges, careers, and, of course, the amphibians and reptiles which are the focus of 50 women in herpetology from all continents where amphibians and reptiles occur. “By sharing our journey in life and career, we will collectively put a spotlight on the diversity of women in our field. We hope this effort will encourage the next generation of herpetologists to follow their dreams.” You can buy this uniquely inspiring book on the Global Women in Herpetology Kickstarter site until it moves to a book publisher. (MK)

July 10, 2023: Pollen is potentially a nutritious food source and widespread in the right season. Whether tadpoles take advantage of pollen and effectively consume pollen may depend on whether they can digest the grains despite its hard outer coats, the season, and feeding morphology. Kloh et al 2023 examined three frog species with different tadpole feeding behaviors to investigate the role of pollen in their diets: Phasmahyla jandaia, which feeds at the water’s surface; Scinax curicica, which feeds in the water column; Odontophrynus juquinha, which feeds on the bottom. Comparing gut contents, pollen digestion, developmental stages, morphology, and seasonality, they found that surface-feeding tadpoles were generally the better consumers and consumed the most pollen. Some seasonal variation existed in the water-column feeders with pollen consumption high in the dry season likely when other food sources are more scarce. They did find all three species consumed pollen regardless of stage. Their work highlights an overlooked food source for amphibians and the importance of conserving the food web of riparian habitats. (MK)

July 3, 2023: Conservation management is challenging for several reasons, including the variety of local stressors that contribute to the decline of a species or community. One common challenge is the gap between research recommendations and the ability to implement those recommendations. Moor et al. (2022) show in their decades-long analysis the effects of mitigation through habitat (pond) creation on the management of twelve declining pond-breeding amphibian species in Switzerland. They analyzed 20 years of data in the densely populated state of Aargau, Switzerland, and found the addition of hundreds of new ponds to the landscape stopped the decline or stabilized the populations of the majority of the monitored amphibians. They demonstrated the significant positive impact of restoring habitat dynamics by increasing habitat availability and connectivity, and how large landscape conservation efforts can benefit threatened amphibians despite all other declines factors. (AChang)

June 26, 2023: Many frogs all over the world are in danger of extinction, but scientists have strategies to try and prevent mass extinctions. Conservation translocation—movement of animals from one place to another—is one such strategy. However, there is no reliable information on whether this method works in the wild for frogs. Researchers from the Memphis Zoo and Oregon State University (Poo et al. 2022) set out to find out: can frogs produced from cryopreserved sperm be used to create new and healthy populations in the wild? Using Fowler's toads (Anaxyrus fowleri), they found that tadpoles from cryopreserved sperm and post-metamorphic toadlets were smaller than their natural counterparts. They project that these early-stage differences in growth continue to become substantial differences in final life fecundity and population trends. Their study shows that more work needs to focus on cryopreservation technologies in order to make them feasible for conservation translocation. (Read more "Can freezing frog sperm help with conservation efforts?") (Sinlan Poo)

June 19, 2023: Parental care in frogs provide an excellent opportunity to examine the evolution of complex sociality, specifically whether increased complexity of care is correlated with the evolution of novel or context-dependent signals as frogs have been models for both animal communication and parental care diversification. Moss, Tumulty, and Fischer (2023) studied the Mimic Poison Frog (Ranitomeya imitator), a remarkable species displaying monogamy, pair bonding, and biparental care of eggs and tadpoles. Specifically, the authors address whether calls elicited in the context of egg feeding – a cooperative parental behavior in which males lead females to tadpole deposition sites and stimulate them to lay trophic eggs – reflect the evolution of novel signal elements. Combining acoustic and video recordings of pairs in the laboratory, they repeatedly sampled calls of the same individuals in three social contexts – advertisement, courtship, and egg feeding – and characterized and compared call types. Consistent with their prediction, egg feeding calls were distinct from either ancestral call type. These calls have lower dominant frequencies and clipped pulse rates. Despite these differences, there was still considerable overlap between call types, both within and between individuals. This overlap suggests that parental care is coordinated through the use of multimodal (e.g., visual and olfactory, in addition to acoustic) cues. Their study highlights the complexity of anuran communication systems and the need to characterize vocal repertoires across a an array of social contexts. (Jeanette Moss)

June 12, 2023: A study on Feihyla hansenae, a rhacophorid treefrog from Thailand with terrestrial eggs, shows that embryos are capable of hatching early to escape flooding, and that failure to hatch results in mortality. By incorporating natural and experimental data into Monte Carlo methods to simulate and compare survival probabilities with and without hatching plasticity, Poo et al. (2023) found an overall increase in submergence survival due to hatching plasticity. As intensity and consistency of rainfall become more unpredictable and more variable due to climate change, there is a clear need for more life history data to increase the accuracy of our predictions on how animals may respond. These results add to the growing body of literature surrounding climate-correlated effects on poorly-studied amphibian populations. (Sinlan Poo)

June 5, 2023: Foam nests are a unique reproductive strategy used by frogs providing eggs and larva protection from desiccation, predation, and suffocation while also aiding in fertilization and providing a food source for developing larvae. More recently, the protein and carbohydrate rich foam also has been associated with the vertical transfer of beneficial microbial communities in rhacophorid frogs. Monteiro et al. (2023) characterized the protein composition and microbiome of the nests of three Leptodactylid species: Adenomera hylaedactyla, Leptodactylus vastus, and Physalaemus cuvieri, with each representing a different spawning habitat type. They found that protein composition was species-specific and was influenced more by spawn habitat type and nest size than phylogenetic relatedness. Many of these proteins were previously unidentified. Additionally, the microbiome community of the nest was unique from the surrounding environment and the adult skin microbiome. These findings show that foam nests have a key functional role in reproduction and highlight the need for conservation efforts to protect nests from anthropic pressures, as each nest has a unique microenvironment. (AChang)

May 29, 2023: De-Oliveira-Nogueira et al (2023) reports a new behavior and relationship between an amphibian and plant: the South American tree frog Xenohyla truncata has been observed feeding on nectar and flowers of the Brazilian milk fruit tree Cordia taguahyensis. The flower structure of this tree species allows the frog to enter and exit the flower easily. During their feeding activity, the pollen grains adhere to the frog’s back and are transported to other flowers while visiting them. Based on this observation, the authors suggest that X. truncata is not only a seed disperser, but also a potential pollinator of C. taguahyensis, or even of other plant species with similar floral structure. Nectar-feeding is an unique natural history behavior among frogs and highlights the importance of fundamental natural history information for this endemic tree frog species, which exclusively lives in the rapidly disappearing Restinga habitat on the coast of Rio de Janeiro in Brazil. With expanding development and habitat destruction, it is feared that losing this frog species, currently threatened with extinction, also means the extinction of a unique amphibian-plant interaction, especially important as it is a first known for a frog. Thus, conservation of this tree frog species has heightened stakes. (UArifin)

May 15, 2023: Infectious disease has been linked to several instances of amphibian population decline and is hypothesized to contribute to worldwide amphibian declines. As a result, there is urgency to better understand host-pathogen-environment interactions in amphibian communities. Researchers can take advantage of cultured cell lines to investigate host-pathogen-environment interactions in controlled experiments that do not require the use of live animals. Amphibian cell lines thus can provide an important and more accessible first step in addressing open research questions which can be followed up with live animal studies. Douglas et al. (2023) reviewed the existing amphibian cell line resources and literature and found that the amphibian invitrome, the collection of amphibian cell lines, consists of at least 159 distinct amphibian cell lines originating from 23 species belonging to five frog families and four salamander families. Despite this impressive history of cell line resources and many curated lines, few have been used to investigate amphibian cellular immune responses. The authors propose that the amphibian invitrome has the potential to transform our understanding of amphibian immune responses at a mechanistic level while limiting use of live amphibians. (MWomack)

May 8, 2023: Neotropical poison frogs are known for their intensive parental care. Male or female parents will carry their tadpoles to bromeliads to provide them with small pools of water where they can develop, safe from fishy predators. In these nutrient poor habitats, some species have evolved egg-feeding, where females lay unfertilized eggs for the tadpoles to eat. In the Peruvian mimic poison frog, Ranitomeya imitator, parents form a pair bond and cooperate in the care of their tadpoles. In this system, Weinfurther et al. (2023) provide preliminary evidence of a symbiotic protist in the guts of the tadpole. In comparative experiments, they switched the diets of R. imitator tadpoles (eggs) with the ancestral diet (detritus) consumed by a related species (R. variabilis) without egg-feeding, and did the reverse (with control treatments for both species). Analyses of gut gene expression revealed elevated expression of proteases in the R. imitator field egg-fed treatment. These digestive proteins came from parabasalians, a group of protists known to form symbiotic relationships with hosts that enhance digestion (especially in termites). Genes encoding these digestive proteins are not present in the R. imitator genome, and phylogenetic analyses shows these mRNA sequences were from parabasalian protists. Bar-coding analyses of the tadpole eukaryotic microbiomes further confirmed this discovery. More study is necessary to confirm whether these parabasalians aid R. imitator tadpoles in protein/ lipid digestion in an egg diet. This may have enabled the exploitation of a key ecological niche (very small, nutrient-poor pools), allowing R. imitator to expand into an area with ecologically similar species (e.g., R. variabilis and R. summersi). In turn, this may have enabled a Müllerian mimetic radiation, one of only a few examples of this phenomenon in vertebrates. (KSummers)

May 1, 2023: Symbiotic skin microbial communities and skin secretions have been studied in frogs for their immunological effects for decades, however, there are still much to discover about all the other roles they may play. Brunetti et al. (2023) examined Burmeister's Treefrog, Boana prasina, for evidence of chemical signaling and found that their skin secretions contained 10 different compound classes of volatile chemicals, some of which were produced by symbiotic Pseudomonas sp. bacteria. Moreover, these odors varied by sex, which in tandem with acoustic signaling, could play a chemical signaling role in sex recognition and assessment during breeding. These findings open the door to questions that could improve our understanding of amphibian breeding behavior and symbiotic associations. (AChang)

April 24, 2023: In a 2023 study, Loeffler-Henry et al. provide new insights into the evolution of aposematism, that is, the warning coloration combined with a chemical defense. They review the apparent paradox inherent in the evolution of aposematism: How can new brightly colored mutants survive when they will attract predator attention before the predators have learned that bright coloration is associated with toxicity? While a variety of potential solutions to this puzzle have offered, none have been definitively demonstrated to apply in general. Here, they focus on the hypothesis that aposematism evolved in gradual stages involving the prior evolution of facultatively presented signals, such as bright colors concealed by limbs, or bright coloration of the underbelly of the animal (and revealed only upon the close approach of a predator). The conditions favoring the evolution of this type of coloration are likely to be much less restrictive, and yet they provide a clear pathway to the evolution of overall bright coloration. The authors carry out an extensive series of phylogenetically- controlled comparative analyses using maximum- likelihood methods, which allows them to make statistically supported inferences about the evolutionary pathways of the evolution of both coloration and defense (toxicity). The results provide support for the hypothesis that conspicuousness evolved via an indirect pathway in which facultative conspicuous coloration evolved first and provided pathways for full conspicuousness to evolve later. There is still considerable work to be done in terms of identifying the specific evolutionary mechanisms that facilitated the evolution of aposematism through each gradual step, but this study provides a valuable roadmap for those kinds of analyses. (KSummers)

April 17, 2023: In a phylogenetic analysis, Ellepola et al (2022) investigates the roles of climate, ecological opportunity and key evolutionary innovations (KEI) in the diversification of rhacophorid frogs, which represent six percent of global amphibian diversity, four distinct reproductive modes, and spans a climatically variable area across mainland Asia, associated continental islands, and Africa. Using a complete species-level phylogeny, they report near-constant diversification rates but a highly uneven distribution of species richness. Montane regions on islands and some mainland regions have higher phylogenetic diversity and unique assemblages of taxa; the study identifies these as cool-wet refugia. Starting from a center of origin, rhacophorids reached these distant refugia by adapting to new climatic conditions (‘niche evolution’-dominant), especially following the origin of KEIs such as terrestrial reproduction (in the Late Eocene) or by dispersal during periods of favorable climate (‘niche conservatism’-dominant). (VV)

April 10, 2023: What compounds do amphibians taste? What role might taste play in the biology of amphibians as they develop from larvae to adults? Using comparative genomics, Hao et al. (2023) found unexpected diversity in the Tas2r taste receptors that detect bitter compounds, more than in any other vertebrate group. By looking at the differential expression of the nearly 200 Tas2r genes in the American Bullfrog (Rana catesbeiana), they found that tadpoles and adults differently express some genes at high levels. This suggests that variation across development in expression of these bitter receptors is related to the different foods (and presumably different preferences) between herbivorous larvae and insectivorous adults. Interesting areas for further research include how these receptors might be distributed within the mouth, including on the unusual taste “discs” of frog tongues, as well as how closely related species might differ in bitter receptors and thus preferences for different prey. (DBlackburn)

April 3, 2023: Researchers are finding amphibians move more frequently and farther across landscapes than often assumed, which has broad conservation implications. Davis et al. (2023) carried out an impressive six-year capture-mark-recapture study across 12 wetlands in Pennsylvania, US, and showed that adult Spotted Salamanders (Ambystoma maculatum) move a surprising distance both within and between breeding seasons. Six percent of males moved among wetlands each day, and in high density populations, males tended to return to the same breeding wetland year after year (had higher site fidelity). Females exhibited higher interannual site fidelity and dispersed farther than males between breeding seasons. This study and others that track amphibian movements are improving our understanding of breeding dispersal probabilities and capabilities. (MW)

March 27, 2023: Pandemics in amphibians, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), have resulted in biodiversity loss at a global scale. Genomic data suggest a complex evolutionary history of Bd lineages that vary in pathogenicity. Africa harbors a significant proportion of global amphibian biodiversity, and multiple Bd lineages are known to occur there; yet, despite the decline of many host species, there are currently no described Bd-epizootics. Ghose et al. (2023) describes the historical and recent biogeographical spread of Bd and assess its risk to amphibians across the continent of Africa. Their study provides a 165-year view of host-pathogen interactions by (i) employing a Bd assay to test 4,623 specimens (collected 1908–2013); (ii) compiling 12,297 published Bd records (collected 1852–2017); (iii) comparing the frequency of Bd-infected amphibians through time by both country and region; (iv) genotyping Bd lineages; (v) histologically identifying evidence of chytridiomycosis, and (vi) modeling future Bd risk. They found a pattern of Bd emergence beginning largely at the turn of the century. From 1852–1999, Bd prevalence is low (3.2% overall) with limited geographic spread, but after 2000, prevalence sharply increases (18.7% overall) with wider geographic spread and multiple Bd lineages that may be responsible for emergence in different regions.They found Bd risk to amphibians to be highest in much of eastern, central, and western Africa. The study documents a largely overlooked yet significant increase in a fungal pathogen that could pose a threat to amphibians across an entire continent and emphasizes the need to bridge historical and contemporary datasets to better describe and predict host-pathogen dynamics over larger temporal scales. (VV)

March 20, 2023: New Guinea – the world’s largest tropical island – is famous for its rugged topography, with snow-capped mountains reaching 4,884 m in elevation (16,024 ft), and a multitude of deeply incised valleys that make ground-based overland travel virtually impossible. This topography is highly conducive to localized speciation and small-range endemism. Oliver et al. (2022) focused on the amphibians of this imposing landscape and find that New Guinea holds the world’s most diverse and intact insular amphibian fauna, with over 7% of global frog species (534 currently recognized species) distributed across less than 0.7% of the world’s land area. Remarkably, the scale of the New Guinea frog fauna is almost certainly substantially underestimated as the authors are aware of about 190 species in collections that have yet to be described. Furthermore, most of the known species were described from the much better surveyed eastern half of the island that represents the country of Papua New Guinea. The frog fauna of the western half of the island (Papua Province, Indonesia) remains relatively understudied and promises to hold additional species beyond the ~700 estimated by the authors. The composition of the New Guinea frog fauna is almost entirely restricted to three families (Microhylidae, Hylidae, Ceratobatrachidae), with the direct-developing microhylids dominating. New Guinea’s rugged topography has likely contributed to its amazingly diverse fauna and simultaneously prevented the sort of large-scale anthropogenic habitat destruction that has allowed the fauna to remain largely intact (only 6% of assessed species are listed as threatened). (JM)

March 13, 2023: Brazil is considered a mega-diverse country for amphibian diversity (1159 amphibian species known so far). However, it is also home to one of the global hotspots of amphibian decline, the coastal Atlantic Forest. To understand the history, nature, and response of species to the precipitous declines, Toledo and colleagues (2023) closely analysed surveys, reports, and museum records with environmental, climatic, and disease data. Their study more than doubled the number of population declines reported in previous studies, placing the Brazilian Atlantic Forest as a global hotspot of amphibian declines with one of the highest rates of declines and extinctions. The height of decline appears to be in 1979 within a decades long trend. Populations, if they recovered, sometimes took as long as 30 or more years. Their use of museum collections showed that specimen records matched the spatiotemporal patterns of declines and extinctions, including the impact of chytridiomycoses; they suspect that historic declines might have impacted many more amphibian populations and species. They also sought correlations of life history traits and phylogeny to help explore patterns of decline. They note some families were disproportionally impacted (specifically Cycloramphidae, Hylodidae, Phyllomedusidae). Their comprehensive report will be an essential guide to conservation, management, and disease surveillance to protect this important amphibian ecology. (MK)

March 6, 2023: One of the most remarkable forms of camouflage observed in nature involves transparency in glass frogs of the family Centrolenidae. These frogs, which are arboreal and typically perch on leaves, have highly transparent ventral skin through which their organs can be clearly seen, as well as green dorsal coloration and green bones that presumably enhance their camouflage. One feature that might disrupt their camouflage is the presence of red blood cells, which are easily seen through the transparent ventral skin. Recently Taboada et al. (2022) showed that the glass frog species Hyalinobatrachium fleischmanni increase their transparency while resting by two to three-fold by removing about 89% of their red blood cells from circulation and packing them within their liver. This exciting new discovery not only provides new information on the nature of transparency in glass frogs but may also inform biomedical research because the ability to densely pack red blood cells into the liver without clotting could have important human health consequences. (JM)

February 27, 2023: Evolutionary transitions in reproductive modes and life-cycles in amphibians has long been a target of study to understanding the diversity of life. Liedtke et al (2022) compares large-scale macroevolutionary patterns across the three orders of amphibians: frogs, salamanders, and caecilians, and includes reproductive and phylogenetic data for 4,025 species. Their analysis indicate aquatic larvae as ancestral for all three groups. The most frequent transitions in each group are to relatively uncommon states: live-bearing in caecilians, paedomorphosis in salamanders, and semi-terrestriality in frogs. All three groups show transitions to more terrestrial reproductive modes, but only in caecilians have these evolved sequentially from most-to-least aquatic. Diversification rates are largely independent of reproductive modes. However, in salamanders, direct development accelerates diversification whereas paedomorphosis decreases it. Overall, the study reports a widespread retention of ancestral modes, decoupling of trait transition rates from patterns of species richness, and the general independence of reproductive modes and diversification. (VV)

February 20, 2023: How do frogs swallow their food? While the mechanics of the frog tongue are well-studied for the prey capture phase of the feeding cycle, little is known of how structures in the mouth move once it is closed. Recent work by Keeffe et al. (2022) investigated the functional morphology of the hard and soft tissues involved in feeding behaviors in the Cane toad, Rhinella marina. Using a combination of high-speed X-ray video, 3D animation software, and dissection, they assessed the role of the skull, jaw, pectoral girdle, tongue, and hyoid apparatus (skeleton supporting the tongue) during a complete feeding cycle. Their results suggest the hyoid apparatus plays an important role in prey transport, potentially helping remove prey from the sticky tongue pad prior to swallowing. They also found that the tip of the tongue consistently travels behind the back of the skull during swallowing, and that tongue protrusion comprises only a small portion of a full feeding cycle. This work raises new questions about the evolution of feeding in frogs, as well as how the observed diversity across frogs in the skeleton of the shoulder and tongue may influence feeding kinematics. (Rachel Keeffe)

February 13, 2023: Poison frogs, with bright colors and potent skin toxins, represent iconic examples of aposematism in rainforests throughout South and Central America. These frogs are also known for intensive parental care– parents carry tadpoles to small pools (phytotelmata) and some species provide trophic eggs as food for their offsprings. Much interest has focused on the question of whether poison frog tadpoles can acquire toxins for protection from predators by consuming eggs from their mothers. Studies have shown two species of Oophaga provide toxins to their tadpoles via obligate trophic egg feeding. In contrast, in Ranitomeya variabilis (and related R. fantastica, R. summersi) do not provide unfertilized eggs to their tadpoles (instead, they subsist on detritus, algae, and insect larvae), although they will sometimes lay fertilized clutches in or above pools that are later cannibalized by tadpoles. Villanueva et al. (2022) investigate this issue in a third species of Oophaga (O. granulifera) and in Ranitomeya imitator and R. variabilis. They found that while O. granulifera receives toxins in its eggs (like other members of this genus), that was not true for either species of Ranitomeya. They infer the degree to which egg feeding is facultative (high in R. variabilis, low in R. imitator, not facultative in Oophaga) is related to the evolution of toxin transfer via egg feeding. This is only a single comparison between the Oophaga and Ranitomeya lineages, so further studies will be necessary for definitive conclusions, but their study provides a fascinating and promising first pass at this question. (KSummers)

February 6, 2023: Evolutionary history and biogeographic patterns give us insight into how species respond to paleogeographic and paleoclimatic changes over a shared landscape, and these in turn can provide a guide for conservation management. In southern China, the landscape is a transitional mosaic with dramatic changes in elevation ranging from an average of 4000 m a.s.l to sea level. Yuan et al. (2022) used multi-locus genetic and environmental data from 78 sites to investigate phylogeographic patterns in the southern Chinese newt genera of Cynops, Paramesotriton, and Pachytriton. Their results showed consistency with major geological events, such as the uplift of the Qinghai-Xizang (Tibet) Plateau. Furthermore, variation in summer monsoons and the complex landscape of montane/submontane forest with lowland areas resulted in barriers that act as both ‘museums’ or refugia of old lineages and ‘cradles’ for new species diversification. These findings can provide a backbone for genetically informed management plans, but education and public awareness are crucial to preventing habitat disturbance and over-harvesting of vulnerable species. (AChang)

January 30, 2023: Some amphibians are able to persist in human-modified habitats, including within cities and intensively managed lands. Which mechanisms allow persistence in such environments? Cayuela et al. (2022) conducted a comprehensive analysis of mark-recapture studies of Yellow-bellied Toad (Bombina variegata) populations across a range of anthropic habitats. These toads breed in early-succession ponds and small pools of natural or anthropic origin. Life history traits can change along the gradient from natural to anthropic habitats according to two demographic scenarios. In the first scenario, the risk of adult mortality decreases with anthropization, associated with concomitant decreases in predation and parasitism rates. In the alternative scenario, increased exposure to contaminants, invasive species, ecological mismatches and other processes promote higher adult mortality risk in human-modified habitats. In this scenario, increased recruitment can compensate for increased adult mortality. Cayuela and collaborators estimated adult recruitment, adult survival, lifespan, and senescence rate from 67 populations of the yellow-bellied toads across western Europe. They convincingly show that toads in anthropogenic habitats have lower adult survival, shorter lifespan, and accelerated senescence than toads in natural habitats. Compensatory recruitment indeed occurs in anthropogenic habitats, where average adult recruitment is 93% higher than in natural habitats. Increased human land disturbance might promote creation of breeding habitats conducive to higher adult recruitment. These findings suggest the important role of human disturbance for maintaining populations of amphibians using early-succession habitats. (ACatenazzi)

January 23, 2023: Biological reserves provide protected refugia against human-mediated habitat degradation, which is one of the strongest conservation concerns for amphibians. The Manu Biosphere Reserve is one of the most biodiverse places on earth with over 155 amphibian species. Serrano-Rojas et al. (2022) surveyed 70 of the amphibian species recorded in the Manu Biosphere Reserve within five sites that span a land-use gradient in the park buffer zone (immigrant agricultural land, forests used by three Indigenous communities, and a regenerating forest) in addition to a reference site in its core protected area. They found the richness and diversity of amphibians in the regenerating forest and the indigenous communities’ forests were similar to that of the core protected area, whereas agricultural land had lower richness and was dominated by generalist species. Their findings underscore that supporting sustainable livelihood activities, cultural practices, and forest protection, which are observed in many Indigenous communities, could help avoid a shift towards intensive agriculture, fulfilling a crucial conservation role. (MWomack)

January 16, 2023: Amphibians may be affected by climate change more than other terrestrial vertebrates, and they have the higher rates of decline in recent years. The Columbia Spotted Frog (Rana luteiventris) is a widespread North American frog that occurs across a variety of climate gradients, from subalpine forests to semi-arid deserts. Pilliod and colleagues (2022) marked 15,885 adult Columbia Spotted frogs with subdermal transponders, with 33% recaptured at least once during their long term study (11-16 years depending on site). Within each population, adult survival and recruitment rates respond uniquely to seasonal temperature and precipitation variables, especially in winter and spring. Seasonal rain is a weak predictor of adult survival but was a useful predictor of juvenile recruitment, especially in three of the populations. Recruitment rates for each population peaked with different environmental gradients, depending on the amount of winter snowfall, and fall temperature and moisture levels. Thus recruitment may be responding to local conditions independently within each population. Their work emphasizes that local conditions and climate gradients need to be accounted for when managing climate effects on populations of amphibian species with broad geographic ranges. (CS)

January 9, 2023: An important life history trait is body size, which can be affected by environmental and evolutionary factors. Acevedo et al. (2022) examined these relationships in the specious, neotropical genus Pristimantis, which has a distribution across wide latitudinal and elevational ranges. Using body size data for all 584 known Pristimantis, phylogenetic information from 257 species, and information on their environments, the authors found that the body size of males, females, and sexual size dimorphism were correlated with climatic variation associated with heat balance (temperature), water availability (precipitation), and habitat availability (elevation). Additionally, despite the majority of species displaying sexual size dimorphism, their trend ran opposite to Rensch's rule, where males are larger then females. This correlation may be the result of fecundity selection, reproductive energy requirements, or heat balancing. Although separate clades show evidence that they are experiencing different selective pressures, the rate of body size evolution appears to be decelerating as the trait reaches an optimum. As this study provides a case for bioclimatic factors in body size evolution, it is a good launching point to generate future selection and macroevolutionary hypotheses of sexual size dimorphism. (AChang)

January 2, 2023: Happy New Year’s! Reflecting on 2022, we had a particularly productive year at AmphibiaWeb. One of the most visible improvements this year is (the much needed) new home page! All of the old links are still present but much more presentable. We hope you love the new home page as much as we do. We published the first "State of the Amphibia" paper (Womack et al 2022) in which we summarize the major research and data trends on Amphibia in the last 5 years. We aim to repeat this every five years to establish a record of and facilitate amphibian research and conservation. We end the year with 152 newly described species (20 mantellids frogs alone thanks to Scherz et al 2022!), a little less than the five-year average of 158. We also nearly doubled the number of new species accounts (140) which reflects both the new editing forms and efforts by student apprentices, but we hope to release even more accounts next year. In 2023, we will launch a new program to expand our network of experts and trained authors-- look out for announcements and opportunities to connect with us. We hope to have an equally productive 2023, so please keep an eye out for new projects, new data-driven pages and graphics, and the same committment as we continue to serve as the knowledge-hub for amphibians.