Amphibian News!

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.