The Night Frog genus Nyctibatrachus (Family Nyctibatrachidae) represents an endemic anuran lineage of the Western Ghats Biodiversity Hotspot, India. Until now, it included 28 recognised species, of which more than half were described recently over the last five years. Our amphibian explorations have further revealed the presence of undescribed species of Nights Frogs in the southern Western Ghats. Based on integrated molecular, morphological and bioacoustic evidence, seven new species are formally described here as Nyctibatrachus athirappillyensis sp. nov., Nyctibatrachus manalari sp. nov., Nyctibatrachus pulivijayani sp. nov., Nyctibatrachus radcliffei sp. nov., Nyctibatrachus robinmoorei sp. nov., Nyctibatrachus sabarimalai sp. nov. and Nyctibatrachus webilla sp. nov., thereby bringing the total number of valid Nyctibatrachus species to 35 and increasing the former diversity estimates by a quarter. Detailed morphological descriptions, comparisons with other members of the genus, natural history notes, and genetic relationships inferred from phylogenetic analyses of a mitochondrial dataset are presented for all the new species. Additionally, characteristics of male advertisement calls are described for four new and three previously known species. Among the new species, six are currently known to be geographically restricted to low and mid elevation regions south of Palghat gap in the states of Kerala and Tamil Nadu, and one is probably endemic to high-elevation mountain streams slightly northward of the gap in Tamil Nadu. Interestingly, four new species are also among the smallest known Indian frogs. Hence, our discovery of several new species, particularly of easily overlooked miniaturized forms, reiterates that the known amphibian diversity of the Western Ghats of India still remains underestimated.
Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous-Paleogene boundary
- Proceedings of the National Academy of Sciences of the United States of America
- Published over 3 years ago
Frogs (Anura) are one of the most diverse groups of vertebrates and comprise nearly 90% of living amphibian species. Their worldwide distribution and diverse biology make them well-suited for assessing fundamental questions in evolution, ecology, and conservation. However, despite their scientific importance, the evolutionary history and tempo of frog diversification remain poorly understood. By using a molecular dataset of unprecedented size, including 88-kb characters from 95 nuclear genes of 156 frog species, in conjunction with 20 fossil-based calibrations, our analyses result in the most strongly supported phylogeny of all major frog lineages and provide a timescale of frog evolution that suggests much younger divergence times than suggested by earlier studies. Unexpectedly, our divergence-time analyses show that three species-rich clades (Hyloidea, Microhylidae, and Natatanura), which together comprise ∼88% of extant anuran species, simultaneously underwent rapid diversification at the Cretaceous-Paleogene (K-Pg) boundary (KPB). Moreover, anuran families and subfamilies containing arboreal species originated near or after the KPB. These results suggest that the K-Pg mass extinction may have triggered explosive radiations of frogs by creating new ecological opportunities. This phylogeny also reveals relationships such as Microhylidae being sister to all other ranoid frogs and African continental lineages of Natatanura forming a clade that is sister to a clade of Eurasian, Indian, Melanesian, and Malagasy lineages. Biogeographical analyses suggest that the ancestral area of modern frogs was Africa, and their current distribution is largely associated with the breakup of Pangaea and subsequent Gondwanan fragmentation.
Fossorialism is a beneficial adaptation for brooding, predator avoidance and protection from extreme climate. The abundance of fossilised burrow casts from the Early Triassic of southern Africa is viewed as a behavioural response by many tetrapods to the harsh conditions following the Permo-Triassic mass-extinction event. However, scarcity of vertebrate remains associated with these burrows leaves many ecological questions unanswered. Synchrotron scanning of a lithified burrow cast from the Early Triassic of the Karoo unveiled a unique mixed-species association: an injured temnospondyl amphibian (Broomistega) that sheltered in a burrow occupied by an aestivating therapsid (Thrinaxodon). The discovery of this rare rhinesuchid represents the first occurrence in the fossil record of a temnospondyl in a burrow. The amphibian skeleton shows signs of a crushing trauma with partially healed fractures on several consecutive ribs. The presence of a relatively large intruder in what is interpreted to be a Thrinaxodon burrow implies that the therapsid tolerated the amphibian’s presence. Among possible explanations for such unlikely cohabitation, Thrinaxodon aestivation is most plausible, an interpretation supported by the numerous Thrinaxodon specimens fossilised in curled-up postures. Recent advances in synchrotron imaging have enabled visualization of the contents of burrow casts, thus providing a novel tool to elucidate not only anatomy but also ecology and biology of ancient tetrapods.
Amphibians, a class of animals in global decline, are present in agricultural landscapes characterized by agrochemical inputs. Effects of pesticides on terrestrial life stages of amphibians such as juvenile and adult frogs, toads and newts are little understood and a specific risk assessment for pesticide exposure, mandatory for other vertebrate groups, is currently not conducted. We studied the effects of seven pesticide products on juvenile European common frogs (Rana temporaria) in an agricultural overspray scenario. Mortality ranged from 100% after one hour to 40% after seven days at the recommended label rate of currently registered products. The demonstrated toxicity is alarming and a large-scale negative effect of terrestrial pesticide exposure on amphibian populations seems likely. Terrestrial pesticide exposure might be underestimated as a driver of their decline calling for more attention in conservation efforts and the risk assessment procedures in place do not protect this vanishing animal group.
Tree frogs climb smooth surfaces utilising capillary forces arising from an air-fluid interface around their toe pads, whereas torrent frogs are able to climb in wet environments near waterfalls where the integrity of the meniscus is at risk. This study compares the adhesive capabilities of a torrent frog to a tree frog, investigating possible adaptations for adhesion under wet conditions. We challenged both frog species to cling to a platform which could be tilted from the horizontal to an upside-down orientation, testing the frogs on different levels of roughness and water flow. On dry, smooth surfaces, both frog species stayed attached to overhanging slopes equally well. In contrast, under both low and high flow rate conditions, the torrent frogs performed significantly better, even adhering under conditions where their toe pads were submerged in water, abolishing the meniscus that underlies capillarity. Using a transparent platform where areas of contact are illuminated, we measured the contact area of frogs during platform rotation under dry conditions. Both frog species not only used the contact area of their pads to adhere, but also large parts of their belly and thigh skin. In the tree frogs, the belly and thighs often detached on steeper slopes, whereas the torrent frogs increased the use of these areas as the slope angle increased. Probing small areas of the different skin parts with a force transducer revealed that forces declined significantly in wet conditions, with only minor differences between the frog species. The superior abilities of the torrent frogs were thus due to the large contact area they used on steep, overhanging surfaces. SEM images revealed slightly elongated cells in the periphery of the toe pads in the torrent frogs, with straightened channels in between them which could facilitate drainage of excess fluid underneath the pad.
In anurans reproductive behavior is strongly seasonal. During the spring, frogs emerge from hibernation and males vocalize for mating or advertising territories. Female frogs have the ability to evaluate the quality of the males' resources on the basis of these vocalizations. Although studies revealed that central single torus semicircularis neurons in frogs exhibit season plasticity, the plasticity of peripheral auditory sensitivity in frog is unknown. In this study the seasonally plasticity of peripheral auditory sensitivity was test in the Emei music frog Babina daunchina, by comparing thresholds and latencies of auditory brainstem responses (ABRs) evoked by tone pips and clicks in the reproductive and non-reproductive seasons. The results show that both ABR thresholds and latency differ significantly between the reproductive and non-reproductive seasons. The thresholds of tone pip evoked ABRs in the non-reproductive season increased significantly about 10 dB than those in the reproductive season for frequencies from 1 KHz to 6 KHz. ABR latencies to waveform valley values for tone pips for the same frequencies using appropriate threshold stimulus levels are longer than those in the reproductive season for frequencies from 1.5 to 6 KHz range, although from 0.2 to 1.5 KHz range it is shorter in the non-reproductive season. These results demonstrated that peripheral auditory frequency sensitivity exhibits seasonal plasticity changes which may be adaptive to seasonal reproductive behavior in frogs.
Of the nearly 6,800 extant frog species, most have weak jaws that play only a minor role in prey capture. South American horned frogs (Ceratophrys) are a notable exception. Aggressive and able to consume vertebrates their own size, these “hopping heads” use a vice-like grip of their jaws to restrain and immobilize prey. Using a longitudinal experimental design, we quantified the ontogenetic profile of bite-force performance in post-metamorphic Ceratophrys cranwelli. Regression slopes indicate positive allometric scaling of bite force with reference to head and body size, results that concur with scaling patterns across a diversity of taxa, including fish and amniotes (lizards, tuatara, turtles, crocodylians, rodents). Our recovered scaling relationship suggests that exceptionally large individuals of a congener (C. aurita) and extinct giant frogs (Beelzebufo ampinga, Late Cretaceous of Madagascar) probably could bite with forces of 500 to 2200 N, comparable to medium to large-sized mammalian carnivores.
A major cause of amphibian declines worldwide is habitat destruction or alteration. Public green spaces, such as golf courses and parks, could serve as safe havens to curb the effects of habitat loss if managed in ways to bolster local amphibian communities. We reared larval Blanchard’s cricket frogs (Acris blanchardi) and green frogs (Rana clamitans) in golf course ponds with and without 1 m terrestrial buffer zones, and released marked cricket frog metamorphs at the golf course ponds they were reared in. Larval survival of both species was affected by the presence of a buffer zone, with increased survival for cricket frogs and decreased survival for green frogs when reared in ponds with buffer zones. No marked cricket frog juveniles were recovered at any golf course pond in the following year, suggesting that most animals died or migrated. In a separate study, we released cricket frogs in a terrestrial pen and allowed them to choose between mown and unmown grass. Cricket frogs had a greater probability of using unmown versus mown grass. Our results suggest that incorporating buffer zones around ponds can offer suitable habitat for some amphibian species and can improve the quality of the aquatic environment for some sensitive local amphibians.
Ranaviruses are pathogens of ectothermic vertebrates, including amphibians. We reviewed patterns of host range and virulence of ranaviruses in the context of virus genotype and postulate that patterns reflect significant variation in the historical and current host range of three groups of Ranavirus: FV3-like, CMTV-like and ATV-like ranaviruses. Our synthesis supports previous hypotheses about host range and jumps: FV3s are amphibian specialists, while ATVs are predominantly fish specialists that switched once to caudate amphibians. The most recent common ancestor of CMTV-like ranaviruses and FV3-like forms appears to have infected amphibians but CMTV-like ranaviruses may circulate in both amphibian and fish communities independently. While these hypotheses are speculative, we hope that ongoing efforts to describe ranavirus genetics, increased surveillance of host species and targeted experimental assays of susceptibility to infection and/or disease will facilitate better tests of the importance of hypothetical evolutionary drivers of ranavirus virulence and host range.
We describe a new species of small strabomantid frog (genusPsychrophrynella) from a humid montane forest in the Peruvian Department of Puno. Specimens were collected at 2,225 m a.s.l. in the leaf litter of primary montane forest near Thiuni, along the Macusani-San Gabán road, in the province of Carabaya. The new species is assigned toPsychrophrynellaon the basis of morphological similarity, including presence of a tubercle on the inner edge of the tarsus, and call composed of multiple notes. We also include genetic distances for 16S rRNA partial sequences between the new species and other strabomantid frogs. The species with lowest genetic distances arePsychrophrynella chirihampatuandPsychrophrynella usurpator. Psychrophrynella glaucasp. n. is readily distinguished from the three other species ofPsychrophrynella(Psychrophrynella bagrecito,P. chirihampatu, andP. usurpator) by its small size, and by having belly and ventral surfaces of legs reddish-brown or red, and chest and throat brown to dark brown with a profusion of bluish-gray flecks. The new species is only known from its type locality. With the discovery ofP. glauca, the geographic distribution ofPsychrophrynellais extended to the Department of Puno, where it was no longer represented after the description of the genusMicrokayla. Furthermore, the Cordillera de Carabaya is the only mountain range known to be home to four of the seven genera of Holoadeninae (Bryophryne,Microkayla,Noblella, andPsychrophrynella), suggesting an intriguing evolutionary history for this group in southern Peru.