Urban growth threatens the lowland Amazonian Manaus harlequin frog which represents an evolutionarily significant unit within the genus Atelopus (Amphibia: Anura: Bufonidae)

The Manaus harlequin frog is an evolutionarily significant clade within the Atelopus hoogmoedi species complex. Analyses of 16S and COI concatenated sequences support Atelopus from the Manaus region as an evolutionary significant unit, sister of all species of a Guiana Shield clade. A previous study showed that subtle changes in stream characteristics influence the Manaus harlequin frog occurrence and density variation at local-scale in a reserve on the outskirts of Manaus. As deforestation is approaching areas where the Manaus harlequin frog occurs, we asked how site and landscape heterogeneity influence the geographic boundaries, occurrence patterns, and density variation of the Manaus harlequin frog. We searched for the frog in 80 plots that measured 250 m by 4 m on banks of first- to third-order streams during the rainy seasons in 2012–2013 and 2016–2019. The plot distribution covered all likely areas of occurrence of the Manaus harlequin frog and extended to the areas where it is substituted by its geographically closest relative on the Guiana Shield. Ecological drivers related to climate, flooding events, and forest structure apparently restrict the Manaus harlequin frog to a patchy distribution in a narrow portion of the interfluve between the Negro and Uatuma Rivers. Densities of individuals varied in response to subtle changes in floodplain and stream characteristics. The Manaus harlequin frog is associated with a very specific habitat that is directly affected by the growth of Manaus, the largest city in Amazonia. We conclude that it is endangered and urgent actions are required for its conservation.     

Batrachochytrium dendrobatidis Infection in the Recently Rediscovered Atelopus mucubajiensis (Anura, Bufonidae), a Critically Endangered Frog from the Venezuelan Andes

The harlequin frog, Atelopus mucubajiensis, is a critically endangered species that was believed to be extinct until 2004, when a single adult female was found in the Venezuelan Andes. Its disappearance after 1994 has been attributed to an increase in the prevalence of the fungal pathogen, Batrachochytrium dendrobatidis, in populations of these frogs. Using histology and Real-Time PCR assays, we tested this adult female positive for B. dendrobatidis. We report for the first time, to our knowledge, infection in a live specimen of A. mucubajiensis. The presence of this pathogen in remaining individuals poses a problem for the long-term persistence of this critically endangered species, as new epidemic episodes of chytridiomycosis could jeopardize the survival of remnant populations.     

Evaluating Sierra Nevada Yellow-Legged Frog Distribution Using Environmental DNA

Genetic tools that identify species from trace DNA samples could supplement traditional survey methods to clarify distributional limits of rare species. For species with legal habitat protection, elevational limits of distributions are used to determine where management actions may affect endangered species. The endangered Sierra Nevada yellow-legged frog (Rana sierrae) generally is found down to 1,370 m, but in the Plumas National Forest, California, USA, there are a number of historical records below this elevation, resulting in protections extending to 1,067 m. This species is phenotypically similar to the foothill yellow-legged frog (R. boylii), with which it occasionally hybridizes. We used a combination of genetic methods to investigate the fine-scale distribution of the Sierra Nevada yellow-legged frog in the Plumas National Forest. We collected and analyzed environmental DNA (eDNA) samples from all accessible lower elevation sites with records of Sierra Nevada yellow-legged frog (n = 17) and swabbed 220 individuals for genetic identification from 2016–2018 to clarify the distribution of this endangered species. We created a climatic suitability model using the validated Sierra Nevada yellow-legged frog records and current (1970–2000) climate models to assess additional highly suitable localities for Sierra Nevada yellow-legged frog presence using eDNA capture. We did not confirm detection of Sierra Nevada yellow-legged frog eDNA at any historical sites and identified all swabbed individuals from below 1,370 m (n = 144) as foothill yellow-legged frogs. We located a new Sierra Nevada yellow-legged frog site (at 1,919 m) during surveys guided by the climatic suitability model. It does not appear after extensive eDNA and genetic sampling that the Sierra Nevada yellow-legged frog occurs below 1,370 m in this portion of their range at present. Our results show that eDNA sampling can be used as an effective management tool to evaluate historical locations and previously unknown suitable localities for current presence of a species of interest. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

皖南凹耳臭蛙地理分布格局与生境选择

凹耳臭蛙(Odorrana tormota)是一种小型山溪蛙类,由于叫声独特,种内具有超声通讯功能而引起国内外相关专家的广泛关注。首次针对皖南凹耳臭蛙地理分布、生境选择以及人为干扰强度对种群密度的影响进行了研究。共调查了9县1区32条不同的山溪,发现其中的16个有凹耳臭蛙分布,除黄山区的香溪和浮溪具文献记录外,其余14个分布点均为首次报道。基于现存凹耳臭蛙分布点的水系关系,推测该物种在皖南的分布呈现出以青弋江、新安江和水阳江三大水系为纽带、间断分布的格局。对其中10个分布点222只凹耳臭蛙生境选择的统计结果表明,在夜晚活动周期内,该物种对乔木、灌木丛、草本植物、岩石、沙滩和倒伏朽木等不同生境的选择具有显著差异(F5,54=25.75,P0.001),栖息在草本植物和灌丛中蛙的数量明显多于栖息在其它几种生境类型中的蛙类。暗示溪流沿岸的草本植物和灌丛对该物种的生存和繁衍具有重要意义,乔木对其非活动周期的隐蔽可能具有不可替代的作用。根据人类活动对其栖息地破坏程度,将人为干扰程度划分为强、中和弱3种不同强度,对不同干扰强度下种群相对密度进行单因素方差分析。结果表明,中等干扰强度下的种群密度显著高于其它两种强度下的种群密度(F2,13=8.155,P=0.005)。推测适度的人为干扰可能增加了栖息地内昆虫的种类和数量,对蛙类的生存和繁衍更为有利。但随着人为干扰强度的增强,对溪流沿岸植被的破坏更为剧烈,种群密度显著下降。     

Hormonal induction of gamete release,and in-vitro fertilisation,in the critically endangered Southern Corroboree Frog, <Emphasis Type="Italic">Pseudophryne corroboree</Emphasis>

Background  

Conservation Breeding Programs (CBP's) are playing an important role in the protection of critically endangered anuran amphibians, but for many species recruitment is not successful enough to maintain captive populations, or provide individuals for release. In response, there has been an increasing focus on the use of Assisted Reproductive Technologies (ART), including the administration of reproductive hormones to induce gamete release followed by in vitro fertilisation. The objective of this study was to test the efficacy of two exogenous hormones to induce gamete release, for the purpose of conducting in vitro fertilisation (IVF), in one of Australia's most critically endangered frog species, Pseudophryne corroboree.     

Microsatellite markers in the endangered Australian northern corroboree frog, Pseudophryne pengilleyi (Anura: Myobatrachidae) and amplification in other Pseudophryne species

Seven microsatellite primer pairs were isolated and characterized in the endangered Australian northern corroboree frog (Pseudophryne pengilleyi). All seven were polymorphic (2–14 alleles) and displayed high heterozygosity (0.036–0.964) in 28 sampled individuals. We also tested the microsatellites on two closely related species. Four were polymorphic in the southern corroboree frog (P. corroboree) and Bibron’s toadlet (P. bibronii). These primers will be useful in studies of conservation genetics and mating systems in Pseudophryne species.     

Persistence at distributional edges: Columbia spotted frog habitat in the arid Great Basin,USA

A common challenge in the conservation of broadly distributed, yet imperiled species is understanding which factors facilitate persistence at distributional edges, locations where populations are often vulnerable to extirpation due to changes in climate, land use, or distributions of other species. For Columbia spotted frogs (Rana luteiventris) in the Great Basin (USA), a genetically distinct population segment of conservation concern, we approached this problem by examining (1) landscape‐scale habitat availability and distribution, (2) water body‐scale habitat associations, and (3) resource management‐identified threats to persistence. We found that areas with perennial aquatic habitat and suitable climate are extremely limited in the southern portion of the species’ range. Within these suitable areas, native and non‐native predators (trout and American bullfrogs [Lithobates catesbeianus]) are widespread and may further limit habitat availability in upper‐ and lower‐elevation areas, respectively. At the water body scale, spotted frog occupancy was associated with deeper sites containing abundant emergent vegetation and nontrout fish species. Streams with American beaver (Castor canadensis) frequently had these structural characteristics and were significantly more likely to be occupied than ponds, lakes, streams without beaver, or streams with inactive beaver ponds, highlighting the importance of active manipulation of stream environments by beaver. Native and non‐native trout reduced the likelihood of spotted frog occupancy, especially where emergent vegetation cover was sparse. Intensive livestock grazing, low aquatic connectivity, and ephemeral hydroperiods were also negatively associated with spotted frog occupancy. We conclude that persistence of this species at the arid end of its range has been largely facilitated by habitat stability (i.e., permanent hydroperiod), connectivity, predator‐free refugia, and a commensalistic interaction with an ecosystem engineer. Beaver‐induced changes to habitat quality, stability, and connectivity may increase spotted frog population resistance and resilience to seasonal drought, grazing, non‐native predators, and climate change, factors which threaten local or regional persistence.     

Spatial and temporal patterns of environmental DNA detection to inform sampling protocols in lentic and lotic systems

The development of efficient sampling protocols for the capture of environmental DNA (eDNA) could greatly help improve accuracy of occupancy monitoring for species that are difficult to detect. However, the process of developing a protocol in situ is complicated for rare species by the fact that animal locations are often unknown. We tested sampling designs in lake and stream systems to determine the most effective eDNA sampling protocols for two rare species: the Sierra Nevada yellow‐legged frog (Rana sierrae) and the foothill yellow‐legged frog (Rana boylii). We varied water volume, spatial sampling, and seasonal timing in lakes and streams; in lakes we also tested multiple filter types. We found that filtering 2 L versus 1 L increased the odds of detection in streams 5.42X (95% CI: 3.2–9.19X) in our protocol, from a probability of 0.51–0.85 per technical replicate. Lake sample volumes were limited by filter clogging, and we found no effect of volume or filter type. Sampling later in the season increased the odds of detection in streams by 1.96X for every 30 days (95% CI: 1.3–2.97X) but there was no effect for lakes. Spatial autocorrelation of the quantity of yellow‐legged frog eDNA captured in streams ceased between 100 and 200 m, indicating that sampling at close intervals is important.     

Auditory response characteristics of the piebald odorous frog and their implications

The piebald odorous frog (Odorrana schmackeri), the large odorous frog (Odorrana livida) and the concave-eared torrent frog (Amolops tormotus) are sympatric species living near the same torrent streams in the vicinity of Mt. Huangshan, China. A recent study demonstrated that A. tormotus can use sound signals involving ultrasonic components for communication in a noisy environment, and another sympatric species, O. livida, can also perceive ultrasonic sound. Here we report data on the hearing range of O. schmackeri by studying auditory evoked potentials and single-unit data from the torus semicircularis. This frog exhibits its two most sensitive peaks at 2 kHz and 3.5–4.0 kHz with thresholds <42 dB SPL, with an upper frequency limit of hearing at 8.5 kHz with threshold of 87 dB SPL. The upper limit is much lower than those of O. livida and A. tormotus, at 22 and 34 kHz, respectively. It suggests that sympatric species may respond differently to similar environmental selection pressures sculpting auditory communication systems.     

Heterochronic shifts during early cranial neural crest cell migration in two ranid frogs

We describe the development of the cranial neural crest cell streams relative to embryonic events such as neural tube formation and somite appearance in two Eurasian frog species belonging to the Ranidae, Rana temporaria and Sylvirana nigrovittata, and demonstrate developmental heterochronies. The mandibular stream appeared well developed in R. temporaria at a time when the embryo was still spherical, the neural folds were elevated, and the neural plate was wide open, thus earlier than known from any frog species so far. The appearance of the second stream and its division into hyoid and branchial portions was clearly accelerated in R. temporaria relative to other embryonic events when compared to S. nigrovittata. For example, in R. temporaria, the hyoid and branchial portions of the cranial neural crest cell streams were separated before the neural folds had started to fuse, whereas in S. nigrovittata this event took place only after the neural folds had fused completely. Such ostentatious heterochronies related to the characters used herein have formerly only been reported from comparisons between species belonging to different higher taxa. Our results re‐confirm that to understand the full dynamics of the evolution of development, studies need to implement comparative embryological approaches, and include phylogenetically relatively closely related taxa.     

Population Recovery following Decline in an Endangered Stream-Breeding Frog (Mixophyes fleayi) from Subtropical Australia

Amphibians have undergone dramatic declines and extinctions worldwide. Prominent among these have been the stream-breeding frogs in the rainforests of eastern Australia. The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has been postulated as the primary cause of these declines. We conducted a capture-mark-recapture study over a 7-year period on the endangered Fleay’s barred frog (Mixophyes fleayi) at two independent streams (30 km apart) in order to assess the stability of these populations. This species had undergone a severe decline across its narrow geographic range. Mark-recapture modelling showed that the number of individuals increased 3–10 fold along stream transects over this period. Frog detection probabilities were frequently above 50% but declined as the populations increased. Adult survival was important to overall population persistence in light of low recruitment events, suggesting that longevity may be a key factor in this recovery. One male and female were present in the capture record for >6 years. This study provides an unambiguous example of population recovery in the presence of Bd.     

Effects of slope and riparian habitat connectivity on gene flow in an endangered Panamanian frog, Atelopus varius

Aim Understanding how heterogeneous landscapes shape genetic structure not only sheds light on processes involved in population divergence and speciation, but can also guide management strategies to promote and maintain genetic connectivity of populations of endangered species. This study aimed to (1) identify barriers and corridors for gene flow among populations of the endangered frog, Atelopus varius and (2) assess the relative contributions of alternative landscape factors to patterns of genetic variation among these populations in a hypothesis testing framework. Location This study took place in western Panama and included all nine of the remaining known populations of A. varius at the time of study. Methods The influence of landscape variables on gene flow among populations was examined by testing for correlations between alternative landscape‐resistance scenarios and genetic distance. Fifteen alternative hypotheses about the influence of (1) riparian habitat corridors, (2) steep slopes, and (3) climatic suitability on patterns of genetic structure were tested in a causal modelling framework, using Mantel and partial‐Mantel tests, along with an analysis of molecular variation. Results Only the hypothesis attributing resistance to dispersal across steep slopes (genetic isolation by slope distance) was fully supported by the causal modelling approach. However, the analysis of molecular variance and the paths of least‐slope among populations suggest that riparian habitat connectivity may influence genetic structure as well. Main conclusions These results suggest that patterns of genetic variation among A. varius populations are affected by the slope of the landscape such that areas with steep slopes act as barriers to gene flow. In contrast, areas of low slope, such as streams and mountain ridges, appear to be important corridors for gene flow, especially among high elevation populations. These results engender important considerations for the management of this critically endangered species.     

Living quarters of a living fossil—Uncovering the current distribution pattern of the rediscovered Hula painted frog (Latonia nigriventer) using environmental DNA

One of the greatest challenges of effective conservation measures is the correct identification of sites where rare and elusive organisms reside. The recently rediscovered Hula painted frog (Latonia nigriventer) has not been seen for many decades and was therefore categorized extinct. Since its rediscovery in 2011, individuals from the critically endangered species have been found, with great effort, only in four restricted sites. We applied the environmental DNA (eDNA) approach to search for new populations of the Hula painted frog in suitable aquatic habitats. We further used the eDNA data to classify the landscape factors associated with the species distribution and to predict its suitable habitats. We sampled 52 aquatic sites in the Hula Valley during the spring of 2015 and 2016 and amplified the samples with a species‐specific qPCR assay. DNA of the Hula painted frog was detected in 22 of the sites, all of which clustered within three main areas. A boosting classification model showed that soil type, vegetation cover and the current and former habitats are all key predictors of the frog's current distribution. Intriguingly, the habitat suitability models reveal a high affinity of the species to its long‐lost habitat of the historical wetlands. Our findings encourage a series of informed searches for new populations of this threatened frog and provide guidance for future conservation management programmes. In the era of global conservation crisis of amphibians, developing the eDNA approach, a reliable detection method for many critically endangered and elusive amphibians, is of particular importance.     

Mitochondrial DNA diversity and historical biogeography of a wet forest-restricted frog (Litoria pearsoniana) from mid-east Australia

MtDNA sequencing was used to investigate the genetic population structure of Litoria pearsoniana, a wet forest-restricted hylid frog, endemic to southeast Queensland and northeast New South Wales, Australia. L. pearsoniana is regarded as endangered under Queensland legislation. Significant genetic divergence among populations of frogs from different rainforest isolates was identified, but the lack of reciprocal monophyly among adjacent isolates suggests this is the result of a relatively recent disruption to gene flow. A paired catchment study within a single rainforest isolate, the Conondale Range, revealed no substantial genetic structuring, indicating the occurrence of terrestrial dispersal among nearby streams either in the recent past or currently. Two major reciprocally monophyletic clades of mtDNA alleles were identified. These corresponded to two geographical regions separated by the Brisbane River valley; one consisting of the Conondale and D’Aguilar Ranges, and the other of the southern isolates in the Main, Border and Gibraltar Ranges. Sequence divergence between the two regions was more consistent with a late Miocene or Pliocene rather than late Pleistocene separation, and is similar to that found among phylogeographic divisions of rainforest reptiles and amphibians in north Queensland rainforests. The molecular evidence for long-term separation of these two regions is corroborated by the pattern of species turnover in the distributions of species of rainforest-restricted amphibians and reptiles. Bioclimatic modelling suggests that appropriate conditions for L. pearsoniana would have been restricted to isolated refuges in each phylogeographic division under cooler and drier climates, such as predicted for the last glacial maximum. Currently isolated montane areas may have been connected transiently during the past 2000 years. Identification of long-term zoogeographic divisions among southeast Queensland rainforest herpetofauna has important implications for conservation and management. Conservation management of L. pearsoniana should be applied at the scale of major rainforest isolates and the conservation status of the species should be assessed independently north and south of the historical division.     

The Boxgrove,England, middle Pleistocene herpetofauna: Paleogeographic,evolutionary, stratigraphic,and paleoecological relationships

Triturus vulgaris (smooth newt), Triturus helveticus or T. vulgaris (palmate or smooth newt), Triturus sp. (newt), Pelobates fuscus (common spadefoot), Bufo bufo (common toad), Bufo calamita (natterjack toad), Bufo sp. (toad), Rana arvalis (moor frog), Rana temporaria (common frog), Rana sp. (frog), Anguis fragilis (slow worm), Lacerta cf. L. vivipara (common lizard), Natrix natrix (grass snake), and Natrix sp. (grass, viperine, or dice snake) were identified at the Middle Pleistocene Boxgrove Site, West Sussex, England. This is the first British fossil record of Pelobates fuscus and the earliest fossil record in Britain for the endangered species Bufo calamita. All of these herpetological species are extant and all of them occur in Britain today with the exception of Pelobates fuscus and Rana arvalis that presently live on the European continent.

The Boxgrove, Westbury, and West Runton British pre‐Anglian Middle Pleistocene herpetofaunas show no apparent differences among themselves in patterns of species composition, diversity, or number of exotics. But these three herpetofaunas together have [1] less species diversity and [2] fewer exotic continental species than in the Cudmore Grove British post‐Anglian Middle Pleistocene herpetofauna.

Only the Terrestral Sequence Unit at Boxgrove yielded enough herpetological species for paleoecological interpretation. These taxa indicate a quiet pool surrounded by a somewhat humid vegetated area that gave way to a more xerophytic sandy area, and a paleoclimate at least as warm and perhaps somewhat warmer than occurs in the area today.     

Food habits of an endangered Japanese frog, Rana porosa brevipoda

We examined the diet of an endangered frog, Rana porosa brevipoda inhabiting rice fields of western Japan, by forced regurgitation of stomach contents. The frog diet consisted of a wide variety of arthropods, and ants, beetles, dipterans, bugs, orthopterans, and spiders, which were especially prominent. These prey taxa were also collected in large numbers by sweep-net samplings made in the frog habitat, and relative abundances of prey taxa in frog diet and those in sweep samples were found to be significantly correlated. Aquatic forms did not contribute much to the frog diet, but were found to be taken more frequently and in larger numbers in irrigated fields than in drained fields. These findings suggest that prey availability around frog habitat is very important to regulate the food items of R. p. brevipoda. On the other hand, terrestrial components of frog habitats are indicated to be important because the frog highly depended on terrestrial invertebrates. From these results, we consider it imperative to preserve terrestrial components linked with aquatic environments to conserve biodiversity in rice field ecosystems.     

Shifts in macrophyte species composition as a result of eutrophication and pollution in Dutch transboundary streams over the past decades

The catchment areas of transboundary streams in the Netherlands have been subject to increasing agricultural and industrial activities over the past decades. To evaluate the effects of these activities on the aquatic vegetation, a study has been carried out in 28 Dutch transboundary lowland streams. Recent data on distribution of 58 aquatic plant species and their growth forms were compared with historical data and were correlated with abiotic variables. Most of these streams lost species that are characteristic for streams and are sensitive to turbidity, eutrophication and pollution (e.g. Potamogeton alpinus, P. polygonifolius, P. densus, Ranunculus peltatus ssp. heterophyllus, Callitriche stagnalis and Myriophyllum alterniflorum.) Species, not common in streams but tolerant to turbidity, eutrophication or pollution (e.g. Potamogeton trichoides, Elodea nuttallii) appeared in many streams or increased in abundance. There was also a shift in growth forms: submerged species decreased or were replaced by emergent/floating-leaved species. Correspondence analysis was carried out to study the relation between the observed changes and the abiotic characteristic of the streams. The magnitude of the shift in species composition was positively correlated with the PO₄ ^3- concentration and pH (which was highly correlated with Cd²⁺) of the water. This leads to the hypothesis that increased input of sewage, agricultural and industrial water causes a change in species composition and main growth forms of aquatic plant species in lowland streams.     

Multiple origins of invasive and ‘native’ water frogs (Pelophylax spp.) in Switzerland

The marsh frog (Pelophylax ridibundus) has been introduced in many areas in Central and Western Europe as a result of commercial trade with Eastern Europe, and is rapidly replacing the native pool frog (P. lessonae). A large number of Pelophylax species are distributed in Eastern Europe and the strong phenotypic similarity between these species is rendering their identification hazardous. Consequently, alien populations of Pelophylax might not strictly be composed of P. ridibundus as previously suspected. In the present study, we analysed the cytochrome‐b and NADH dehydrogenase subunit 3 genes of introduced and native Pelophylax species from Switzerland (299 individuals) in order to properly identify the source populations of the invaders and the genetic status of the native species. Our study highlighted the occurrence of several genetic lineages of invasive frogs in western Switzerland. Unexpectedly, we also showed that several populations of the native pool frog (P. lessonae) cluster with the Italian pool frog P. bergeri from central Italy (considered by some authors as a subspecies of P. lessonae). Hence, these populations are probably also the result of introductions, meaning that the number of native P. lessonae populations is fewer than expected in Switzerland. These findings have important implications concerning the conservation of the endemic pool frog populations, as the presence of multiple alien species could strongly affect their long‐term subsistence. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 442–449.     

The Reproductive Biology and Larvae of the First Tadpole-Bearing Frog,Limnonectes larvaepartus

Most of the reproductive modes of frogs include an exotrophic tadpole, but a number of taxa have some form of endotrophic development that lacks a feeding tadpole stage. The dicroglossid frog genus Limnonectes ranges from China south into Indonesia. The breeding biologies of the approximately 60 described species display an unusual diversity that range from exotrophic tadpoles to endotrophic development in terrestrial nests. There have been mentions of oviductal production of typical, exotrophic tadpoles in an undescribed species of Limnonectes from Sulawesi, Indonesia. Here we examine newly collected specimens of this species, now described as L. larvaepartus and present the first substantial report on this unique breeding mode. Typical exotrophic tadpoles that are retained to an advanced developmental stage in the oviducts of a female frog are birthed into slow-flowing streams or small, non-flowing pools adjacent to the streams.