Heleophrynidae Research Articles

Fine-scale drivers of extinction risk: tadpole occupancy dynamics of the Table Mountain Ghost Frog (Heleophryne rosei)

Over the last four decades much progress has been made towards recognising causes of global amphibian declines, but knowledge of fine scale drivers, particularly for specialised species, remains poor, inhibiting conservation effectiveness. The case of the Table Mountain Ghost frog (Heleophryne rosei) provides an example of this, listed as Critically Endangered for the last 15 years with limited conservation actions identified due to a lack of information about threat mechanisms and magnitude of declines. To address this, we investigated H. rosei tadpole occupancy dynamics over three years in stream pools on Table Mountain in Cape Town, South Africa, the only locality where this species occurs. Tadpole spatiotemporal distribution was examined as a function of abiotic and biotic factors to quantify habitat requirements, rank threats, and identify conservation actions. Heleophryne rosei tadpole occupancy was negatively correlated with levels of fine sediments (silt and sand), which embed larger substrates and decrease the diversity of benthic microhabitat. Increased abundance of these fine sediments was also associated with higher extinction probabilities. Localised habitat degradation from hiking paths, alien vegetation, and flow manipulation were identified as the primary threats to this species, increasing the sources of fine sediments and inhibiting the fluvial systems ability to effectively flush these sediments out. Our results demonstrate the importance of pore space refugia for mountain headwater stream-adapted amphibians and provides the required data to inform management decisions for this Critically Endangered species.

Breeding phenology and behaviour of the Endangered Hewitt’s ghost frog Heleophryne hewitti in the Baviaanskloof World Heritage Site, Eastern Cape Province, South Africa

ABSTRACT Given the potential impact of climate change on amphibians, there is a need to establish baseline phenological data for vulnerable species and to investigate their responses to changing climatic conditions. We recorded vocalisations of Hewitt’s ghost frog Heleophryne hewitti in the Baviaanskloof World Heritage Site, South Africa, to investigate its breeding phenology and vocalisation behaviour. Our objectives were to: 1) characterise seasonal and diel vocalisation patterns, 2) examine relationships between environmental variables and calling behaviour and 3) evaluate the effectiveness of acoustic recording as a monitoring technique. We employed automatic vocalisation recognition software to detect calls and used hurdle regression to model the relationships between environmental variables and the number of calls produced. Our study confirmed that H. hewitti is a seasonal prolonged breeder, with reproductive activity occurring from early to late spring. We found that while relative humidity seemed to influence the probability of calling, none of the weather variables appeared to have a strong influence on the number of calls produced. Acoustic monitoring combined with automatic vocalisation recognition has proven to be a viable technique for monitoring this species. Further investigation of cues for breeding initiation is required to understand the impacts of climate change on this species.

Assessing water conditions for Heleophryne rosei tadpoles and the conservation relevance

The Table Mountain Ghost Frog (Heleophryne rosei) is endemic to the Table Mountain massif and is Critically Endangered. Other than clear, clean perennial stream flow, the optimal aquatic conditions required by their larvae are unknown. Dissolved oxygen, temperature, pH, electro-conductivity, aspect and permanence of flow are the independent variables measured seasonally at two sampling altitudes at 12 rivers of the massif. Using a logistic regression model we found that a permanence of water flow and lower water temperature were significant predictors of tadpole presence. Streams with mean summer temperature above 17.2 °C, at 300 m – 400 m above sea level, do not have tadpoles. Summer and autumn abstraction should be avoided, while a summer water temperature above an average of 17.2 °C is a threshold of potential concern for management authorities responsible for biodiversity conservation, threat mitigation efforts, and bulk-water supply and abstraction.Conservation implications: The Environmental Water Reserve has not been determined for streams of Table Mountain. The requirements of the Critically Endangered Table Mountain Ghost Frog (Heleophryne rosei) can be adopted as the minimum conditions to support this species and associated communities. Perennial flow, an average January water temperature of 17.2 °C or lower.

Preliminary evaluation of non-native rainbow trout (Oncorhynchus mykiss) impact on the Cederberg ghost frog (Heleophryne depressa) in South Africa’s Cape Fold Ecoregion

We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites above and below a waterfall that marks the upper distribution limit of O. mykiss. Heleophryne depressa abundance was significantly greater above the waterfall than that below it, and, because there was no significant difference in measured environmental variables, O. mykiss presence is identified as the most likely explanation for the observed decrease in H. depressa abundance.

Correlation between development and increase of number of labial tooth rows in ghost frog tadpoles (Anura: Heleophrynidae)

The family Heleophrynidae is restricted to Southern Africa and comprises two genera with seven species. Tadpoles are well adapted, with huge sucker mouths, to live in the fast flowing headwaters of mountain streams. The unique sucker-like mouth has numerous transverse rows of labial teeth, which are used to attach themselves to the rock surface and to scrape algae from the rocks. In this paper data on the ontogenetic increase of labial tooth rows in tadpoles of four species of ghost frog are presented. Notes on the development of tadpoles and mouthparts are also presented.

The use of diatoms in the conservation management of Hewitt’s Ghost frog

The use of diatoms in the conservation management of Hewitt's ghost frog Distribution patterns of diatoms were investigated to determine the impact of shading on diatoms, which form the main diet of the endangered frog species, Heleophryne hewitti. Although diatom community composition is influenced by shade coverage, it does not affect tadpole grazing potential. The main factor threatening H. hewitti tadpoles is the degradation or loss of suitable habitat due to accumulation (pine needles, sediment etc.) and not degradation of water quality.

The use of the South African Diatom Index as a concervation management tool for Hewitt’s Ghost frog

Distribution patterns of diatoms were investigated to determine the impact ofshading on the distribution of diatomes, which form the main diet of the endangered frogspecies, Heleophryne hewitti.

Genetic differentiation among five populations of the South African ghost frog, Heleophryne natalensis

Allozyme electrophoresis was used to analyse genetic heterogeneity in five ghost frog populations ( Heleophryne natalensis) ( Hewitt, 1913) from different localities in South Africa. A population of the congeneric H. purcelli, was used as a reference group. A total of 25 loci were resolved from 14 enzymes and an unspecified protein. Of the 25 loci resolved, eight were variable within or across populations, revealing an overall polymorphism of 32% but not more than 8% in any individual population. Four of the H. natalensis populations sampled were monoallelic, whereas the fifth population displayed an average heterozygosity of 2.97%. However, there was considerable variation among H. natalensis populations, including monomorphic populations, with fixed allelic differences at three loci. Gene flow among H. natalensis populations was 0.156–0.915 migrants per generation for four pairwise comparisons but zero for the remaining six pairs; the latter is unusual for conspecific populations. The overall intraspecific fixation index value for H. natalensis was 0.876, not much lower than the interspecific F ST value of 0.912 calculated when data for H. natalensis and H. purcelli was pooled for comparison. This confirms low gene flow and tight selection within microhabitats. Genetic distances ranged from 0.008 to 0.128 between conspecific populations, increasing to 0.182–0.284 between the H. natalensis populations sampled, and H. purcelli. The results are discussed with reference to the relationship between low genetic heterogeneity, response to selection and habitat tolerance of frogs.

The status of some rare and endangered endemic reptiles and amphibians of the southwestern Cape Province, South Africa

At least 14 herpetological species are endemic to the southwestern Cape Province, RSA. Five, the geometric tortoise Psammobates geometricus, the Cape platanna Xenopus gilli, the micro frog Microbatrachella capensis, the Table Mountain ghost frog Heleophryne rosei an d McLachlan's girdled lizard Cordylus mclachlani, are in immediate need of conservation measures to ensure their continued long-term survival. The first four species mentioned are listed as endangered. Habitat destruction and degradation, genetic hybridization and restricted distribution ranges are the four most important factors responsible for the critical conservation status of these species. Nature reserves, declared nature areas, careful managing of remaining habitat and an increased human awareness are of vital importance to their survival. Only the future establishment of new and additional reserved areas will ensure the protection of viable populations of these five species.