@ WWW Virtual Library Sri Lanka
OCCASIONAL PAPERS No. 2 OF THE WILDLIFE HERITAGE TRUST
Evaluating Sri Lanka’s amphibian diversity
Rohan Pethiyagoda* & Kelum Manamendra-Arachchi*
* Wildlife Heritage Trust of Sri Lanka, 95 Cotta Road, Colombo 8, Sri Lanka; e-mail: email@example.com ; firstname.lastname@example.org
Based on a five-year field survey, Sri Lanka’s amphibian fauna has been found to comprise more than 250 species (compared with 54 species recognised in the current literature), mostly confined to the rain forests of the island’s wet zone (precipitation > 2,000 mm yr-1). The Old World tree frogs (family Rhacophoridae), until now considered to be represented in the island by only 17 species, are in fact represented by ca. 200 species. Many of these species have remained undiscovered until now because little systematic surveying has been done, and also because the rainforest canopy, the habitat of most of the ‘new’ species, remains largely unexplored in Sri Lanka. Extinctions have almost certainly taken place within the amphibian fauna of the island: the very small areas of distribution (often < 0.5 km2) of most of the species, remarkably high local endemicity and the loss of more than 90% of the island’s former rainforest habitats have combined to put many species at risk. The principal threats to this fauna are the continuing loss of habitat caused by human activity, aggravated possibly by steadily declining rainfall, increasing temperature, atmospheric pollution and declines in arthropod prey as a result of widespread pesticide use.
The recent accretion of species makes Sri Lanka a unique refuge of amphibian diversity, and its wet zone in particular, a global amphibian hotspot. The habitats of many of these species are at risk, and urgent measures are needed for their conservation.
Key words: Amphibia, exploration, Sri Lanka, biodiversity, conservation, Rhacophoridae.
While Kirtisinghe (1957) recognised 35 species-group amphibian taxa from Sri Lanka, Dutta & Manamendra-Arachchi (1996) recognised a total of 53 species, mentioning in an appendix however, that the actual diversity is in fact much higher (see also Manamendra-Arachchi & Pethiyagoda, 1998). Except for two revisional treatments (Clarke, 1983; Nussbaum & Gans, 1980), most recent taxonomic work on the Sri Lankan Amphibia has consisted of casual descriptions of single new species (e.g. Bogert & Senanayake, 1966; Fernando et al., 1994; Fernando & Siriwardhane, 1996; Manamendra-Arachchi & Gabadage, 1996) and not comprehensive revisions or reviews with keys to the species (e.g. Dutta & Manamendra-Arachchi, 1996; Manamendra-Arachchi & Pethiyagoda, 1998). What is more, much of the work that has been reported up to now has been based on casual discoveries and not on methodical surveys.
In 1993, with assistance from the WWF Small Grants Programme, we began a systematic survey of the Sri Lankan Amphibia. It was soon apparent that the actual diversity of species (based on visual and auditory diagnosability) was in fact far higher than had hitherto been suspected. While this programme was under way, our attention was drawn to the work of S.K. Dutta (1985), who in the course of a PhD programme at the University of Kansas, had examined much of the type material of Sri Lankan amphibians lodged in numerous museums world wide. In 1995 a decision was taken to revise partially Dutta’s taxonomic work and combine it with our own diagnoses, distribution data, figures and photographs of live specimens, to produce Dutta & Manamendra-Arachchi (1996). As was made clear in that work itself, our treatment was essentially an exposition of the ‘state of the art’, with no new names being introduced or new species described; the wealth of additional material we had accumulated, yet to be reported on, was retained for future study once a satisfactory sample became available.
Our survey work has continued without interruption since 1993. With the exploratory phase of this project nearing completion, we have commenced writing a series of papers revising the taxonomy of Sri Lankan Amphibia. In these, we will be diagnosing and describing ca. 200 new species of Rhacophoridae, almost all of them endemic to Sri Lanka’s wet-zone (sensu Domroes, 1998; annual precipitation > 2,000 mm) forests. In this article we summarise our methodology and results, in the hope that this will help draw attention to the unique contribution the Amphibia make to Sri Lanka’s biodiversity and the need therefore, to focus fresh attention toward their conservation.
The survey work was carried out throughout Sri Lanka except the northern and eastern parts of the island, which were not accessible because of the on-going separatist war. Samples were obtained from 235 locations (see Fig. 1) following a variety of methods (Heyer et al., 1994). As the primary aim of the survey was to make a biodiversity assessment, the sampling effort varied greatly from one site to another, the survey having been designed primarily to yield the maximum number of species records from each location sampled. The locations sampled too, are strongly biased by their having been chosen because we thought it more likely that they would yield more species records. In a few instances we also searched selectively for rare species known only from museum specimens with discrete locality data. Because little forest survives in the wet zone (sensu Domroes, 1998) north of the Kalu River and west of the central massif, these areas have received lower priority in our survey schedule until recently; the results below should be viewed with this bias in mind.
Except for the Rhacophoridae, the material examined in this study is detailed in Dutta & Manamendra-Arachchi (op. cit.) and Manamendra-Arachchi & Pethiyagoda (1998a), upon which works the species identifications too (except for Rhacophoridae), are based. In all, 93 species of Rhacophoridae are included in this study. This represents approximately 50% of the total rhacophorid species hitherto recorded from Sri Lanka by us. At the present time, we have restricted ourselves to describing only those hitherto-undescribed taxa for which we have series of 3 or more preserved adult specimens together with clear colour photographs (ca. 100), while we continue accumulating material for those species for which we have less (ca. 100). This material is presently lodged in the collection of the Wildlife Heritage Trust of Sri Lanka (WHT).
The need to describe a large number of hitherto undescribed species discovered in the survey makes it imperative that all the available type material relating to the Amphibia of Sri Lanka and southern India be examined. This we have already commenced doing, working with the collections of the Natural History Museum, London, U.K.; Academy of Natural Sciences, Philadelphia, U.S.A.; and Zoological Survey of India, Southern Regional Station, Chennai. Examination of the remaining material, at Naturhistorisches Museum, Basel, Switzerland; Universität Humboldt Zoologisches Museum, Berlin, Germany; and Naturhistorisches Museum, Vienna, Austria, is expected to be completed by early 1999.
We have also commenced a separate project to accumulate a library of anuran vocalisations, and to develop new techniques for analysing and characterising calls. Whereas conventional sonograms offer a useful means of characterising time-varying spectra for long-duration ‘open ended’ signals (e.g. speech), they are handicapped by being two-dimensional and inconvenient to quantify. Several elegant techniques offer themselves however, for characterising and quantifying repetitive, short-duration signals such as amphibian vocalisations. We have with significant success applied techniques such as digital pre-emphasis filtering, fast Fourier transform (FFT) and joint time-frequency analysis (JTFA) to anuran vocalisations, obtaining useful suites of frequency– and time-domain characters. Three-dimensional (time, frequency, amplitude) surface-plot graphs too, offer much promise in representing amphibian calls. These characterisations are more intuitively recognisable and therefore more readily diagnosed than those obtained by conventional sonography.
In addition to diagnosis by conventional morphometric analysis and vocal characterisation, we decided also to test our ‘species concept’ at the molecular level. Tissues from multiple specimens of what we considered to be distinct species from restricted localities (e.g. a 100x100m plot) were subjected to mtDNA analysis (work in progress with J. Schulte), with very encouraging results.
Taxonomic results will be published primarily through separate revisions for the genera of amphibians we presently recognise from Sri Lanka: Philautus Gistel, 1848; Polypedates Tschudi, 1838; Rhacophorus Kuhl & van Hasselt, 1822; and Theloderma Tschudi, 1838. While we recognise several informal groupings within these genera based on synapomorphies, we do not intend investigating problems at generic and suprageneric level because we lack funds and representative material from other parts of the Old World. We intend to publish treatments similar to that of Dutta & Manamendra-Arachchi (1996), with unambiguous field-level diagnoses, illustrated keys, concise descriptions accompanied by clear colour photographs, and accurate distribution data for all the species. Our aim will be primarily to focus attention on the unique diversity of Sri Lanka’s amphibian fauna, and to make names available for hitherto undescribed species, enabling further study of their biology, especially where relevant to conservation.
Plates 1-4 show a representative sample of photographs of living examples of previously undescribed rhacophorids from Sri Lanka, which we are now in the process of describing.
The examination of type specimens has also served to expose several problems which require resolution. We find that many species names in use are in fact junior subjective synonyms; in some, syntype series comprise several (up to six) species; in others, the types have been lost. In order to stabilise species-group nomenclature therefore, it is necessary to designate lectotypes and neotypes in many cases, and also to decide which, if any, species known only from museum specimens should be described and named.
Table 1 presents the gross distribution of the Sri Lankan Amphibia obtained in the WWF-WHT survey of 1993-98, based on four widely-accepted regions (Senanayake et al., 1977; Ashton & Gunatilleke, 1987; Wijesinghe et al., 1993): dry zone, wet zone, montane zone (>500 m), and Knuckles hills.
This new assessment of the fauna suggests that Sri Lanka is one of the amphibian hotspots of the world (see Table 2), with the highest density of species per unit area (approx. 3.9 species per 1,000 km2). Given its size, and especially the size of its wet zone (approx. 15,000 km2: Ashton & Gunatilleke, 1987), where much of the amphibian diversity and almost all the amphibian endemicity is concentrated, the diversity of the island’s amphibian fauna is remarkable.
Table 2. Species diversity of Amphibia in selected ‘megadiversity’ countries of the world. (Source: W.E. Duellman, in Mittermeier et al., 1992; Janzen,1983.)
Country Total no. of Species density
amphibian spp. 1,000km-2
Brazil 516 0.06
India 182 0.06
Zaire 216 0.09
Indonesia 270 0.13
Venezuela 197 0.22
Colombia 407 0.36
Ecuador 358 1.3
Costa Rica 140 2.75
Sri Lanka ca. 250 3.9
The preponderance of arboreal species (Rhacophoridae) among the Sri Lankan Anura is unusual even by the standards of the known fauna. When the rhacophorid species presently being described by us are included, the Old World tree frogs of Sri Lanka will total rather more than 85% of the island’s anuran fauna. This diversity is high, compared to other regions for which the Rhacophoridae have been reviewed: India has 56 rhacophorid species (Dutta, 1997); Nepal, 7 (Anders et al., 1998; Shah, 1995); Bangladesh, 4 (Khan, 1996); Borneo, 21 (Inger & Stuebing, 1997); China, 43 (Zhao & Adler, 1993); Japan, 8 (Sengoku et al., 1996); west Africa, 61 and east Africa, 87 (Schiøtz, 1967; 1975).
We feel that the reason so much of the Sri Lankan amphibian fauna has remained cryptic for so long is because relatively little exploration has been done in the forest layers above human eye level (say 2m). (However, where surveys of rainforest canopy faunas have been made elsewhere, enormous increments to known diversity have resulted, especially among arthropods (Stork et al., 1997)). Unfortunately, no estimates of canopy faunas have yet been made in Sri Lanka; when such studies are made, they may shed light on the high diversity observed among the amphibians. This is particularly relevant because arthropods are the primary prey group for arboreal amphibians, and we speculate that their diversity could reflect also on the diversity of their predators.
It appears that ours has been the first systematic survey of the amphibian fauna of Sri Lanka’s remaining rainforest habitats. It is largely this that accounts for the discovery of a plethora of ‘new’ species. Perhaps equally importantly, we made a conscious effort to extend our survey as far as possible above ground level and into the canopy.
The present accretion of species to the Amphibian fauna, while on a much larger scale, is consistent with the results of other systematic faunal surveys we (WHT) have conducted during the past decade (Fig. 2). This work has served to increment the primary freshwater fish fauna by 13 species (23%) (Pethiyagoda, 1991, 1994; Pethiyagoda, work in progr.); the freshwater crab fauna by ca. 50 species (>300%) (Ng, 1994a; 1994b; Ming, 1998; Bahir, 1998; Bahir, work in progr.); and the agamid lizards by 2 species (15%) (Pethiyagoda & Manamendra-Arachchi, 1998). Work in progress by ourselves suggests that significant discoveries can be expected also among the lizards (Gekkonidae, Scincidae) and small mammals (Soricidae and Muridae).
We also note that a feature remarkable among the Sri Lankan Rhacophoridae is the exceedingly small range of distribution of many species, often less than 0.5 km2. The majority of Sri Lankan rhacophorids belong to the genus Philautus, and Das (in litt.) suggests that the high diversity observed might be in part attributable to their reproductive mode (direct development), which probably restricts their dispersion, unlike in species with aquatic eggs or larvae, which could disperse with flooding or flowing water (high diversity and local endemicity are also observed in the Neotropical frogs of the genus Eleutherodactylus (Leptodactylidae), many of which breed in phytothelms).
Except for Haly (1886), hardly any distribution data are available for the Sri Lankan Amphibia prior to Kirtisinghe (1957), most taxonomic descriptions having merely given the type locality as ‘Ceylon’. Although both these authors provided distribution data for most species they recognised, many of their identifications were clearly based on composite ‘species’ (Dutta & Manamendra-Arachchi, 1996), and cannot be verified as there is no record of the material examined by them. Senanayake et al. (1977) for the first time analysed the distribution of Amphibia (and other taxa) in Sri Lanka, referring however, only to 16 endemic species they recognised. Although they mentioned that the methods on which their taxonomic decisions were based would be described elsewhere, we are not aware of any such subsequent publication by them and cannot therefore directly compare their data with ours (again, the material examined is not specified).
Adams (1929) and Wadia (1941; 1945) had divided Sri Lanka’s topography into three loosely-defined plains of erosion (= peneplains), a scheme Senanayake et al. (1977) followed in their biogeographic analysis (see Gaussen et al. (1968) and Domroes (1998) for a discussion of Sri Lanka’s climatic zones). Ashton & Gunatilleke (1987) recognised 15 floristic regions in the island, while Wijesinghe et al. (1993) divided the island into six bioclimatic zones.
Excluding the Rhacophoridae, the dry zone, which extends over approximately 65% of the island’s land area, contains both the fewest number of species (15) and endemics (2). The montane zone, on the other hand, is the smallest (in terms of area of remaining natural habitat) but contains the largest number of both species (18) and endemics (13). When the Rhacophoridae are included, it is the higher part of the central massif that contains both the highest number of species (64) and endemics (92). This is also the smallest of our four regions, and even here the area of natural forest cover is only ca. 92,000 ha, i.e. 1.4% of the island’s land area (Weerakoon, pers. comm.).
The lowlands of both the dry and the wet zones contain only 2 widely-distributed rhacophorid species, Polypedates cruciger and P. cf. maculatus, although small pockets of moist habitat within the dry zone (e.g. Monaragala and possibly Ritigala) each contain rhacophorid species restricted to them.
The faunas of each of the four regions identified here is characteristic, with many species found in one being absent in the others. Weed species such as Bufo melanostictus, Euphlyctis cyanophlyctis and Limnonectes limnocharis however, are common to all zones. Of the species shared also with southern India, three (Uperodon systoma, Hoplobatrachus tigerinus and Tomopterna breviceps) are restricted to the dry zone. All but a handful of rhacophorid species appear to have extremely small ranges of distribution, often less than 0.5 km2.
Our results also bear out Crusz’s (1973) assertion that the montane zone represents the most conservative element in Sri Lanka’s endemic fauna. As is the case with the other vertebrate groups, the amphibian fauna of the island too, separates into two broad categories: a generalised, depauperate and widely-distributed low-country fauna including mostly species shared also with southern India; and a moist-forest, montane fauna that is more restricted in distribution but more diverse (Blandford, 1901; Senanayake et al., 1977; Erdelen, 1989; Gans, 1990; Pethiyagoda, 1991; Das, 1996).
We speculate that as more distribution data become available, correlations will become apparent between Ashton & Gunatilleke’s (1987) 15 floristic regions and amphibian distributions. While we have not yet observed significant differences in the amphibian faunas between some of their floristic regions (e.g. 2, 3, 4), others clearly contain distinctive suites of amphibian species (e.g. 5, 6, 7 and 13-15). Given the highly localised and ‘pocketed’ distributions of the vast majority of Rhacophoridae in Sri Lanka (Table 1), it has to be noted that no regional analysis is meaningful for this fauna at the species level based on the available data. Once synapomorphies are deduced and the phylogeny of the species is better understood, it is possible that useful biogeographic patterns will emerge.
Das (1996) points out that the savannah-type vegetation of Sri Lanka’s northern dry zone has perhaps been a more effective barrier to the migration of reptile species from the mainland than the shallow stretch of sea that separates southern India from Sri Lanka, which has been intermittently spanned by a continental land bridge until recently (see below). This appears to be the case also with the amphibians, for only two endemic amphibian species are found generally distributed in the dry zone, and even then only in relatively moist habitats within it. The other amphibian species recorded from the dry zone are also shared with southern India.
The history of sea-level fluctuation suggests that the most recent separation between Sri Lanka and India took place only in the late Pleistocene (Jacob, 1949; McKerrow & Scotese, 1990; Graedel & Crutzen, 1995) and it is therefore perhaps to be expected that little morphological differentiation would have occurred between the immigrant fauna of the most recent invasion and the mainland populations. Morgan-Davies (1958a,b), Kirtisinghe (1957) and Boulenger (1920) among others have recognised subspecies based on slight differences observed between Sri Lankan populations and their Indian counterparts. We do not comment on these observations as we ourselves have not yet subjected specimens from the two populations to careful comparison (work in progress).
While it is tempting to make biogeographic analyses of the Sri Lankan amphibian fauna in the context of the Asian or Indian faunas, we have refrained from doing so because we feel that the systematics of the taxa in question are far from sufficiently well developed (or are the subject of contention), particularly at the generic level. In any event, much remains to be done on the systematics and distribution of the amphibian fauna of peninsular India. While it is true that in recent years there has been a renewed interest in the Amphibia of south Asia, it is also true that this is the group least well researched of all the vertebrate groups in the region. No meaningful biogeographic analysis is possible in the absence of reliable and generalised taxonomic studies of the fauna of the entire south Asian region, a factor evidently overlooked in the only attempt at an analysis of which we are aware (Tiwari, 1991).
Wheeler (1995) and Kottelat (1995) warn against biogeographic conclusions drawn from samples in which the systematics are poorly worked out. The alleged similarities between the Sri Lankan fauna and the Madagascan and Malayan faunas should be viewed with caution not only until the status of Sri Lankan vertebrate systematics is improved, but also that of the other regions concerned. For example, several systematic criteria from which Senanayake (1990) drew biogeographic conclusions have now been demonstrated to be incorrect: the cyprinid fish genus Horadandia is not endemic to Sri Lanka (Rema Devi & Menon, 1992); the belontiid fish genus Macropodus does not occur either in Sri Lanka or in India (Liem, 1963); and the agamid lizard genus Cophotis is not common to Sri Lanka and Sumatra (Moody, 1980; Manthey & Grossmann, 1997).
No data are yet available on population trends of Sri Lankan amphibians, although monitoring programmes are now in place (A. de Silva, pers. comm.). However, the present results suggest that almost all the endemic species are dependent on moist, near closed-canopy forest habitats. Further, many of them were found to comprise small, localised populations (whether localisation was caused by habitat fragmentation or for other reasons is not yet known).
Localised faunas run a higher risk of falling prey to catastrophic events such as severe droughts and forest fires than more widely distributed ones (Diamond, 1975). For this reason, it is alarming that (as at 1983) only 9.1% of Sri Lanka’s lowland wet zone was forested, and of that forest only 22% was considered still undisturbed (Gunatilleke & Gunatilleke, 1983).
The position as regards the highlands of the central massif is even more critical. Habitat degradation here has been even more severe (Pethiyagoda, 1994), and an increase in temperature and decline in precipitation (as much as 25% during the past century) (Abeywickrema et al., 1991; Schaefer, 1998) can have only worsened an already bad situation. The widespread application of pesticides and herbicides (ca. 4,250 MT per year on an area of some 200,000 ha: Pethiyagoda, 1994) in the tea plantations that now occupy all but the highest peaks poses a further threat to the amphibian fauna, especially directly to aquatic larvae, and indirectly to adults, by drastically reducing the availability of arthropod prey.
Of particular concern are the results of a recent meteorological survey (Gunawardena et al., 1998) which showed pH values as low as 3.88 for mist passing through the canopy of tropical montane cloud forests (TMCF) in the Horton Plains National Park (alt. ca. 2,000m). Sri Lanka’s TMCFs contain a remarkably high floral diversity (Werner, 1995) and ca. 50 species of amphibians, almost all of them local.
Pethiyagoda (1994) observed that Sri Lanka’s protected area network (PAN), which is mostly centred around the large-mammal fauna of the lowland dry zone, contributed little to the conservation of indigenous freshwater fishes. This is even more the case with amphibians, especially as the zones with the highest amphibian diversities (wet and montane) are also poorly covered by the PAN.
As shown above, the south-western wet zone, the central massif and the Knuckles Range have the characteristics of land-islands (sensu MacArthur & Wilson, 1963, 1967; Diamond, 1975) and the continuing fragmentation of this habitat for human activity could have a serious impact on the amphibian fauna they contain.
The large number of small lowland wet-zone forest reserves (<5km2), given their high amphibian species diversity, and separated as they are from each other by large tracts of cultivated land, would be interesting areas in which to study the dynamics of amphibian populations (these compare with Diamond’s (1975) ‘archipelagos’). MacArthur and Wilson (1967) and Diamond (1975) predict that while species tolerant of the ‘barrier’ habitat would maintain or increase their relative dominance, species unable to do so would decrease (i.e. have a higher extinction rate) as a function of the area of the ‘island’, and inversely with the distance from the next nearest island. It is also not yet known whether species such as Bufo melanostictus, Polypedates cruciger and P. cf. maculatus, which are associated mainly with human-modified habitats, have expanded their previous (‘natural’) ranges and established a higher relative dominance following habitat disturbance.
Such a study would be of even greater importance given the fact that ca. 200 hitherto undescribed species were recorded in the course of the present survey. The vast majority of these species are restricted to small areas of the wet zone. This further reinforces the argument that special conservation measures are necessary in these areas. The discovery of several ‘new’ species from the Knuckles Range also supports our recognition of that region as a distinct biogeographic zone (K).
The most immediate threats to the Sri Lankan amphibian fauna would appear to be the loss and fragmentation of natural habitats (see also Wijeyamohan et al., 1994). It is clear from examination of specimens collected in the 19th century and preserved in European museums (many of them undescribed and unnamed) that widespread extinctions have occurred among Sri Lanka’s Rhacophoridae, a unique element of in the island’s biodiversity.
Since Honegger (1981) recorded the first post-1600 AD amphibian extinctions, declining amphibian populations world wide have become the subject of growing concern (e.g. Blaustein & Wake, 1995; Griffiths & Beebe, 1992). Given the highly localised populations of many rhacophorid species in Sri Lanka, the loss of more than 80% of the island’s biodiversity-rich wet-zone forests during the past 150 years (Gunatilleke & Gunatilleke, 1983) suggests that part of the anuran diversity too, may have been lost. This is corroborated by the large (>15) number of species known from 19th century museum specimens alone (unknown from living populations), which suggests that widespread extinctions have taken place in the Sri Lankan amphibian fauna.
Biodiversity among the Sri Lankan Amphibia is clearly much higher than was previously suspected, and it is expected that on-going revisional work on the systematics of this fauna will see an increase in the number of recognised species, taking the island’s total to ca. 250 (it being noted that Kirtisinghe (1957) recognised only 37, while Dutta & Manamendra-Arachchi (1996) recognised 53). Given this situation, it is imperative that the remaining extent of natural forest in Sri Lanka should be conserved at least until more complete exploration can take place.
Even prior to the discovery of this ‘new’ fauna, considerable attention had been paid to the conservation of Sri Lanka’s Amphibia. Regulations promulgated in 1993 under the Fauna & Flora Protection Ordinance gave absolute protection to almost all the endemic species then recognised. Alongside this, several individuals and NGOs have devoted considerable attention to the conservation of the island’s Amphibia, most notably Anslem de Silva and the Amphibian & Reptile Research Organisation (ARROS).
Given the explosion in species diversity now being recorded, it is clear that Sri Lanka is one of the world’s hotspots for amphibian biodiversity. The level of speciation seen in the island is rare among vertebrates, and is to us reminiscent of the radiation of cichlid fishes in the African lakes Malawi, Tanganyika and Victoria (Lake Victoria alone has upwards of 500 cichlid species which are thought to have evolved during the past 12,400 years from one or a few closely-related ancestors (Meyer et al., 1990; Johnson et al., 1996; Seehausen et al., 1998)).
We are grateful to Anslem de Silva (ARROS) for inviting our views on the conservation of Sri Lanka’s amphibian fauna. We thank Mangala de Silva (University of Peradeniya) for initiating the WHT Amphibian Survey in 1993 by making available to us an award from the Small Grants Scheme of WWF International for Conservation-Oriented Research in Sri Lanka; from 1995 onwards the WHT Survey has been funded by WHT Publications (Pvt.) Ltd. We thank Mohommed M. Bahir and Sudath Nanayakkara (WHT) for their field work, upon which this study is based. We also thank Indraneil Das (Universiti Malaysia Sarawak) for visiting Sri Lanka at our invitation to help us devise sampling methods and also sharing with us his knowledge of the Asian Amphibia. We are grateful to him and Devaka Weerakoon (University of Colombo) for commenting on this manuscript and helping us to improve it in many ways. Finally we thank Andreas Nöllert (Jena, Germany) for permitting us to use many of his photographs and joining us in the field.
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