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The speciose genus Limnonectes exhibits a broad range of reproductive behavior and sizes at maturity. Two Southeast Asian species are near the low end of the size range and near one extreme of reproductive habits (their larvae are said to have direct development). Limnonectes hascheanus and L. limborgi are small, having a maximum snout-vent length of less than 40 mm, with reduced webbing and females with enlarged, pigment-less ova. The distinctions between these species have not been clear and L. limborgi has been treated as a junior synonym of L. hascheanus. We show that these two nominal species differ in size, development of odontoids in adult males, in extent of webbing, and mitochondrial and nuclear DNA sequence data. Their geographic ranges scarcely overlap, with L. hascheanus apparently being restricted to the southern part of the Malay Peninsula and L. limborgi being distributed in a large arc from southern Myanmar northward to northern Thailand and Laos before curving around to central Laos, northeastern Thailand, Cambodia, and southern Vietnam. Because the holotype of L. limborgi appears to have been lost, we describe a neotype, using a specimen from southern Myanmar studied by Boulenger.

Aim We seek to relate the present distributions of frogs and snakes of Sundaland and the known geological history of the region. Location From the Isthmus of Kra to Java and Sulawesi. Methods We relate the known ecological requirements of frogs and snakes to their geographical distributions and information on geological history. Results Microhabitat requirements for larvae of various groups of frogs are strong predictors of the breadth of their geographical distributions. At the species level, the frog faunas of the Malay Peninsula and Sumatra are the most similar. The Sulawesi frog fauna, mainly derived from Sundaland lineages, shows almost no similarity to the other frog faunas at the species level. The ecological zones occupied by snake species show association with the breadth of their geographical distributions There are only minor differences among similarity ratios for the Malay Peninsula-Sumatran, Malay Peninsula-Borneo, and the Borneo-Sumatra pairs. The Sulawesi snake fauna has distinctly lower similarity with the faunas of the other areas. The similarity ratios between faunas are larger for snakes than for frogs. This difference between the two groups reflects the difference between them in ability to cross salt water barriers, frogs being extremely vulnerable to saline water. Also snakes may establish founder populations more easily as a single gravid female or one carrying stored sperm may introduce a clutch into previously unoccupied territory. Conclusions A few species of frogs and snakes probably reached their present, almost ubiquitous distributions in Sundaland within the last few millenia or even more recently. Other widely distributed species may have been able to disperse among land masses within Sundaland until 10,000-17,000 yr BP; the frogs of this category are common in environments that almost certainly characterized the exposed area of the South China Sea. The distributions of other frogs common to the Malay Peninsula, Sumatra and Borneo probably antedate the Pleistocene, as their larval development requires hilly topography which was not generally available on the Pleistocene-exposed bed of the South China Sea. Many of the endemic species of frogs and snakes probably owe their origins to events of the Miocene or earlier. Several genera of frogs and one genus of snakes have undergone extensive speciation and display considerable sympatry and elevational stratification of species, suggesting their present distributions are the result of events as old as the Eocene. We have cast these conclusions in the form of hypotheses that can be tested mainly by the use of molecular genetics, but in some cases, by additional field sampling.

Using data for 25,780 species categorized on the International Union for Conservation of Nature Red List, we present an assessment of the status of the world's vertebrates. One-fifth of species are classified as Threatened, and we show that this figure is increasing: On average, 52 species of mammals, birds, and amphibians move one category closer to extinction each year. However, this overall pattern conceals the impact of conservation successes, and we show that the rate of deterioration would have been at least one-fifth again as much in the absence of these. Nonetheless, current conservation efforts remain insufficient to offset the main drivers of biodiversity loss in these groups: agricultural expansion, logging, overexploitation, and invasive alien species.

In adjacent areas of broadleaf evergreen forest, deciduous dipterocarp forest, and agricultural land in northeastern Thailand, >4,000 individuals of 105 species of reptiles and amphibians were systematically collected. The position of capture of each individual was recorded in terms of a complex microhabitat code. The 3 environments differ substantially in pattern of human disturbance, in vegetation structure, and in range and predictability of temperature and total evaporation, the evergreen forest having the most buffered climate near the ground. Of the 3 environments studied, the evergreen forest has the most diverse and distinct herpetofauna, and the largest percentage of autochthonous species. The evergreen forest community has more southern or tropical affinities, while the deciduous forest community has more northern affinities. Analysis of the use of microhabitat categories by coexisting species reveals significant differences, even among the most similar sets of species. Differences in species richness among the three communities are not explained by differences in microhabitat diversity, mean niche breadth, or mean niche overlap. However, an ith nearest neighbor analysis of the dispersion of niche centers in resource space reveals closer packing and larger and more distinct guilds in the evergreen forest: the environment richest in species and the most predictable in climate. Both a graphical treatment and an analysis of sets of species grouped a priori according to their general natural history confirm the existence of larger and significantly tighter guilds in the evergreen forest. It is suggested that unpredictable environments tend to prevent the formation of distinct guilds, while the greater species richness of more predictable environments may be a function of guild formation.

1. Along streams draining hilly rain forest in Sarawak and having widths of 10-70 ft (3-21 m), we find an assemblage of roughly twenty-five species of frogs either restricted to the riparian habitat for all postmetamorphic functions or tied to streams for breeding activities. 2. Nine species dominate the communities in the four streams having widths in excess of 20 ft (6 m). These nine species may be grouped into four main ecological types: large, strictly terrestrial, weakly clustered, riparian species; small to large, partially arboreal, weakly clustered, riparian species; small, partially arboreal, strongly clustered, riparian species; and one large, mainly arboreal, strongly clustered species that is not restricted to stream banks. 3. Phylogenetically related species tend to be associated in the same ecological types which leads to the conclusion that historical factors have been more important than contemporary ecological forces in the niche distribution of these species. 4. Equitability values based on the collections of the six study streams show little variation, which suggests similarity in community organization. Closer inspection of the relative abundances of ecological types on the several streams reveals a basic difference between the two smaller streams and the other four. Equitability values, therefore, provide a refined measure of similarity in community structure in detail only if examination of ecological types and their relative proportions indicates rough similarity at a coarse scale.

Intensive collecting carried out over an entire year in 20 square miles of lowland rain forest in Borneo yielded 72 species of amphibians and reptiles considered to be regular inhabitants of the forest floor. Thirty-eight of these species, plus 12 that are \"refugees\" in the sense that they do not live primarily in this habitat, were collected in 402 quadrats randomly distributed over the forest floor. The average species diversity per individual was H' = 4.26 ± 0.21 bits, using Pielou's (1966a) method for estimating H' and its standard error from individual quadrats. This much diversity is equivalent to 28.3 hypothetical \"equilibrium\" species having relative abundances distributed according to the \"broken stick\" model of MacArthur (1957, 1960). The ratio of 28.3 to 84 (72 regular plus 12 refugee species) gives an \"equitability\" value (Lloyd and Ghelardi, 1964) of E = 0.34. Treating frogs, lizards, and \"snakes\" separately, we obtain diversity values of 3.30, 3.10, and 2.86 and equitability values of 0.47, 0.67, and 0.28 for the three groups, respectively. Although an equitability of E = 0.34 is well above the \"ecological minimum\" of E = 0.17 that would characterize 84 species having a lognormal distribution (Preston, 1962), it is surprisingly far below the \"ecological maximum\" of E = 1.0 that one would expect from the \"equilibrium\" community of a rain forest-a community rich in species, presumably having relatively constant, equable, predictable conditions for life. This leads us to re-examine the assumption that the rain forest floor environment is relatively constant and predictable. In respect of temperature it certainly is, but not so with rainfall. There is no dry season, but the spacing of heavy rainfalls (more than 1 inch in 24 hr) has an essentially random pattern. Rains of this intensity cause raging floods in the small streams in which many of the frog species breed. Conceivably this might often result in catastrophic mortality. The endless disturbance of intense rains may therefore prevent the community from achieving the theoretical equilibrium. Specimens obtained by general collecting were combined with those caught in the quadrats to form a total forest floor collection for this area of rain forest. Applying Pielou's (1967) method for partitioning diversity by taxonomic hierarchy, only a small part of the total species diversity (0.72 out of 4.65) is attributable to congeneric species living in the same habitat. This holds true also when frogs, lizards, and snakes are considered separately.

Males and females of four species of lizards from a Bornean rain forest appear to breed continuously through the year. Testes of these species, Cyrtodactylus malayanus, C. pubisulcus, Draco melanopogon, and Draco quinquefasciatus, produce sperm at all times. Production of eggs by the females shows no seasonal pattern. Females of six other species from the same area also appear to breed continuously. Clutch size in these rain forest species is distinctly smaller than that in lizards from the tropical parts of Asia having strongly marked dry seasons. The continuous reproductive patterns of the rain forest species probably increase interactions between species as temporal isolation is eliminated. Whatever effects these have on their community are not pulse—like, in contrast to the effects of lizards in seasonal climates. Year—round reproduction probably buffers population fluctuations and may be one of the factors contributing to the great diversity of rain forest faunas.

Two large samples of amphibians and reptiles from lowland primary rain forests in Borneo come from communities that appear to have densities similar to that of a Bornean community previously reported (Lloyd et al. 1968). To this group may be added a much smaller sample from a primary rain forest in peninsular Malaysia. Densities of nonriparian terrestrial frogs and lizards in these Indo-Malayan communities are about an order of magnitude smaller than those reported from lowland forests in Central America (Scott 1976). Indo-Malayan forests are peculiar among rain forests because of supraannual synchronized mast fruiting of dipterocarp trees that dominate them (Wood 1956; Ashton 1969). I suggest that this habit reduces the number of seed-eating insects and associated arthropod predators on the floor of these forests, thereby reducing the food supply of floor-dwelling frogs and lizards and acting to limit the populations of these animals below levels achieved in neotropical forests. Large samples of frogs and lizards obtained in two strongly seasonal forests in northeastern Thailand show that combined frog-plus-lizard densities in these two communities are very close to that measured in Borneo. Although both Thai forests are also dominated by dipterocarp species of trees, it is less clear that their seed production acts as a limiting factor. There is, however, one brief reference to mast fruiting in seasonal dipterocarp forests of Thailand. Both Thai communities differ from the Indo-Malayan ones in having much lower densities of frogs and much higher densities of lizards. If the combined density of these animals is limited by food supply in the Thai communities, reduction in the populations of frogs, which are strongly affected by a harsh seasonal climate, should lead to a counterbalancing increase in the numbers of terrestrial lizards. Terrestrial frogs in two disturbed forests in peninsular Malaysia seem to be three to four times more numerous than in Bornean and Malayan primary rain forests. This difference may reflect the seasonal limitation of those two samples, the abundance of species that might be called commensals of man, or some other unknown factor.

Interspecific competition is often advanced as an explanation for replacement of species by ecological counterparts. Where environments are stable, as in controlled laboratory experiments, interspecific competition usually leads to the extinction of one species. In a complex natural environment, fluctuations in physical and biotic factors may long delay competitive exclusion. The existence of three related species of frogs (genus Rama) confined to stream in tropical rain forest provided an opportunity to manipulate natural populations and thus to study the relation between overlap in niches and interspecific competition. A rain forest area was chosen because it lacks significant seasonal variation in rainfall, temperature, and photo—period and consequently prevents seasonal specialization of the fauna. These three species, R. blythi, R. ibanorum, and R. macrodon, proved to be very similar in habits. Rana blythi is larger than the other two and usually was found farther from the stream bed. Rana macrodon reaches sexual maturity faster than the others and R. ibanorum lays fewer eggs. Nonetheless it is clear that their niches overlap extensively. Populations of these frogs were studied on surveyed portions of three streams by mark and release techniques. Populations of R. blythi on one stream (Sungei Ensurai) and R. ibanorum on another (Sungei Sekentut) were initially much smaller than the respective populations on the other streams. Following removal of R. blythi from Sungei Sekentut and of R. ibanorum from Sungei Ensurai, leaving the populations on Sungei Serbong as controls, R. blythi on Sungei Ensurai appeared almost to double in numbers and to reach the population levels originally found on the other streams. Population estimates of R. ibanourm on Sungei Sekentut fluctuated, being larger at midyear; statistical support for this variation is weak. Rana macrodon seemed to quadruple its numbers on Sunge Sekentut. There is evidence that macrodon is in the process of invading this part of Borneo and may be doing so at the expense of R. ibanorum. Maximum population levels for the blythi and ibanorum may be fixed by intraspecific competition, which in turn may be responsible for maintaining the coexistence of these related species.