Djoko T. Iskandar

An Ancient Origin for the Enigmatic Flat-Headed Frogs (Bombinatoridae: Barbourula) from the Islands of Southeast Asia

Background The complex history of Southeast Asian islands has long been of interest to biogeographers. Dispersal and vicariance events in the Pleistocene have received the most attention, though recent studies suggest a potentially more ancient history to components of the terrestrial fauna. Among this fauna is the enigmatic archaeobatrachian frog genus Barbourula, which only occurs on the islands of Borneo and Palawan. We utilize this lineage to gain unique insight into the temporal history of lineage diversification in Southeast Asian islands. Methodology/Principal Findings Using mitochondrial and nuclear genetic data, multiple fossil calibration points, and likelihood and Bayesian methods, we estimate phylogenetic relationships and divergence times for Barbourula. We determine the sensitivity of focal divergence times to specific calibration points by jackknife approach in which each calibration point is excluded from analysis. We find that relevant divergence time estimates are robust to the exclusion of specific calibration points. Barbourula is recovered as a monophyletic lineage nested within a monophyletic Costata. Barbourula diverged from its sister taxon Bombina in the Paleogene and the two species of Barbourula diverged in the Late Miocene. Conclusions/Significance The divergences within Barbourula and between it and Bombina are surprisingly old and represent the oldest estimates for a cladogenetic event resulting in living taxa endemic to Southeast Asian islands. Moreover, these divergence time estimates are consistent with a new biogeographic scenario: the Palawan Ark Hypothesis. We suggest that components of Palawans terrestrial fauna might have “rafted” on emergent portions of the North Palawan Block during its migration from the Asian mainland to its present-day position near Borneo. Further, dispersal from Palawan to Borneo (rather than Borneo to Palawan) may explain the current day disjunct distribution of this ancient lineage.

Adaptive Radiation and Ecological Opportunity in Sulawesi and Philippine Fanged Frog (Limnonectes) Communities

Because island communities are derived from mainland communities, they are often less diverse by comparison. However, reduced complexity of island communities can also present ecological opportunities. For example, amphibian diversity on Sulawesi Island is lower than it is in the Philippines, but Sulawesi supports a surprising diversity of Sulawesi fanged frogs (Limnonectes). Here we examine molecular, morphological, and geographical variation of fanged frogs from these two regions. Using genealogical concordance, morphology, and a Bayesian approach to species delimitation, we identified 13 species on Sulawesi, only four of which have been previously described. After evolutionary history is accounted for, a model with multiple body size optima in sympatric species is favored over a “random-walk” model of body size evolution. Additionally, morphological variation is higher among sympatric than nonsympatric species on Sulawesi but not in the Philippines. These findings suggest that adaptive radiation of fanged frogs on Sulawesi was driven by natural selection to infiltrate ecological niches occupied by other frog lineages in the Philippines. This supports a role of ecological opportunity in community assembly: diversification in mature communities, such as the Philippines, is limited by a dearth of unoccupied ecological niches. On Sulawesi, evolutionary novelties originated in a predictable and replicated fashion in response to opportunities presented by a depauperate ancestral community.

Phylogeography and historical demography of Polypedates leucomystax in the islands of Indonesia and the Philippines: evidence for recent human-mediated range expansion?

Southeast Asias widespread species offer unique opportunities to explore the effects of geographical barriers to dispersal on patterns of vertebrate lineage diversification. We analyzed mitochondrial gene sequences (16S rDNA) from a geographically widespread sample of 266 Southeast Asian tree frogs, including 244 individuals of Polypedates leucomystax and its close relatives. Our expectation was that lineages on island archipelagos would exhibit more substantial geographic structure, corresponding to the geological history of terrestrial connectivity in this region, compared to the Asian mainland. Contrary to predictions, we found evidence of numerous highly divergent lineages from a limited area on the Asian mainland, but fewer lineages with shallower divergences throughout oceanic islands of the Philippines and Indonesia. Surprisingly and in numerous instances, lineages in the archipelagos span distinct biogeographical provinces. Phylogeographic analyses identified four major haplotype clades; summary statistics, mismatch distributions, and Bayesian coalescent inference of demography provide support for recent range expansion, population growth, and/or admixture in the Philippine and some Sulawesi populations. We speculate that the current range of P. leucomystax in Southeast Asia is much larger now than in the recent past. Conversion of forested areas to monoculture agriculture and transportation of agricultural products between islands may have facilitated unprecedented population and range expansion in P. leucomystax throughout thousands of islands in the Philippine and Indonesian archipelagos.

Effects of Land-Use Change on Community Composition of Tropical Amphibians and Reptiles in Sulawesi, Indonesia

Little is known about the effects of anthropogenic land-use change on the amphibians and reptiles of the biodiverse tropical forests of Southeast Asia. We studied a land-use modification gradient stretching from primary forest, secondary forest, natural-shade cacao agroforest, planted-shade cacao agroforest to open areas in central Sulawesi, Indonesia. We determined species richness, abundance, turnover, and community composition in all habitat types and related these to environmental correlates, such as canopy heterogeneity and thickness of leaf litter. Amphibian species richness decreased systematically along the land-use modification gradient, but reptile richness and abundance peaked in natural-shade cacao agroforests. Species richness and abundance patterns across the disturbance gradient were best explained by canopy cover and leaf-litter thickness in amphibians and by canopy heterogeneity and cover in reptiles. Amphibians were more severely affected by forest disturbance in Sulawesi than reptiles. Heterogeneous canopy cover and thick leaf litter should be maintained in cacao plantations to facilitate the conservation value for both groups. For long-term and sustainable use of plantations, pruned shade trees should be permanently kept to allow rejuvenation of cacao and, thus, to prevent repeated forest encroachment.

Impending conservation crisis for Southeast Asian amphibians

With an understudied amphibian fauna, the highest deforestation rate on the planet and high harvesting pressures, Southeast Asian amphibians are facing a conservation crisis. Owing to the overriding threat of habitat loss, the most critical conservation action required is the identification and strict protection of habitat assessed as having high amphibian species diversity and/or representing distinctive regional amphibian faunas. Long-term population monitoring, enhanced survey efforts, collection of basic biological and ecological information, continued taxonomic research and evaluation of the impact of commercial trade for food, medicine and pets are also needed. Strong involvement of regional stakeholders, students and professionals is essential to accomplish these actions.

Electromorphs and Phylogeny in Muroid Rodents

How do we infer phylogenetic relationships from electrophoretic studies? What is the value of such phylogenies? What can we infer from these phylogenies about the processes of divergence? These are the questions that we have tried to answer empirically by analyzing genetic variability in 76 taxa of rodents, most of them being muroids. Our approach is comparable to that of Patton and Avise (1983), and is aimed at comparing the values of quantitative and qualitative analyses of electrophoretic data. However, their material and ours differ in evolutionary patterns, and the results differ accordingly in some respects.

Habitat use by stream-breeding frogs in south-east Sulawesi, with some preliminary observations on community organization

The habitat associations of stream-breeding frogs were examined along a series of stream transects on Buton Island in south-east Sulawesi, Indonesia. Of the eight frog species located along streams, four were observed breeding in stream habitats. We examined spatial habitat partitioning among these species. Three of the four species were found to be associated with a non-random selection of the available perch sites. Strong partitioning between species in habitat associations was found; partitioning of the available habitat space was primarily associated with differences in proximity to stream features, and in the height of perch sites. General observations indicated that oviposition sites of most species were associated with the microhabitats in which the adult frogs were found. All four stream-breeding species appear to have synchronous breeding phenologies and the spatial relationships of these species within the habitat space appear to reflect partitioning of calling sites and oviposition sites. The stream-breeding frog community in this region of Sulawesi has much lower species richness and less specialized habitat use compared with other tropical stream-breeding frog communities in the region. Abstrakt (Bahasa Indonesia): Asosiasi habitat antara katak dengan lingkungan diteliti pada jenis-jenis amfibi riparia sepanjang transek sungai di pulau Buton, Sulawesi Tenggara, Indonesia. Dari delapan jenis katak yang ditemukan sepanjang sungai, empat jenis di antaranya berkembang biak pada waktu penelitian ini berlangsung. Telah diamati pula pola pemisahan habitat antar jenis-jenis yang diamati. Tiga dari empat jenis ditemukan secara acak pada semua macam tempat hinggap. Pemisahan habitat antar jenis mempunyai korekasi yang sangat kuat terhadap jarak dari sungai dan ketinggian tempat hinggap. Walaupun demikian tempat peneluran sangat erat berasosiasi dengan iklim mikro masing-masing jenis. Keempat jenis yang diamati, masing-masing mempunyai musim peneluran yang relatif sinkron dan mencerminkan pemisahan habitat sesuai dengan tempat melakukan panggilan kawin dan tempat bertelur. Pola yang diamati dibandingkan pula dengan data yang terdapat dari Borneo. Disimpulkan bahwa katak yang berkembang biak di sungai-sungai di Buton, Sulawesi mempunyai keanekaragaman jenis yang rendah dan juga relatif tidak terspesialisasi dalam penggunaan habitat.

Nest Site Selection, Larval Hatching, and Advertisement Calls, of Rana arathooni from Southwestern Sulawesi (Celebes) Island, Indonesia

We provide information on the basic reproductive ecology, chorusing behaviors, and adver- tisement calls of Rana arathooni from southwestern Sulawesi, Indonesia. Nest sites in leaf litter and wet detritus are congregated on the steep banks of large, rapidly flowing mountain streams. When disturbed, hatchlings break free of the egg capsule and tumble down rocks or slide down muddy banks to the water below. The combination of choice of steep banks as nest sites and unusual behavior of the larvae suggests an unusual predator escape strategy. Larvae may avoid aquatic predators by extending development period on land but can rapidly evade predation and escape to the water below when threatened by terrestrial predators. Males form small choruses, with most individuals calling from under leaf litter and within the nest. The advertisement call of Rana arathooni is unusually complex and invariant and call structure is unique in that modulation of amplitude and frequency are inversely correlated.

A novel reproductive mode in frogs: a new species of fanged frog with internal fertilization and birth of tadpoles.

We describe a new species of fanged frog (Limnonectes larvaepartus) that is unique among anurans in having both internal fertilization and birth of tadpoles. The new species is endemic to Sulawesi Island, Indonesia. This is the fourth valid species of Limnonectes described from Sulawesi despite that the radiation includes at least 15 species and possibly many more. Fewer than a dozen of the 6455 species of frogs in the world are known to have internal fertilization, and of these, all but the new species either deposit fertilized eggs or give birth to froglets.

Genetic Divergence and Evolutionary Relationship in Fejervarya cancrivora from Indonesia and Other Asian Countries Inferred from Allozyme and MtDNA Sequence Analyses

To elucidate genetic divergence and evolutionary relationship in Fejervarya cancrivora from Indonesia and other Asian countries, allozyme and molecular analyses were carried out using 131 frogs collected from 24 populations in Indonesia, Thailand, Bangladesh, Malaysia, and the Philippines. In the allozymic survey, seventeen enzymatic loci were examined for 92 frogs from eight representative localities. The results showed that F. cancrivora is subdivided into two main groups, the mangrove type and the large- plus Pelabuhan ratu types. The average Nels genetic distance between the two groups was 0.535. Molecular phylogenetic trees based on nucleotide sequences of the 16S rRNA and Cyt b genes and constructed with the ML, MP, NJ, and BI methods also showed that the individuals of F. cancrivora analyzed comprised two clades, the mangrove type and the large plus Pelabuhan ratu / Sulawesi types, the latter further split into two subclades, the large type and the Pelabuhan ratu / Sulawesi type. The geographical distribution of individuals of the three F. cancrivora types was examined. Ten Individuals from Bangladesh, Thailand, and the Philippines represented the mangrove type; 34 Individuals from Malaysia and Indonesia represented the large type; and 11 individuals from Indonesia represented the Pelabuhan ratu / Sulawesi type. Average sequence divergences among the three types were 5.78–10.22% for the 16S and 12.88–16.38% for Cyt b. Our results suggest that each of the three types can be regarded as a distinct species.