Harold K. Voris

High level of cryptic species diversity revealed by sympatric lineages of Southeast Asian forest frogs

Amphibians tend to exhibit conservative morphological evolution, and the application of molecular and bioacoustic tools in systematic studies have been effective at revealing morphologically ‘cryptic’ species within taxa that were previously considered to be a single species. We report molecular genetic findings on two forest-dwelling ranid frogs from localities across Southeast Asia, and show that sympatric evolutionary lineages of morphologically cryptic frogs are a common pattern. These findings imply that species diversity of Southeast Asian frogs remains significantly underestimated, and taken in concert with other molecular investigations, suggest there may not be any geographically widespread, forest-dwelling frog species in the region. Accurate assessments of diversity and distributions are needed to mitigate extinctions of evolutionary lineages in these threatened vertebrates.

Phylogeny, evolutionary history, and biogeography of Oriental-Australian rear-fanged water snakes (Colubroidea: Homalopsidae) inferred from mitochondrial and nuclear DNA sequences.

Homalopsid snakes are widely distributed throughout Southeast Asia and form the ecologically dominant component of the herpetofauna over much of their range. Although they are considered well differentiated from other colubrid lineages, several aspects of their radiation including within-family relationships, temporal patterns of species diversification, and biogeographic history remain under studied. We analyzed sequence data from four genes (three mitochondrial and one nuclear) for 22 species of the Homalopsidae to generate the most comprehensive phylogeny of the family to date. We also estimated divergence times within the family using a model of independent but log-normally distributed rates of evolution in conjunction with two external fossil calibrations. Using this chronogram, we inferred historical patterns of species diversification within the family. Finally, we used previously published sequence data for 172 snake species to test for the monophyly of the Homalopsidae. Phylogenetic analysis reveals strong support for homalopsid monophyly with an estimate age of the crown group of approximately 22 MYA. The family comprises three major clades which all originated 18-20 MY. Lineage through time plots reveal that homalopsids experienced a significantly higher rate of effective cladogenesis in their early history, consistent with a hypothesis of adaptive radiation. We discuss several Miocene and Pliocene paleogeographic factors that might underlie observed patterns of temporal diversification and biogeography.

Organization of a community of tadpoles in rain forest streams in Borneo

Samples of 29 distinct larval forms of anurans were collected in streams flowing through primary rain forest at Nanga Tekalit, Sarawak, at three periods spaced over 22 years. This assemblage of tadpoles lives in torrents, riffles, shingle areas, open pools, leaf drifts, protected side pools, potholes in rocky banks, bank seepages, and pools of small intermittent streams. Positive associations of species in types of microhabitats and co-occurrence within sites lead to recognition of four taxonomically heterogeneous groups: one concentrated in leaf drifts; one using riffles, shingle areas, and open pools; one concentrated in potholes; and one using side pools and potholes. Most pairs of larval forms having strong negative association are characterized by differences in morphology and feeding behaviour; they show little evidence of competitive relations. Between-sites variation in species composition differs among the types of microhabitats, leaf drifts showing the least amount of variation. Species composition within a site shows less change over intervals of 1-5 days than over intervals of 13-18 days. Variation in species composition is greater between sites than within sites over intervals of 9-31 days. Organization in this community seems to be effected by three factors: reproductive behaviour of adults and morphological and behavioural adaptations of tadpoles.

A comparison of amphibian communities through time and from place to place in Bornean forests

We sampled riparian frogs along 18 streams at eight localities in Borneo. At four of these sites we sampled during more than one year. Altogether 49 species were included in our study and total sample size was 13,249. We measured overlap in species occurrences and arrays of abundances within and among localities. Variation over the time span of our study was minor within communities. Overlaps between streams at a locality were generally higher than overlaps of pairs of streams from different localities. Environmental variation, particularly in stream width and gradient, had a clear effect on both intra-and inter-locality overlaps. Although rainfall varied between localities and within localities over time, that variation did not seem to affect overlaps among or within communities. Environmental factors did not account for all differences in overlaps between communities. Instead, regional processes, perhaps the timing of barriers or speciation events, appear to have been responsible for geographic restrictions of several species, leading to variation in overlap values.

Age of the Mangrove Crab Scylla serrata at Colonization by Stalked Barnacles of the Genus Octolasmis

Cyprid larvae of the lepadomorph Octolasmis colonize the gill chambers of the edible mangrove crab, Scylla serrata (Forskaal, 1755), sometimes in debilitating numbers. We set out to determine when, in the life cycle of the host, barnacle infestation begins. A total of 856 mangrove crabs, ranging in size from 10.9 to 132.3 mm carapace width (instars 5 to 18), were collected from natural populations in Phuket, Thailand, and examined for these barnacles. Almost a third harbored one or more barnacles. The smallest crab to host a barnacle was 34.3 mm (instar 10); 233 smaller crabs, representing instars 5-9, had none. Infestations by more than one barnacle were uncommon among crabs of less than 70 mm carapace width (instar 13). The percentage of crabs hosting barnacles increased as the crabs approached sexual maturity, and the magnitude of infestation on individual crabs increased with their size. The distribution of octolasmids on the gills of immature crabs differed from that on mature crabs. In the former, all barnacles were on the inside of the gill surfaces and none were on the outside, whereas in the latter, 11% were on the outside of the gills. The numbers of barnacles on the inside and the outside of the gills is a function of the number of barnacles in the gill chamber. The major inhalant aperture size, and gill chamber size were eliminated as possible factors limiting infestation. Instars 10 and 11 may be suboptimal for infestation by octolasmids because the intermolt time between instars does not allow sufficient time for production of barnacle nauplii. Current data do not permit us to distinguish the relative influences of microhabitat use, host hormonal changes, and behavioral changes on infestation.

Snake circumvents constraints on prey size

For animals who are unable to take bites out of their food, the size of the food item that can be consumed is constrained by the maximal size of the mouth opening (gape) — snakes are an example of gape-limited predators and they usually swallow their prey whole. Here we describe unique feeding behaviours in two closely related species of snake, which circumvent their gape limitation by removing and consuming pieces from newly moulted crabs that are too large to be swallowed intact. This evolutionary innovation is surprising, as the needle-like teeth and highly mobile bones that facilitate the capture and engulfment of large, whole prey by snakes are ill-suited both to cutting and to generating large bite forces.

Marine Snake Diets: Prey Composition, Diversity and Overlap

--, AND S. G. HOFFMAN. 1980a. Local population size as a determinant of mating system and sexual composition in two tropical reef fishes (Thalassoma spp.). Evolution 34:508-518. AND . 1980b. Population density and the economics of territorial defense in a coral reef fish. Ecol. 61:772-780. , AND D. R. ROBERTSON. 1978. Sexual patterns in the labroid fishes of the Western Caribbean, I: The wrasses (Labridae). Smithsonian Contrib. Zool. 254:1-27. , AND E. G. LEIGH. 1975. Sex change and sexual selection. Science 190:633-638.

Phylogenetic Relationships of the Oriental-Australian Rear-Fanged Water Snakes (Colubridae: Homalopsinae) Based on Mitochondrial DNA Sequences

Abstract The Homalopsinae (Oriental-Australian rear-fanged water snakes) is a small (34 species, 10 genera) colubrid subfamily notable for its ecological and morphological diversity. Despite considerable interest in the ecology and evolution of this group, phylogenetic relationships within the subfamily are poorly resolved. We present the results of a molecular phylogenetic study of the homalopsines based on partial sequence of three mitochondrial genes (12S and 16S ribosomal RNA and cytochrome b) from 14 ingroup species, five Old and New World natricines and the Old World colubrid, Dinodon semicarinatus. Maximum likelihood analysis in combination with bootstrapping and Bayesian Markov chain Monte Carlo methods for assessing phylogenetic confidence revealed that the single most likely topology contained a number of well-supported nodes. Homalopsine monophyly was strongly supported with respect to the outgroups included in our study. Cantoria violacea, a morphologically distinctive marine crustacean eater, formed the sister group to the rest of the homalopsines. Enhydris, the most species-rich genus in the subfamily, was polyphyletic with respect to other homalopsines although five morphologically and ecologically similar species formed a well-supported clade. The marine crustacean eaters Fordonia leucobalia and Gerarda prevostiana, also formed a novel clade. We discuss the evolutionary and ecological implications of this phylogeny for the Homalopsinae.

Growth, Reproduction and Population Structure of a Marine Snake, Enhydrina schistosa (Hydrophiidae)

A population of the beaked sea snake, Enhydrina schistosa was sampled at Muar, Malaysia over a nine month period. Males and females have synchronous annual reproductive cycles. Gestation extends from November to February and March. The growth of young E. schistosa was rapid (about 0.12 cm per day) with no major seasonal decline. The rate of growth in snout-vent length slows after the first 18 months post-parturition. Males and females mature in about 18 months and females give birth to their first clutch of young at about 24 months. Clutch size increases with the size of the female and can reach thirty or more. Estimates of survival indicate that about 10 to 20% of the newborn snakes survive the first year of life and about 6% of the females survive to reproduce. Snakes four or

Herpetology: Snake circumvents constraints on prey size

For animals who are unable to take bites out of their food, the size of the food item that can be consumed is constrained by the maximal size of the mouth opening (gape) — snakes are an example of gape-limited predators and they usually swallow their prey whole. Here we describe unique feeding behaviours in two closely related species of snake, which circumvent their gape limitation by removing and consuming pieces from newly moulted crabs that are too large to be swallowed intact. This evolutionary innovation is surprising, as the needle-like teeth and highly mobile bones that facilitate the capture and engulfment of large, whole prey by snakes are ill-suited both to cutting and to generating large bite forces.