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.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Society for the Study of Amphibians and Reptiles is collaborating with JSTOR to digitize, preserve and extend access to Journal of Herpetology.ABSTRACT-Larvae of two species of rhacophorids are reported from tree holes in Thailand. One, referred to Theloderma stellatum, has a body nearly as wide as long and a denticle formula of 1:3+3/1+1:11. Internally, it has large branchial baskets with many rows of dense gill filters, but only two filter cavities. It has secretory cells in its branchial food traps, but they are not arranged in ridges. Its buccal musculature is slight. The larva of the second species, referred to Philautus (cf. carinensis) has a truncated snout, anteriorly directed mouth, denticle formula I/O, and unusually shaped beaks with the upper portion concave but serrations confined to the lower. It has huge buccal musculature. In this form all branchial structures associated with suspension feeding, and respiratory gill filaments, are absent.Both larvae have large, anteriorly placed glotta, which are evidently adaptations for aerial respiration. The Theloderma has a peculiar mosaic of feeding structures associated with dietary extremes of microphagy and macrophagy. Its gut contents consist of both large and small food items. The Philautus larva has features of an obligate macrophagous larva. From its gut contents it appears to eat only frog eggs.Certain arboreal tadpoles for the New World tropics, e.g., Hyla zetecki and others, resemble these Philautus tadpoles in form and diet. No analog of larval Theloderma stellatum is yet known from the American tropics.
A simulation model is presented incorporating a variable time to maturity resulting from density-dependent scarcity of resources for the immature stages. This mechanism is shown to be capable of regulating a population and the model population persists under these conditions. The model is qualitatively robust to changes in the parameters: resource input rate, offspring input rate, and immature death rate. Implications drawn from the model behavior with respect to pest control, "r-selection" under "K" conditions and field experiments are discussed.
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