Document: YEO-3-99-103

Intraspecific competition within and between hatching cohorts of oophagous tadpoles of the Taiwanese tree frog, Chirixalus eiffingere.

KAM, Y.* ¹, Y.H.CHEN ¹, Y.S.SU ² and Y.S.LIN ²

National Changhua University of Education, Changhua, 50058 TAIWAN R.O.C. ¹
National Taiwan University, Taipei, TAIWAN R.O.C. ²

Abstract:
We studied the dynamic interactions within and between different hatching cohorts of Chirixalus eiffingeri tadpoles reared in pools in bamboo stumps at the Experimental Forest of the National Taiwan University at Chitou, Taiwan, during 1997 and 1998. In a 2 by 3 factorial experiment (Experiment I), we assessed the effects of early-hatching tadpoles (none, 10 medium, or 10 large tadpoles) and the brood size of late-hatching tadpoles (10 or 20 small tadpoles) on the growth, survivorship, and metamorphosis of late-hatching tadpoles. Early-hatching (medium and large) tadpoles significantly affected the growth, survivorship, survivorship at metamorphosis, tadpole period, and body mass at metamorphosis of late-hatching tadpoles. The effects of medium and large tadpoles on small tadpoles were similar. An increase in the brood size of late-hatching tadpoles prolonged the tadpole period but did not affect their body mass at metamorphosis or survivorship at metamorphosis. In Experiment II, we studied the effects of the number of early-hatching tadpoles on late-hatching tadpoles. There were four treatments: 20 late-hatching tadpoles (20S), 30 late-hatching tadpoles (30S), 10 late- and 10 early-hatching tadpoles (10S10L), and 10 late- and 20 early-hatching tadpoles (10S20L). Early-hatching tadpoles decreased the growth and survival of late-hatching tadpoles. All late-hatching tadpoles in the 10S20L treatment died, whereas an increase in brood size of late-hatching tadpoles, from 20 to 30, did not affect the survivorship at metamorphosis. Experiments I and II demonstrated that the number, but not the developmental stage, of early-hatching tadpoles had detrimental effects on the growth and development of the late-hatching tadpoles, which has important implications for the reproductive strategies of female frogs. The time when the second clutch of eggs is laid is critical to the overall reproductive success of female frogs. Female frogs should lay a second clutch of eggs only after the early-hatching tadpoles are low in number, which may reduce brooding cost (i.e., supply of trophic eggs) and intraspecific competition between the two cohorts of tadpoles.

Keywords: frogs

This abstract is being presented at: 8:30 AM in session:
Oral Session #38: Amphibian Ecology.