VARIATION IN REPRODUCTIVE CHARACTERISTICS OF THE STREAM FROG COLOSTETHUS-TRINITATIS ON THE ISLAND OF TRINIDAD

We compared reproductive characteristics of the dendrobatid frog Colostethus trinitatis at the Tamana cave in the Central Range hills and at five forest stream sites in the Northern Range hills of Trinidad. There were significant differences between sites in adult female body size, intraovarian clutch size (in absolute terms and relative to body size) and the size of tadpoles carried by male frogs. Clutch sizes ranged from 6 to 13 in the Northern Range samples and from 12 to 26 at Tamana. Adult male body size was similar at all sites. Tadpoles carried by male C. trinitatis at Tamana were significantly smaller (mean length 14.2 mm) than those carried by males at the five Northern range sites (mean length 16.4-16.7 mm). The smallest clutches and largest tadpoles were found at Mount St Benedict, where there was evidence of size-selective predation on tadpoles by fish. Tamana, where clutches were large and tadpoles small, differed from the Northern Range sires in terms of the physical environment (cave vs forest) and the abundance of invertebrates. We discuss possible ultimate and proximate causes of the differences in clutch size and tadpole size, particularly size-selective predation and availability of food.