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 Born eo. At four of these sites we sampled during more than one year. Altog ether 49 species were included in our study and total sample size was 13,249. We measured overlap in species occurrences and arrays of abund ances within and among localities. Variation over the time span of our study was minor within communities. Overlaps between streams at a loc ality were generally higher than overlaps of pairs of streams from dif ferent localities. Environmental variation, particularly in stream wid th and gradient, had a clear effect on both intra-and inter-locality o verlaps. Although rainfall varied between localities and within locali ties over time, that variation did not seem to affect overlaps among o r within communities. Environmental factors did not account for all di fferences 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, leadi ng to variation in overlap values.