PARENT SESSION
Poster Session #29: Animal Population and Community Ecology.
Wednesday, August 8, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
48
Species abundance distributions are not self-similar across spatial scales in aquatic microcosms.
Kolasa, Jurek1, Romanuk, Tamara1, 1
ABSTRACT- The possibility that distributions of species and their abundances in space obey mathematical principles of fractal self-similarity has great theoretical and practical implications, especially in fields such as conservation and protected area management. Self-similarity however implies scale-invariance. This means that species abundance patterns and the dominance-diversity curves used to display these patterns at different spatial scales should 1) have the same general structure and 2) exhibit constant variance regardless of spatial scale. Recent papers have all shown that species abundance patterns may exhibit fractal properties - an exciting and controversial result. In this paper we test the hypothesis that rank abundance patterns are self-similar. We use a unique model system composed of micro-invertebrate assemblages inhabiting small coastal rock pools. We compare the variance within rank-abundance distributions across different spatial scales by first creating hypothetical communities of different sizes by randomly aggregating data from natural pools and then standardizing the rank-abundance curves so they become scale-independent. The variance in species abundance patterns clearly changed as a function of scale resulting in rejection of the null hypothesis of self-similarity. This result implies that rank abundance patterns recorded at various scales of resolution (including spatial and temporal) are fundamentally different, may be caused by different processes, and thus may not be directly compared.
KEY WORDS: abundance, community, scale, self-similarity