An empirical assessment of community-wide species interaction strengths in the rocky intertidal.
Wood, Spencer*,1, Shurin, Jonathan1, Lilley, Stacie2, Schiel, David2, 1 University of British Columbia, Vancouver, BC, Canada2 University of Canterbury, Christchurch, New Zealand
ABSTRACT- The strength and distribution of interaction strengths among community members may be related to species richness and the distribution of abundances. Strong negative interactions may reduce richness, while communities with highly skewed interaction coefficients (many weak and few strong interactions) may be richer, but with uneven abundances. We performed a meta-analysis of pair-wise interaction strengths from 20 species removal experiments in the rocky intertidal, across a range of local scales and habitats in New Zealand and North America. Our results confirm expectations based on theory and a few empirical studies which suggest that communities are characterized by many weak and few strong interactors. Mean community-wide interaction strength ranged from negative to positive, suggesting that different locations are characterized predominately by facilitation and others by inhibition. However, the distribution of interaction intensities was generally normally distributed, suggesting that community-wide interaction strength is not disproportionately skewed toward weak interactions. Contrary to theoretical expectations, we show no relationships between species interaction strengths and community diversity. These are possibly reflections of facilitative and multi-trophic interactions yet to be accounted for by simplified theoretical assemblages of species. The results suggest that community-wide interaction strength shows considerable variation by geographic location and habitat, but may not be strongly coupled to diversity in the rocky intertidal.
Key words: community-wide interaction strengths, species diversity, meta-analysis, rocky intertidal
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