CSIRO Marine and Atmospheric Research
Past Seminars

Friday, 01 August 2003 11.30am (Tas time)

CSIRO Auditorium and via videoconference to Floreat and Cleveland

Dr Piers Dunstan

CSIRO Marine Research

Linking species richness, variability and invasion resistance in a model marine community

Despite widespread acceptance of the importance of species richness on community dynamics and invasion resistance, the mechanisms linking richness with invasions are poorly understood. Here I investigate the dynamics of a temperate marine epibenthic community in Tasmania to determine the relationship between species richness and invasion resistance. Invasion resistance is negatively correlated with species richness. I develop an individual-based spatial model of this community. The model is used to examine processes influencing the relationship between invasion resistance, variability and species richness and how these relationships change with patch size

The invasibility of the community is strongly correlated with the variability of cover and thus with the availability of free space. However, the patterns of variability are strongly dependent on patch size. In small patches, community variability is positively correlated with species richness. In larger patches this pattern changes and community variability is negatively correlated with species richness. These changes are the result of species-specific differences in the relationship between colony size and the probability of mortality. Because larger colonies have a lower probability of mortality, when colonies attain large sizes and dominate space, reducing diversity, total cover is more stable and the community more resistant to invasion. These results suggest a broader continuum of relationships between variability, invasibility and richness that are strongly dependent on the exact relationship between individual size and mortality for each species in the community

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