The Role of Dispersal and Disturbance in Determining Spatial Heterogeneity in Sedentary Organisms

• Published in: Ecology (Durham) 2000-07, Vol.81 (7), p.2011-2026
• Main Authors: Reed, Daniel C., Raimondi, Peter T., Carr, Mark H., Goldwasser, Lloyd
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Biological diversity; California; Channel Islands National Park; Cold regions; colonization; Dispersal; disturbance; Ecology; El Niño; Environmental aspects; Flowers & plants; Forest ecology; Fundamental and applied biological sciences. Psychology; Hurricanes; kelp forest; Larvae; Larval development; Marine; Marine ecology; National parks; Organisms; Plants; Population ecology; propagule; Sea water ecosystems; sedentary organisms; Seeds; spatial heterogeneity; Spatial variability; Species; spore; Spores (Botany); Storms; Synecology; USA, California; variability
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/0012-9658(2000)081[2011:trodad]2.0.co;2

The dispersal ability of seeds, spores, and larvae can greatly influence spatial heterogeneity in the abundance of plants and sedentary animals, especially after a severe and widespread disturbance has caused extensive population declines and opened large areas for colonization by propagules. However, little work has been done on the relationship between propagule dispersal and spatial heterogeneity in species abundance. We hypothesize that, shortly after a disturbance, spatial variability in abundance of sedentary organisms is negatively related to the dispersal potential of a species' propagules, and that this negative relationship diminishes over time as populations recover from the disturbance. To evaluate this hypothesis, we examined temporal changes in spatial patterns of abundance in a diverse group of sedentary marine organisms, whose propagules differ greatly in dispersal potential. The data set was derived from long-term monitoring of the kelp forest communities of Channel Islands National Park and contained annual estimates of abundance of 27 species from nine phyla collected at 16 sites on five different islands during 1986-1994. Among-site variability in the abundance of plants and animals was negatively related to the plank-tonic duration of a species' propagules. The negative relationship disappeared over time in some regions, but not in others. This disappearance resulted primarily from species with relatively limited dispersal becoming more uniformly distributed over time; among-site variability of species with more widespread dispersal changed little. Differences among regions in the rate at which the negative relationship diminished over time suggested regional differences in rates of recovery from the 1982-1984 El Nino disturbance. These differences among regions may have resulted in part from differences in the frequency and intensity of sea urchin grazing, and in part from regional differences in the distances separating sites where abundances were measured. Our findings support the hypothesis that differential dispersal after large disturbances can significantly influence spatial heterogeneity in assemblages of sedentary organisms.