Document: JOH-3-35-3

Metapopulation dynamics of cobble beach plants: Effects of patch quality and isolation on community composition and richness.

BRUNO, J.F.*

Brown University, Providence, RI, USA ¹

Abstract:
Many communities are facilitated by the presence of foundation species that create habitat islands and reduce environmental stress to tolerable levels. The purpose of this study was to examine how the quality and spatial arrangement of such biologically-generated habitats effect the large-scale distribution and dynamics of species that inhabit them. The study system was the cobble beach plant community, an assemblage of intertidal forbs that is only found behind fringing beds of the grass Spartina alterniflora. Spartina reduces flow velocity and stabilizes the substrate, thereby reducing the burial of seeds and seedlings of other species. Most Spartina beds are small (< 30 m in length) and unoccupied by any cobble beach plant species, and a there is a strong, positive relationship between bed length and plant species richness. Results from field experiments indicate that long beds reduce wave-related disturbance much more than smaller beds and that the required degree of habitat modification for successful population establishment is quite variable among species. Rare species appear to be habitat specialists, preferring a small cobble/gravel microhabitat that is generally only found behind beds longer than 100 m. This apparently generates a nested distributional pattern in which species that are rare on a landscape scale are restricted to the longest Spartina beds. Additionally, population transitions (i.e. colonization and extinction) were strongly correlated with bed length and isolation (distance to the nearest neighboring conspecific population). Thus in this system, landscape-scale patterns of species distributions, dynamics, richness, and composition appear to be controlled by habitat patch attributes such as size and spacing.

Keywords: metapopulation dynamics, rarity, species richness, landscape, plant community ecology

This abstract is being presented at: 3:15 PM in session:
Oral Session #65: Wetlands, Estuaries and Salt Marshes.