PARENT SESSION
Oral Session #74: Spatial Ecology: Models and Methods. Presiding: C. Loehle.
Friday, August 10, 2001. 8:00 AM to 11:30 AM. Hall of Ideas E.

Combining multiple sources of heterogeneity: a model of environmental variation and dispersal-induced patterning .

NELSON, KAREN¹, PALMER, MARGARET¹, ¹

ABSTRACT- Theoretical ecologists have repeatedly shown that local dispersal and interactions can induce spatial patterning of abundance even in homogeneous landscapes. However, most modellers have assumed a homogeneous environment; ironically, this assumption has hampered the testing of patterning theory. It is an open question whether and how patterning will be manifested in a heterogeneous environment. Here we model patterning caused by local dispersal in a heterogeneous landscape. We manipulate patch quality via differences in carrying capacity, intrinsic growth rates, and density dependence; maximum contrast; and scale of heterogeneity. We show that dispersal-induced patterning is robust to non-systematic variability, and to patterned variation if the scales of heterogeneity and dispersal are markedly different. Where scales are similar, patterning is most irregular. Two scales associated with patterning in a homogeneous environment are also important in a heterogeneous landscape. We suggest that these scales may correspond to the 'functional heterogeneity' (sensu Kolasa and Rollo 1991) of the heterogeneous system. More generally, when multiple sources of heterogeneity are combined, fundamentally different outcomes may occur when the scales of the two processes are similar vs. when they are different.

KEY WORDS: pattern formation, scale, dispersal, functional heterogeneity