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In this paper we review, develop, and differentiate among concepts associated with environmental patterning (patch,-division, and heterogeneity), spatial and temporal scales of ecological proaesses (ecological neighborhoods), and responses of organisms to environmental patterning (relative patch size, relative patch duration, ielative patgh isolation" and grain lespoqse), We gencralizc the concept of ecological neighborhoods to represent regions-of activity or influence during periods of t'ime appropri.aleto-particular ecological processes. Therefore, there is no single ecol6gical neighborhood for any given organism, but rather a number of neighborhoods, each appropriate to different processes. Neighborhood sizes can be estimated by examining the cumulative distribution of activity or influence of an organism as a function of increasingly. large spatial units. The spatial and temporal dimensions of neighborhoods provide the scales necessary for assessing environmental patterning relaiive to particular ecological processes for a given species. Consistent application of the neighborhood-concept will assist in the choice of appropriate study-units, comparisons among different studies, and comparisons between empirical studies and-theoretical postulates.

Although ballast water has received much attention as a source of aquatic invasive species, aquariums and trade in aquarium and ornamental species are emerging as another important source for species likely to invade aquatic habitats. These species are spread throughout the world in a generally unregulated industry. The recent focus on the aquarium trade as a possible mechanism for environmentally sustainable development poses an especially dangerous threat, although this has so far escaped the attention of most environmentalists, conservationists, ecologists, and policy makers.

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Accurately predicting the pattern and rate of spread of invading species is difficult, particularly for species that disperse long distances. Though relatively rare, and often stochastic, long-distance dispersal events increase the maximum rate and geographic extent of invasion. Human activities are responsible for the spread of many exotic species, particularly aquatic species such as the zebra mussel, which are primarily transported within North America by recreational boaters. We estimated spatial and temporal patterns of boating traffic among Wisconsin's inland waterbodies using results of a large, randomized survey of recreational boaters conducted by the Wisconsin Department of Natural Resources. Of the survey respondents, Ͼ90% of boaters traveled locally, within a county or to adjacent counties, 8.4% moved Ͼ50 km, and only 0.8% moved extreme long distances (Ͼ261 km, two standard deviations above the mean of intercounty travel). Extreme longdistance boater movements were correlated positively with greater numbers of registered boaters in source and destination counties, and with greater surface area and numbers of named lakes in destination counties. We compared the observed spatial and temporal patterns of the zebra mussel invasion to those estimated from recreational boater movement by simple diffusion models. Diffusion models underestimated the maximum rate and geographic extent of the zebra mussel invasion and overestimated the invasion of suitable habitats within this extent. Patterns of recreational boater activity in Wisconsin were a better predictor of the observed zebra mussel invasion pattern because they provided probabilistic estimates of invasion at finer spatial resolution. These estimates may be used to manage the spread of boater-dispersed aquatic invaders. To slow the spread of boaterdispersed aquatic invaders such as the zebra mussel, management efforts should target highfrequency, long-distance boater movements, and regions with the greatest volume of source and/or destination boater movement.

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