On genes and geography: a landscape perspective on genetic variation in natural plant populations

Landscape ecology tends to be concerned with larger-scale spatial organization of ecological phenomena and their reciprocal effects on processes and patterns. Comparatively little work has focused on the role of plant genetic variation in the coarse-scaled, broad-extent studies common to landscape ecology. I suggest that this results in part from a built-in bias owing to the perceptual view that the study of organic patterns should be human-centered and that they are dominated by environmental effects. I argue that to determine the agents of pattern formation and add greater explanatory breadth for the analysis of larger-scale ecological processes, it is sometimes necessary to narrow our focus to microscales and integrate fine-scale patterns of genetic variation with larger-scale distributional phenomena, particularly in view of expanding knowledge of the amount and importance of within-species genetic diversity. I summarize a recent review of the literature on genetic diversity in plants which shows that the levels and distribution of genetic variation varies broadly with geography, among other life-history traits. Hierarchy theory is suggested to provide a useful heuristic framework for integrating fine-scale genetic information as it affects observed phenomena at landscape and regional scales of organization. I conclude that a more comprehensive assessment of genetic variation in natural plant populations at various hierarchical levels is essential in view of concerns for loss of species owing to habitat fragmentation and global change.