Differences in the pattern of organization of organisms may lead to different patterns of evolution, genetics and ecology, Plants and animals differ in their fundamental patterns of organization. Plants consist of a series of repeating units that compete with one another, while animals consist of mutually interdependent systems that cannot compete. As a result, plants may be able to take advantage of somatic mutations in ways that are not available to animals. Somatic mutations arising in plants can be inherited by naturally occurring mechanisms of sexual and asexual reproduction. Long life span, large clone size, and the complete regeneration of buds each year may permit an indivdual plant or clone to evolve. Plants may even develop as mosaics of genetic variation. Evolution by individual plants and/or development as mosaics of genetic variation may prevent herbivores from breaking the defenses of their host plants. This evolution may also result in greater "fine tuning" to local environments leading to ecotypic variation.

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Gunnison's prairie dogs (Cynomys gunnisoni) are social North American ground squirrels whose social system has been shown to vary with food resource distributions, as predicted by the habitat variability–mating system model. We expanded this model to include the effects of variations in population densities, in addition to resource distributions, on both the social system and the individual mating strategies of Gunnison's prairie dogs. Specifically, we predicted that monogamy would be associated with uniform resources, regardless of population density, giving way to polygyny with increasing resource patchiness at intermediate densities, and to multiple males and females at high population densities. In addition, we predicted inbreeding at low densities and outbreeding at high densities on the basis of naturally low levels of genetic eity in this species. We tested these predictions by comparing social systems and mating strategies at two prairie dog colonies near Flagstaff, Arizona, during a 3—yr period of population increase. We observed variations in sociality to vary in the predicted fashion at both colonies, providing support for the plant patchiness–population density model.

We tested the predictions of Slobodchikoff s habitat variability – mating system model using the social system of Gunnison's prairie dog (Cynomys gunnisoni). The model predicts that when resources are abundant and patchily distributed, social groups will include several females, while scarce, uniformly distributed resources will lead to smaller groups with single females. Gunnison's prairie dogs form family groups consisting of a single adult male and female(s), and their young of the year, which occupy fixed spatial territories within a colonial framework. Resource abundances and distributions were characterized and compared at two colonies in northern Arizona. Resource abundance did not vary between colonies, while two separate measures showed resource distribution to be significantly more patchy at one colony than at the other. As predicted, there were significantly more territories with multiple females at the patchy colony, while single-female territories predominated at the uniform colony. While the differences in resource abundance between colonies were not significant from a statistical standpoint, sizable differences were observed, with the direction of the difference opposite to that predicted by the model.