Species Diversity and Community Organization in Desert Seed‐Eating Ants

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Patterns of species diversity and community organization in desert seed-eating ants were studied in 10 habitats on a longitudinal gradient of increasing rainfall extending from southeastern California, through southern Arizona, and into southwestern New Mexico. Local communities of harvester ants include 2-7 common species, and at least 15 species from five genera of Myrmecines compose the total species pool in these deserts. Ant species diversity is highly correlated with mean annual precipitation, an index of productivity in arid regions. Communities are structured on the basis of competition for food, and interspecific differences in worker body sizes and colony foraging strategies represent important mechanisms of resource allocation. Seed size preferences, measured for native seeds and in food choice experiments with seeds of different size but uniform nutritional quality, are highly correlated with worker body sizes. Species of similar body size can coexist within local habitats if they differ in foraging strategy. Interspecific aggression and territorial defense and microhabitat partitioning all appear to be relatively unimportant in these ant communities.Patterns of species diversity and community organization in harvester ants are strikingly similar to those reported for communities of seed-eating rodents that occupy many of the same desert habitats. Separate regressions of within-habitat species diversity against the precipitation index of productivity for the two groups correspond closely in slope, intercept, and proportion of explained variation. Resource allocation on the basis of seed size characterizes local communities of both ants and rodents. Parallels between these two groups suggest that limits to specialization and overlap may be specified by parameters such as resource abundance and predictability that affect unrelated taxa similarly.

Environment heterogeneity and seasonal effects in ground-dwelling ant (Hymenoptera: Formicidae) assemblages in the Parque Estadual do Rio Doce, MG, Brazil

“…Therefore, statistical analysis may be overestimating this discrepancy and any affirmation could be wrong. Davidson (1997aDavidson ( , 1997b, studying deserted habitats in North America, found a similar pattern between diversity of ants and amount of precipitation. Humid environments present higher diversity of ants although, during dry season, in neotropical semidecidual forests, many species can be sampled in function of more foraging activity and seed/fruit production by trees.…”

On Caste Ratios in Ant Colonies: Population Responses to Changing Environments

“…For carnivores such as F. obscuripes, however, prey availability and prey size differentiation through a season may be more difficult to track. Interspecific competitive effects are very important in structuring desert ant communities (Davidson, 1977) but were notable only occasionally at Illinois Beach. Variable scales in the fluctuations of selection intensity, which is the key to variability of caste structures (Oster and Wilson, 1978), accounts for the response differential between reports of caste structure change in the literature and the observation for this species that environmental change results in reduced variability of caste proportions.…”

The development of an ant colony's foraging range

“…Ecological studies show that food is a limiting resource for desert granivores (Brown & Davidson 1977;Davidson 1977Davidson , 1985. Many aspects of harvester ant behaviour indicate that foraging is important to colony survival.…”