Organisms may compete for a great variety of limiting resources, such as food and habitat and, in the case of plants, light and pollinators. Direct mechanisms of competition, as highlighted by interactions between yellow crazy ants and hermit crabs on Tokelau, include resource and interference competition, while indirect mechanisms of competition that are mediated by other species are also widespread in ecological communities. Introductions of species into novel environments allow ecologists to study competitive interactions in real time. Interspecific competition can lead to competitive exclusion when two or more species occupy similar niches. A variable environment, niche shift, and niche partitioning can promote species coexistence. Theoretical models, such as the Lotka–Volterra competition model, help identify conditions in which two or more competing species can coexist. When conservation ecologists introduce two or more species as biological control agents, they must consider potential competitive interactions among the introduced species, keeping in mind the factors that promote the coexistence of the introduced species.

Whereas most books emphasize cases of expansion, this chapter focuses on cases in which the United States does not expand. These cases - Fiji, Kiribati, Tahiti, Tokelau, and Tuvalu- challenge grand narratives of America’s path in the Pacific. The islands had strategic value, large markets, and souls to save. Yet, there was little if any interest from the US government in annexation. Using a structured, focused comparison, we attribute these instances of non-expansion to three causes: an island lacks commodities or labor for the entrepreneur to exploit; the entrepreneur dies or is arrested before the imperial lobby matures; or the entrepreneur establishes themselves in territories already controlled by foreign empires who can offer protection from local threats. These cases are interesting, brief stories about the American commercial experience abroad that have been ignored by scholars of American imperialism.