Habitat space is a limiting resource for coral-dwelling gobies. The species pictured, Gobiodon histrio, coexists with an ecologically similar species in the same genus, Gobiodon erythrospilus, by means of a competitive lottery for vacant corals. There is evidence that the two species compete for vacant space, and a removal of one species results in an increase in the abundance of the other species. Although the lottery hypothesis was first developed for coral-dwelling fish, data supporting the hypothesis has remained elusive, and the data collected on this species was a notable development. This photograph originally appeared on the cover of Ecology (85:3) in March of 2004.