Dr. Gill concentrates on general unsolved problems in evolutionary ecology and chooses a diverse array of organisms for empirical and experimental work. Currently he is concerned with three questions: (1) how does adaptive evolution occur in species which have chronic patterns of reproductive failure imposed by unpredictable environmental conditions?; (2) how do complex life cycles evolve in animals?; and (3) how do long-lived hosts, such as trees and mammals, evolve traits of resistance against fast-evolving pests and parasites? The answer to the first question was studied in montane populations of amphibians and now is being explored in a population of orchids. The answer to the second is being sought in field studies of a gall-making aphid on witch-hazel leaves. The answer to the third question is being sought in the theory of genetic mosaicism within individuals. Areas of continuing research interest are interspecific competition in encrusting lichens, community structure and island biogeography of ants in the bull-thorn acacias mutualism, and pollutant stream ecology in Costa Rica.
