Character displacement
Character displacement was first explicitly explained by William L. Brown Jr. and E. O. Wilson in 1956: "Two closely related species have overlapping ranges.
It also plays a role in speciation by reinforcement in such that allopatric populations overlapping in sympatry exhibit greater trait divergence.
[4] The results of numerous studies contribute evidence that character displacement often influences the evolution of resource acquisition among members of an ecological guild.
[5] Competitive release, defined as the expansion of an ecological niche in the absence of a competitor, is essentially the mirror image of character displacement.
Following the dissemination of the concept, character displacement was viewed as an important force in structuring ecological communities, and biologists identified numerous examples.
During the late 1970s and early 1980s, however, the role of competition and character displacement in structuring communities was questioned and its importance greatly downgraded.
[9] Rigorously testing these criteria necessitates a synthetic approach, combining areas of research like community ecology, functional morphology, adaptation, quantitative genetics and phylogenetic systematics,[5] While satisfying all six criteria in a single study of character displacement is not often feasible, they provide the necessary context for researching character displacement.
[11] Studies have been performed in a wide variety of taxa—a few groups having disproportionately contributed to the understanding of character displacement: mammalian carnivores, Galapagos finches, anole lizards on islands, three-spined stickleback fish, and snails.
[1] David Lack found that when the two species Geospiza fortis and G. fuliginosa occurred on large islands together, they could be distinguished unequivocally by beak size.
The lizard genus Anolis on the islands in the Caribbean has also been the subject of numerous studies investigating the role of competition and character displacement in community structure.
Other studies have found Plethodon salamander species that demonstrate character displacement from aggressive behavioral interference rather than exploitation.
Studies on other fish species have shown similar patterns of selection for benthic and limnetic morphologies,[5] which can also lead to sympatric speciation.
[26] Introduced species have also provided recent "natural experiments" to investigate how rapidly character displacement can affect evolutionary change.
