Evol Ecol Res 9: 675-695 (2007)     Full PDF if your library subscribes.

Niche expansion: coupled evolutionary branching of niche position and width

Hiroshi C. Ito* and Masakazu Shimada

Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguroku, Tokyo 153-8902, Japan

Author to whom all correspondence should be addressed.
e-mail: itoh9@dolphin.c.u-tokyo.ac.jp


Question: Does evolutionary niche expansion of a consumer population from its original resource to a new resource induce coupled evolutionary branching of niche position and width?

Key assumption: The position and width of an individual resource utilization pattern (niche) are evolutionary traits, which form a two-dimensional phenotype space. The resource distribution is bimodal.

Methods: The possibility of evolutionary branching through resource competition was examined with adaptive dynamics theory, i.e. an extension of ESS theory. Evolutionary dynamics was also simulated using an individual-based model with sexual reproduction.

Conclusion: Diversification in niche position only is suppressed by directional evolution of niche width. Nevertheless, evolutionary branching occurs almost always in this model, and involves joint diversification of niche width and niche position. When specialist strategies that initially utilize only one resource undergo evolutionary branching, the incipient branches differ strongly in niche width. Eventually, the branch with the larger niche width will develop into a specialist utilizing the new resource.

Keywords: adaptive dynamics, evolutionary branching, niche width, resource competition, resource utilization pattern.

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