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International Journal of Evolutionary Biology
Volume 2012 (2012), Article ID 418964, 10 pages
http://dx.doi.org/10.1155/2012/418964
Review Article

The Role of Reticulate Evolution in Creating Innovation and Complexity

Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269-3125, USA

Received 3 February 2012; Revised 8 May 2012; Accepted 10 May 2012

Academic Editor: Wen Wang

Copyright © 2012 Kristen S. Swithers et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Reticulate evolution encompasses processes that conflict with traditional Tree of Life efforts. These processes, horizontal gene transfer (HGT), gene and whole-genome duplications through allopolyploidization, are some of the main driving forces for generating innovation and complexity. HGT has a profound impact on prokaryotic and eukaryotic evolution. HGTs can lead to the invention of new metabolic pathways and the expansion and enhancement of previously existing pathways. It allows for organismal adaptation into new ecological niches and new host ranges. Although many HGTs appear to be selected for because they provide some benefit to their recipient lineage, other HGTs may be maintained by chance through random genetic drift. Moreover, some HGTs that may initially seem parasitic in nature can cause complexity to arise through pathways of neutral evolution. Another mechanism for generating innovation and complexity, occurring more frequently in eukaryotes than in prokaryotes, is gene and genome duplications, which often occur through allopolyploidizations. We discuss how these different evolutionary processes contribute to generating innovation and complexity.