Sprent, J. I. “Evolution and diversity of legume symbiosis.” In Nitrogen-fixing leguminous symbioses , pp. 1-21. Springer, Dordrecht, 2008.
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The potential for nodulation in extant plants appears to be confined to a branch of angiosperms known as the Rosid I clade (Soltis et al., 2000). All legumes are found in one branch of this clade (Figure 1). However, it is becoming increasingly evident that the genetic basis of nodulation in legumes (and probably actinorhizal plants too; see Volume 6, Nitrogen-fixing Actinorhizal Symbioses of this series) has been acquired following duplication and modification of older genetic elements, some of which date back to the origin of land plants and even earlier. Before tracing some of these elements, a brief description of different types of extant nodule will be given, followed by an historical consideration of events necessary before legumes evolved and nodulation became a possibility. This discussion leads to a consideration of nodulation and non-nodulation in the three subfamilies of legumes and how and when nodules may have evolved. Throughout, the emphasis will be on the plant partner of this symbiosis. (Read the full chapter from the PDF file by copying the URL from ‘URL2’, Page no. 20)