Supertree Analysis of the Plant Family Fabaceae

The “Tree-of-Life” is a national and international project to collect information about the origin, evolution, and diversity of organisms, with the goal of producing a tree of all life on Earth (Pennisi, 2003). The obstacles to achieving this goal are many. From questions related to the kinds and number of data to be used, to building that phylogeny, to the methodological and computational resources required to analyze the massive amounts of data expected to be necessary to bring this to fruition. The development of efficient methods for phylogenetic analyses of thousands (hundreds of thousands) of taxa has become increasingly important to this endeavor, as well as somewhat controversial. Supertree construction is one of these methods proposed for reconstructing phylogenies on a large scale (Bininda-Emonds, 2004). This method combines phylogenetic trees (topologies), which overlap taxonomically, rather than the primary data, to produce a larger tree using standard methods of analyses such as parsimony. This method also has the advantage of being able to incorporate trees derived from many different kinds of data into tree estimation. For the study presented here, a comprehensive literature search identified 185 phylogenetic trees published since 1984 on the plant family Fabacaeae (the “legumes”). Of these, 68 trees were chosen for supertree analysis and were divided into three major groups, two of which correspond to strongly-supported monophyletic groups identified by recent studies that sampled extensively across the family and are based on standard phylogenetic analyses of single data sets (e.g. gene sequences). Supertrees of taxa that correspond to the three subfamilies Mimosoideae, Caesalpinioideae, and Papilionoideae will be presented here.