A PHYLOGENETIC APPROACH TO THE PROBLEM OF DIFFERENTIAL LINEAGE SORTING

A test that can detect the influence of differential lineage sorting o n phylogenetic signal in integrated studies with two or more loci is p resented. Hitherto unexplored consequences of relationships among gene trees and species trees are made explicit, revealing potential influe nces of differential lineage sorting on phylogenetic signal. These inf luences can result in observable consequences, in particular an increa se in signal when sequences or characters are combined among taxa to c reate a mixed-character taxon. Simulations of nucleotide evolution ref lecting two gene phylogenies within a five-taxon species phylogeny wer e used to demonstrate and justify the mixed-character taxon test. An e mpirical example of lineage sorting during the evolution of Robineae i s presented that appears to resolve conflict between morphological and organellar chloroplast DNA (cpDNA) signal.