Phylogenetic position and life cycles of test species. Schematic representation of the SSU rRNA phylogeny of all social amoebas, with solitary amoebas as outgroup. DF and PP reside in groups 1 and 2, respectively. They differ from DD by generally forming small clustered and/or branched fruiting structures from a single aggregate, in which prespore cells differentiate first and the stalk is formed by dedifferentiation of prespore cells at the apex. In contrast, group 4 taxa form robust solitary unbranched fruiting structures and set aside appropiate proportions of prestalk cells after aggregation. They also differentiate into three additional cell types that support the stalk and spore head, and their sorogens can migrate extensively to seek optimal spots for fruiting body construction (Schaap et al. 2006; A Skiba and P Schaap, in prep.).
