Section Arachis includes cultivated peanut (A. hypogaea), an allotetraploid, and closely related wild species, most of which are diploids. Moretzsohn et al. use sequences from three single-copy genes and microsatellite markers to investigate evolutionary relationships within the section and find that whilst high intraspecific variability is evident, there is good support for most species and the results are consistent with genome groups defined by cytogenetics. Using a molecular clock, the divergence of the major genome groups is estimated as between 2.3 and 2.9 million years ago, indicating that speciation rates are very high. The phylogenetic analyses show that A. duranensis and A. ipaënsis are the genome donors to A. hypogaea.