PNAS108(2011),9910–9915; DOI10.1073/pnas.1102811108. Aracely A. Lutes, Diana P. Baumann, William B. Neaves, Peter Baumann. Abstract and Results: tetraploid hybrids, genetic/cytological verification and independently reproducing female lineages. Full text pmc.ncbi.nlm.nih.gov/articles/PMC3116429/ .