Evolution of Hedera (the ivy genus, Araliaceae):: Insights from chloroplast DNA data

Hedera L., the ivy genus, comprises approximately 16 taxa distributed throughout Europe, North Africa, Macaronesia, and Asia. Phylogenetic relationships within Hedera were examined using chloroplast DNA restriction site variation and noncoding sequence data. The cpDNA data were compared with the published nuclear ribosomal internal transcribed spacer (ITS) data. Phylogenetic incongruence between the two data sets is evident, with no identical clades shared between the topologies. Three centers of diversification for Hedera are hypothesized: Europe, Western Asia, and the Macaronesian region, with allopolyploidization playing a major part in the evolution of Hedera. The maternal parents of the polyploid species H. hibernica, H. iberica, and H. pastuchovii are identified on the basis of the comparison of the chloroplast DNA phylogeny and the ITS topology. The diploid H. helix is supported as the maternal parent of the tetraploid H. hibernica. The comparison of the cpDNA and the ITS phylogenies also indicates that H. canariensis was the diploid maternal ancestor that hybridized with H. hibernica, resulting in the formation of H. iberica. The maternal parent of the hexaploid H. pastuchovii is perhaps H. nepalensis var. sinensis. Diversification of taxa in each region is relatively recent, as indicated by relatively low levels of sequence divergence.