Phylogenetic Relationships and Hybridizations among Cranberries (Vaccinium, Ericaceae)

Abstract

Cranberries, often classified as Oxycoccus, represent a group within the genus Vaccinium (Ericaceae). They comprise one or two species distributed across the cool temperate regions of the Northern Hemisphere and one species native to North America. Previous studies have discussed their species classification, polyploidization, and hybridization based on morphology, ploidy levels, and genetic variation. However, these studies have primarily focused on local populations, despite the widespread geographical distribution of the group. To enhance our understanding of the species classification and to identify potential interspecific hybridizations, the present study investigated the phylogenetic relationships among cranberries across their distributional range, utilizing nucleotide sequences of chloroplast DNA (trnL intron, trnL- trnF, psbA-trnH, and trnS-trnG) and nuclear ribosomal DNA (internal transcribed spacers; ITS). Among cranberries, four lineages were identified in the phylogenetic relationships based on chloroplast haplotypes and ITS-types. The ITS tree revealed that V. microcarpum is distinct from V. oxycoccos but more closely related to V. macrocarpon, and that V. oxycoccos is paraphyletic, comprising two geographically distinct lineages. Furthermore, interspecific hybridization and introgression (chloroplast capture) were detected between V. oxycoccos and other species, and occasionally between the different lineages within V. oxycoccos, suggesting secondary contact after speciation or lineage differentiation.