Genetic variation reveals broad-scale biogeographic patterns and challenges species’ classification in the Kunzea ericoides(kānuka; Myrtaceae) complex from New Zealand

ABSTRACTKunzea(kānuka) in New Zealand comprises ten endemic species following a recent taxonomic revision, several of which are abundant, widespread and ecologically important as early successional colonisers. The species are difficult to recognise in the field in many areas, some plants appear intermediate between species and it has been argued hybrids are common. Microsatellite markers are used to investigate genetic variation in these ten species. The species are only weakly supported as they are characterised by low differentiation as reported by FSTand high allele migration (Nm). FSTvaried between 0.027 (K. robusta) and 0.084 (K. triregensis). The allopatric K. triregensisand K. salteraehad the highest difference in pairwise FSTat 0.155 and the sympatric K. robustaand K. serotinathe lowest at 0.005. Allele pairwise net migration (Nm) varied between 1.36 (K. triregensisand K. salterae) and 45.24 (K. robustaand K. serotina). The two most widespread species, K. robustaand K. serotina, are genetically indistinguishable and share northern and southern genotypic clusters. Six species or groups of species are recognised in the Structure analysis but these too are characterised by low FSTand high allele migration (Nm). Four genotypic clusters shown by Structure analysis are distributed along a north to south latitudinal gradient cutting across species boundaries and corresponding with established biogeographic regions of New Zealand. This provides the strongest pattern of genotypic variation in the study. The weak level of genetic support for the ten Kunzeaspecies, lack of breeding barriers between them, and problems in recognising some of the species in the field, raises questions as to their validity. However, given the ecological, conservation and economic importance of Kunzea, the ten species currently circumscribed should be retained until decisions are made as to how to recognise the variation within the species complex.