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Keywords:

  • Parasitic plants;
  • RAPD;
  • AMOVA;
  • genetic distance;
  • gene flow;
  • conservation;
  • volcanic disturbance;
  • Dactylanthus taylorii;
  • Balanophoraceae

Aim

Dactylanthus taylorii Hook. f. (Balanophoraceae) is an endemic, endangered root-holoparasitic flowering plant in New Zealand. We investigated genetic variation within and among populations of the species over its entire known distribution range to study distinctness of populations, geographical distribution of genetic variation, the level of gene flow among populations and implications of the findings for conservation.

Location

Populations of D. taylorii were sampled from the central, eastern and western North Island of New Zealand and from the only known population on an offshore island (Little Barrier Island) off the north-east coast of the North Island.

Methods

Random amplified polymorphic DNA (RAPD) profiles were obtained from inflorescence samples of 146 tuber clumps in seventeen populations. We used UPGMA cluster analysis based on Nei's genetic distance and analysis of molecular variance (AMOVA) to calculate partitioning of genetic variation within and among populations and the relationship between geographical and genetic distance.

Results

Reproducible RAPD markers, including several that were specific to single populations, show that all populations sampled are unique. Populations can be grouped into two main clusters based on genetic variation, corresponding to an eastern and western distribution, respectively, and separated by the Taupo Volcanic Zone. Genetic variation is predominantly (63%) among as opposed to within populations and is not correlated with geographical distance below the regional scale.

Main conclusions

Results indicate long isolation and restricted gene flow among populations, both of which are interpreted mainly as characteristics of the species rather than as results of human influence. Widespread disturbance of vegetation through repeated volcanic events, with a dominant eastern direction of ash flow and tephra formation, are seen as the likely mechanism for the regional grouping of genetic variation into two clusters. Results support the national coordination of conservation management of D. taylorii and identify priorities for protection. Because geographical distance is not a good indicator for genetic similarity, findings cannot be extrapolated to populations that have not been sampled; the usual concept of nearest-provenance-based sourcing (eco-sourcing) of seeds for restoration may not apply to the species.