Variable clonality and genetic structure among disjunct populations of Banksia mimica.

Various factors influence patterns of genetic diversity within and between populations that are important considerations for plant conservation. Both clonality and population genetic differentiation are key factors informing conservation actions, especially for rare species. Banksia mimica is a rare species that occurs in three disjunct locations in the biodiversity hotspot of the southwest Australian Floristic Region of Western Australia. Extant populations are suspected to have varying levels of clonality and high levels of genetic differentiation due to geographic disjunction. A genetic analysis was undertaken in order to confirm clonal reproduction and obtain initial estimates of genotypic diversity, and to assess genetic diversity within, and genetic structure among, populations. Genotypic richness ranged from 0.210 to 1.00 supporting observations in the field of variable degrees of clonal growth. The most clonal populations showed genetic signals of greater levels of observed heterozygosity than expected heterozygosity and negative F_IS values that were not present in other populations of B. mimica or populations of the nonclonal sister taxon B. vestita. There was strong genetic structure with high genetic divergence among geographically disjunct population groups (global F_ST = 0.392, D_ST = 0.475), as is often found within the Australian flora. Genetic differentiation among disjunct populations located on the Whicher Scarp and more northern populations approached, or was greater than, that between Whicher populations and populations of the sister taxa B. vestita. This result is consistent with several other species that show genetic differentiation in disjunct populations located on the Whicher Scarp geomorphological formation. Results suggest a reassessment of the taxonomy and identification of evolutionary significant units for populations of B. mimica would support effective conservation management of this species. [ABSTRACT FROM AUTHOR]