Assessment of genetic variability among Grevillea parviflora subsp. parviflora and closely related taxa

Abstract

This research was undertaken with the aim to identify the robustness of available genetic markers (chloroplast DNA sequences and nuclear microsatellites) to differentiate G. parviflora subsp. parviflora (Gpp) from five closely related taxa within the Linearifolia Group of grevilleas; particularly G. humilis subsp. humilis (Ghh) in the Lake Macquarie area. One chloroplast region had a consistent character that separated the northern populations of Gpp (northern: Hunter area) from populations in the south of its range (southern: Cumberland Plains area) and all other taxa. This character was an 11 base pair sequence inversion. An assessment of over 50 microsatellite loci led to the identification of nine primer pairs that consistently amplified variable product in the target taxon. Genetic profiling using the microsatellites from a minimum of 10 individuals per taxon demonstrated a number of important issues: (1) some individuals amplify three alleles at one or more loci, suggesting possible aneuploidy or triploidy; (2) some individuals from the same population have identical, or near identical, genotypes which may be indicative of vegetative propagation; (3) genetic profiles among all samples were complex and the microsatellite loci provided moderate support for some of the taxa while other samples suggest a likely history of admixture, hybridisation, or the mis-identification of plant material. These possibilities need to be assessed along with morphological studies being undertaken by Mr Bob Makinson as a complementary component to this research. Particular consideration should be given to the southern populations of the focal taxon which, based on cpDNA and microsatellites, were genetically more similar to the geographically closer G. parviflora subsp. supplicans. Overall, the genetics tools (cpDNA and microsatellites) show great promise for delineating northern populations of G. parviflora subsp. parviflora and for deeper investigations into population genetic structure including the number of unique genotypes within and among populations, the physical spread of clonal genotypes within populations, the genetic differentiation and the genetic health (as assessed by heterozygosity and inbreeding) of populations of this threatened taxon.