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Spatial genetic structure reflects extensive clonality, low genotypic diversity and habitat fragmentation in Grevillea renwickiana (Proteaceae), a rare, sterile shrub from south-eastern Australia.

Abstract

BACKGROUND AND AIMS

The association of clonality, polyploidy and reduced fecundity has been identified as an extinction risk for clonal plants. Compromised sexual reproduction limits both their ability to adapt to new conditions and their capacity to disperse to more favourable environments. Grevillea renwickiana is a prostrate, putatively sterile shrub reliant on asexual reproduction. Dispersal is most likely limited by the rate of clonal expansion via rhizomes. The nine localized populations constituting this species provide an opportunity to examine the extent of clonality and spatial genotypic diversity to evaluate its evolutionary prospects.

METHODS

Ten microsatellite loci were used to compare genetic and genotypic diversity across all sites with more intensive sampling at four locations (n = 185). The spatial distribution of genotypes and chloroplast DNA haplotypes based on the trnQ-rps16 intergenic spacer region were compared. Chromosome counts provided a basis for examining genetic profiles inconsistent with diploidy.

KEY RESULTS

Microsatellite analysis identified 46 multilocus genotypes (MLGs) in eight multilocus clonal lineages (MLLs). MLLs are not shared among sites, with two exceptions. Spatial autocorrelation was significant to 1·6 km. Genotypic richness ranged from 0 to 0·33. Somatic mutation is likely to contribute to minor variation between MLGs within clonal lineages. The eight chloroplast haplotypes identified were correlated with eight MLLs defined by ordination and generally restricted to single populations. Triploidy is the most likely reason for tri-allelic patterns.

CONCLUSIONS

Grevillea renwickiana comprises few genetic individuals. Sterility has most likely been induced by triploidy. Extensive lateral suckering in long-lived sterile clones facilitates the accumulation of somatic mutations, which contribute to the measured genetic diversity. Genetic conservation value may not be a function of population size. Despite facing evolutionary stagnation, sterile clonal species can play a vital role in mitigating ecological instability as floras respond to rapid environmental change.

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  • Authors+Show Affiliations

    ,

    Royal Botanic Gardens Melbourne, Birdwood Avenue, South Yarra, Victoria 3141, Australia School of Botany, The University of Melbourne, Victoria 3010, Australia Elizabeth.James@rbg.vic.gov.au.

    NSW Office of Environment and Heritage, PO Box 733, Queanbeyan, NSW 2620, Australia Department of Environmental Management & Ecology, La Trobe University, PO Box 821, Wodonga, Victoria 3689, Australia.

    Source

    Annals of botany 114:2 2014 Aug pg 413-23

    MeSH

    Alleles
    Australia
    Base Sequence
    Chromosomes, Plant
    DNA, Chloroplast
    Ecosystem
    Genetic Variation
    Genotype
    Geography
    Meristem
    Microsatellite Repeats
    Plant Infertility
    Principal Component Analysis
    Proteaceae
    Reproduction, Asexual

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    24737718