Conservation implications of clonality and limited sexual reproduction in the endangered shrub Acanthocladium dockeri (Asteraceae)

Abstract

Allozyme electrophoresis was used to determine the extent of clonality in four naturally occurring populations of Acanthocladium dockeri F.Muell. from the mid-north of South Australia. A total of 33 loci was scored for at least 16 plants from each population. The four known populations of A. dockeri represent four quite distinct genetic clones. Each natural population consists of a single genet, and no indication of any correlation between geographical proximity and genetic similarity was found. Seed set in flowers was very low (0.6% of florets), probably owing to low pollen germinability. Seedlings raised from A. dockeri seed collected at Hart displayed obvious genetic affinities to their parent, but were nevertheless genetically distinct. Differences were consistent with the derivation of this seed by selfing of the Hart genet. A. dockeri is considered at high risk of extinction because of its low genetic diversity, poor seed production, lack of seedling recruitment and population growth by clonal reproduction alone. On the basis of the outcomes of this research, the following recommendations for conservation management of A. dockeri are made: (1) all four extant genets should be preserved in their respective habitats; (2) at least one ex situ collection of all four extant genets should be maintained at a secure site as an insurance against population loss; (3) further surveys are required to potentially locate new populations with superior fertility; and (4) mixing of clones or seed provenances into a single population should be avoided until appropriately designed experimental translocations have evaluated the possible consequences of such mixing on competitive, reproductive and genetic responses of populations.