Population structure in the clonal, woody wetland plant Melaleuca ericifolia (Myrtaceae): an analysis using historical aerial photographs and molecular techniques
2012
Robinson, Randall | James, Elizabeth A | Boon, Paul I
Analyses of historical aerial photographs from 1957 to 2003 were combined with two molecular techniques to examine population structure of the swamp paperbark (Melaleuca ericifolia Sm., Myrtaceae) in Dowd Morass, a large, brackish-water wetland of the Gippsland Lakes, Australia. Molecular markers (microsatellites and inter-simple sequence repeats) demonstrated that the large, dome-shaped stands of M. ericifolia evident in the field were individual genets and that adjacent genets did not intermingle. The development of 18 individual stands visible in aerial photographs from 1964 to 2003, but absent from 1957 images, allowed us to calculate that stands expanded at (individual) mean rates of 25–77 m2 year–1 over the period 1964–2003. Rates of lateral expansion, however, varied significantly between 1964 and 2003; the mean rates were highest in 1978–1982 and 1982–1991 (75 ± 7 and 73 ± 9 m2 year–1, respectively) and significantly lower in 1991–2003 (45 ± 3 m2 year–1). A slowing of lateral expansion rate may indicate stand senescence, although competition and space limitations as clones abut each other may also be relevant processes. Clonality has several important implications for the conservation and rehabilitation of Melaleuca-dominated wetlands in south-eastern Australia, including the ability of plants to maintain themselves under adverse hydrological and salinity regimes.
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