Congruence between environmental parameters, morphology and genetic structure in Australia’s most widely distributed eucalypt, Eucalyptus camaldulensis |
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Authors: | P A Butcher M W McDonald J C Bell |
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Institution: | (1) CSIRO Forest Biosciences, P.O. Box E4008, Kingston, ACT 2604, Australia;(2) CSIRO Forest Biosciences, Private Bag 5, Wembley, Western Australia, 6913, Australia |
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Abstract: | Eucalyptus camaldulensis is one of the most widely utilised eucalypts. It is also the only eucalypt that occurs across the Australian continent, playing
a key ecological role as fauna habitat and in riverbank stabilisation. Despite its ecological and economic importance, uncertainty
remains regarding the delineation of genetic and morphological variants. Nine hundred and ninety trees from 97 populations,
representing the species’ geographic range were genotyped using 15 microsatellite loci and patterns of diversity compared
with restriction fragment length polymorphisms in 29 of these populations. Both markers showed that despite having a riverine
distribution, downstream seed dispersal has had less influence than geographic distance on dispersal patterns. Spatial patterns
in the distribution of microsatellite genotypes were compared with environmental parameters and boundaries defined by river
systems, drainage basins and proposed subspecies. Significant genetic differences among populations within river systems indicated
that rivers should not be treated as a single genetic entity in conservation or breeding programmes. Strong geographic trends
were evident with 40% of variation in genetic diversity explained by latitude and moisture index. Isolation by distance and
significant correlations between genetic distance and environmental parameters for most loci suggest historical factors have
had more influence than selection on current patterns of distribution of genetic diversity. Geographic structuring of molecular
variation, together with congruence between genetic and morphological variation indicate that E. camaldulensis should be treated as a number of subspecies rather than a single variable taxon. High levels of genetic diversity and geographic
trends in the distribution of variation provide a firm basis for further exploration of the species’ genetic resources. |
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Keywords: | Eucalyptus camaldulensis Genetic structure Microsatellites RFLP Morphology |
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