Jackson-et-al-1999-Mol-Ecol.pdf (692.86 kB)
Chloroplast DNA evidence for reticulate evolution in Eucalyptus (Myrtaceae)
journal contribution
posted on 2023-05-16, 11:54 authored by Jackson, HD, Dorothy SteaneDorothy Steane, Bradley PottsBradley Potts, Rene VaillancourtRene VaillancourtFour highly differentiated chloroplast DNA (cpDNA) lineages were identified in the forest tree species Eucalyptus globulus Labill. (Myrtaceae) in Australia using restriction site polymorphisms from Southern analysis. The cpDNA variation did not conform with ssp. boundaries, yet there was a strong geographical pattern to the distribution of the lineages. One lineage (C) was geographically central and widespread, whereas the other three lineages were found in peripheral populations: Western (W), Northern (N) and Southern (S). Thirteen haplotypes were detected in E. globulus, seven of which belonged to clade C. At least three of the cpDNA lineages (C, N and S) were shared extensively with other species. On the east coast of the island of Tasmania, there was a major north-south difference in cpDNA in the virtually continuous distribution of E. globulus. Northern populations harboured haplotypes from clade C while southeastern populations harboured a single haplotype from clade S. This difference was also reflected in several co-occurring endemic species. It is argued that the extensive cpDNA differentiation within E. globulus is likely to originate from interspecific hybridization and 'chloroplast capture' from different species in different parts of its range. Superficially, this hybridization is not evident in taxonomic traits; however, large-scale common garden experiments have revealed a steep cline in quantitative genetic variation that coincides with the haplotype transition in Tasmania. Our cpDNA results provide the strongest evidence to date that hybridization has had a widespread impact on a eucalypt species and indicate that reticulate evolution may be occurring on an unappreciated scale in Eucalyptus.
History
Publication title
Molecular EcologyVolume
8Issue
5Pagination
739-751ISSN
0962-1083Department/School
School of Natural SciencesPublisher
Blackwell Science LtdPlace of publication
LondonRepository Status
- Restricted