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Assessing pollen mediated gene flow at the landscape level


Matt Larcombe searches for hybrids among his seedlings. [Image: Matt Larcombe]




A blue gum plantation in Victoria Valley (Victoria) represents a potentially strong pollen source that may impact on the remnant native gene pool. [Image: Matt Larcombe]


­Subproject 4.2.6 has a new PhD student at the University of Tasmania.  Matt Larcombe will be investigating the management of gene flow from plantation to native eucalypts. Matt was awarded a competitive Forest and Wood Products Australia (FWPA) PhD scholarship to carry on and extend the research program developed by Dr Robert Barbour (formerly of UTAS).

Eucalypts are well known for having weak reproductive barriers between closely related species, resulting in interspecific hybridisation or, put another way, gene flow between species. Robert Barbour (formally of UTAS) identified that gene flow from locally exotic shining gum (Eucalyptus nitens) plantations was occurring in Tasmania (read more), and that a similar risk existed in other states where Tasmanian blue gum (Eucalyptus globulus) plantations exist outside the natural range of the species (read more). Matt’s project is focused on identifying barriers to gene flow between plantation and native eucalypts to determine when, where and how gene flow from plantations should be managed.

One aspect of this study is to assess how far pollen moves from plantations. This can be done by collecting open pollinated seed from cross compatible species (i.e. those known to hybridise with E. globulus) along landscape scale transects away from mature (flowering) plantations. This seed is then grown on and the seedlings screened for the presence of hybrids with E. globulus (hybrids display morphology intermediate between the two parent species). The degree of hybridisation along the transect then indicates the distance of effective pollen flow.

Matt has recently undertaken his first field trip in search of potentially suitable landscapes for establishing such transects in South Australia and Victoria. The success of these types of studies depends on finding suitable landscapes. In particular the site needs to have one pollen source (plantation) only, the plantation must be mature, the plantation and the neighbouring native species must have flowering overlap, and hybridisation needs to be occurring. Matt identified several potential sites where transects of between 2 km and 13 km can be established. Sites of particular interest were identified in the Grampians and the Green Triangle. From each potential site open pollinated seed was collected from trees beside the plantations for a pilot study to determine whether or not hybridisation is occurring. The seeds are now germinating in the glasshouse, and hybrids should be identifiable in two to three months.
Biobuzz issue eleven, May 2010