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Genetic diversity study reveals link between Irish oak and oak populations on Iberian peninsula

January 5, 2011

Irish oak; genetic diversity & the Iberian connection

Colin T. Kelleher, Trevor R. Hodkinson, Daniel L. Kelly and Gerry C. Douglas (2010)

For full details of this COFORD funded research see: http://www.coford.ie/iopen24/pub/COFORD-Connects/rm18.pdf

Here is a brief summary:

Native oak woods cover a very small proportion of the land area in Ireland(approximately 0.1 %). Coverage has diminished since 5000 BC, due primarily to human influence in the form of woodland utilisation and land conversion to livestock grazing and crop production.

The woodland remnants thus represent a scarce and valuable resource. However, little is known about the genetic diversity of woodlands in Ireland. A COFORD-funded study obtained data on genetic characteristics of oak woods in Ireland (Kelleher et al. 2002). This was the first study to analyse molecular genetic characteristics of a native tree species.

The study revealed an underlying geographical genetic structure in Irish oak populations and presented estimates of diversity from both nuclear and chloroplast DNA analyses (Kelleher et al. 2002, 2004a, 2005). A follow-up study funded by the National Parks and Wildlife Service sampled more populations in an attempt to further investigate geographic patterns.

The current study shows a genetic link between Irish oak and those that originated in the Iberian Peninsula refugium. From the results it is clear that Ireland has four main types of oak, these are Quercus petraea with haplotype 12, Q. petraea with haplotype 10, Q. robur with haplotype 12 and Q. robur with haplotype 10.

The haplotype distribution supports pollen data for a postglacial colonisation of oak from the south, as Irish populations are shown to have a link with those from the Iberian Peninsula. The levels of genetic diversity are lower in Irish populations than that found in many other European populations. Although there is some evidence for inbreeding in Irish oak populations, it is not likely to be an important factor in their genetic fitness as they are outbreeding wind pollinated trees.

The techniques used in this project offer great potential for use in other tree species in Ireland. Many of our native species have been analysed in genetic studies across Europe and thus there is an opportunity to situate Irish populations into this framework. Work is ongoing in the National Botanic Gardens to characterise other native tree species in a European context.

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