Genetic Polymorphisms in Populations of Aesculus hippocastanum across Europe (project completed 2011)

Northern populations of Aesculus hippocastanum are not more genetically depleted than southern populations, thus suggesting that diversity for this species is not correlated with latitudinal distribution.

Genetic diversity in Aesculus hippocastanum (Hippocastanaceae) across European naturalised populations.

Aesculus hippocastanum has been described as a recalcitrant species by several groups. However, the level of seed desiccation tolerance in this species, as well as a few other parameters, was described as depending on the geographical origin. It was concluded that the heat sum was of major influence on the seed development time and, indirectly, on the desiccation behaviour which is maturation dependent, i.e. that phenotypic effects were at play. However, a presumption in this study was an identical genetic background in all sample populations. A. hippocastanum trees are thought to originate from the Balkans, and to have dispersed as an ornamental tree throughout Europe in recent history dating back no further than c. 400 years. This corresponds to c. 10 generations, and genetic similarity is therefore a reasonable presumption.

To investigate if genetic drift occurred in A. hippocastanum trees throughout Europe, genetic diversity studies were conducted on seeds from Greece, Poland, Norway and the UK. AFLPs were used to characterise genetic diversity. Genetic diversity was compared to seed physiological polymorphisms described previously. The null hypothesis was adopted that differences in genetic diversity are present between these populations that correlate with the observed differences in seed physiology. Differences in genetic variation were indeed found, and appeared to correlate with variation in the phenotypic behaviour.

The objective of this project was to evaluate the use of AFLPs in differentiating among populations of A. hippocastanum. The purpose was to better understand how genetic diversity between populations contributes to differences in seed physiology.