Thursday, 31 December 2009

Genetic conservation of the True Service (Sorbus domestica)

A very useful account of the true service tree (Sorbus domestica) was written by Peter Rotach of the Department of Forest Sciences at the Swiss Federal Institute of Technology, Zürich in 2003 (details at end of this entry).

As well as an excellent illustrated description of the tree, there is much information and recommendations on how best to conserve this globally scarce species.  This rarity, in common with many Sorbus , is discussed by Rotach who regards it as the natural habit of this and other tree species.

Research findings, he says, "suggest that the genetic system of naturally rare species seem to be well adapted to low densities. Long-distance gene flow, dynamic meta-population structures with local
extinction and recolonisation, long-distance migration events through effective seed dispersal and a mixed reproductive system may be key elements for maintaining genetic diversity in rare species like S. domestica.  While vegetative reproduction conserves
genetic diversity even in the smallest populations, long distance pollen and seed dispersal guarantee recolonisation."

Judging by the very restricted distribution of many Sorbus species, long distance migration must, however, be a rare event.

In regard to the uses of true service fruit, Rotach says they were, and still sometimes are, used "for conserving apple cider" as well as for producing "high quality liquors, and for specialist products such as marmalades."  (I wonder if he means eaux-de-vie or ratafia, i.e. liqueur, and a sort of membrillo paste or cotignac rather than a marmalade).

He does not, however, mention that the fruit is still sold, apparently for eating raw, in areas where the tree is well know such as Italy and the south of France.  Nor does he mention cormé, a sort of true service cider (on which I will write at boring length on some future date).

At the end of Rotach's paper there is a useful distribution map and a short list of references.

The map shows that the tree occurs from north central Turkey to Morocco and north to Britain where the Wyre Forest site appears to be the most northerly of any.  The bulk of the trees however occur in Greece, the Balkans, Italy, France and Spain.  As with many tree species, the distribution would seem to indicate that it is tolerant of a wide range of climatic conditions.  While some populations are, no doubt, genetically adapted to their local climate, it seems a bit premature to worry, in the light of the various climate change projections, about the general welfare of trees with such wide distributions .


Rotach P. (2003) EUFORGEN Technical Guidelines for genetic conservation and use for service tree (Sorbus domestica).  International Plant Genetic
Resources Institute, Rome, Italy.

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