True Service-tree (Sorbus domestica, Rosaceae) in the British Isles: Rare but diverse

Abstract

True Service-tree (Sorbus domestica L.) is an extremely rare and only spontaneously occurring tree species in the British Isles. Its populations are characterised by low census size and strong fragmentation. Uni- and bi-parentally inherited markers were used to study the regional genetic make-up of the species. We analysed 31 samples from six different sites across south Wales and south-west England, spanning the whole putative natural occurrence in Britain. Genetic diversity in the entire British population (all six sites) was unexpectedly high, with 2.912 alleles per locus (nuclear DNA) and three different maternal lines (chloroplast DNA). In contrast, diversity within sites was low as we found identical multilocus microsatellite genotypes in five out of the six sampled locations. Finally, comparison with a pan-European dataset of S. domestica revealed a close association between British and French populations rather than with populations from the Mediterranean area or Balkan Peninsula. The putative native status of S. domestica in the British Isles is discussed based on our population genetic results as well as on ecological and historical aspects.