DNA analysis of Castanea sativa (sweet chestnut) in Britain and Ireland: Elucidating European origins and genepool diversity

PLoS One. 2019 Sep 25;14(9):e0222936. doi: 10.1371/journal.pone.0222936. eCollection 2019.

Abstract

Castanea sativa is classified as non-indigenous in Britain and Ireland. It was long held that it was first introduced into Britain by the Romans, until a recent study found no corroborative evidence of its growing here before c. AD 650. This paper presents new data on the genetic diversity of C. sativa in Britain and Ireland and potential ancestral sources in continental Europe. Microsatellite markers and analytical methods tested in previous European studies were used to genotype over 600 C. sativa trees and coppice stools, sampled from ancient semi-natural woodlands, secondary woodlands and historic cultural sites across Britain and Ireland. A single overall genepool with a diverse admixture of genotypes was found, containing two sub groups differentiating Wales from Ireland, with discrete geographical and typological clusters. C. sativa genotypes in Britain and Ireland were found to relate predominantly to some sites in Portugal, Spain, France, Italy and Romania, but not to Greece, Turkey or eastern parts of Europe. C. sativa has come to Britain and Ireland from these western European areas, which had acted as refugia in the Last Glacial Maximum; we compare its introduction with the colonization/translocation of oak, ash, beech and hazel into Britain and Ireland. Clones of C. sativa were identified in Britain, defining for the first time the antiquity of some ancient trees and coppice stools, evincing both natural regeneration and anthropogenic propagation over many centuries and informing the chronology of the species' arrival in Britain. This new evidence on the origins and antiquity of British and Irish C. sativa trees enhances their conservation and economic significance, important in the context of increasing threats from environmental change, pests and pathogens.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA, Mitochondrial / genetics
  • DNA, Mitochondrial / isolation & purification
  • Fagaceae / genetics*
  • Genetic Variation
  • Introduced Species*
  • Ireland
  • Microsatellite Repeats / genetics
  • Phylogeny
  • Phylogeography
  • Plant Dispersal*
  • Trees / genetics*
  • United Kingdom

Substances

  • DNA, Mitochondrial

Grant support

RJ received funding for this study from the University of Greenwich (UK). The Future Trees Trust (FTT) funded Karen Russell ‘KR’ (K Russell Consulting Ltd) to provide samples from the FTT collection for DNA analysis. DNA analysis was undertaken by Dr Claudia Mattioni ‘CM’ (IRET), whose laboratory costs for this project were contributed to by FTT; RJ and KR prepared a preliminary report to FTT. FTT also supported Rob Jarman ‘RJ’ (University of Gloucestershire) by contributing to the laboratory costs of DNA analysis of the Historic trees samples, undertaken by Dr Claudia Mattioni (IRET). The specific roles of these authors are articulated in the ‘author contributions’ section. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript