Patterns of genetic variation in Colchicum autumnale L. and its conservation status in Ireland: a broader perspective on local plant conservation

Abstract

Colchicum autumnale L. (Colchicaceae) is classed as an endangered plant species in Ireland, with a highly localised distribution centred on the Nore Valley in the southeast. The high resolution Amplified Fragment Length Polymorphism genetic fingerprinting technique was used to clarify a question over the native status of the species and to assess its Irish conservation status through comparison with populations throughout northwestern Europe. The analysis of 20 populations with three selective primer pairs yielded 155 markers, 90% of which displayed polymorphism. Allele frequency was estimated using a Bayesian approach and based on this, total gene diversity (Ht) was 0.305 and mean within-population gene diversity (Hw) was 0.142. Irish populations contain comparatively moderate levels of genetic diversity and are unlikely to be susceptible to the deleterious effects of inbreeding depression. Analysis of Molecular Variance revealed that populations were significantly differentiated, with 68% of variation partitioned among populations and 32% within. Neighbour-joining and ordination analyses revealed a major biogeographic division between populations, suggesting that post-glacial migration in northwest Europe was driven from at least two separate glacial refugia and that the re-colonisation of Britain and Ireland is likely to have occurred via a western seaboard route from an Iberian glacial refugium. The total evidence points to C. autumnale being a native component of the Irish flora and its endangered IUCN (World Conservation Union) country status should therefore make it a priority for national conservation efforts. The study illustrates the point that a broader geographical perspective is fundamental to the assessment of the conservation status of regionally threatened plant species.