Current status and conservation genetics of Alder buckthorn Frangula alnus in Northern Ireland Bradley, C., Preston, S., Provan, J., & Reid, N. (2009). Current status and conservation genetics of Alder buckthorn Frangula alnus in Northern Ireland. Northern Ireland Environment Agency. Document Version: Publisher's PDF, also known as Version of record Queen's University Belfast - Research Portal: Link to publication record in Queen's University Belfast Research Portal General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made to ensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in the Research Portal that you believe breaches copyright or violates any law, please contact [email protected]. Download date:30. Sep. 2021 Natural Heritage Research Partnership Current status and conservation genetics of Alder buckthorn Frangula alnus in Northern Ireland Quercus Project QU08-03 Prepared for the Northern Ireland Environment Agency (NIEA) by Drs. Caroline Bradley, Jane Preston, Jim Provan & Neil Reid, Natural Heritage Research Partnership, Quercus This report should be cited as: Bradley, C., Preston, S.J., Provan, J. & Reid, N. (2009) Current status and conservation genetics of Alder buckthorn Frangula alnus in Northern Ireland. Report prepared by the Natural Heritage Research Partnership, Quercus for the Northern Ireland Environment Agency, Northern Ireland, UK. Quercus project QU08-03 Quercus hosts the Natural Heritage Research Partnership between the Northern Ireland Environment Agency and Queen's University Belfast. www.quercus.ac.uk ii Executive Summary 1. Alder buckthorn (Frangula alnus) is one of Ireland’s rarest tree species and is a Priority Species for Conservation Action in Northern Ireland and protected under the Wildlife (NI) Order (1985). 2. Surveys were carried out during summer 2007 at sites formerly occupied by the species in Northern Ireland to ascertain its current distribution and status. 3. Only one remaining population of Alder buckthorn was found in Northern Ireland at Peatlands Park, County Armagh. 4. A complete inventory of the Peatlands Park population was undertaken during summer 2008. A total of 139 individual trees were found, georeferenced, tagged and a sample of leaf and seed tissue taken for genetic analysis. 5. There was no evidence that the Peatlands Park population had ever undergone a genetic bottleneck. 6. Levels of genetic diversity were lower than those previously reported for populations elsewhere e.g. Spain, but observed levels of heterozygosity were nevertheless high suggesting that biparental inbreeding is not a major threat. 7. Allele frequencies at all eight loci examined were similar in adult trees and their seeds suggesting that seeds are a largely representative repository of genetic diversity for the next generation. 8. There was no broad-scale genetic structuring indicating a general lack of barriers to pollen dispersal with frequent long-distance cross pollination events (up to 850m). Fine- scale genetic structuring was present and probably due to limited seed dispersal. 9. High incidence of fruiting in Peatlands Park is indicative of high levels of cross- pollination and perhaps shorter generation times making the population more similar to central European populations than those of the Mediterranean or Iberia which tend to have lower incidence of fruit and higher incidence of ovule loss due to limited cross- pollination. 10. Despite low abundance and restricted distribution, the Alder buckthorn population at Peatlands Park contains a notably high level of genetic diversity. iii 11. We make two recommendations for further potential action: i. To preserve existing high levels of genetic diversity and ensure that rare alleles are not lost from the Peatlands Park population through genetic drift, consideration should be given to artificially seeding plants. We have identified 55 individual trees that possess rare alleles (present in less than 5% of the total population). It should be relatively simple, and not particularly costly, to harvest seed from specific trees to artificially plant areas within Peatlands Park close to the parental population. ii. Rare and isolated populations are at risk from stochastic extinction events. Consideration should be given to resurveying sites formerly occupied by Alder buckthorn pre-1980 to confirm the restricted nature of the species’ distribution. To safeguard the future survival of the species in Northern Ireland further consideration should be given to establishing populations at sites other than Peatlands Park, for example, repatriating the species on formerly occupied sites. iv Contents Executive Summary ..................... iii Contents ..................... v 1.0 Introduction ..................... 1 2.0 Methods ..................... 3 2.1 Plant surveys and sampling ..................... 3 2.3 Assessment of intraspecific genetic diversity ..................... 3 2.4 Statistical Analyses ..................... 3 3.0 Results ..................... 5 3.1 Current distribution and status of Alder buckthorn ..................... 5 3.2 Levels and patterns of genetic diversity ..................... 6 3.3 Levels of pollen flow between population fragments ..................... 9 4.0 Discussion ..................... 11 5.0 Recommendations ..................... 12 6.0 Acknowledgements ..................... 12 7.0 References ..................... 13 Appendix 1 ..................... 14 Appendix 2 ..................... 15 Appendix 3 ..................... 16 v Alder buckthorn genetics Quercus 1.0 Introduction By definition, populations of rare species have low abundance and are often isolated from other similar populations making them particularly vulnerable to stochastic extinction. Rare populations usually have low levels of genetic variation due to increased genetic drift and a higher risk of inbreeding (Hedrick & Kalinowski, 2000; Cole, 2003). Genetically depauperate populations have reduced evolutionary potential, which further increases their risk of extinction (Hansson & Westerberg, 2002; Frankham, 2005). Consequently, knowledge of the levels and patterns of genetic diversity within populations of rare or threatened species is vital in the formulation of rational, sustainable conservation plans (Hedrick 2004). Alder buckthorn (Frangula alnus) is a small deciduous shrub up to 4-5m in height, with wide-spreading branches, inconspicuous greeny-white flowers and round fruits up to 1cm in diameter which ripen in October or November. It prefers moist acid soils along riverbanks and does well on peat. Although widespread throughout temperate Europe, it is one of Ireland’s rarest trees (Fig. 1). In Northern Ireland, the species is protected under the Wildlife (NI) Order (1985) and is a Priority Species for Conservation Action. Fig. 1 Alder buckthorn distribution throughout Ireland. Source: NBN Gateway. 1 Alder buckthorn genetics Quercus Alder buckthorn is exclusively sexual (Medan, 1994) with hermaphroditic flowers being pollinated by a wide variety of insect species including Hymenoptera, Diptera, Coleoptera and occasional Lepidoptera (Hampe, 2005). In controlled pollination studies, almost no selfing or geitinogamy (pollination from a flower on the same plant) occurred, indicating the existence of self-incompatibility mechanisms (Medan, 1994). Field studies suggest that limited fruiting is the result of low levels of cross- pollination (Medan, 1994; Hampe, 2005). Due the highly restricted nature of the distribution of Alder buckthorn in Northern Ireland and the importance of gene flow in fragmented populations the aims of the current project were to: • Determine the current distribution of Alder buckthorn in NI; • Determine levels and patterns of interspecific genetic diversity, including the potential for inbreeding; • Identify levels of pollen dispersal between remaining population fragments, and; • Formulate a rational conservation plan with the aim of maintaining existing genetic diversity. 2 Alder buckthorn genetics Quercus 2.0 Methods 2.1 Plant surveys and sampling A total of 46 historical records for Alder buckthorn distribution were collated from 1832 to 2004 using the Centre for Environmental Data and Recording (CEDaR) and the NBN Gateway. To assess the species current distribution those sites where the species was known to occur after 1980, that also possessed a grid reference of at least 6-figures, were surveyed during summer 2007 to ascertain the current distribution and status of the species (Appendix 1). During summer 2008, all individual adult trees located at Peatlands Park, Co. Armagh, were numerically tagged, georeferenced and leaves were taken for genetic analyses. Seeds were also collected from between one and six berries from selected adult plants (Appendix 2). 2.2 Assessment of intraspecific genetic diversity All individual adult plants and a selection of seeds were genotyped at eight microsatellite loci: FaA3, FaA7, FaA104, FaA110, FaB7, FaB9, FaB101 and FaB106 (Riguiero et al. 2009). PCR was carried out in a total volume of 10 μl containing 100 ng genomic