Abstract
Alder buckthorn (Frangula alnus) is one of Ireland’s rarest tree species, and in Northern Ireland the species is now restricted to a single population in Peatlands Park, Co. Armagh numbering ca. 140 mature trees. Genotyping of 95% of the trees at nine nuclear microsatellite loci revealed that levels of genetic diversity within this population were generally lower than those reported from larger populations in Spain. Analysis of six chloroplast microsatellite loci revealed no variation. The level of FIS was significantly higher than that in the Spanish populations, as well as in other populations across Europe, potentially indicating inbreeding. Spatial autocorrelation analysis indicated some evidence of fine-scale genetic structuring, most likely due to limited seed dispersal, but the overall level of differentiation between subpopulations was low, indicating high levels of gene flow, probably due to cross-pollination by bees. Our results are consistent with a gradual population expansion from a limited number of individuals. We suggest that more immediate conservation efforts might be best focused on ensuring suitable habitat for the continued recovery of this isolated population.
Highlights
Populations of endangered or threatened species tend to be small and/or isolated and are vulnerable to stochastic processes
There are records of the F. alnus previously occurring on the northern side of the Lough, as well as a single tree in Drumawhey Bog, County Down[12], these are extinct, the former natural woodland having been replaced by a broadleaf plantation[10]
The aim of the present study was to determine the levels of and patterns of genetic diversity in the remaining population to discover (1) whether there is any evidence for a genetic bottleneck, (2) if the establishment from a relatively limited number of individuals has been accompanied by a degree of inbreeding, and (3) whether there is any significant genetic substructuring within the population
Summary
Populations of endangered or threatened species tend to be small and/or isolated and are vulnerable to stochastic processes These problems are further exacerbated at the genetic level, where the increased effects of genetic drift and potential for inbreeding can lead to low levels of genetic variation[1, 2]. The present-day surviving population has been part of Annagarriff Nature Reserve in Peatlands Park, County Tyrone since 1978, and the species is protected under the Wildlife (NI) Order (1985) and is a Priority Species for Conservation Action The history of this population, which currently numbers ca. As F. alnus is considered an invasive pest species in many countries[19, 20], our findings could shed light on the genetic demography of this recently expanded population with respect to similar invasive populations
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