Willow species diversity and hybridisation
 
A key feature of sub-arctic willows is their tendency to hybridise, and this hybridisation leads to taxonomic complexity (difficulty in identifying species and hybrids). This is important from a conservation perspective, as it is not possible to know the conservation status of an entity, and hence address its conservation needs, unless the taxon in question can be identified. Based on morphological data, it appears that some species are more likely to hybridise than others, and there is some evidence that hybridisation increases in frequency, as density of the parental species decreases (David Mardon, pers comm. 2000). As sub-arctic willows are declining, and as hybrids have different attributes to their parental taxa, this will inevitably have knock-on effects for other organisms (Fritz et al., 1998; Orians et al., 2000). However, it is currently not possible to unambiguously define the diversity of willow species and hybrids present in Scotland based on morphological data alone. Molecular data are required to supplement morphological observations to overcome the extreme difficulties of identification.

For the current project molecular markers were developed and used to investigate the extent and dynamics of hybridisation among sub-arctic willows, and to allow the identification of species and hybrids.