Morphology and pollen fertility of native and non-native bluebells in Great Britain

There is considerable concern that the native British bluebell Hyacinthoides non-scripta (Asparagaceae) is at risk due to hybridisation with naturalised British non-native bluebells. However, the taxonomic identity of British non-natives is uncertain, and they are either referred to as Spanish bluebells, H. hispanica, or as hybrids between H. non-scripta and H. hispanica. To establish whether a detailed morphological analysis can shed light on the taxonomic identity of non-native British bluebells. We measured 28 morphological characters and recorded the pollen fertility of native and non-native bluebells in Britain and compared these with H. hispanica populations from Portugal. British non-native bluebells appeared morphologically close to H. hispanica but occupied a separate phenotypic space. All three taxa showed high morphological variability with overlapping ranges, however, at least 92.8% of trait means were significantly different between any pair-wise taxon comparison. Sixty per cent of continuous traits were significantly larger in British non-native bluebells compared to H. non-scripta and H. hispanica. In contrast, pollen fertility was significantly lower in British non-natives (79%) compared to H. non-scripta (94%) and H. hispanica (84%). These results are consistent with, however, do not provide conclusive evidence for, the possible hybrid status of British non-native bluebells.