Taxonomic uncertainty and a continental conundrum:Polypodium macaronesicumreassessed

Abstract

Data from the chloroplast trnL-F region are used to test the delimitation of putative diploid species in the Polypodium cambricum aggregate. In particular, we investigate the distinctiveness of the Macaronesian Polypodium macaronesicum, P. azoricum and the continental P. cambricum, investigate molecular diversity patterns within Macaronesia and establish the identity of putative P. macaronesicum material collected from an area in southern Spain, where it co-occurs with other Macaronesian elements. The analysis supports the distinction of Macaronesian and continental plants, with accessions from Macaronesia resolved as monophyletic. Greater haplotype diversity was found in Macaronesia than on the continent. All Macaronesian haplotypes were restricted to a single archipelago and were resolved into archipelago groupings in statistical parsimony analysis, suggesting limited dispersal between archipelagos. Morphological traits distinguish Azorean plants, but there are no clear morphological traits to distinguish Madeiran and Canarian plants. The recognition of P. macaronesicum as a distinct taxon is proposed, with two subspecies, one Azorean and one Madeiran–Canarian. Material from southern Spain referred to P. macaronesicum is shown to exhibit the Azorean haplotype, consistent with its morphology. This would represent a novel relationship for the flora of this continental Macaronesian enclave area if the occurrence of this taxon – collected only once in the region – is confirmed. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 449–460.