Species delimitation in Nicotiana sect. Suaveolentes (Solanaceae): reciprocal illumination leads to recognition of many new species

In this volume of Curtis's Botanical Magazine, we increase the number of species recognised in Nicotiana sect. Suaveolentes to 38, up from the 21 recorded in the Flora of Australia published 39 years ago, but we estimate the final number is likely to exceed 60. We examine the reasons why so many unrecognised species exist. Several Australian and American botanists have previously specialised in Nicotiana but did not detect such diversity. We have carried out many fieldtrips, seen most known species in the wild and have grown these accessions from diverse areas side-by-side in cultivation to avoid basing decisions about species characteristics on features heavily influenced by environmental plasticity. In the end, we conclude that it is a mixture of focused and extensive fieldwork and more recent genomic, genetic and karyological studies combined in the process of reciprocal illumination, that has enabled us to describe so many new species. We also briefly focus on the topic of why Nicotiana is so species-rich in Australia.