Taming the beasts: challenges of identification in big plant genera

Background and aims Navigating morphological diversity in large plant genera with hundreds of species remains a challenge, making identification in these groups daunting. Traditional text-based identification tools are either lacking or if published, they are behind pay-walls; they can also be difficult to use due to length and technical language and are often heavily reliant on reproductive characters. Methods In this paper, we present lessons learnt from building accessible multi-access keys to the large and economically important genus Solanum that currently includes 1,239 accepted species. We use a set of characters selected from monographs and expert assessment and the online key generation platform Xper3 to create two multi-access keys for Solanum. Results The process we used for Solanum involves first identification of the correct infrageneric group, followed by a second key that enables species-level identification. This two-step identification process is faster to produce and enables the publication of keys in a stepwise manner. Breaking down a large genus into more bite-sized chunks by using a small set of vegetative characters is key to success, helping users to confidently narrow down their options. Conclusions In Solanum most clades and even species are defined by multiple rather than single putative apomorphies, which means multi-access keys are optimal for fast and accurate identification. Traditional dichotomous keys are not ideal for large groups because they become extremely lengthy and difficult with limited material. Multi-access, online keys can be constructed before a taxonomic treatment is complete, allowing for improved character understanding. The identification strategy used for Solanum can be generalised to other large genera to enable easier user access to a significant proportion of plant diversity.