Calibration, verification and stepwise analysis for numerical phenetics: Olinia (Oliniaceae) as an example

AbstractCalibration and verification techniques are discussed in the context of numerical phenetic analysis. Calibration is introduced to evaluate the character set, decide on the type of phenetic algorithm to be used, and determine the level at which to recognize taxonomic entities. Clusters are verified by analyzing sub-samples of specimens. This determines whether the groups obtained are dependent on the variation represented by particular specimens or on variation between taxa to which the specimens belong. A stepwise procedure was used to improve resolution on the ordination axes and thus to visualize differences between phenetically similar taxa. The application of these techniques in Olinia Thunb. supports the recognition of six clearly defined clusters which correspond to O. emarginata Burtt Davy, O. micrantha Decne, O. ventosa (L.) Cufod., O. capensis (Jacq.) Klotzsch, O. radiata Hofmeyr & Phill. and O. vanguerioides Bak. The analyses further revealed one highly variable group, referred to as the O. rochetiana complex, which includes O. aequipetala (Del.) Cufod, O. usambarensis Gilg, O. volkensii Engl., O. macrophylla Gilg, O. ruandensis Gilg, O. discolor Mildbraed and O. huillensis Welw. ex A.R. Fernandes

Selecting the best candidates for resurrecting extinct-in-the-wild plants from herbaria

Resurrecting extinct species is a fascinating and challenging idea for scientists and the general public. Whereas some theoretical progress has been made for animals, the resurrection of extinct plants (de-extinction sensu lato) is a relatively recently discussed topic. In this context, the term ‘de-extinction’ is used sensu lato to refer to the resurrection of ‘extinct in the wild’ species from seeds or tissues preserved in herbaria, as we acknowledge the current impossibility of knowing a priori whether a herbarium seed is alive and can germinate. In plants, this could be achieved by germinating or in vitro tissue-culturing old diaspores such as seeds or spores available in herbarium specimens. This paper reports the first list of plant de-extinction candidates based on the actual availability of seeds in herbarium specimens of globally extinct plants. We reviewed globally extinct seed plants using online resources and additional literature on national red lists, resulting in a list of 361 extinct taxa. We then proposed a method of prioritizing candidates for seed-plant de-extinction from diaspores found in herbarium specimens and complemented this with a phylogenetic approach to identify species that may maximize evolutionarily distinct features. Finally, combining data on seed storage behaviour and longevity, as well as specimen age in the novel ‘best de-extinction candidate’ score (DEXSCO), we identified 556 herbarium specimens belonging to 161 extinct species with available seeds. We expect that this list of de-extinction candidates and the novel approach to rank them will boost research efforts towards the first-ever plant de-extinction