Multivariate morphometric analysis supported by an anatomical approach to assess species delimitation in Xyris (Xyridaceae) in New Caledonia

International audience

anglais. Xyridaceae are represented in New Caledonia only by the genus Xyris, the description of which was last revised in the 1960s, and three endemic species were recognized there at that time, X. pancheri, X. neocaledonica and X. guillauminii. However, no specimens of X. guillauminii were reported from P or L, although some type material was present. In addition, most material was unidentified at the species level in international herbaria (up to 45% for the NOU herbarium), showing that the family had not been studied in the framework of the Flore de la Nouvelle-Calédonie. In total, 129 herbarium specimens were examined for an ascendant hierarchical classification and a principal coordinates analysis based on 18 morphological characters regarded as diagnostic at the species level (including six used in the original revision). The analyses revealed three well-delimited groups that potentially correspond to species-level units. A sub-sampling of 21 specimens, representative of these three groups, was studied anatomically (leaf cross-sections) and by scanning electron microscopy (leaf surface and seeds) and provided ten additional characters. This additional dataset validated the taxonomy in three species-level units. The resulting entities were then compared with nomenclatural types, which showed that the first corresponded to X. neocaledonica, the second represents a well-delimited, undescribed species, and the third includes types of both X. pancheri and X. guillauminii, this last being in need of synonymization. The findings of the present study provide a basis for undertaking a taxonomic revision of Xyris in New Caledonia, including the description of the new species. All New Caledonian species have an axile placentation and a trilocular ovary, so they belong to Xyris section Pomatoxyris, which is no longer endemic to Australia.