Hidden diversity at the edges of maps: morphometrics of Carex sect. Uncinia (Cyperaceae) helps unravel taxonomic diversity in subantarctic and remote archipelagos

Subantarctic islands constitute some of the most remote terrestrial environments on Earth and represent the southernmost limits of non-glaciated land. Despite their comparatively low vascular plant diversity, several taxa are reported as widely distributed across multiple archipelagos without detailed comparative taxonomic assessment. In Carex sect.

Uncinia (Cyperaceae), the broadly circumscribed C. brevicaulis and C. austrocompacta complexes, have long been assumed to represent single species with wide and disjunct distributions across remote oceanic islands far from continental landmasses. In this study, a comparative morphometric approach was employed to reassess species limits within these complexes across subantarctic and Pacific archipelagos. Multivariate analyses revealed consistent morphological discontinuities corresponding to geographically structured lineages.

The results support the recognition of four distinct species within the C. brevicaulis complex and five within the subantarctic C. austrocompacta complex, some of them newly described here. These findings reveal substantial hidden diversity in oceanic Carex and demonstrate the effectiveness of quantitative morphology in resolving taxonomic complexity in morphologically reduced groups.