Spicoid morphology of Mapanioideae (Cyperaceae): an evolutionary perspective

Cyperaceae subfamily Mapanioideae have reproductive units called spicoids, which are interpreted alternatively as flowers or partial inflorescence, and little is known about morphological variation of spicoids from an evolutionary perspective. Combining morphological and evolutionary analyses, we aimed to assess variation in spicoid morphology and its evolutionary significance. Spicoid morphology of 48 species of Mapanioideae was analysed, and variable characters were selected for downstream analyses. The results showed that the general spicoid morphology is consistent within genera and that character states can vary within genera, supporting molecular phylogenetic relationships. The presence of lateral keeled scales, the number of lateral stamens, inner scales, inner stamens and pistil merosity were shown to be variable. Possible ancestral spicoid morphology was reconstructed as resembling the current morphology of Hypolytrum. Based on the most frequent evolutionary changes observed, the increase in the number of parts (number of inner scales, inner stamens and pistil merosity) seems to be a recurrent process in spicoid evolution, contradicting a previous hypothesis that assumed changes in spicoid morphology towards reduction. Combining molecular and morphological analyses allows us to refine our knowledge of the evolutionary history of Mapanioideae and enhances the understanding of the evolution of Cyperaceae.

Automated summary

By analyzing the spicoid morphology of 48 species of Cyperaceae subfamily Mapanioideae, it was found that the general spicoid morphology is consistent within genera, while character states can vary within genera, supporting molecular phylogenetic relationships. Various features of spicoid morphology, such as the presence of lateral keeled scales, the number of lateral stamens, inner scales, inner stamens, and pistil merosity, were shown to be variable, indicating potential evolutionary changes. The increase in the number of parts seems to be a recurrent process in spicoid evolution, contradicting previous hypotheses of morphological reduction.