A new species of Neomicrocalamus (Poaceae: Bambusoideae) from Thailand and the reduction of Temochloa indicated by morphological and molecular investigations

Temochloa and Neomicrocalamus are closely related bamboo genera exhibiting a complex taxonomy and substantial morphological overlap. Their phylogenetic relationships and generic delimitation remain insufficiently resolved and are further complicated by intermediate morphological character states in the newly discovered species N. patellaris described in this study. Phylogenomic analyses were undertaken using plastome and 97 partial or complete nuclear gene regions. Results were combined with morphological reassessment of Temochloa and Neomicrocalamus to support the taxonomic subsumption of Temochloa under Neomicrocalamus. Inclusion of N. patellaris in the plastome and nuclear phylogenetic analyses yielded congruent, well supported, topologies and revealed intermixing of species between the two genera. Neomicrocalamus patellaris was recovered as sister to T. liliana, the type species of Temochloa. Phylogenetic reconstructions further showed that Temochloa is polyphyletic, with T. elegans nested within Neomicrocalamus. Shared characters of the two genera include a climbing or scrambling habit, a similar mid-culm branch complement, culm leaves lacking a distinct sheath–blade junction, needle-like blade tips, and modified pseudospikelets. Therefore, phylogenomic and morphological evidence support transferring Temochloa to Neomicrocalamus to achieve a monophyletic generic circumscription. Two species formerly recognized in Temochloa, T. elegans and T. liliana, are transferred to Neomicrocalamus, and N. patellaris is newly described.