Phylogeny of Mimophytum (Boraginaceae: Omphalodeae) reveals geographic and climatic divergence in the Sierra Madre Oriental

Mimophytum includes eleven species with affinity for limestone and is distributed along the Sierra Madre Oriental (SMOr) in Mexico, with one species reaching Texas. Despite previous phylogenetic studies, the evolution of Mimophytum is unclear because of inappropriate sampling. Therefore, the interpretation of the evolution of morphology and biogeography is biased. We performed a phylogenetic analysis with plastid and nuclear DNA regions. Also, we carried out an ancestral character state reconstruction. We estimated the divergence time and ancestral ranges of the genus and internal clades. Finally, we performed an ancestral reconstruction of climatic variables. Results indicate that Mimophytum is a monophyletic group with two main clades with geographic and climatic congruence. Extended and entire-erose nutlet wing margin resulted in ancestral state for Mimophytum, suggesting anemochory as the diaspore syndrome. The annual growth and dimorphic fruits evolved independently in M. alienum and M. alienoides, while glochidiate nutlet wing margin is diagnostic of the clade including M. omphalodoides, M. benitomartinezii and M. richardsonii. Mimophytum arose in the Miocene at 13.33 mya in the Gran Sierra Plegada and diversified along northern and southern subprovinces of the SMOr. Diversification of Mimophytum in the SMOr was driven by morphological adaptations to climate changes. Citation: Martínez-Poiré A., Rodríguez A. & Sánchez D. 2025: Phylogeny of Mimophytum (Boraginaceae: Omphalodeae) reveals geographic and climatic divergence in the Sierra Madre Oriental. – Willdenowia 55: 305–324. Version of record first published online on 26 September 2025.