Abstract A few genera have been analysed using spatial phylogenetics to reveal historical biogeographical patterns. Melampodium is well known with regard to its distribution, phylogeny, and taxonomy, but lacks a biogeographical assessment. The aims here were to categorize sites by phylogenetic endemism and associated environmental variables, characterize phylogenetic structure, and identify phyloregions. Species occurrences were compiled within 1° grid cells, and a chronogram was constructed using the matK marker. Categorical analysis of neo- and palaeo-endemism was applied, followed by Wilcoxon tests across 36 environmental variables to assess differentiation among endemism types. Phylogenetic structure was evaluated using the net relatedness index and nearest taxon index, whereas phylogenetic Sorensen dissimilarity was used to identify phyloregions. All phylogenetic endemisms were found in Mexico: neo-endemism in the north-west, palaeo-endemism in the centre, mixed-endemism in the west, and super-endemism in Baja California Sur, some of which were supported by chromosomal evidence. Palaeo-endemisms are associated with higher elevations and greater environmental stability since the Pliocene than neo-endemisms. Phylogenetic clustering characterized northern Mexico (sect. Melampodium) and Central America (sect. Serratura), while significant overdispersion was found only in the Tehuacán–Cuicatlán Valley. Three phyloregions were identified, one Nearctic and two Neotropical lineages. These findings reinforce Mexico as the primary centre of Melampodium diversification and endemism.
Morales-Garduño et al. (Fri,) studied this question.