Acanthaceae in the State of Mexico, Mexico: keys, ecological data, images, and documented occurrences

Background and Aims: Previous published accounts of the numbers and composition of species of Acanthaceae in the State of Mexico vary widely. Therefore, we sought to clarify both of these floristic components so as to provide an up-to-date account for use by students, scientists, government officials, and the general public, in efforts to better understand and preserve plants of this family in the state. Methods: Field and herbarium studies, as well as some taxonomic revisions, were undertaken to provide data for an identification key to all genera and species of Acanthaceae in the state, and to offer for each species descriptive information, biotic communities of occurrence, elevational range, floral and fruiting phenologies, specimens examined, and relevant discussions. Key results: Occurrences of 61 species in the family Acanthaceae are documented from the State of Mexico. Fifty-five of these are believed to be native there, and six represent naturalized non-natives. Two species (Poikilacanthus capitatus and Pseuderanthemum hirsutum) are recognized as endemic there, and at least 11 species appear to be newly documented from the state. A new nomenclatural combination, Pseuderanthemum hirsutum, is proposed for the species previously treated as Buceragenia hirsuta, and Beloperone longibracteata is recognized as a new synonym of Justicia sphaerosperma. Images are provided for 60 of the 61 species treated. Conclusions: Despite its small size, the State of Mexico is the eighth richest Mexican state in numbers of species of Acanthaceae. Factors promoting species richness in the state include diversity of biotic communities, broad elevational range, and proximity to other species-rich states. Although known from all of the state’s major biotic communities, most of the native Acanthaceae occur in the south-central and southwestern regions of the state, where both tropical deciduous and oak forests are prevalent.