Mexico is a megadiverse country. Presently, 22 126 species of angiosperms have been registered within its territory and 11 001 are considered to be endemic. However, their geographical distributions are far from homogeneous. In addition, Mexico is the center of diversification of several groups. Our analysis focused on such groups. The aims were to identify areas of species richness and endemism. A data matrix with 766 species and 25 579 geographical records was analyzed. It included Calochortus (Liliaceae); Bletia (Orchidaceae); Tigridieae (Iridaceae); Amaryllidaceae; Poliantheae, Echeandia (Asparagaceae); Crassulaceae; Hylocereus (Cactaceae); Solanum, Lycianthes and Physalinae (Solanaceae); Salvia section Membranaceae (Lamiaceae); and Cosmos and Dahlia (Asteraceae). Using Geographic Information Systems, we determined richness and distribution based on: (i) Mexican political divisions, (ii) biogeographical regions and provinces, (iii) a grid of 0.5 × 0.5° cells, and (iv) elevation. The areas of endemism were estimated using the endemicity analysis. The highest number of taxa and endemic plants were concentrated within the Transmexican Volcanic Belt in the Mexican Transition Zone. This mountain range has been recognized as a province on the basis of geologic, tectonic, geomorphologic, physiographic and biogeographic criteria. It is a 1000 km long volcanic arc that extends east to west through Central Mexico and is variably from 80 to 230 km wide, between 17°30′ to 20°25′N and 96°20′ to 105°20′W. Our results represent a local deviation from the global richness latitudinal gradient of angiosperm species.

Lycianthes, the third most species-rich genus in the Solanaceae, is distributed in both the New and Old Worlds and is especially diverse in Mexico. Here we provide an identification key, taxonomic descriptions, distribution maps, and illustrations of specimens, trichomes, flowers, and fruits for the 53 known Lycianthes taxa of Mexico and Guatemala. The new combination Lycianthes scandens (Mill.) M.Nee is made and replaces the name Lycianthes lenta (Cav.) Bitter, which is placed in synonymy. Within L. scandens, two varieties are recognized (Lycianthes scandens var. scandens and Lycianthes scandens var. flavicans (Bitter) J.Poore & E.Dean, comb. nov.). In addition, one new species (Lycianthes rafatorresii E.Dean, sp. nov.) is described from eastern Mexico, and 10 names (either recognized taxa or synonyms of recognized taxa) are lectotypified, including the names Solanum heteroclitum Sendtn., S. rantonnetii Carrière, and S. synantherum Sendtn. The species L. multiflora Bitter and L. synanthera (Sendtn.) Bitter are excluded from the treatment, as research indicates that they do not occur in Mexico and Guatemala, however full synonymy for both names is given.

Solanum piliferum was first described by Bentham in 1840, based on material collected in the state of Oaxaca, Mexico. In 1919, the species was transferred to the genus Lycianthes by Friedrich August Georg Bitter and became the type species of his series Piliferae. This article provides a key to separate the Mexican species included by Bitter in series Piliferae, with updated species descriptions, synonymy, typification, distribution, and images of characteristics (trichomes, flowers, fruits, seeds). We address the misplacement of L. stephanocalyx and L. coffeifolia in this series and suggest limiting the series to just the species L. caeciliae, L. pilifera and L. quichensis based on habitat preferences, floral morphology, and seed characters. However, the series is not recircumscribed at this time.

Two cloud forest species of Lycianthes are newly described: L. breedlovei from the state of Chiapas, Mexico and L. fredyclaudiae from the state of Baja Verapaz, Guatemala. Both species have orange-brown, multangulate-stellate trichomes in which the rays of the trichome are rebranched, white to pale lilac flowers (with darker violet-purple lobes in L. breedlovei), and unequal stamens. Morphologically, they resemble L. hortulana of Honduras, but both new species have previously been misidentified as L. cuchumatanensis. This article provides species descriptions, maps of geographic distributions, drawings of trichomes, and images of the flowers and specimens of the two new species, as well as a comparison chart of morphological characters used to separate L. breedlovei and L. fredyclaudiae from similar species.

Lycianthes moziniana (Solanaceae: Capsiceae) is a perennial herb with edible fruits that is endemic to Mexico. Three varieties are recognized, all known in the Mexican Transition Zone. Lycianthes moziniana var. margaretiana grows in the Sierra Madre Oriental, whereas L. moziniana var. moziniana is common along the Trans-Mexican Volcanic Belt and in the Sierra Madre Occidental. Lycianthes moziniana var. oaxacana is found exclusively in the Sierra Madre del Sur. The Mexican Transition Zone is a complex geological, climatic and biogeographical area, the result of tectonic and volcanic activity that has promoted genetic divergence and speciation. We determined the genetic variation and structure of L. moziniana. Using phylogeographical approaches, we described the demographic history and evolutionary processes leading its divergence. The intergenic spacers rpl32-trnL and ycf1 were sequenced for 133 individuals pertaining to 15 populations. The genealogical relationships were analysed using haplotype networks. Finally, based on ecological niche models, we inferred the palaeodistribution of L. moziniana during the Pleistocene. The genetic differences and the haplogroups matched the three described varieties. Geological and climatic events of the Mexican Transition Zone facilitated these results. The Trans-Mexican Volcanic Belt isolated the populations of the Sierra Madre Oriental and the Sierra Madre del Sur, while allowing the migration to the Sierra Madre Occidental, during the middle Holocene.