No abstract

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.

Broad phylogenetic analyses of Crassulaceae have retrieved a large clade comprising as much as one‐third of the species diversity present in the family as a whole. This so‐called Acre clade (Sedoideae) includes familiar genera such as Echeveria, Graptopetalum, and Thompsonella, and while it is consistently recovered in studies at the family level, relationships within the clade as well as the monophyly of many of the constituant genera have yet to be established. Results of a phylogenetic study of a genus within the Acre clade, Thompsonella, are here reported. Morphological evidence was gathered and molecular (nuclear ETS and ITS) DNA sequences were generated for forty‐seven taxa from the Acre clade, including all recognized members of Thompsonella. Parsimony analysis of the combined data retrieved Thompsonella as a monophyletic group and retrieved species in Graptopetalum, Thompsonella, Echeveria, Pachyphytum and Sedum sect. Pachysedum in a clade; this group was previously identified as the “Echeveria group”. Results indicate that only a few genera in the Acre clade are monophyletic and that to establish their generic limits further sampling mainly in the large Echeveria and Sedum genera is needed. Results from morphological and molecular analyses disagree in the position of T. mixtecana. However, an additional restricted analysis performed solely with cpDNA (rps16) placed this species within Thompsonella, suggesting a hybrid origin.

Antecedentes: La Sierra Madre del Sur (SMS) se ubica paralela al Océano Pacífico, desde Jalisco a Oaxaca. Es la provincia más biodiversa de México, con 7,016 especies de plantas vasculares. Preguntas: ¿Cuántas y cuáles son las plantas vasculares endémicas de la SMS y en qué tipos de vegetación habitan? ¿Cuántos se encuentran en alguna categoría de riesgo? Especies de estudio: Las plantas vasculares endémicas. Sitio y años de estudio: Provincia biogeográfica SMS, México; de 2016 a 2020. Métodos: Se generó una base de datos a partir de información de herbarios, bases de datos electrónicas y literatura especializada. Resultados: Se registraron 1,133 especies, agrupadas en 370 géneros y 91 familias; de estas últimas destacaron con un mayor número de géneros y especies Asteraceae (75 y 250, respectivamente), Orchidaceae (40, 123), Rubiaceae (22, 74), Bromeliaceae (5, 64) y Lamiaceae (10, 63). Los géneros con mayor riqueza fueron Salvia (46), Ageratina (39), Tillandsia (37) y Echeveria (29). Se registraron 15 géneros endémicos y 129 especies se reportaron en alguna categoría de riesgo. En la SMS el bosque de coníferas y encino registraron 828 especies, seguido del bosque mesófilo de montaña (235) y el bosque tropical caducifolio (114). Conclusiones: El endemismo en la SMS es heterogéneo, ya que se localizó en los bosques de coníferas y encino de las subprovincias Sierra Madre del Sur Oriental (estados de Guerrero y Oaxaca) y en la Sierra Madre del Sur Occidental (estado de Jalisco).

Through an exhaustive literature review, field exploration and revision of herbaria, the presence of 861 native species of lianas in Mexico is documented, pertaining to 250 genera and 59 families. A total of 25.9 % ( n = 224) of the species and three genera are endemic to Mexico. The 15 most diverse families account for 80.1 % of the species and 85.7 % of endemics. The 18 richest genera comprise 38.1 % ( n = 328) of the species and approximately 50 % of the endemic. Chiapas is the state with the greatest diversity because it includes 65.4 % of the total species, whereas Oaxaca is the richest state in terms of endemism (49.6 %). Regardless of their area, the most diverse states are also notable for their endemism. The lianas found in only one state encompassed 16.5 and 26 % of the total number of species and endemics, respectively. Among the five recognized biomes in Mexico, the tropical humid forest and the tropical seasonally dry forest stand out for their number of species ( n = 692, 80.3 %) and number of endemics ( n = 134, 59.8 %), respectively. At the level of vegetation type, the tropical deciduous forest ranks first in both attributes. The number of lianas species decreased significantly with altitude. Our results demonstrate the importance of the contribution of lianas to the richness and endemism of Mexican flora and justify the development of initiatives to ensure their long-term conservation.