Alpine vegetation is scarce in central Mexico (≈150 km2) and occurs on the 11 highest peaks of the Trans-Mexican Volcanic Belt (TMVB). Timberline occurs at (3700) 3900 m, and at 4750 m vascular plants cease to exist. The alpine vascular flora comprises 237 species from 46 families and 130 genera. Asteraceae (44), Poaceae (42), and Caryophyllaceae (21) possess 45% of the species; none of the remaining families have more than 10 species. Four species are strict endemics, and eight others are near endemics. Thirteen species are restricted to alpine vegetation but also occur outside the study area. Seventy-seven species are endemic to Mexico, 35 of which are endemic to the TMVB. In terms of biogeography, the strongest affinities are with Central or South America. Fifteen species are also native to the Old World. Size of the alpine area seems to not be the determining factor for its floristic diversity. Instead, the time since and extent of the last volcanic activity, in addition to the distance from other alpine islands, appear to be important factors affecting diversity. There is evidence for upward vegetational shifts having occurred during the last century.
Resumen: Se presenta una revisión taxonómica para las especies mexicanas de Argythamnia subgénero Ditaxis (Euphorbiaceae), un taxón neotropical poco estudiado de aproximadamente 50 especies, al que algunos autores tratan como género independiente. En México se registran 14 especies y un taxón infraespecífi co, de las cuales siete especies y una variedad son endémicos del país. Argythamnia ingramii y A. silviae se proponen como nuevas para la ciencia y por primera vez se registra a A. simulans en el territorio mexicano. Además, A. micrandra, A. neomexicana y Ditaxis discolor, tres especies reconocidas recientemente se tratan como sinónimos, y se designa lectotipo para A. humilis. Se proporciona una clave para determinación, descripciones morfológicas, información bibliográfi ca, lista de ejemplares examinados, datos ecológicos, comentarios taxonómicos y mapas de distribución para todos los taxa. Palabras clave: diversidad, especies nuevas, Malpighiales. Abstract:A taxonomic revision of the Mexican species of Argythamnia subgen. Ditaxis (Euphorbiaceae) is provided. This subgenus is a little-studied neotropical assemblage of approximately 50 species, considered by some authors to be a genus. Fourteen species and one additional variety occur in Mexico, and seven species and one variety are endemic. Two species, Argythamnia ingramii and A. silviae are proposed as new to science and A. simulans is reported for the fi rst time from the country. In addition, A. micrandra, A. neomexicana, and Ditaxis discolor, three species that have been recently recognized as distinct are here reduced to synonymy, and a lectotype for A. humilis is designated. A key to the taxa, bibliographic information, morphological descriptions, list of specimens examined, ecological data, taxonomic comments, and distribution maps are given. (Ingram, 1967(Ingram, y 1980b. Las características que sirven para diferenciar los subgéneros pueden apreciarse en el Cuadro 1. Por otra parte, el subgénero Ditaxis (Vahl ex A.Juss.) Croizat, con alrededor de 50 especies, es el sugénero más diverso y el menos estudiado. Su estatus taxonómico ha sido históricamente inconsistente y se ha debatido si debe reconocerse como género independiente (p.ej. Radcliffe-Smith, 2001) o como taxa infragenérico de Argythamnia (p.ej. Ingram, 1980a). Debido a su complejidad taxonómica, varios autores han señalado la necesidad de hacer una revisión taxonómica para resolver la problemática que lo circunda (Ingram, 1970;Webster, 1994;McVaugh, 1995;Steinmann y Felger, 1997). La presente revisión taxonómica resuelve en gran parte dicha problemática, aunque trata solamente las especies mexicanas del subg. Ditaxis. Materiales y métodosSe recopiló la información referente a Argythamnia en revisiones, fl oras y listados, así como los protólogos de las especies presentes en México. Se consultaron las bases de datos electrónicas de los herbarios GH, TEX, UC y US, además de la de Tropicos (MO); y se realizaron salidas a campo para colectar material fresco y tomar fotografías de algunas es...
The subtribe Ditaxinae in the plant family Euphorbiaceae is composed of five genera (Argythamnia, Caperonia, Chiropetalum, Ditaxis and Philyra) and approximately 120 species of perennial herbs (rarely annual) to treelets. The subtribe is distributed throughout the Americas, with the exception of Caperonia, which also occurs in tropical Africa and Madagascar. Under the current classification, Ditaxinae includes genera with a questionable morphology-based taxonomy, especially Argythamnia, Chiropetalum and Ditaxis. Moreover, phylogenetic relationships among genera are largely unexplored, with previous works sampling <10% of taxa, showing Ditaxinae as paraphyletic. In this study, we inferred the phylogenetic relationships within Ditaxinae and related taxa using a dataset of nuclear (ETS, ITS) and plastid (petD, trnLF, trnTL) DNA sequences and a wide taxon sampling (60%). We confirmed the paraphyly of Ditaxinae and Ditaxis, both with high support. Following our phylogenetic results, we combined Ditaxis in Argythamnia and upgraded Ditaxinae to the tribe level (Ditaxeae). We also established and described the tribe Caperonieae based on Caperonia, and transferred Philyra to the tribe Adelieae, along with Adelia, Garciadelia, Lasiocroton and Leucocroton. Finally, we discuss the main morphological synapomorphies for the genera and tribes and provide a taxonomic treatment, including all species recognized under each genus.
La familia se encuentra ampliamente distribuida en las regiones tropicales del mundo (excepto en Australia) y forma parte de Cucurbitales. Está integrada por Hillebrandtia, un género monotípico y endémico a Hawai, y Begonia, que con unas 1400 especies es uno de los géneros más grandes de plantas. Algunos autores reconocen también Symbegonia a nivel genérico, pero recientes estudios moleculares sugieren que este grupo de 12 especies de Nueva Guinea forma parte de Begonia.
Abstract:The new species Dioscorea megaphylla (Dioscoreaceae) is described and illustrated with photographs. It is known only from the type locality, along the coastal foothills of the Sierra de Coalcomán in the municipality of Aquila, Michoacán, Mexico, where it grows in rocky canyons and hillsides with tropical subdeciduous forest at elevations of 550-600 m. As the specifi c epithet suggest, this species is distinctive due to the size of its leaves, and these are the largest within the genus Dioscorea and measure as much as 60 cm long and 65 cm wide. Unlike most members of the genus, fl owering occurs at the end of the dry season on newly produced stems before the leaves mature. Dioscorea megaphylla belongs to sect. Macrogynodium and is closely related to D. nelsonii and D. carpomaculata. Key words: Disocorea, Mexico, section Macrogynodium. Resumen:Se describe e ilustra Dioscorea megaphylla (Dioscoreaceae) como especie nueva. Se conoce solamente de la localidad tipo, en montañas bajas de la parte sur de la Sierra de Coalcomán, municipio de Aquila, Michoacán, México, donde crece en laderas y cañadas rocosas con bosque tropical subcaducifolio a elevaciones de 550-600 m. Como el epíteto específi co lo indica, la especie se distingue por el tamaño de sus hojas, que son las más grandes del género Dioscorea y llegan a medir hasta 60 cm de largo y 65 cm de ancho. A diferencia de la mayoría de los miembros del género, la fl oración se presenta al fi nal de la temporada seca y en tallos nuevos antes de que las hojas se desarrollen. Dioscorea megaphylla pertenece a la sección Macrogynodium y está cercanamente emparentada con D. nelsonii y D. carpomaculata.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.