Resumen. Se describe la composición fl orística, la riqueza y la diversidad de especies de un bosque tropical caducifolio en la provincia fl orística Cuenca del Balsas, México. Se seleccionaron 4 sitios de 1000 m 2 cada uno, censándose los árboles, arbustos y lianas con d.a.p. ≥ 1 cm. En total se registraron 1456 individuos, pertenecientes a 82 especies, 56 géneros y 24 familias. Independientemente del sitio y de la forma de crecimiento, Leguminosae fue la familia con mayor número de especies y de individuos. Los géneros más diversos fueron Bursera (Burseraceae) y Cordia (Boraginaceae) con 9 y 4 especies, respectivamente. La riqueza entre los sitios varió de 43 a 55 especies y su similitud fue más alta en el nivel de familia que en el de especie. Los árboles fueron la forma de crecimiento con mayor riqueza de especies. Respecto a otros bosques tropicales caducifolios de México y del mundo, los sitios que se estudiaron en este bosque ocupan una posición baja en cuanto a sus valores de riqueza y estructura.Palabras clave: árboles, composición fl orística, diversidad, lianas.
Alpine ecosystems represent varied climates and vegetation structures globally, with the potential to support rich and functionally diverse avian communities. High mountain habitats and species are under significant threat from climate change and other anthropogenic factors. Yet, no global database of alpine birds exists, with most mountain systems lacking basic information on species breeding in alpine habitats, their status and trends, or potential cryptic diversity (i.e., sub-species distributions). To address these critical knowledge gaps, we combined published literature, regional monitoring schemes, and expert knowledge from often inaccessible, data-deficient mountain ranges to develop a global list of alpine breeding bird species with their associated distributions and select ecological traits. This dataset compiles alpine breeding records for 1,310 birds, representing 12.0% of extant species and covering all major mountain regions across each continent, excluding Antarctica. The Global Alpine Breeding Bird dataset (GABB) is an essential resource for research on the ecological and evolutionary factors shaping alpine communities, as well as documenting the value of these high elevation, climate-sensitive habitats for conserving biodiversity.
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: Mediante una revisión de información bibliográfi ca y de herbario, se analizó el espectro de dispersión de árboles y lianas de localidades con bosque tropical caducifolio en América, con el objetivo de determinar si este atributo se modifi ca al considerar diferentes conjuntos fl orísticos, como fl oras leñosas regionales o parcelas de muestreo de 0.1 ha. Para estas últimas, se cuantifi có el grado de similitud del espectro de dispersión, obtenido mediante el conteo de especies o por el número de individuos. A una escala local, las proporciones de los síndromes de dispersión fueron similares entre la fl ora y lo obtenido en los muestreos, pero los síndromes de dispersión difi rieron entre sí de manera signifi cativa. A nivel Neotropical, el análisis entre tres fl oras también varió signifi cativamente entre síndromes. Las comparaciones entre parcelas mostraron que existen diferencias signifi cativas entre localidades, tanto entre síndromes de dispersión como entre la interacción síndrome-localidad. Este resultado persiste al analizar formas de crecimiento de manera independiente o considerando su abundancia. Las divergencias encontradas entre localidades no fueron explicadas por la latitud o variables climáticas; pero tanto a nivel local como Neotropical, estas son más claras para las formas de crecimiento, ya que la zoocoria es más importante para árboles y la anemocoria para lianas. Los resultados constatan la complejidad del fenómeno de la dispersión de especies leñosas del bosque tropical caducifolio, por lo que futuros estudios deberán indagar con más detalle la infl uencia de la escala espacial, así como factores proximales e históricos. Palabras clave: árboles, Chamela, lianas, síndromes de dispersión.Abstract: Through a bibliographic and herbarium review, an analysis was conducted of the dispersal spectrum of woody plants in various locations of the tropical deciduous forest of America. Our aim was to determine whether modifi cations to the dispersal spectrum exist among different fl oristic groups, particularly in the fl oristic checklist or within plots of 0.1 ha. The degree of similarity among dispersal spectra was estimated, considering the number of species or individuals. At the local scale, percentages of dispersal syndromes did not differ among the fl ora obtained by sampling, but the dispersal syndromes differed signifi cantly from each other. At the Neotropical level, the dispersal syndromes of three fl oras also differed signifi cantly. At plot level, different sites also differed signifi cantly in terms of dispersal syndromes and in syndrome-site interactions. This result persisted on analysis of different growth forms or when considering abundance. Inter-site differences were not explained by latitude or climatic variables. At both local and Neotropical levels, the differences were more evident in terms of growth form, since trees and lianas were more zoochorous and anemochorous, respectively. This study demonstrates the complexity of dispersal in woody species of the tropical decid...
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