An analysis of the distribution patterns of 124 Mexican gymnosperm species was undertaken, in order to detect the Mexican
areas with high species richness and endemism, and with this information to propose areas for conservation. Our study includes
an analysis of species richness, endemism and distributional patterns of Mexican species of gymnosperms based on three different
area units (states, biogeographic provinces and grid-cells of 1° × 1° latitude/longitude). The richest areas in species and
endemism do not coincide; in this way, the Sierra Madre Oriental province, the state of Veracruz and a grid-cell located in
the state of Oaxaca were the areas with the highest number of species, whereas the Golfo de México province, the state of
Chiapas and a grid-cell located in this state were the richest areas in endemic species. A weighted endemism and corrected
weighted endemism indices were calculated, and those grid-cells with high values in both indices and with high species richness
were considered as hotspots; these grid-cells are mainly located in Southern and Central Mexico. 相似文献
Montane cloud forests in the Neotropics harbor a great wealth of biological diversity and a large number of endemic species. Here, we present (i) a comprehensive data mining exercise of fungi from Neotropical montane cloud forests (NMCF), (ii) an extensive review of the current knowledge of fungal richness, distribution and composition, and (iii) a preliminary analysis of fungal endemicity in Mexican montane cloud forests. Based on a survey of literature and other sources, we assembled a database of 6349 records representing 2962 fungal species in NMCF. The computed individual-based species rarefaction curve remained non-asymptotic, and the extrapolation curve estimated an expected increment of 42% in the number of species by doubling the sampling effort. Fungal species richness was highest in NMCF from Mesoamerica, particularly from Mexico and Costa Rica. Fungi from Mesoamerica, Caribbean and South America are significantly different at diverse taxonomic levels, and there is a little overlap in the fungal species recorded from these regions. The analyses of endemicity of the Mexican dataset performed with parsimony and Bayesian methods were highly complementary. They showed the following areas of endemicity supported by the congruent distribution of fungal species: (i) two main regions in the Trans-Mexican Volcanic Belt (TMVB); (ii) a region in the southern part of Veracruz; and (iii) a region located in the eastern part of TMVB with affinities with Sierra Madre Oriental and the Chiapan-Guatemala Highlands. This last area was supported by five species of Glomeromycota and is consistent with an area of endemicity previously found in vascular plants. In this study, we provide a perspective on gaps in knowledge regarding the diversity and distribution of fungi in NMCF, and provide a full dataset of fungal records with geographical, bibliographic and taxonomic information. 相似文献
Biogeographical affinities among cloud forests in the Neotropical region were studied through a track approach, by constructing
generalised tracks based on the results of a parsimony analysis of endemicity (PAE). Distributional data on 946 genera and
1,266 species of vascular plants (Pteridophyta, angiosperms, and gymnosperms) from 26 cloud forest patches from Colombia,
Costa Rica, Cuba, Honduras, Jamaica, Mexico, Peru, Puerto Rico, and Venezuela were analysed; and four localities from eastern
and western United States were also included as outgroups. The track analysis identified six generalised tracks: a first one
that includes the majority of the cloud forests of Mexico, Central America, the Antilles, and northern Colombia; a second
one that includes southern Mexico and northern Central America; a third one that includes the mountains in northwestern South
America; a fourth one that includes the mountains in southwestern South America; and two others in western and eastern United
States. It is concluded that the Neotropical cloud forests are closely related and that those of the Caribbean subregion exhibit
complex relationships, which could be due to the complex tectonic history of the area.
Received February 22, 2001 Accepted May 1, 2001 相似文献
Several members of the most ancient living lineages of flowering plants (angiosperms) inhabit humid, woody, mostly tropical habitats. Here we assess whether one of these forest types, the cloud forests of Mexico (CFM), contain a relatively higher proportion of phylogenetically early-diverging angiosperm lineages. The CFM houses an extraordinary plant species diversity, including members of earliest-diverging angiosperm lineages. The phylogenetic composition of CFM angiosperm diversity was evaluated through the relative representation of orders and families with respect to the global flora, and the predominance of phylogenetically early- or late-diverging lineages. Goodness-of-fit tests indicated significant differences in the proportional local and global representation of angiosperm clades. The net difference between the percentage represented by each order and family in the CFM and the global flora allowed identification of clades that are overrepresented and underrepresented in the CFM. Early-diverging angiosperm orders and families were found to be neither over- nor underrepresented in the CFM. A slight predominance of late-diverging phylogenetic levels among overrepresented clades, however, was encountered in the CFM. The resulting pattern suggests that cloud forests provide habitats where the most ancient angiosperm lineages have survived in the face of accumulating species diversity belonging to phylogenetically late-diverging lineages. 相似文献
Abiotic fluctuations in montane ecosystems trigger changes in the hydric functional traits of tree species. These variations are better recognized in tree species inhabiting montane humid ravine slopes with different elevation, as is the case of many areas across the Mexican Neotropical montane forests. Little is known about the response of tree towards elevation gradients and abiotic changes. In this study, we analyzed the leaf morphological variation of two rare and Mexican endemic Symplocos species (S. coccinea and S. speciosa) occurring eastern Mexico on sites with different microclimate and elevation but similar floristic composition. We quantified how the abiotic factors (i.e. canopy openness, soil temperature, soil moisture, and litter depth) and site elevation influence the leaf traits of these tree species. Symplocos coccinea (with toothed leaf margins) is adapted to high humid conditions and high canopy coverage, while S. speciosa (with almost entire leaf margins) is resilient to environments with moisture deficit and high temperatures. Process-based research with fine-spatial scales at montane ecosystems are needed to understand the resilience and morphological variations of montane tree species under climate change worldwide. In this study, we confirmed that the Symplocos leaf morphological traits (i.e. leaf length, leaf width, leaf shape index, leaf base angle and vein density) are strongly influenced by abiotic conditions (i.e. canopy openness, litterfall depth, soil moisture and soil temperature).
Mexico is considered a megadiverse country containing more than 10% of the world's biodiversity. The distribution of this species richness and endemism is different among the different Mexican states. We examined the species richness patterns of 13 families of vascular plants (including ferns, gymnosperms and angiosperms) in Mexico using political divisions (states) as units of analysis. We analysed the species richness values (absolute richness, endemic richness and restrictive richness) of these plant families using stepwise multiple regression analysis, assessing their relationship with a set of 10 environmental variables (expressed as heterogeneity coefficients). A combined cluster analysis with multidimensional scaling analysis (MDS) and an analysis of similarities were also undertaken to define the spatial–geographical patterns. Additionally, we proposed a methodological strategy to determine which states of Mexico have priorities for conservation. Our results suggested that the three species richness values used were significantly predicted by environmental factors, especially by climatic heterogeneity. Notwithstanding that a linear pattern was recognized, the Mexican states were gathered in four groups, which were confirmed by the MDS and the cluster analysis: (1) the Yucatan Peninsula, (2) arid Mexico, (3) the Mexican Transition Zone and (4) the megadiverse states. We proposed that 12 Mexican states include all the environmental conditions and are candidates for developing conservation programmes: (1) Quintana Roo, Tabasco and Yucatán, (2) Baja California, Chihuahua and Sinaloa, (3) Guerrero, Jalisco and Nuevo León and (4) Chiapas, Oaxaca and Veracruz. 相似文献