Vegetation Heterogeneity and Life-Strategy Diversity in the Flora of the Heterogeneous Landscape of Nizanda, Oaxaca, Mexico

Abstract

We updated the floristic checklist of the Nizanda region, Isthmus of Tehuantepec (southern Mexico), characterized the occurring plant communities based on dominant species, and described the region's flora according to life form, growth form, growth type, and growth habit spectra. Ten years of botanical exploration, along with surveys in 188 100-m 2 samples from different vegetation types, provided the baseline floristic information. Ordination and classification analyses were performed to examine the degree of differentiation between communities. Geographical ranges of all species were used to assess biogeographical relationships of this flora. The inventory includes 920 species (553 genera, 124 families). More than one-third of the families were represented by a single species, whereas the 10 richest families had 43% of the species richness. Dendrograms showing plot classification at three taxonomic levels (species, genus and family) revealed savannah as the most strongly differentiated community amid seven vegetation types. Regarding growth forms, forbs and trees prevailed. Phanerophytes were the most common life form category, whereas herbs and woody plants were the dominant growth types. The largest richness for all taxonomic levels was recorded in the tropical dry forest. The expanded floristic knowledge gained for the Nizanda region provided better criteria to revise the classification scheme of its vegetation. Our preliminary biogeographical analysis illustrates the role of the Isthmus of Tehuantepec as a corridor for thermophilous floras between two oceanic watersheds, and as a natural distributional limit for several Mesoamerican plant species.

Linajes de angiospermas endémicas en México: zonas de alto endemismo para la conservación

“…Furthermore, among the habitats of Tehuantepec, the tropical dry forests harbor the largest diversity including several taxa of endemic angiosperm (Acosta et al, 2003;Pérez-García et al, 2010).…”

A new species of Amyris (Rutaceae, Toddalioideae, Amyridinae) from Mexico

“…Amyris jorgemeavei grows on calcareous rocky soil at an elevation of 65-300 m. The new taxon is sympatric with A. elemifera Linnaeus (1759: 1000), a name not included by Chiang Cabrera & Ramos (2011), but the latter is more widely distributed in the region and occurs in other vegetation and soil types (Pérez-García et al 2010).…”

Relating species richness to the structure of continuous landscapes: alternative methodological approaches

“…In Nizanda, such regions correspond to areas covered by savannas and tracts of secondary vegetation, both of which in turn encompass the largest forb richness according to plant inventories (Pérez‐García et al. ).…”

“…Pérez‐García et al. () showed that although trees are not the most prominent component in the flora of Nizanda, they are key structural components of the tropical dry forest, the xerophytic vegetation, and the sub‐deciduous forest, while they are virtually absent from savannas and secondary vegetation. Our analysis showed that legume tree richness was negatively associated with two measures of dominance in the landscape (negative coefficients for LPI and LPIAM), but also with a measure of landscape heterogeneity (SHDI), which in theory should be opposite to LPI.…”

“…We did this in a highly complex semi‐natural landscape, where plant diversity is very high (Pérez‐García et al. ).…”