Amazon plant diversity revealed by a taxonomically verified species list

Abstract

Recent debates on the number of plant species in the vast lowland rain forests of the Amazon have been based largely on model estimates, neglecting published checklists based on verified voucher data. Here we collate taxonomically verified checklists to present a list of seed plant species from lowland Amazon rain forests. Our list comprises 14,003 species, of which 6,727 are trees. These figures are similar to estimates derived from nonparametric ecological models, but they contrast strongly with predictions of much higher tree diversity derived from parametric models. Based on the known proportion of tree species in neotropical lowland rain forest communities as measured in complete plot censuses, and on overall estimates of seed plant diversity in Brazil and in the neotropics in general, it is more likely that tree diversity in the Amazon is closer to the lower estimates derived from nonparametric models. Much remains unknown about Amazonian plant diversity, but this taxonomically verified dataset provides a valid starting point for macroecological and evolutionary studies aimed at understanding the origin, evolution, and ecology of the exceptional biodiversity of Amazonian forests.

Keywords: Amazonia; floristics; rain forests; seed plants; species diversity.

Fig. 1.

Species richness of seed plants in the lowland Amazon rain forests (<1,000 m). Numbers of species are shown by country (and the Guiana Shield area) for all seed plants and for trees. The background shows the Amazon forest in Serra da Mocidade National Park, Brazil. Image courtesy of Ricardo Azoury (photographer).

Fig. S1.

Species-rich seed plant families and genera recorded in lowland Amazon rain forests. The 20 most species-rich families (A) and genera (B) of the entire flora, and the 20 most-species rich families (C) and genera (D) for trees only.

Fig. 2.

Biologically meaningful delineation of the lowland rain forest biome across Amazonia (light-green outline). Areas >1,000 m elevation are shown in black (https://www2.jpl.nasa.gov/srtm/), major rivers are shown by light-blue lines, and the Amazon watershed itself is outlined with a dark-blue dotted line. Areas with >90% tree canopy cover are shown in green based on satellite data from 2000 (45). Our delineation (purple line) was derived by visualizing areas within the multiple watersheds ≤1,000 m elevation that have >1,300 mm annual mean rainfall [slightly below the threshold of Malhi et al. (46)], 18 °C minimum and 24 °C maximum annual mean temperature (lower limit follows the Koppen classification for tropical forests), and climatic water balance (precipitation minus potential evapotranspiration) >0 throughout the year. The northern limit shows complexity, with multiple excluded areas around the tepuis due to high elevation and/or low annual mean rainfall. Large areas highlighted in white, notably in northern Bolivia (Beni savanna/llanos de Moxos) and in the border area of Venezuela, Guyana, and Brazil (Guianan savannas), are excluded due to higher annual mean temperatures (>24 °C). Climatic data were obtained from ref. .