Background:

La Chinantla, a topographically and geomorphologically complex region, and probably the most humid in the country, hosts a diverse but largely unknown biota, particularly at higher elevations.

Questions:

How many plant species are present in La Chinantla? How are these species distributed along the elevational gradient encompassed in the region?

Studied species:

Lycopodiophyta, Pteridophyta, Gimnospermopsida, Magnoliidae, Eudicots, Monocots.

Study sites and years of study:

We studied the flora of the La Chinantla hyper-humid region, Northern Oaxaca Range, southern Mexico, from 1993 to 2017.

Methods:

We collected 2,654 specimens in 73 main localities distributed across an elevational range from 250 to 3,020 m (but concentrated above 800 m). Numerous experts in plant taxonomy examined the specimens and provided or confirmed identifications.

Results:

The checklist of the vascular plants includes 1,021 species, 471 genera and 162 families of vascular plants. The specimens/species ratio (2.6) reflected a satisfactory collecting effort. The most diverse families were Asteraceae, Rubiaceae, and Orchidaceae, whereas the most speciose genera were Peperomia, Miconia and Piper. Most listed species are herbs (47.3 % of the total) and trees (35.2 %), whereas the terrestrial (85.4 %) and epiphytic (15.9 %) growth habits were the most frequent ones (some species presented more than one growth form or growth habit category).

Conclusions:

Based on the magnitude of the current checklist, we estimate that the actual number of species in this region must be around 1,650. The recorded richness of vascular plant species of La Chinantla confirms the large diversity and uniqueness of its flora and calls for efficient conservations efforts to ensure its maintenance in the future.

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