Background:

Despite their great diversity and the grave threats they face, temperate prairies have been overlooked.

Question:

This study addresses the ecosystem and taxonomic diversity of plants in the temperate prairies of Oaxaca.

Studied species:

All vascular plants.

Study site and dates:

The volcanic (VG) and calcicole grasslands (CG) and the oak savannas (OS) of northern Oaxaca in 2021 and 2022.

Methods:

After delimiting these three systems, we collected vouchers and described the vegetation and its conservation status.

Results:

VG and CG were the most diverse. In VG diversity is favored by grazing, and its suppression promotes exotic-plant invasion and diversity losses. CG has been heavily impacted by agriculture, overgrazing and pine afforestation. OS were the least diverse but the least sampled, and harbor plants that are important for conservation. In total we found 857 vascular plant species (although data show that this is a substantial underestimation), being the second most diverse grasslands in North America and encompassing 25 % of the species in the Tehuacán-Cuicatlán Valley in just 0.7 % of its area. The most diverse families were Asteraceae, Poaceae, Fabaceae, Lamiaceae and Euphorbiaceae. 37 % of the species are endemic to Mexico, with some microendemisms (3) and 26 threatened species. Four new taxa were discovered.

Conclusions:

Our results highlight the importance of studying and preserving the intertropical temperate prairies of Mexico due to the rapid destruction they face.

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