Background:

Mexico has a high diversity of aquatic and subaquatic plants that occur between 1,000 and 2,500 m of elevation, although a larger proportion of aquatic plants is concentrated at lower altitudes. Temporary wetlands harbor close to 73 % of the aquatic species in Mexico. These systems are under a strong anthropogenic pressure and suffer constant degradation.

Questions:

i) How many species grow in highland temporary wetlands? ii) Are they floristically similar? iii) Is there a latitudinal pattern of species richness?

Studied groups:

Charophyta, Pteridophyta, Angiosperms.

Study site and years of study:

Central Mexico (39 wetlands) from 2015 to 2016.

Methods:

We collected in 39 temporary wetlands for two years. We made a presence/absence list of species per locality, and calculated floristic similarities and correlations between wetlands. We include data characterizing life form, plant use, and conservation status.

Results:

We found 126 species belonging to 80 genera and 38 families. The richest families were Cyperaceae, Asteraceae, and Poaceae. As to genera, Eleocharis, Cyperus, and Juncus had more species. Species with the widest distributions were Persicaria mexicana, Marsilea mollis, Luziola fluitans, Heteranthera peduncularis, and Nymphoides fallax. We found five different life forms – all herbaceous, including 27 threatened species, 24 species with economic use, 48 endemic species, and 19 cosmopolitan species. In addition, we found 20 species recorded for the first time in some states included in our study, and two species of Eleocharis that might represent undescribed species. The richest wetland harbors 40 species, the poorest has only five. Wetlands were comparable to each other in species composition, and species richness increases towards the south.

Conclusions:

Temporary wetlands harbor a high floristic diversity and are similar to each other. Lower latitudes host higher numbers of species.