Distributional patterns of the strictly aquatic vascular flora in the state of Tamaulipas, Mexico

Abstract

Patterns of distribution and richness of strictly aquatic vascular plants of the state of Tamaulipas, Mexico, were analyzed. We registered 93 species of strictly aquatic vascular plants, which 62 are typical from lentic environments. The Rio Tamesi sub-basin contains the highest number of species (68, 73.1\%), There are no endemic species to the state of Tamaulipas, but we found 2 species endemic to Mexico (Lobelia purpusii and Oserya coulteriana). Twenty nine species (31.2\%) are considered rare, because they are present in a single sub-basin; only 2 species are widely distributed in most of them (Bacopa monnieri and Echinodorus berteroi). A parsimony analysis of endemicity (PAE) of the hydrological sub-basins represented in this state based on the shared presence of species suggested that the strictly aquatic vascular plants have a nested distributional pattern. We conclude that these plants in Tamaulipas are part of the same floristic unit and that their distribution follow altitudinal, latitudinal and climatic gradients.