The Yucatan Peninsula as biogeographic province consists of the Mexican states of Campeche, Quintana Roo, and Yucatan, a more natural area also includes the northern regions of Belize, and Guatemala, and it is known as the Yucatan Peninsula Biotic Province. This province has karst geology, low surface hydrography, elevations below 350 meters, and a gradient of precipitation that allows the formation of different plant associations and the deciduous forest, semideciduous forest, and the evergreen forest are the most commons ones. The floristic information of this region is constantly updated. In the present work, this process is exemplified through an update for the endemic vascular flora and the recognition of new records from the last floristic checklist of the Mexican Yucatan Peninsula (Carnevali et al., 2010). Likewise, the application of a density index of botanical collection (IDCB, number of botanical collections /area) has been proposed, as a tool to evaluate the state of floristic knowledge by country, state or other administrative political unit. For example, a previous estimation for the Yucatan state yielded an index of 159 samples/km 2. This parameter was calculated for the entire region and the three states. In general, the floristic knowledge of the region is still in progress (new species, and new records), the state best collected is Yucatan, followed by Quintana Roo and Campeche. These last two states require more botanical collections, especially outside the area of influence of roads and populated centers.

An assessment of the extinction risk of the endemic plants from the Yucatán Peninsula Biotic Province (YPBP) was performed based on distributional data (B criteria of the IUCN) using the GeoCAT tool. The YPBP is located in southeastern Mexico and comprises the Mexican states of Campeche, Quintana Roo, and Yucatán, and the northernmost portion of Belize (districts of Belize, Corozal, and Orange Walk), as well as a portion of northern Guatemala (most of the department of Petén). An analysis of the YPBP flora identified 167 endemic taxa, 154 of which grow in at least one of the three Mexican states (Campeche, Quintana Roo, and/or Yucatán), whereas another 13 occur exclusively in Belize and/or Guatemala. Eighty-five are in some category of risk (50.9%): 17 taxa (10.18%) are categorized as Critically Endangered (CR), 40 (23.95%) as Endangered (EN), and 28 (16.77%) as Vulnerable (VU). Eighty-one (48.5%) species are not threatened: 12 (7.19%) as Near Threatened (NT) and 69 (41.32%) as Least Concern. A single species (0.6%) is considered Data Deficient (DD). The greatest number of endemic species and endemic threatened species inhabit dry and subhumid forests, and some inhabit semi-evergreen forests. The habits of endemic species and threatened endemic species are diverse, but trees, grasses, and shrubs predominate. The official system of protected natural areas (PNA) does not guarantee the conservation of all endemic species in the region. Ninety-eight (58.68%) of the endemic taxa have more than one population (record) within a PNA.

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