Using geographic range data to support the extinction risk assessment of an endangered species via the IUCN’s and Mexico’s National Risk Assessment Method

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Gisel Garza and Teresa Patricia Feria Arroyo, Biology, The University of Texas Rio Grande Valley, Edinburg, TX, Crystian S. Venegas Barrera, Instituto Tecnológico de Ciudad Victoria, Ciudad Victoria, Mexico, José G. Martínez-Avalos, Forest, Institute of Applied Ecology, Universidad Autónoma de Tamaulipas, Mexico, Victoria, Mexico, Jon Dale, American Forests, Washington, DC

Background/Question/Methods
Designating transboundary species into an appropriate extinction risk category is important for the species’ conservation at both national and global levels. Walker’s Manihot, Manihot walkerae, is an endangered plant species that is endemic to the transboundary region of south Texas and northeastern Mexico. Manihot walkerae is listed as endangered in the IUCN’s Redlist, however, no previous assessment has been done for this species using Mexico’s National Risk Assessment methodology (MER) and it is not listed in Mexico’s NOM-059-SEMARNAT. The main goal of this research was to determine if M. walkerae can be included in an extinction risk category using assessments of its geographic range criteria globally and in Mexico. Manihot walkerae was assessed with criteria A, B, and C of the IUCN and criteria A, B, C, and D of the MER through the use of distributional data, land-use and human footprint layers. We constructed a model of M. walkerae’s potential geographic distribution, using the MaxEnt algorithm, to incorporate it under the IUCN’s criteria B and Mexico’s MER criteria A. Additionally, we estimated percent of potential distribution that was converted into croplands and urban built-up areas to estimate the decline in habitat quality (IUCN criteria A2c).
Results/Conclusions
Manihot walkerae can be considered an endangered species based on the IUCN’s assessment method under criteria B2ac and C2a, and as a threatened species in Mexico using the MER. The predicted geographic distribution (PGD) and extent of occurrence (EOO) of Manihot walkerae designated it as vulnerable within the criteria B1 category, since both exceed the 5,000 km2 endangered threshold value but are less than 20,000 km2. However, if we subtract transformed lands from M. walkerae’s PGD it leaves 5,938 km2, a 48% loss which is close to meeting the endangered threshold value. Manihot walkerae is a very restricted species in Mexico, since it covers less than 5% of Mexico’s total area, which is the threshold value for very restricted species under criterion A. The IUCN assessment performed here supports the previous IUCN designation of M. walkerae as endangered, while in Mexico, no previous assessment for this species has been attempted in the past. Our work can help advocate for the listing of M. walkerae as a threatened species on the List of Species at Risk under Mexican Official Norm NOM-059-SEMARNAT and to establish sound conservation plans to protect this globally endangered species.