The Manihot walkerae is a threatened herbaceous species in Texas U.S. and Tamaulipas Mexico. This specie has a narrowed distribution related to the Tamaulipan Thornshrub on Hidalgo Texas, and San Fernando, Abasolo, and Soto la Marina Mexico. During the last years, the agriculture had impacted the plant communities due to it expansion. This work evaluated the population structure on each two 1500m2 sampling quadrants on Peñitas, Texas and San Fernando, Tamaulipas. Furthermore, the distance and aspect of the nearest potential nurse plants were measured and evaluated by variance and Chi-Square analysis because the nurse plants have an important support on the protection of environmental adversities, and the establishment and growth of individuals during their youth stage. Accordingly, to the literature, the nurse plants are an essential aspect for herbaceous species like Manihot walkerae.
Results/Conclusions
The Peñitas population demonstrated a demographic structure of “J” inverted while the San Fernando had a discontinue distribution. The population density in Texas was from 220 individuals/hectare and 307 individuals/hectare in Mexico. The Texas population showed a nursing plant preference for the Celtis palida species. In contrast, the Mexican population had an association with the Condalia hookeri species. The two populations showed a 95% relationship with a south aspect preference from the nurse plant. Furthermore, the 56% of the south aspect preference are 100 centimeters from the nurse plant. On the other hand, the results pointed out a narrowed population density with low recruitment of smaller individuals of 30 centimeter of height. The low population density and the low number of youth individuals in the two study areas can be related to fragmented habitat, overgrazing and agriculture expansion that can be the principal causes of populations risk persistence in Texas and Mexico.