Diversity of anurans in oil palm plantations in a human-dominated landscape in southeastern Mexico

Oil palm plantations are expanding in Mexico, primarily in areas already dominated by induced grasslands and other crops. There is a large body of information on the reduction of biodiversity in oil palm plantations compared to conserved forests. However, only a few studies have been performed in already anthropized matrices where almost all the natural vegetation has been replaced. To determine the effect of oil palm plantations located in an anthropized landscape on amphibian biodiversity, we obtained amphibian species richness and abundance using 48 transects distributed among seven oil palm plantation estates situated in the Gulf of Mexico lowlands in southeastern Mexico and compared with the observed amphibian biodiversity obtained from 15 previously published amphibian surveys on the area. Our survey in the oil palm plantations resulted in 1,977 individuals belonging to 15 species from seven anuran families. Although anuran diversity varies among the studied plantation estates, few significant differences were detected. We observed that the species richness in oil palm plantations represents 41.7% of the species detected in the region. However, we observed that more than half of the species (21 of 36) that have been detected in the region appeared in less than 30% of the sites studied, and the 15 remaining species that are more frequently detected in the area, 12 (80%) are present in oil palm plantations. Our study region has a long history of agricultural use and is already heavily fragmented. Thus, the remarkable similarity observed between the anuran species found in oil palm plantations and the most frequent amphibian species in the Gulf of Mexico lowlands can be explained by an already depauperate landscape dominated by species that are disturbance-tolerant or benefited from habitat modifications. Oil palm plantations in the region will expand in the future. Our results show that if the expansion continues to replace induced grasslands or other crops will have a reduced impact on the anuran biodiversity in this region. However, this expansion should preserve the remanent secondary growth forest patches distributed along the landscape to maintain the regional anuran diversity.