Resilience and vulnerability of herpetofaunal functional groups to natural and human disturbances in a tropical dry forest

Natural and anthropogenic disturbances alter animal populations in complex ways. Shifts in population size and taxonomic species diversity as such may not always completely reflect the effects of forest disturbance on faunal communities. In this study, we used a functional ecological approach to detect resilient and vulnerable species including anurans (frogs and toads), lizards and snakes, after Hurricane Jova hit the Pacific Coast of Mexico in 2011. Using population abundances, we compared functional traits including habitat preference, body size and reproductive type of the herpetofauna inhabiting tropical dry forest vegetation under a chronosequence of successional stages: active pastures, 0 y; early-forests, 5-6 y; young-forests, 8-10; intermediate-forests 15-17 y; and old-growth continuous forests. A total of 4093 individuals representing 17 species of anurans, 18 lizard species and 25 snake species were recorded. Overall, successional stage and Hurricane Jova affected the number of anurans and lizards in contrasting ways. For example, while the total number of anurans declined significantly after the hurricane in all successional stages (from 736 to 512 individuals), lizard populations significantly increased (from 1084 to 1612), except in old-growth forests. In contrast, neither disturbance type significantly affected the density of snakes (from 81 to 69). Regarding functional traits, there were complex trajectories of change in species abundances according to successional stage after the hurricane. For lizards, abundance within different functional traits was correlated with the chronosequence after Hurricane Jova. Density of terrestrial and medium-sized lizard species increased with successional age, while arboreal and small-sized lizards decreased. For anurans, terrestrial and large-sized species declined elsewhere, while medium- and small-sized species increased in pastures after Hurricane Jova. Furthermore, riparian frogs with aquatic reproduction were recorded only in pastures. The herpetofauna of the tropical dry forest on the Pacific Coast of Mexico is composed of a mixture of species resilient and/or vulnerable to the synergetic impact of human and natural disturbances. Under the present scenario of land-use and land-cover change, therefore, the preservation of old-growth forest tracts in the human-dominated landscape of the study region is extremely important.