Cumulative effects of high intensity hurricanes on herpetofaunal assemblages along a tropical dry forest chronosequence

Abstract

If combined with anthropogenic disturbances and global climatic change, hurricanes may lead to major effects on animal populations and assemblages. The combined effects of cumulative natural and human disturbances on vertebrates have been little studied. There is evidence that herpetofaunal assemblages are sensitive in species richness, abundance, and diversity to anthropogenic and natural disturbances, or to their interaction. In the Pacific coast of Jalisco, Mexico, we aimed to evaluate the cumulative effects of hurricanes Jova (2011) and Patricia (2015) on herpetofaunal assemblages along tropical dry forest successional stages by comparing before and after the hurricanes. We conducted a long-term survey (2009 to 2018) on anuran, lizard and snake populations within five dry forest successional stages (from 0 to > 50 years after forest clearance), including the following: active pastures, early forests, young forests, intermediate forests, and old-growth forests as experimental controls. We hypothesized that cumulative effects of hurricanes will result in a general pattern of a decrease in abundance, richness and diversity, and an increase in evenness of anurans, lizards and snakes. We also expected that herpetofaunal diversity will decrease and evenness will increase in those stages with higher vegetation complexity, such as old-growth forest (OGF), and an increase in similarity and evenness in herpetofaunal assemblages in all successional stages. Overall, the abundance of anurans, lizards and snakes significantly decreased after hurricanes, but only for lizards and anurans the interaction of successional stage-hurricane was significant. Furthermore, species richness and diversity increased for lizards and decreased for snakes after hurricanes landed. Although, the pattern of anuran species richness among successional stages was similar after hurricanes, the richness in OGF markedly diminished after hurricanes.Interestingly our results showed that tropical dry secondary forests, under the impact of low intensity hurricanes, might function as buffers that promote herpetofauna resilience. However, cumulative effects of hurricanes resulted in a homogenization tendency among successional stages, suggesting a negative effect for ecosystem functioning. The changes in the buffering role of secondary forests highlights the importance of these ecosystems for conserving biodiversity in times when hurricane disturbances are increasing in frequency and intensity. Overall, we discuss how the complex interactions between human and natural disturbances such as hurricanes might be a factor that contributes to maintain biotic diversity in anthropic landscapes of tropical dry forests.