Do plant-herbivore interactions persist in assisted migration plantings?

Biotic interactions are expected to be impacted by rising temperatures due to climate change, particularly in climate-threatened ecosystems such as the tropical montane cloud forest (TMCF). In assisted migration plantings, novel interactions between previously non-overlapping species may emerge while other interactions may disappear. However, these processes require study. Herbivory is particularly important in tree early stages, and can vary with elevation and plant species traits. We assessed whether leaf herbivory occurs in translocated tree saplings and varies with elevation, and whether herbivory affects sapling growth in six shade-tolerant TMCF tree species translocated to seven enrichment plantings along an elevation gradient (1,250-2,500 m a.s.l.), including sites located above the reported distributional limit of the species, in eastern Mexico. Given the conservative strategy of the studied plant species, limited damage was expected. Since insects are ectothermic, we expected decreasing herbivory pressure with increased elevation. After 4 years, sapling survival was high (77.9-92.1%). Moderate herbivory was recorded in all species and at all sites (1.0-6.6%), with no effect on growth in any of the species. Herbivory decreased with elevation in three species and was unaffected in the other three. The results indicate that plant-herbivore interactions can continue at new locations; however, the contribution of generalist and specialist insect herbivores requires further study. The reduced herbivory at higher elevation in some species supports the expected trend, which could represent an advantage for upward assisted migration of endangered TMCF tree species in restoration plantings to mitigate climate change effects.

Automated summary

The study assessed leaf herbivory in translocated tree saplings of six shade-tolerant TMCF tree species in eastern Mexico along an elevation gradient, finding moderate herbivory with no significant effect on sapling growth. Herbivory decreased with elevation in some species, supporting the expected trend and potentially benefiting upward assisted migration of endangered TMCF tree species to mitigate climate change effects.