Though tropical landscapes are the biodiversity hotspots of the world, studies estimate that up to 36% of tropical forests are going to disappear by year 2050. This disappearance can be accelerated by introduced exotic species because of their ability to modify invaded sites and alter nutrient cycling. In this study, we assessed whether invasion of Zingiber spectabile (beehive ginger) alters mean abundance of leaf litter arthropods (arthropods) across forest types at Las Cruces Biological Station (LCBS) in Costa Rica, since arthropods are ecological indicators used to detect anthropogenic impacts. We also determined if degree of herbivory on Z. spectabile predicted mean abundance of arthropods across forest types. We hypothesized that invasion of Z. spectabile would decrease mean abundance of arthropods in all forest types because arthropods have not adapted to the environment created by the plant. We further predicted that degree of herbivory on Z. spectabile would predict mean abundance of arthropods found across forest types since we expected a large proportion of herbivory to be produced by non-flying arthropods such as ants. We sampled arthropods by setting up 18 paired point comparison pitfall traps in invaded and non-invaded sites in primary, primary selectively logged, and secondary forests.
Results/Conclusions
Our results showed that invasion of Z. spectabile had no significant effect on mean abundance of leaf litter arthropods across all forest types. Rather, mean abundance of arthropods was significantly reduced due to habitat type, in this case, in the secondary forest (F2, 33 = 6.55, P = 0.004). The significant decrease in mean abundance of arthropods in the secondary forest was due to deforestation on the once, interconnected highland forest which has altered the secondary forest’s canopy structure and species composition. Since leaf litter arthropods rapidly respond to ecological changes, the large-scale disturbance posed a dramatic effect on their abundance. Contrary to our hypothesis on herbivory, degree of herbivory predicted mean abundance of beetles and crickets across forest types. Most of the beetles we collected were herbivores and detritivores and literature support that crickets increase consumption in the presence of a predator. We recommend conducting further studies regarding the effects of Z. spectabile on leaf litter arthropods in comparison to native species in LCBS and incorporating environmental variables. Additional data will help make better decisions for restoration and conservation of tropical landscapes.