Arthropod communities in the spider diet differ between native and invaded sites,
Our results show that in areas modified by invasive ginger, spiders are consuming a very different, but partially overlapping, spectrum of prey items compared to spiders in native forest (Figure 4). Spiders in native forest are preying predominantly on Hemipterans and show a narrow selection of prey while the diets of spiders in ginger are more varied, and consist of prey orders uncommonly found in the diets of spiders collected from native forest (Figure 5). In invaded sites, a more diverse prey community was detected in totality, reflected in the individual diets of spiders as well which showed wider breadth than spiders from native sites. Trophic dispersion has been detected in other studies following invasion, which can be followed by destabilization of the food network (Wainright et al. 2021).
Spiders in ginger also appear to be consuming more prey, when using sequencing reads as a proxy measurement for abundance (Figure 2). Invasive plants have been found to increase the abundance of available arthropods that can serve as prey in some studies. For example, a study in the Iberian Peninsula found a much higher abundance of generalist herbivore species on nonnative plants (Rodríguez et al. 2019). This increase may partially be due to the provision of shelter (Landsmanet al. 2020). A similar result was found for arthropods associated with invasive tamarisk in Colorado (Uhey et al. 2020). Spiders make site settlement decisions based on multiple factors, predominantly microhabitat and prey availability (Riechert & Gillespie 1986). If there is abundant potential prey and if ginger provides additional protection through the dense plant structure, spiders may perceive the habitat to be highly suitable (Gillespie & Tabashnik 1994). However, unpublished data from arthropod sampling in this invasion of ginger did not detect higher densities of arthropod prey. The higher reads in the diets of spiders in ginger may then point towards suboptimal prey, where the spiders must consume more prey to meet their nutritional requirements.