The Galápagos archipelago is recognized worldwide by the large diversity of endemic species which have persisted in a very diversified environment. However, it is also subject to treats such as the increasing urbanization, tourism, cattle raising, and agriculture which have changed the landscape at different levels. Exotic species were also transported into the islands causing negative effects in native communities. Legume plants are among the most diverse taxon of plants in Santa Cruz, the most populated island, constituting an important resource for insects, which establish communities that may vary across landscapes and host plants. We analyzed the changes in the diversity and structure of networks of insects associated to seeds of exotic legume plants across four different landscapes and two levels of functional diversity: (1) plants-seed feeders-parasitoids (PSP), and (2) PSP+Predators+Phytophagous (PSPPP). We collected seed pods of exotic legume plants according to its availability on four landscapes: road side, urban, wooded pasture, and forest tree plantation. Seeds pods were inspected for insects every 24 hours, during 20 days, and insects were collected for identification. We built and compared bipartite networks for each landscape x level of diversity, calculating connectance, nestedness, robustness, and Shannon diversity.
Results/Conclusions
When comparing networks between two levels of functional diversity we found, as expected, that diversity of interactions was larger in PSPPP networks. We also found that nestedness was higher in the landscapes urban, and wooded pasture, in the PSPPP network. There were not strong differences in robustness and connectance, which appears surprising because it shows that in this case the susceptibility of the networks to perturbation are not associated to diversity of interactions. Diversity of interactions, and robustness were higher in the wooded pastures, which indicates that among highly transformed landscapes, this may offer resources that provide better stability to the insect communities. In addition, we recorded for the first time two species of Bruchinae (Coleoptera), two new host plant-bruquid associations, a new species of Bruquinae, and a new record of Hymenoptera parasitoid for the Galapagos. This study will continue sampling communities of insects in native legumes and in other islands of the archipelago.