Print PageOne overlooked driver of biodiversity loss is co-extinctions: the loss of species as a result of the extinction of species upon which they depended. Global warming is expected to increase extinction rates. However, the effects of climate change on biodiversity loss through co-extinctions remain unknown. One group of organisms that is highly susceptible to co-extinctions is insect herbivores because their life cycles are closely bound to their host plants. Under projected climate change, tropical plants will rely on altitudinal migrations to persist. Insect herbivore distributions will be affected by both climate and host plant distribution changes. This project evaluates host plant extinctions and cascades of associated insect herbivore co-extinctions under projected climate change in a tropical altitudinal gradient (Barva transect, Costa Rica). We used plants from the order Zingiberales and their insect herbivores, Cephaloleia beetles, as our study system. We are compiling the following datasets to model cascades of insect herbivore co-extinctions under projected climate change: 1. plant and insect herbivore altitudinal distributions and 2. insect herbivore diets. We are determining plant-herbivore associations by amplifying plant DNA barcodes (rbcL, trnH-psbA, ITS) from insect gut contents. Here we explore the following questions to assess the accuracy of DNA barcodes to determine insect herbivore diets. 1. how many hours after leaf tissue consumption is it possible to detect the host plant species of an insect herbivore using plant DNA barcodes? 2. in herbivores that simultaneously fed on two host plant species from the same genus, is it possible to identify host plants at a species level? 3. for insects that fed on multiple host plants in a short time period, is it possible to identify their hosts? 4. what is the sampling effort required to detect all plant herbivore interactions in the community?
Results/Conclusions
We successfully extracted plant DNA from insects that previously fed on two congeners from the following genera: Calathea (Marantaceae), Costus (Costaceae), Heliconia (Heliconiaceae) and Renealmia (Zingiberaceae). We also successfully extracted plant DNA from herbivores that simultaneously fed on three host plant species. We recovered DNA sequences from at least the rbcL gene and CO1 gene for all beetle species. Using rarefaction curves, we calculated the number of individuals required to detect the full diet breadth of generalist and specialist rolled-leaf beetles. Using DNA barcodes to identify insect herbivore diets has the potential to elucidate community-level processes such as cascades of co-extinctions under projected climate change.
