Predicting extinction risk and novel host use in a complete Lepidoptera-plant food network

Background/Question/Methods

Humans have dramatically altered plant communities throughout the world by causing extinctions of native flora and establishing populations of non-native plants.  It would be very useful to predict the consequences of plant extinctions and introductions on communities of higher trophic levels.  We conducted a retrospective analysis of a nearly complete food network of 2403 plants and 900 Lepidoptera (moth and butterfly) herbivores in Central Europe in order to assess the effects of plant extinctions and non-native introductions on herbivores.  

Results/Conclusions

Models of extinction cascades due to realistic patterns of plant loss consistently underestimated the actual number of regional moth extinctions in central Europe, suggesting that host-loss is only one of many factors that drive herbivores to extinction.  Models that allowed herbivores to switch hosts onto related, but previously unused plants decrease the expected extinction rate of Lepidoptera, and models which assigned a higher likelihood of extinction to native plants than non-native plants resulted in an increased Lepidoptera extinction rate.  Within our dataset, 633 novel interactions between Lepidoptera and non-native plant species were observed.  Herbivore host breadth and plant phylogenetic relationships between native and non-native plants correctly predicted about two-thirds of these novel interactions.  Both plant extinctions and novel introductions have predictable effects on herbivore communities.