Location: Invasive Plant Research LaboratoryTitle: Specificity of extrafloral nectar induction by herbivores differs among native and invasive populations of tallow tree Author
Submitted to: Annals Of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2013
Publication Date: 6/13/2013
Publication URL: http://aob.oxfordjournals.org/cgi/reprint/mct129? ijkey=N4IGy8ykJYrYzaX&keytype=ref
Citation: Wang, Y., Carrillo, J., Siemann, E., Wheeler, G.S., Zhu, L., Gu, X., Ding, J. 2013. Specificity of extrafloral nectar induction by herbivores differs among native and invasive populations of tallow tree. Annals Of Botany. DOI: 10.1093/aob/mct129. Interpretive Summary: Invasive plants establish in new areas far from their native range and are presented with a suite of novel conditions unlike their native communities. Among these differences, the invasive species may encounter generalist herbivores in their introduced range that are very different than those from their native range. New evolutionary changes occur in these invaded areas that potentially influence methods being developed for control of these invasive plants. Plants produce both direct and indirect defenses that protect them against insect feeding. Examples of the direct defense include trichomes, spines, and secondary metabolites. Indirect defenses include leaf domatia, induced volatile compounds, and extrafloral nectaries (EFN). These extrafloral nectaries are important resources produced by plants that attract and provide nourishment to predators of insects that damage plants. They may contain sugars and amino acids and their production is often induced to higher levels in response to herbivore damage. We found that the EFN production was greater by invasive (USA) plants compared with native (Chinese) plants. Specialist herbivores, like those developed for biological control, stimulated EFN more than generalists for native populations. These results suggest that EFN indirect defenses are retained in invasive populations, likely due to mechanical damage and the generalist herbivory that occurs in the introduced range. However, responses specific to specialist herbivory may be lost in the introduced range where specialists are absent.
Technical Abstract: Invasive plants are released from specialist herbivores and encounter novel generalists in their introduced ranges so their defenses may vary between native and introduced ranges. But few studies have examined how constitutive and induced indirect defenses change during plant invasion. We compared the constitutive extrafloral nectar (EFN) production of native and invasive populations of tallow tree (Triadica sebifera) and used leaf clipping, and damage by native specialist and generalist caterpillars to examine inducible EFN. Invasive populations had more leaves producing constitutive EFN than native populations did but volume and sugar content did not differ. Induction increased EFN but herbivores stimulated EFN more than clipping did. Specialist herbivory stimulated EFN more than generalists did for native populations. The number of leaves with EFN, volume and sugar content were all higher (1.7, 2.2, and 2.6 times, respectively) with specialist induction versus generalists for native populations but did not vary for invasive populations. Strength of induction varied between generalists. These results suggest that constitutive and induced indirect defenses are retained in invasive populations, likely due to mechanical damage and generalist herbivory occur in the introduced range. However, responses specific to specialist herbivory may be lost in the introduced range where specialists are absent.