Whence and whither the Convolvulus psyllid? An invasive plant leads to dietary expansion and range expansion by a native insect herbivore (Hemiptera: Triozidae)

Authors: Horton, David; KAUR, NAVNEET - University Of Idaho; Cooper, William - Rodney; MILICZKY, EUGENE - Washington State University; BADILLO VARGAS, ISMAEL - Texas A&M Agrilife; ESPARZA-DIAZ, GABRIELLA - Texas A&M Agrilife; RASHED, ARASH - University Of Idaho; WATERS, TIMOTHY - Washington State University; WOHLEB, CARRIE - Washington State University; JOHNSON, DANIEL - University Of Lethbridge; KAWCHUK, LAWRENCE - Agri Food - Canada; JENSEN, ANDY - Oregon State University

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2018
Publication Date: 2/25/2019
Citation: Horton, D.R., Kaur, N., Cooper, W.R., Miliczky, E., Badillo Vargas, I., Esparza-Diaz, G., Rashed, A., Waters, T., Wohleb, C., Johnson, D., Kawchuk, L., Jensen, A. 2019. Whence and whither the Convolvulus psyllid? An invasive plant leads to dietary expansion and range expansion by a native insect herbivore (Hemiptera: Triozidae). Annals of the Entomological Society of America. 112(3):249-264. https://doi.org/10.1093/aesa/say063.
DOI: https://doi.org/10.1093/aesa/say063

Interpretive Summary: Arrival and spread of exotic plants in North America is thought to contribute to spread of native plant-feeding insects into regions outside their original range, including spread by pest insects into regions previously free of the pest. Well-documented examples of this process, however, are rare. Scientists with USDA-ARS-TTFVRU, Wapato, WA in cooperation with scientists at Washington State University, University of Idaho, Texas A&M, University of Lethbridge, Agriculture and Agri-Food Canada, and the Washington State Potato Commission used a specialist psyllid of morning glories as a model system to show how an exotic invasive weed, field bindweed, has led to range expansion of the psyllid. The approach combined analyses of plant DNA to identify native hosts of the psyllid, rearing trials to confirm suitability of those plants to the psyllid, and biogeographic analyses to show distribution of native hosts versus distribution of the exotic weed. With this approach, cooperators plausibly reconstructed the psyllid’s pre-bindweed geographic range in North America, and concluded that arrival of field bindweed in North America has indeed led to range expansion by the psyllid. The approach developed here should have broad applicability in evaluating the role of exotic plant species in post-arrival spread of specialist insect herbivores.

Technical Abstract: Arrival of plant species outside of their native range may lead to changes in structure and function of the native insect fauna that include shifts in host use by herbivores. Well-documented examples showing that host shifts onto invasive plant species also lead to range expansion of native insects are surprisingly rare. Evidence for range expansion requires some understanding of the insect’s distribution preceding arrival of the exotic species. This information may often not be available. The North American psyllid Bactericera maculipennis is a specialist on plants in the Convolvulaceae. A recent study hypothesized that the psyllid’s geographic range has expanded following its colonization of an exotic and invasive weed, field bindweed (Convolvulus arvensis). Efforts to test this idea run into the same retrospective problems typical of these analyses, in that the psyllid’s host plant and its geographic distribution preceding arrival of C. arvensis are uncertain. We used the psyllid’s current association with C. arvensis to guide efforts in identifying its natal (pre-bindweed) host, reasoning that a host shift by a specialist herbivore such as B. maculipennis onto an exotic species would be more likely if natal and exotic species are closely related. Phylogenetic analyses of plants, rearing trials, and field records led us to target species within the genus Calystegia (hedge and false bindweeds) as natal hosts of B. maculipennis. A biogeographic analysis of Convolvulaceae then led us to propose that association of B. maculipennis with Calystegia resulted in historical concentration of the psyllid in California where Calystegia is highly diverse and where the psyllid is known to be widespread. Current presence of the psyllid in regions lacking Calystegia but with heavy presence of C. arvensis led us to conclude that arrival of the exotic weed in North America has indeed led to range expansion by the psyllid. In sum, by targeting close relatives of the exotic host as possible natal hosts for B. maculipennis, we were able to plausibly reconstruct the psyllid’s pre-bindweed geographic concentration. That reconstruction was then used to build a defensible case that arrival of the invasive C. arvensis in North America has led to range expansion by this host-specialized psyllid.