Variation in plant defences among populations of a range‐expanding plant: consequences for trophic interactions

Abstract

SummaryAlthough plant-herbivore-enemy interactions have been studied extensively in cross-continental plant invasions, little is known about intra-continental range expanders, despite their rapid spread globally.Using an ecological and metabolomics approach, we compared the insect performance of a generalist and specialist herbivore and a parasitoid, as well as plant defence traits, among native, exotic invasive and exotic non-invasive populations of the Turkish rocket, Bunias orientalis, a range-expanding species across parts of Eurasia.In the glasshouse, the generalist herbivore, Mamestra brassicae, and its parasitoid, Microplitis mediator, performed better on non-native than on native plant populations. Insect performance did not differ between the two non-native origins. By contrast, the specialist herbivore, Pieris brassicae, developed poorly on all populations. Differences in trichome densities and in the metabolome, particularly in the family-specific secondary metabolites (i.e. glucosinolates), may explain population-related variation in the performance of the generalist herbivore and its parasitoid. Total glucosinolate concentrations were significantly induced by herbivory, particularly in native populations.Native populations of B. orientalis are generally better defended than non-native populations. The role of insect herbivores and dietary specialization as a selection force on defence traits in the range-expanding B. orientalis is discussed.

Effects of generalist herbivory on resistance and resource allocation by the invasive plant, Phytolacca americana

“…While many studies have examined the impact of generalist herbivory on plant resistance, they have produced inconsistent results. In some cases, invasive populations have higher resistance to generalists than native populations (Leger & Forister, ; Caño et al ., ; Liao et al ., ), while results from other studies have found the opposite pattern (Siemann & Rogers, ; Hull‐Sanders et al ., ; Fortuna et al ., ). Such observed differences may be caused by a species‐specific response, especially when only a few generalists are examined.…”

Rapid growth and defence evolution following multiple introductions

“…Although analysis of neutral markers suggests genetic drift has been particularly strong in Australia (van Boheemen et al, 2017), we did not reveal any increase in inducible variation. The growing body of literature testing constitutive versus inducible defence in native and introduced ranges frequently report inconsistent results varying from reductions, to maintenance, to increases in either defence (Agrawal et al, 2015;Beaton, Zandt, Esselman, & Knight, 2011;Carrillo, Wang, Ding, Klootwyk, & Siemann, 2012;Cipollini & Lieurance, 2012;Cipollini et al, 2005;Eigenbrode et al, 2008;Fortuna et al, 2014;Gu et al, 2014;Macel et al, 2017;Wang et al, 2013Wang et al, , 2012 and calls for more detailed research on the cost-benefit trade-offs of the various responses.…”

Species pools and differential performance generate variation in leaf nutrients between native and exotic species in succession

“…A subset of those species also possessed faster root turnover, which was associated with higher N uptake and faster growth capacity between native and exotic congeners (Smith, Fridley, Goebel, & Bauerle, 2014). Furthermore, selective herbivory on native and exotic species may additionally alter nutrient and energy transfer in invaded ecosystems (Cincotta, Adams, & Holzapfel, 2009;Fortuna et al, 2014).…”