Data from: Mismatches between the resources for adult herbivores and their offspring suggest invasive Spartina alterniflora is an ecological trap

1. Plant invasions can alter the behavior and performance of native
herbivorous insects because the insects are evolutionarily naïve to the
novel plants. An ecological trap results when native insects prefer
invasive plants over their native hosts but suffer reduced fitness on the
invaders. Although such traps are predicted to occur frequently given the
prevalence of invasive plants, empirical support for ecological traps and
their underlying mechanisms remains sparse. 2. We examined the potential
for the invasive plant Spartina alterniflora to act as an ecological trap
for the native moth Laelia coenosa, which previously fed mainly on the
indigenous plant Phragmites australis in a Chinese saltmarsh. We surveyed
Laelia egg densities on Spartina and Phragmites in the field, and
determined adult oviposition preference and offspring development on the
two plant species. To investigate the causes of adult preference and
offspring performance patterns, we compared resource abundance in the
field, plant-odor attractiveness, and leaf nutritional and defensive
traits between Spartina and Phragmites. 3. We found that Laelia egg
density and female preference for ovipositing were higher on Spartina than
Phragmites. However, performance of offspring was poorer on Spartina than
Phragmites. Spartina dominated a larger area and had greater leaf biomass
than Phragmites in the field, and volatile odors released by Spartina were
more attractive to Laelia females than those released by Phragmites.
Although leaf C, C:P ratio, and terpenoid content did not differ
significantly between the two plant species, Spartina leaves were tougher
and more waxy, had lower N, and had higher concentrations of alkaloids and
phenolics than Phragmites leaves. 4. Synthesis: Our data suggest that
invasive Spartina can create an ecological trap for the native insect
Laelia. This trap appears to result from environmental cues (resource
availability and leaf odors) that attract the herbivore to the plant, but
do not reliably predict the dietary qualities (nutrition and defenses)
that negatively affect herbivore offspring performance. These findings
reveal an important negative effect of plant invasions on resident
herbivores and highlight the roles of resource availability and plant
traits at different life stages of the insect.