DOI: 10.5061/dryad.0p468
title: Data from: Nontarget herbivory by a weed biocontrol insect is limited to spillover, reducing the chance of population-level impacts

description: Insects approved for classical biocontrol of weeds are often capable of
 using close relatives of their target weed for feeding, oviposition, or
 larval development, with reduced preference and performance. When
 nontarget herbivory occurs and is suspected to reduce survival, growth, or
 fecundity of individual plants, and insects are capable of reproducing on
 their nontarget host, characterization of spatial and temporal patterns of
 the occurrence and intensity of herbivory is valuable for predicting
 potential population-level effects. Here, we perform a novel post-release
 manipulative field experiment with a root-feeding biocontrol weevil,
 Mogulones crucifer, released in Canada to control the rangeland weed
 Cynoglossum officinale, to test for its ability to establish on the
 nontarget plant Hackelia micrantha. After Cynoglossum, M. crucifer
 exhibits its highest preference for and performance on Hackelia spp. We
 released M. crucifer on Canadian rangeland sites with naturally occurring
 populations of H. micrantha growing interspersed with the target weed or
 in the near absence of the target weed. Adult weevil feeding on
 surrounding plants was monitored for three summers after release (years 0,
 1, and 2), and, subsequently, subsets of plants were destructively sampled
 to determine M. crucifer oviposition levels. Additional oviposition and
 larval development data were obtained from seven non-experimental sites
 where weevils were released zero, three, or four years earlier. M.
 crucifer was not detected on experimental sites without C. officinale
 after two years, and nontarget herbivory was restricted to rare, low-level
 spillover. Visible evidence of adult herbivory (i.e., scars on shoots) was
 associated with oviposition in 90% of targets but only 30% of nontarget
 plants. We infer, through ecological refuge theory, that nontarget
 population-level impacts from M. crucifer spillover are unlikely because
 of temporal, spatial, and probabilistic refuges from herbivory, and make
 recommendations for monitoring and management of biocontrol systems with
 similar attributes, such as removing target plants around nontarget
 populations of interest. Because M. crucifer is among the least
 host-specific of the modern weed biocontrol agents, and H. micrantha is
 likely one of its most highly preferred nontargets, these conclusions are,
 arguably, generally applicable to other nontarget plants and biocontrol
 systems.
description: Catton et al Fig 1 data
 June 8 2013This data file was used
 to generate Figure 1 in Catton et al. (2015). It contains the results for
 the presence or absence of M. crucifer herbivory scars on Cynoglossum
 officinale and Hackelia micrantha plants target common or target rare
 sites (where applicable) in years 0, 1, and 2 following a point release of
 300 M. crucifer on each site on 4 June 2009.Catton et al Fig 2 data
 June 10 2013This data file was used
 to generate Figure 2 in Catton et al. (2015). It contains the results of
 dissectionsfor M. crucifer eggs and larvae in Cynoglossum officinale and
 Hackelia micrantha plants on M. crucifer release sites where both plant
 species were present.Catton et al Fig 3 data
 June 17 2013This data file was used
 to generate Figure 3 in Catton et al. (2015). It contains the results of
 dissection for M. crucifer eggs and larvae in Hackelia micrantha plants
 relative to the level of C. officinale herbivory on each site, expressed
 as the back-transformed mean ln(number of eggs per C. officinale plant +1)
 on M. crucifer release sites where both plant plant species were
 present.Catton et al Fig 4 data
 June 4 2014This data file was used
 to generate Figure 4 in Catton et al. (2015). It contains the results of
 dissection for M. crucifer eggs and larvae in Cynoglossum officinale and
 Hackelia micrantha plants on release sites in years where M. crucifer was
 known to be present.Experimental Release
 Site dissections after 2 years Dec 7 2014This data file was used
 to test for M. crucifer population establishment on experimental target
 common and target rare release sites after 2 years. It displays
 Cynoglossum officinale and Hackelia micrantha plants sampled and dissected
 in search of M. crucifer eggs and larvae. Plants were kept refrigerated
 between harvest and dissection, and whole plants were
 dissected.