title: Development and application of molecular gut-content analysis to detect aphid and coccinellid predation by Harmonia axyridis (Coleoptera: Coccinellidae) in Italy.
abstract: Despite their positive effect in reducing pest populations, exotic generalist predators sometimes become invasive and contribute to the displacement of indigenous species in the same trophic level. Although laboratory experiments have linked intraguild predation (IGP) to these interactions, field evidence and quantification of IGP are still lacking for most systems. The recent establishment of the exotic Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in Italy raises concern about the detrimental effect that the ladybird could have on native coccinellids. Here we assessed, under laboratory conditions, the acceptability and suitability of eggs of 2 native ladybirds, Adalia bipunctata L. and Oenopia conglobata (L.), as prey items for H. axyridis larvae. Then we developed primers for molecular gut-content analysis to detect predation by H. axyridis on the 2 ladybirds and on the aphid Eucallipterus tiliae L. Species-specific 16S primers were developed for the 3 species and laboratory feeding trials were conducted to quantify the rate of prey DNA breakdown in the gut of H. axyridis. Moreover, to field evaluate primers, H. axyridis 4th instars (n = 132) were systematically collected from linden trees in northern Italy and screened for the presence of prey DNA. Seventy-three percent and 7% of field collected H. axyridis were positive for aphid and coccinellid DNA, respectively. Predation upon aphid and A. bipunctata was lower than predicted if density dependent consumption was expected, while predation upon O. conglobata was significantly higher. Here, we provided the first evidence of IGP among feral populations of H. axyridis and indigenous ladybird beetles, occurring in Italy.
authors.affiliation: Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno 74, Perugia, 06121, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Rondoni
authors.affiliation: Department of Entomology, University of Kentucky, S-225 Agricultural Science Center North, Lexington, KY, 40546-0091, USA.
authors.forename: Kacie J
authors.initials: KJ
authors.lastname: Athey
authors.affiliation: Department of Entomology, University of Kentucky, S-225 Agricultural Science Center North, Lexington, KY, 40546-0091, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Harwood
authors.affiliation: Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno 74, Perugia, 06121, Italy.
authors.forename: Eric
authors.initials: E
authors.lastname: Conti
authors.affiliation: Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno 74, Perugia, 06121, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Ricci
authors.affiliation: Department of Entomology, University of Kentucky, S-225 Agricultural Science Center North, Lexington, KY, 40546-0091, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Obrycki
mesh_terms: D000818:Animals; D001042:Aphids; D001517:Coleoptera / Q000737:chemistry*; D005766:Gastrointestinal Contents / Q000737:chemistry*; D058865:Introduced Species; D007814:Larva / Q000737:chemistry; D010063:Ovum; D011235:Predatory Behavior
keywords: Adalia bipunctata; Eucallipterus tiliae; intraguild interactions; Oenopia conglobata; biological control; nontarget effect