Periodic Reporting for period 2 - INVASIoN (Impact of invasive alien true bug species in native tropich webs)
Reporting period: 2018-03-01 to 2019-02-28
The invasion of a common pest in different continents, as the BMSB, poses serious threat to numerous agro-ecosystems. In this view, the project aims to achieve a deep understanding of the interactions among the alien pest and other insect community members associated with the same local crop in order to identify eco-friendly management tactics that can successfully control and reduce the pest status of native and invasive alien true bug species.
This multidisciplinary approach has the goal to advance the state of the art in the field of invasive ecology of herbivore pests in order develop effective biological control programmes.
The project was structured into six work packages:
WP1 - Impact of alien herbivore invasion on local tritrophic interactions;
WP2 - Learned responses of parasitoids to infochemical evolutionary traps in a climate change context;
WP3 - Contest behaviour of local egg parasitoids for possession of co-evolved and non-coevolved hosts
WP4 - Patch time allocation of local egg parasitoids after alien herbivore invasion: behavioural and modelling approaches
WP5 - Use of molecular tools to define novel tritrophic interactions after alien herbivore invasion
WP6 - Genetic structure of invasive alien herbivores across Europe and North America
Based on these research activities, the main results achieved can be summarised as follow: 1) demonstration of H. halys ability to impact the plant volatile-mediated signalling in local tritrophic webs (both in Europe and North America) by interfering with indirect plant defence induced in response to local pentatomid feeding and oviposition activities; moreover, it was demonstrated for the first time that zoophytophagous predator attacks induce indirect plant defences similarly to those defence strategies adopted by plants as a consequence of infestations of herbivorous insects (WP1); 2) demonstration of the role of the experience in modifying foraging behaviour of local egg parasitoids by exploiting host chemical footprints of an invasive and not-associated host; in particular it was described the first known case of negative effects of associative learning in parasitoids, since the native egg parasitoid T. podisi, after a first experience on traces and eggs of H. halys, learned to exploit the cues of this non-associated host, thus increasing the risk of ‘evolutionary trap’ for the native parasitoid species (WP2); 3) demonstration of the ability of native egg parasitoids to exploit chemical footprints and egg masses of the alien species, although with a low emergence of adult parasitoids (WP4); 4) demonstration of the ability of an alien pest in interfering with the host location behaviour of native egg parasitoids since the contamination by footprints of H.halys modifies the patch time allocation of T. basalis in the areas where its natural host is present; moreover, it was evidenced that parasitoid patch-leaving decision rules appear to be under significant intra-population genetic variation (WP4); 5) demonstration of capacity of local egg parasitoids species to parasitize egg masses of an invasive host, and of plants in recognizing H. halys oviposition as a warning signal that induces pre-activation of plant defences against future nymphal herbivory and recruitment of local egg parasitoids; moreover, it was evidenced possible non-target effects on a native predator (WP5); 6) demonstration of a relatively high level of genetic diversity in populations of the H. halys that invaded European and North American countries; in particular among the 14 different haplotypes retrieved 2 of them, found in specimens from Canada, Italy and USA, were detected for the first time (WP6).