Impact of invasive alien true bug species in native tropich webs

Periodic Reporting for period 2 - INVASIoN (Impact of invasive alien true bug species in native tropich webs)

Periodo di rendicontazione: 2018-03-01 al 2019-02-28

When invasive herbivorous insect species invade new environments, they can not only cause serious economic losses to attacked economically important crops, but they also interact with local species, modifying the structure of local food webs with effects cascading across trophic levels. The INVASION project, by adopting a multidisciplinary approach to study the ecological impact of an alien insect invasion, investigates both the basic and applied consequences determined by the brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Heteroptera: Pentatomidae), which is a pest of Asian origin that has recently invaded both North America and Europe, causing severe economic losses in orchards and field crops. The main project objectives are: 1) to evaluate the impact of alien herbivore invasion on local tritrophic interactions; 2) to evaluate the responses of parasitoids to infochemical evolutionary traps in a climate change context; 3) to study the contest behaviour of local egg parasitoids for possession of co-evolved and non-coevolved hosts; 4) to investigate the patch time allocation of local egg parasitoids after alien herbivore invasion using behavioural and modelling approaches; 5) to elucidate the molecular aspects of indirect plant defences against invasive and local pest species; 6) to investigate the genetic structure of invasive alien herbivores across Europe and North America.
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.

The activities proposed in the INVASION project require a multidisciplinary approach that includes knowledge of biological control, behavioural and chemical ecology, invasive ecology, statistical and mathematical modelling, and genetic structure of insect populations. The Consortium involved in the project provides a combination of scientists from Europe and North America to address key scientific issues related to basic and applied ecology of an invasive herbivore species, which poses serious risks to agriculture. The research units of the Consortium based in Europe are: University of Palermo (UNIPA) - Italy, University of Perugia (UNIPG) - Italy, University of Nottingham (UNINOT) – United Kingdom, Institut National de la Recherche Agronomique (INRA) - France, Benaki Phytopathological Institute (BPI) – Greece. The North American research units are located in Canada at the Université de Montréal (UDEM) - Canada and Agriculture and at the Agri-Food Canada (AAFC).

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).

The results achieved by the project will be relevant for the improvement of the research and the innovation potential of the collaborating teams in terms of both fundamental and applied ecology. In the short term, progress in fundamental research is expected by characterizing the ecological consequences of an alien herbivore invasion in a multi-trophic perspective. In the long term this project can potentially generate environmental, agricultural and socio-economic impacts by applying invasive ecology concepts to reduce pesticide inputs in integrated pest management. In particular several work packages are focused on behavioral and chemical ecology of egg parasitoids (which are the main biological control agent of stink bugs) and manipulation of infochemicals to improve their efficiency in biological pest control is a promising strategy to minimize pesticide use in agriculture. An important part of the INVASION project has already been devoted to result dissemination and networking. The project has already strengthened the networking activities between European and Canadian researchers and long lasting collaborations have been established. Members of the Consortium have attended several key international conferences and have visited international research institutes where results of the project were disseminated.

Figure 1 - INVASION overview of the planned work packages

Figure 2 - INVASION overview of the tritrophic systems

Periodic Reporting for period 2 - INVASIoN (Impact of invasive alien true bug species in native tropich webs)

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