UNCORRECTED PROOF ARTICLE INFO Article history: Received 10 April 2016 Received in revised form 18 June 2016 Accepted 10 July 2016 Available online xxx Keywords: Air pollution Calluna vulgaris heathlands Herbivory Lochmaea suturalis Predation ABSTRACT Elevated nitrogen (N) deposition impacts the structure and functioning of heathland ecosystems across Europe. Calluna plants under high N-inputs are very sensitive to secondary stress factors, including defoliation attacks by the heather bee- tle. These attacks result in serious damage or death of Calluna, its rapid replacement by grasses, and the subsequent loss of heathland. We know very little about the mechanisms that control the populations and trigger outbreaks of the heather beetle, impeding proper management measures to mitigate the damage. We investigated the effects of N deposition on the relationships between the heather beetle, its host plant, and two arthropod predators at building (rejuvenated through fire) and mature heathlands. The study combines field manipulation experiments simulating a range of N deposition rates (0, 1, 2, 5 g N m −2 year −1 for 2 years, and 5.6 g N m −2 year −1 for 10 years), and food-choice laboratory experiments testing the preferences of adults and larvae of the heather beetle for N-treated Calluna plants, and the preferences of predators for larvae grown on plants with different N-content. The larvae of the heather beetle achieved the highest abundances after the long-term (10-year) addition of N at mature Calluna plots in the field. Contrary to the adults, the larvae foraged preferentially on the most N-rich Calluna shoots under laboratory conditions. Predators showed no aggregative numeri- cal responses to the accumulation of heather beetle larvae at high N-input experimental plots. During the feeding trials, predators consumed a small number of larvae, both in total and per individual, and systematically avoided eating the lar- vae reared on high-N Calluna shoots. Our study showed that the most severe defoliation damage by the heather beetle is inflicted at the larval stage under prolonged availability of high-N inputs, and that arthropod predators might not act as effective regulators of the beetle's populations. Effects of N deposition on the heather beetle, its host plant and two predators were investigated by a long-term field ma- nipulation study, laboratory rearing and food-choice experiments. © 2016 Published by Elsevier Ltd. Environmental Pollution xxx (2016) xxx-xxx Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com Disruption of trophic interactions involving the heather beetle by atmospheric nitrogen deposition ☆ Angela Taboada a, b, ∗ , Elena Marcos a, b , Leonor Calvo a, b a Area of Ecology, University of León, E-24071 León, Spain b Institute of Environmental Research (IMA), University of León, E-24071 León, Spain 1. Introduction Global rates of atmospheric nitrogen (N) deposition from anthro- pogenic emissions of total N (NO y and NH x , primarily associated with fossil fuel combustion and food production) are projected to double by 2050 (Galloway et al., 2004), exceeding the critical load thresholds that have detrimental effects on human health and the en- vironment (Dentener et al., 2006; Galloway et al., 2008; Sala et al., 2010). Elevated N inputs impact both ecosystem composition and functioning, by (1) altering multiple fundamental processes such as decomposition, microbial activity, plant growth and productivity, and species interactions, and by (2) increasing plant susceptibility to sec- ondary stress and disturbance factors (i.e., frost, drought, pathogens, and pests) (Bobbink et al., 2010; Krupa, 2003; Ochoa-Hueso et al., 2011; Throop and Lerdau, 2004). Especially vulnerable to excess N ☆ This paper has been recommended for acceptance by Dr. Hageman Kimberly Jill. ∗ Corresponding author. Area of Ecology, Department of Biodiversity and Environmental Research, University of León, Campus Vegazana s/n E-24071 León, Spain. Email address: angela.taboada@unileon.es (A. Taboada) accumulation are N-limited ecosystems adapted to low levels of N availability (Sala et al., 2010), like semi-natural heathlands dominated by heather, Calluna vulgaris (L.) Hull (hereafter Calluna) (Fagúndez, 2013; Phoenix et al., 2012; Stevens et al., 2016). Both N-manipula- tion experiments (e.g., Calvo et al., 2005, 2007; Härdtle et al., 2009; Power et al., 2004) and field-scale surveys (e.g., Jones and Power, 2012; Southon et al., 2013) evidenced N-driven changes in the com- position, diversity and functioning of heathlands, highlighting atmos- pheric N deposition as a major driver of heathland decline across Eu- rope. Many studies have revealed increases in the annual shoot growth, leaf nutrient content, and flowering of Calluna plants in response to the experimental addition of N (e.g., Friedrich et al., 2011; Power et al., 1998a; Uren et al., 1997; von Oheimb et al., 2010). And yet, few studies have explicitly linked the enriched Calluna nutritional quality induced by N to its greater sensitivity to biotic stress, particularly to insect attack (Hartley et al., 2003; Kerslake et al., 1998; Power et al., 1998b). Similarly, growing number of researches investigate the re- sponse of heathland vegetation to N deposition in combination with multiple drivers of global change (e.g., land-use change: Härdtle et al., 2009; climate change: Meyer-Grünefeldt et al., 2015), overlook- ing possible interactions with insect herbivory (see Gladbach, 2010; http://dx.doi.org/10.1016/j.envpol.2016.07.023 0269-7491/© 2016 Published by Elsevier Ltd.