Breaking down insect stoichiometry into chitin-based and internal elemental traits: Patterns and correlates of continent-wide intraspecific variation in the largest European saproxylic beetle * Grzegorz Orlowski a, * , Lucyna Mr  oz b , Marcin Kadej c , Adrian Smolis c , Dariusz Tarnawski c , Jerzy Karg d , Alessandro Campanaro e , Marco Bardiani f , Deborah J. Harvey g , Marcos M  endez h , Arno Thomaes i , Al Vrezec j , Krzysztof Ziomek a , Andrzej L. Rudecki b , Detlef Mader k a Institute of Agricultural and Forest Environment, Polish Academy of Sciences, Bukowska 19, PL-60-809, Pozna n, Poland b Department of Ecology, Biogeochemistry and Environmental Protection, Faculty of Biological Science, University of Wroclaw, Kanonia 6/8, PL-50-328, Wroclaw, Poland c Department of Invertebrate Biology, Evolution and Conservation, Institute of Environmental Biology, Faculty of Biological Science, University of Wroclaw, Przybyszewskiego 65, PL-51-148, Wroclaw, Poland d Faculty of Biological Sciences, Department of Nature Conservation, University of Zielona G ora, Zielona G ora, Prof. Z. Szafrana 1, PL-65-516, Zielona G ora, Poland e Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria e Centro di ricerca Difesa e Certificazione, Firenze, Italy f Reparto Carabinieri Biodiversit a di Verona, Centro Nazionale Carabinieri Biodiversit a “Bosco Fontana”, Mantova, Italy g School of Biological Sciences, Royal Holloway University of London, Egham, UK h  Area de Biodiversidad y Conservacion, Universidad Rey Juan Carlos, Mostoles, Madrid, Spain i Research Institute for Nature and Forest (INBO), Brussel, Belgium j National Institute of Biology, Ljubljana, Slovenia k Hebelstraße 12, D-69190, Walldorf, Germany article info Article history: Received 19 September 2019 Received in revised form 21 January 2020 Accepted 23 January 2020 Available online 13 March 2020 Keywords: Insect chitin Metal compartmentalization Elemental composition Trace elements Internal metal concentrations Exoskeleton Chitin-bound metals abstract Stoichiometric, trophic and ecotoxicological data have traditionally been acquired from patterns of variation in elemental traits of whole invertebrate bodies, whereas the critical issue of the extracellular origin of some portion of elements, such as those present in ingested food and internal organs, has been ignored. Here we investigated an unexplored, yet crucial, question relating to whether, and to what degree, metals from two major body fractions: exoskeleton (elytra) and internal (body organs with gut material present in abdomens), are correlated with each other in wild populations of the largest Euro- pean saproxylic insect, the Stag Beetle Lucanus cervus, and how metals from these two fractions vary with insect size and local habitat conditions. We examined the continent-wide variation in the concentrations of 12 chemical elements (Ca, Mg, K, Na, Mn, Fe, Zn, Cu, As, Cd, Pb and Ni) measured in the elytra and abdomen of specimens from 28 populations inhabiting an urban-woodland habitat gradient across the species’ entire distributional range from Spain to Russia. Across populations, elemental concentrations (except Ni and Pb) were 2e13 times higher in abdominal samples than in elytra, and the magnitude of these differences was related to both insect size and local habitat conditions. Smaller individuals from both woodland and urban habitat tended to have higher concentrations of trace elements (Zn, As, Cd, Pb and Ni). The concentration of only six elements (Mg, K, Na, Mn, Cd and Ni) was correlated in the elytra and abdomen at the individual and population levels, implying a limitation to the broader applicability of * This paper has been recommended for acceptance by Wen-Xiong Wang. * Corresponding author. E-mail addresses: orlog@poczta.onet.pl (G. Orlowski), lucyna.mroz@uwr.edu.pl (L. Mr oz), marcin.kadej@uwr.edu.pl (M. Kadej), adrian.smolis@uwr.edu.pl (A. Smolis), dariusz.tarnawski@uwr.edu.pl (D. Tarnawski), turew@poczta.onet.pl (J. Karg), ale.naro@gmail.com (A. Campanaro), bardianimarco@gmail.com (M. Bardiani), d.harvey@ rhul.ac.uk (D.J. Harvey), marcos.mendez@urjc.es (M. M endez), arno.thomaes@inbo.be (A. Thomaes), al.vrezec@nib.si (A. Vrezec), dr.detlef.mader@web.de (D. Mader). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol https://doi.org/10.1016/j.envpol.2020.114064 0269-7491/© 2020 Elsevier Ltd. All rights reserved. Environmental Pollution 262 (2020) 114064