Survival, reproduction and population growth of the bee pollinator, Osmia rufa (Hymenoptera: Megachilidae), along gradients of heavy metal pollution DAWID MORO  N, 1 HAJNALKA SZENTGYO ¨ RGYI, 2 PIOTR SK  ORKA, 3 SIMON G. POTTS 4 and MICHA Ł WOYCIECHOWSKI 2 1 Polish Academy of Sciences, Institute of Systematics and Evolution of Animals, Krak ow, Poland, 2 Institute of Environmental Sciences, Jagiellonian University, Krak ow, Poland, 3 Institute of Zoology, Pozna n University of Life Sciences, Pozna n, Poland and 4 School of Agriculture, Policy and Development, Reading University, Reading, Berks, UK Abstract. 1. Bees are one of the most important groups of pollinators in the temperate zone. Although heavy metal pollution is recognised to be a problem affecting large parts of the European Union, we currently lack insights into the effects of heavy metals on wild bee survival and reproduction. 2. We investigated the impact of heavy metal pollution on the wild bee Osmia rufa (Hymenoptera: Megachilidae) by comparing their survival, reproduction and population dynamics along two independent gradients of heavy metal pol- lution, one in Poland and the other in the United Kingdom. We used trap nests to evaluate the response of fitness and survival parameters of O. rufa. To quan- tify the levels of pollution, we directly measured the heavy metal concentration in provisions collected by O. rufa. 3. We found that with increasing heavy metal concentration, there was a steady decrease in number of brood cells constructed by females and an increase in the proportion of dead offspring. In the most polluted site, there were typi- cally 3–4 cells per female with 50–60% dead offspring, whereas in unpolluted sites there were 8 to 10 cells per female and only 10–30% dead offspring. More- over, the bee population growth rate (R 0 ) decreased along the heavy metal pol- lution gradients. In unpolluted sites, R 0 was above 1, whereas in contaminated sites, the values tended to be below 1. 4. Our findings reveal a negative relationship between heavy metal pollution and several fitness parameters of the wild bee O. rufa, and highlight a mecha- nism whereby the detrimental effects of heavy metal pollution may severely impact wild bee communities. Key words. Apoidea, cadmium, contamination, lead, pollinators, trap nest, zinc. Introduction Contamination of the natural environment with various products of human activity, including heavy metals, is a long lasting problem (Nriagu, 1996). Pollutants accumu- late efficiently in litter and soil due to their high affinity for organic substances and clay particles (Walker et al., 2012). Although many metals are essential for the bio- chemistry and physiology of organisms (e.g. iron, copper and zinc), all become toxic when the required levels are greatly exceeded (Newman & Clements, 2008). Other met- als, such as mercury, plutonium and lead, often called xenobiotic metals, are not used by organisms in any bio- chemical process and can become highly toxic in concen- trations above their natural, background, levels (Newman Correspondence: Dawid Moro n, Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Sławkowska 17, 31-016 Krako´ w, Poland. E-mail: dawidmoron@poczta.onet.pl; Michał Woyciechowski, Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, 30-387 Krako´w, Poland. E-mail: michal.woyciechowski@uj.edu.pl Ó 2013 The Royal Entomological Society 113 Insect Conservation and Diversity (2014) 7, 113–121 doi: 10.1111/icad.12040