RAPID COMMUNICATIONS Immediate Effects of Nectar Robbing by Palestine Sunbirds (Nectarinia osea) on Nectar Alkaloid Concentrations in Tree Tobacco (Nicotiana glauca) Rainee L. Kaczorowski & Avi Koplovich & Frank Sporer & Michael Wink & Shai Markman Received: 16 December 2013 /Revised: 16 March 2014 /Accepted: 18 March 2014 /Published online: 2 April 2014 # Springer Science+Business Media New York 2014 Abstract Plant secondary metabolites (PSMs), such as alka- loids, are often found in many parts of a plant, including flowers, providing protection to the plant from various types of herbivores or microbes. PSMs are also present in the floral nectar of many species, but typically at lower concentrations than in other parts of the plant. Nectar robbers often damage floral tissue to access the nectar. By doing so, these nectar robbers may initiate an increase of PSMs in the floral nectar. It is often assumed that it takes at least a few hours before the plant demonstrates an increase in PSMs. Here, we addressed the question of whether PSMs in the floral tissue are immedi- ately being released into the floral nectar following nectar robbing. To address this research question, we investigated whether there was an immediate effect of nectar robbing by the Palestine Sunbird (Nectarinia osea) on the concentration of nectar alkaloids, nicotine and anabasine, in Tree Tobacco (Nicotiana glauca). We found that the concentration of anabasine, but not nicotine, significantly increased in floral nectar immediately following simulated nectar robbing. These findings suggest that nectar robbers could be ingesting greater amounts of PSMs than they would if they visit flowers legit- imately. As a consequence, increased consumption of neuro- toxic nectar alkaloids or other PSMs could have negative effects on the nectar robber. Keywords Anabasine . Birds . Foraging . Nicotine . Pollinator . Secondary metabolites Introduction Plant secondary metabolites (PSMs), such as alkaloids, can effectively defend plant tissues against many types of herbi- vores (Rosenthal and Berenbaum 1992; Bennett and Wallsgrove 1994; Wink 1998, 2010). These compounds may be constitutive, always present in some part of the plant, or their production or allocation to different parts of the plant may be induced upon some form of damage to the plant. According to optimal defense theory, tissues closely associat- ed with plant fitness should have the most defenses (McKey 1974, 1979). In support of this theory, many studies have found that reproductive structures, like flowers, may have more PSMs than vegetative tissues (reviewed in Kessler and Halitschke 2009; but see McCall and Fordyce 2010). Strauss et al. (2004) found that flower petals alone had 20 % more constitutive PSMs than the leaves of Raphanus sativus. More- over, Euler and Baldwin (1996) found that the concentration of nicotine, the predominant PSM in Nicotiana attenuata, was highest at the base of the corolla, which surrounds the valuable ovary of the flower. This location is also where floral nectar is typically found. The assumed primary function of floral nectar is to attract and reward pollinators. However, PSMs are found in the floral nectar of many plant species (Baker 1977; Adler 2000; Irwin et al. 2004), although typically at much lower concentrations than in other plant tissues (Detzel and Wink 1993; Adler et al. 2012; Manson et al. 2012; Cook et al. 2013; Manson et al 2013). Various pollinators may discriminate against nectars containing PSMs (Detzel and Wink 1993; Tadmor-Melamed et al. 2004; Singaravelan et al. 2005; Kessler and Baldwin 2006; Kessler et al. 2008; Köhler et al. 2012), potentially reducing the number and/or duration of their floral visits and affecting plant fitness (Adler and Irwin 2005). These results may suggest that chemical defenses in nectar could be non- adaptive; perhaps simply a consequence of defending other R. L. Kaczorowski : A. Koplovich : S. Markman (*) Department of Biology & Environment, University of Haifa at Oranim, 36006 Tivon, Israel e-mail: markmans@research.haifa.ac.il F. Sporer : M. Wink Institute of Pharmacy and Molecular Biotechnology (IPMB), Heidelberg University, Im Neuenheimer Feld 364, D-69120 Heidelberg, Germany J Chem Ecol (2014) 40:325–330 DOI 10.1007/s10886-014-0411-7