Discovery of a CI-inducing Wolbachia and its associated fitness costs in the biological control agent Aphytis melinus DeBach (Hymenoptera: Aphelinidae) Casandra J. Vasquez a , Richard Stouthamer a , Gilsang Jeong b , Joseph G. Morse a,⇑ a Department of Entomology, University of California, Riverside, CA 92521, USA b Department of Agricultural Biology, National Academy of Agricultural Science, RDA, Suwon 441-853, Republic of Korea article info Article history: Received 6 July 2010 Accepted 6 June 2011 Available online 12 June 2011 Keywords: Biological control Aonidiella aurantii Fecundity Longevity Endosymbiont abstract Wolbachia is an endosymbiotic bacterium that infects a large percentage of arthropods and can affect the fitness of its host. Here we verified for the first time that the biological control agent Aphytis melinus DeBach is infected with a Wolbachia that causes complete cytoplasmic incompatibility, and conducted an insectary and field survey to determine the infection frequency. A. melinus appears to suffer fitness costs associated with infection based on measurements of longevity and fecundity. We also quantified the Wolbachia titers of A. melinus reared at different temperatures and found that, although not com- pletely cured, increased temperature resulted in a significant reduction in the number of Wolbachia cop- ies found in an individual wasp. Implications of our results for biological control are discussed. Ó 2011 Elsevier Inc. All rights reserved. 1. Introduction Wolbachia is a gram-negative obligate intracellular bacterium that is estimated to infect from 16% up to 76% of arthropod species (Werren et al., 1995; Jeyaprakash and Hoy, 2000; Hilgenboecker et al., 2008) and is likely to be found in a large percentage of bio- logical control agents (Floate et al., 2006). It is a reproductive par- asite in the a subdivision of the proteobacteria that is vertically transmitted from mother to offspring, although horizontal trans- mission has been observed (Haine et al., 2005). Wolbachia can alter its host’s reproduction via cytoplasmic incompatibility (CI), parthe- nogenesis induction, feminization of genetic males, and male-kill- ing (Stouthamer et al., 1999; Hurst et al., 1999; Merçot and Poinsot, 2009). Because it can severely modify host reproduction and sex ratios, Wolbachia is of great interest to biological control practitioners. It has been proposed as an environmentally friendly method that might be used to manage pest species, transform disease vectors, and/or improve beneficial insects (Bourtzis, 2008). Although there are conflicting hypotheses on the effect that Wolbachia has on its host, with some stating that it is likely to impart a physiological cost in its host (Stouthamer et al., 1999) and others expecting a mutualistic relationship to evolve over time (Werren et al., 2008), evidence of how Wolbachia affects fitness has been incon- clusive ranging from harmful to neutral to beneficial. The most severe fitness cost attributed to Wolbachia was docu- mented by Min and Benzer (1997) using a virulent Wolbachia strain named popcorn, which drastically reduces adult lifespan in Drosophila melanogaster Meigen. The virulent strain has been hor- izontally transferred between species, it has been proposed as a potential means of reducing vector-borne disease transmission by driving desirable genes into populations (McGraw et al., 2001; Brownstein et al., 2003), and such a strategy was recently imple- mented via transinfection in the dengue fever mosquito, Aedes aegypti (L.) (Turley et al., 2009). Drosophila simulans Sturtevant males infected with Wolbachia experienced a significant decrease in sperm production and sperm competitiveness, even though sperm do not actually transmit the bacterium (Snook et al., 2000; de Crespigny and Wedell, 2006). The parasitoids Trichogramma deion Pinto and Oatman and Trichogramma pretiosum Riley suffered a decrease in fecundity (Stouthamer and Luck, 1993) and an in- crease in embryonic mortality (Tagami et al., 2001); Trichogramma kaykai Pinto and Stouthamer suffered a decreased competitive ability (Huigens et al., 2004), a lower net reproductive rate, and an improved intrinsic rate of natural increase (Miura and Tagami, 2004) when infected with Wolbachia. Conversely, there are examples of mutualistic relationships between Wolbachia and its host. In D. melanogaster, Wolbachia infection has been correlated with increased survival in the labora- tory for both unmated males and females (Fry and Rand, 2002). Alexandrov et al. (2007) found that by removing Wolbachia from female D. melanogaster using antibiotics, the lifespan and compet- itiveness of the cured (but genetically similar) females decreased. A control study showed that the observed effects were not the result 1049-9644/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.biocontrol.2011.06.006 ⇑ Corresponding author. Fax: +1 951 827 3086. E-mail address: joseph.morse@ucr.edu (J.G. Morse). Biological Control 58 (2011) 192–198 Contents lists available at ScienceDirect Biological Control journal homepage: www.elsevier.com/locate/ybcon