University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln U.S. Department of Agriculture: Agricultural Publications from USDA-ARS / UNL Faculty Research Service, Lincoln, Nebraska 2012 The relationship between variable host grouping and functional responses among parasitoids of Antispila nysaefoliella (Lepidoptera: Heliozelidae) Candace Low Cornell University, [email protected] Sonja J. Scheffer USDA-ARS, [email protected] Matthew L. Lewis USDA-ARS, [email protected] Michael W. Gates USDA-ARS, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/usdaarsfacpub Low, Candace; Scheffer, Sonja J.; Lewis, Matthew L.; and Gates, Michael W., "The relationship between variable host grouping and functional responses among parasitoids of Antispila nysaefoliella (Lepidoptera: Heliozelidae)" (2012). Publications from USDA-ARS / UNL Faculty. 1111. https://digitalcommons.unl.edu/usdaarsfacpub/1111 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Publications from USDA-ARS / UNL Faculty by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Molecular Ecology (2012) 21, 5892–5904 doi: 10.1111/mec.12061 The relationship between variable host grouping and functional responses among parasitoids of Antispila nysaefoliella (Lepidoptera: Heliozelidae) CANDACE LOW,* SONJA J. SCHEFFER,† MATTHEW L. LEWIS† and MICHAEL W. GATES†‡ *Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA, †Systematic Entomology Laboratory, USDA-ARS, Beltsville, MD 20705, USA, ‡Systematic Entomology Laboratory, USDA-ARS, National Museum of Natural History, Smithsonian Institution, Washington, DC 20013-7012, USA Abstract Our study investigated the importance of variability in the parasitoid community as a source of selection on host group size using a field population of the tupelo leafminer, Antispila nysaefoliella Clemens, which specializes on tupelo, Nyssa sylvatica Marsh. Larvae were collected from leaves with variable numbers of larvae and screened for parasitism using polymerase chain reaction of mitochondrial cytochrome oxidase I using markers designed specifically for amplifying parasitoid DNA while excluding host DNA. This method of selective PCR was effective for detecting the presence and identifying species of immature stages of three hymenopteran superfamilies: Chalci- doidea, Ichneumonoidea and Platygastroidea, which represented 83.4%, 16.0% and 0.6% of the total detectable parasitism, respectively. Our resulting sequences were then calibrated with sequences from identified adult parasitoids that had been either reared or field-captured. A cluster analysis revealed 10 distinct clades that showed differences in attack patterns with respect to host traits and season. Total parasitism followed an inverse density-dependent or density-independent pattern with respect to host density (number per leaf). However, when parasitoid taxa were considered separately, one clade, which could be a cryptic species of Pnigalio maculipes Crawford (Chalcidoidea: Eulophidae), was found to increase its per leaf attack rate with host density. Our results suggest that parasitoid community composition and differences among species in their attack strategies can play a large role in determining the adaptive advantage of host grouping. Keywords: community ecology, dilution effect, DNA barcoding, field survey, functional response, life history strategy, mtDNA COI Received 27 December 2011; revision received 20 August 2012; accepted 23 August 2012 et al. 2005; Tosh et al. 2006; Low 2008a; Ioannou et al. Introduction 2009; Morrell et al. 2011). One well-documented benefit For many decades, empirical and theoretical studies of grouping is safety from predation or natural enemy have investigated the cost–benefit continuum of group- attack (Clark & Mangel 1986; Coster-Longman et al. ing with an effort to understand the selective pressures 2002; Krause & Ruxton 2002). However, being part of a that shape grouping behaviour, group size or clutch larger group can also increase the risk of detection by size (Hamilton 1963, 1971; Clark & Mangel 1986; Cos- predators, intensify resource competition, make parental ter-Longman et al. 2002; Krause & Ruxton 2002; Jackson care more costly and reduce resource quality through synergistic effects (Caraco & Wolf 1975; Clark & Mangel Correspondence: Candace Low, Fax: + 607-255-8088; 1986; Turner & Pitcher 1986; Hughes et al. 2002; Low E-mail: [email protected] 2008a). The evolution of grouping and its impacts on © 2012 Blackwell Publishing Ltd HOST GROUPING AND PARASITOID RESPONSES 5893 ecological and social interactions continues to be parasitoid) and extreme variation of host traits, a novel actively researched because of its key role in the organi- approach was necessary to accurately assess a large zation of biological systems and its nonlinear dynamical sample of hosts gathered from the field. Compared with effects (Buss 1981; Ives 1989; Avile´s 1999; Krause & traditional methods used to detect and identify parasi- Ruxton 2002; Fordyce & Shapiro 2003; Lett et al. 2004; toids within hosts, such as dissection and rearing, Solomon & Crist 2008). respectively, our study applied selective amplification Every organism exists either singly or with others, of parasitoid DNA to quantify the timing, presence and and each numerical context is associated with social species of parasitoids from within a background of host and ecological conditions that carry potential fitness DNA (Greenstone 2006; Gariepy et al. 2007, 2008; Kaar- consequences for the individual. Therefore, achieving tinen et al. 2010; Santos et al. 2011; Smith et al. 2011; the optimal size of an egg clutch, flock or herd, for Gariepy & Messing 2012). By using taxon-specific prim- example, is a basic but dynamic ecological and evolu- ers, we were able to assign parasitism (confirm presence tionary problem that all organisms must solve (Charnov and identify species) and minimize sources of error that 1976; Hassell & May 1986; Charnov & Skinner 1988; are typical of traditional methods due to: the difficulties Kagata & Ohgushi 2004). However, selection gradients of seeing and finding minute eggs, larvae, or pupae can be highly variable across time, space and with within a host, and rearing immature stages to adults respect to the life history stage of the study organism, that would then have to be identified using morpholog- and optima are not likely to be static. Therefore, to fully ical keys or DNA sequencing (Hebert et al. 2003). Our understand the significance of adaptive grouping as a approach simplified the data gathering process, and defence strategy, the functional response of the selective increased both accuracy and throughput. agent(s) to prey (or host) group size and its variability across time and prey (or host) ontogeny must be con- Materials and methods sidered explicitly. Specifically, knowledge of the func- tional form by which natural enemies respond to prey Natural history traits, in general, is essential for making accurate pre- dictions of ecological and evolutionary dynamics The study site is located within a privately owned (Abrams 1982; Abrams & Matsuda 1997; Benrey & Den- mixed deciduous forest in Clarke County, Virginia (39° no 1997; Schmitz et al. 1997; Schreiber et al. 2000; Reader 00.85′N, 78°03.88′W). In the spring, soon after the leaves & Hochuli 2003; Krivan & Eisner 2006; Abrams et al. of Nyssa sylvatica have flushed, adults emerge and per- 2007). sist in high abundance for ~4 weeks. Mating occurs In this study, we conducted an ecological survey near dusk and oviposition occurs throughout the day. using molecular genetics to determine the patterns of Adults can be found easily by sight on the undersides parasitism associated with host group size in a natural of leaves or moving between leaves and branches. Mul- population of the tupelo leafminer, Antispila nysaefoliella tiple females have been observed to search and oviposit Clemens (Lepidoptera: Heliozelidae), which is a special- on the same leaves, either in succession or simulta- ist of tupelo, Nyssa sylvatica Marsh (Cornales: Nyssa- neously. Therefore, larvae that occur on the same leaves ceae). We tested the prediction that if group size is a are not necessarily all from the same female. Observa- response to parasitism, then variation in group size tional and unpublished experimental data indicate that should correspond to the attack preferences and behav- eggs deposited in the spring lay dormant on leaves for iours of the parasitoid community collectively. How- several months before hatching into larvae. This sug- ever, if there is high variability in the assemblage of gests that timing of egg hatch can determine the real- parasitoid species, then would host grouping patterns ized larval group size, which may be under selection by correspond to the attack behaviours of the parasitoid forces that occur after the adult female is long gone. community at large or to particular species of parasi- The current study provides the first empirical evidence toids? We expected that host group size would be opti- on the potential importance of the interaction between mized either for the average attack behaviour of all larval group size and emergence timing on survival parasitoid species or only for the most frequent parasit-