Ant Tending of Miami Blue Butterfly Larvae (Lepidoptera: Lycaenidae): Partner Diversity and Effects on Larval Performance (Report‪)‬

The larvae of many lycaenid butterflies (Lepidoptera: Lycaenidae) interact with ants in relationships ranging from brood parasitism in ant colonies to mutualism in which both species benefit. Approximately 60% of the ant-associated lycaenid species are facultative myrmecophiles that are tended by several different ant species, usually on the larval host plant (Pierce et al. 2002). Lycaenid larvae in such relationships generally emit semiochemicals from a pair of tentacular organs and secrete a sugar-rich solution from a dorsal nectary organ to attract and retain their ant guards (Axen et al. 1996; Axen 2000; Daniels et al. 2005), which then protect the larvae from predators and parasitoids (Pierce & Mead 1981; Fiedler et al. 1996). Additionally, larvae of some lycaenid species pupate inside ant nests, where the ants presumably protect them until adult eclosion (Wagner 1995; Dejean & Beugnon 1996). Thus, these associations entail an exchange of goods and services that usually results in net benefits for both partners (Pierce et al. 1987; Cushman et al. 1994). However, there is often substantial variation in quality among potential partners in facultative, diffuse mutualistic systems that may result in negative or neutral consequences for the survival and performance of the interacting species (Bronstein 2001; Miller 2007). Evaluating partner quality in purportedly mutualistic relationships is necessary to understand the ecological conditions and evolutionary processes that influence the outcome of the relationship (Bshary & Grutter 2002; Ness et al. 2006). A central question in research on lycaenid-ant mutualisms is how interactions with different ant species affect larval performance (Axen 2000; Fraser et al. 2001; Weeks 2003). The physiological cost of provisioning ants with a sugar-rich exocrine secretion leads to reduced growth of ant-tended larvae in some systems (Pierce et al. 1987; Baylis & Pierce 1992), but growth of ant-tended larvae in other systems is similar to or greater than that of untended larvae (Fiedler & Holldobler 1992; Cushman et al. 1994; Wagner & Del Rio 1997; Fraser et al. 2001). Because pupal mass is often correlated with adult reproductive output in Lepidoptera (Gotthard 2008), the growth consequences for larvae of ant tending could have subsequent effects on individual fitness (Elgar & Pierce 1988). Furthermore, because the relative importance of adult size and timing of adult emergence may differ between conspecific males and females (Fagerstrom & Wiklund 1982; Gotthard et al. 2000), in some lycaenid species there are sex differences in the effects of ant tending (Fiedler & Holldobler 1992). Assessing the effects of ant tending on lycaenid larvae and identifying the factors that explain variation in the interaction among and within species are central issues for furthering our understanding of these complex relationships.