Ant Species Identity has a Greater Effect than Fire on the Outcome of an Ant Protection System in Brazilian Cerrado Kleber Del-Claro 1,3 and Robert J. Marquis 2 1 Instituto de Biologia, Universidade Federal de Uberl^ andia (UFU), CP 593, Uberl^ andia, MG, CEP 38400-902, Brazil 2 Department of Biology and Whitney R. Harris World Ecology Center, University of Missouri-St. Louis, One University Boulevard, St. Louis, MO, 63121, U.S.A. ABSTRACT Although fire- and ant–plant interactions influence the community structure and dynamics of Neotropical savannas, no previous studies have considered their simultaneous effects on target host plants. We monitored the effect of ant exclusion for 3 years on leaf area loss to leaf chewing insects, thrips abundance, and reproductive output of the extrafloral nectary-bearing shrub, Peixotoa tomentosa (Malpighia- ceae). We predicted that the impact of ants on herbivores and plants would depend on the ant species, and that fire would reduce the effect of ants. We deliberately chose control plants that differed in their occupant ant species. Fire occurred in the second year of the study, allowing us to determine its effect on the benefit afforded by ants. Ants reduced leaf area loss and thrips abundance, and increased fruit and seed production in all 3 years. Some ant species were more effective than others, while plants with multiple ant spe- cies suffered higher leaf area loss than plants with a single ant species. In the year following the fire, leaf damage was greater than in the other years, regardless of the ant species, and the proportional effect of ants in reducing damage was less. Interactions affecting thrips abundance did not change following fire, nor was the benefit to the plant proportionally reduced. Overall, the identity of the ant species had a greater effect than did the occurrence of fire on the ant–herbivore–plant interaction: the identity of the ant species influ- enced leaf area loss, thrips numbers, and bud and seed production, while fire only modified the impact of ants on the amount of leaf area consumed by insect herbivores. Key words : abiotic factors; ant–plant interactions; Brazil; Cerrado; extrafloral nectaries; fire; thrips. EXTRAFLORAL NECTARIES (EFNS), WHICH ATTRACT ANTS AND OTHER INVERTEBRATES THAT FEED ON THEIR SECRETIONS (Byk & Del-Claro 2011), have been present in Angiosperms since the Oligocene (Pemberton 1992). Ants visiting EFN-containing plants often protect those plants by eating, hindering, or driving away herbi- vores (Bentley 1977, Horvitz & Schemske 1984, Koptur 1984, Vilela et al. 2014). In turn, plant growth and seed production are often higher (Del-Claro et al. 1996, Oliveira 1997, De la Fuente & Marquis 1999, Nascimento & Del-Claro 2010). Not all studies, however, suggest that EFNs are beneficial for plants (O’Dowd & Catchpole 1983, Rashbrook et al. 1992, Bronstein 1998, Mody & Linsenmair 2004, Chamberlin and Hol- land 2009). Differences in behavior among the ant species attracted to plants containing EFNs influence the effect of the EFNs (Del-Claro & Oliveira 2000, Mody & Linsenmair 2004, Palmer et al. 2008, Nahas et al. 2012, Del-Claro et al. 2013). The abiotic environment may also contribute, although this is much less studied (Bronstein 1998, Vilela et al. 2014, Yamawo et al. 2014). Clarifying which factors influence the effect of EFNs is an important starting point for understanding how these ant–herbi- vore–plant interactions evolved and were maintained, and for identifying their contribution to the structure and functioning of food webs. This is particularly true for tropical systems where plant species with EFNs are most abundant (Rico-Gray & Olive- ira 2007, Bronstein 2009, D attilo et al. 2014). Plants with EFNs are common in the savannas of South America, Africa, and Asia (Rico-Gray & Oliveira 2007). Because fire is such an important environmental factor in savanna vege- tation (Alves-Silva & Del-Claro 2014), it is likely that fire, in addition to ant species identity, influences the nature of interac- tions between ants, herbivores, and plants with EFNs. In Brazil- ian savanna (the Cerrado), EFNs occur on more than 25 percent of the tree species and up to 30 percent of individual trees (Rico-Gray & Oliveira 2007). Fire is considered to be a principal determinant of Cerrado vegetation structure and plant diversity (Miranda et al. 2002). One obvious mechanism by which fire might influence the interactions between plants and ants visiting EFNs is through its impact on insect herbivores and ants. Cerrado arthropod density and ant species richness are known to decline in fire-disturbed areas as a result of direct mortality, diminished resources, and less favorable microclimates (Vasconcelos et al. 2009). Although both ant–plant interactions (Del-Claro & Torezan-Silingardi 2009) and fire (Vasconcelos et al. 2009) play an important role in the community structure and dynamics of Cerrado (Alves-Silva & Del-Claro 2014), their simultaneous effects on plants in any tropical savanna system are unknown. Received 9 June 2014; revision accepted 26 February 2015. 3 Corresponding author; e-mail: delclaro@ufu.br ª 2015 The Association for Tropical Biology and Conservation 459 BIOTROPICA 47(4): 459–467 2015 10.1111/btp.12227