title: Floral visitation by the Argentine ant reduces pollinator visitation and seed set in the coast barrel cactus, Ferocactus viridescens.
abstract: Mounting evidence indicates that trade-offs between plant defense and reproduction arise not only from resource allocation but also from interactions among mutualists. Indirect costs of plant defense by ants, for example, can outweigh benefits if ants deter pollinators. Plants can dissuade ants from occupying flowers, but such arrangements may break down when novel ant partners infiltrate mutualisms. Here, we examine how floral visitation by ants affects pollination services when the invasive Argentine ant (Linepithema humile) replaces a native ant species in a food-for-protection mutualism with the coast barrel cactus (Ferocactus viridescens), which, like certain other barrel cacti, produces extrafloral nectar. We compared the effects of floral visitation by the Argentine ant with those of the most prevalent native ant species (Crematogaster californica). Compared to C. californica, the Argentine ant was present in higher numbers in flowers. Cactus bees (Diadasia spp.), the key pollinators in this system, spent less time in flowers when cacti were occupied by the Argentine ant compared to when cacti were occupied by C. californica. Presumably as a consequence of decreased duration of floral visits by Diadasia, cacti occupied by L. humile set fewer seeds per fruit and produced fewer seeds overall compared to cacti occupied by C. californica. These data illustrate the importance of mutualist identity in cases where plants balance multiple mutualisms. Moreover, as habitats become increasingly infiltrated by introduced species, the loss of native mutualists and their replacement by non-native species may alter the shape of trade-offs between plant defense and reproduction.
authors.affiliation: Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, University of California, San Diego, Mail Code 0116, 9500 Gilman Drive, La Jolla, CA, 92093, USA, kelevan@ucsd.edu.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: LeVan
authors.forename: Keng-Lou James
authors.initials: KL
authors.lastname: Hung
authors.forename: Kyle R
authors.initials: KR
authors.lastname: McCann
authors.forename: John T
authors.initials: JT
authors.lastname: Ludka
authors.forename: David A
authors.initials: DA
authors.lastname: Holway
mesh_terms: D000818:Animals; D001000:Ants / Q000145:classification; D001516:Bees; D029421:Cactaceae / Q000502:physiology*; D002140:California; D017753:Ecosystem; D035264:Flowers; D058865:Introduced Species; D057048:Plant Nectar; D054817:Pollination; D012639:Seeds / Q000502:physiology*; D013559:Symbiosis
chemical_list: D057048:Plant Nectar
references.citation: Proc Biol Sci. 2007 Dec 7;274(1628):2951-7
references.pmid: 17878138
references.citation: PLoS One. 2012;7(8):e43869
references.pmid: 22952793
references.citation: Trends Ecol Evol. 2006 Apr;21(4):208-16
references.pmid: 16701087
references.citation: Ecology. 2008 May;89(5):1364-74
references.pmid: 18543629
references.citation: Proc Natl Acad Sci U S A. 2010 Oct 5;107(40):17234-9
references.pmid: 20855614
references.citation: Ecol Lett. 2010 Dec;13(12):1459-74
references.pmid: 20955506
references.citation: Ecology. 2007 Aug;88(8):1994-2004
references.pmid: 17824431
references.citation: Oecologia. 1998 Jun;115(1-2):206-212
references.pmid: 28308454
references.citation: PLoS One. 2011;6(6):e20689
references.pmid: 21695187
references.citation: Am Nat. 2003 Aug;162(2):242-56
references.pmid: 12858267
references.citation: Oecologia. 1980 Jul;46(1):68-74
references.pmid: 28310628
references.citation: Ecology. 2010 Jan;91(1):57-64
references.pmid: 20380196
references.citation: Ecology. 2009 Sep;90(9):2384-92
references.pmid: 19769117
references.citation: Ecology. 2006 Apr;87(4):912-21
references.pmid: 16676535