Playing the system: The impacts of invasive ants and plants on facultative ant-plant interactions
Book Chapter
Koptur, S, Jones, IM, Liu, H. (2017). Playing the system: The impacts of invasive ants and plants on facultative ant-plant interactions
. 249-266. 10.1017/9781316671825.013
Koptur, S, Jones, IM, Liu, H. (2017). Playing the system: The impacts of invasive ants and plants on facultative ant-plant interactions
. 249-266. 10.1017/9781316671825.013
Introduction Extrafloral nectaries (EFNs) are sugar-secreting glands located outside of flowers; they are structurally diverse, and may be found on almost any vegetative or reproductive plant structure (Bentley, 1977a; Koptur, 1992). Although a wide range of ecological functions have been suggested for EFNs (Baker et al., 1978; Becerra & Venable, 1989; Wagner & Kay, 2002; Gonzalez-Teuber & Heil, 2009; Heil, 2011), they are most noted for providing indirect defense against herbivory by attracting natural enemies (Janzen, 1966; Inouye & Taylor, 1979; Koptur 1984; Heil et al., 2001; Heil, 2015). Ants represent the most common visitors to EFNs, and have regularly been observed to benefit host plant fitness (Bentley, 1977b; Koptur, 1992; Rosumek et al., 2009; Heil, 2015). Myrmecophytes are plants that provide domatia, and food bodies and/or EFN, and engage in obligate interactions with ants (Chapters 10 and 11). A far greater number of plants, however, known as myrmecophiles, provide only EFN and engage in facultative interactions with ants. Because of the non-specialized nature of their interactions, the EFN that these plants provide is open to exploitation by any number of ant species, some of which may provide no benefits, or even negatively affect plant fitness (Koptur & Lawton, 1988; Torres-Hernandez et al., 2000; Ness et al., 2006). This variation in partner quality represents an important ecological cost of EFN production for plants. In this chapter, however, we focus not on the costs for individual plants, but on the costs for native species and ecosystems. We address the question: Does EFN in disturbed environments support and facilitate species invasions? The Role of Plant-Based Resources in Supporting Invasive Ants In the southern United States, no invasive ant species is more ubiquitous than the red imported fire ant, Solenopsis invicta. The uncontrolled spread of this highly invasive species is, in part, a result of its ability to infiltrate mutualistic networks. Wilder et al. (2011) showed that a lack of interspecific competition in its invasive range has allowed S. invicta to dominate plant-based carbohydrate resources, both EFN and hemipteran honeydew. Indeed, stable isotope analyses have shown that S. invicta occupies a lower trophic position in the United States than in its native Argentina, where other arboreal foraging ants can exclude it from mutualist-derived resources (ibid.).
