Invasive ants disperse seeds farther than native ants, affecting the spatial pattern of seedling recruitment and survival
Mutualists can vary in the quantity and quality of service which they provide to their partners. Variation in seed disperser quality depends on seed-processing traits, dispersal distance, and deposition location, all of which ultimately affect plant fitness. Here, we compared these aspects of seed dispersal quality between a native and an invasive ant species, and examined how they affect competition and plant performance. Using experimental mesocosm communities, we examined how these two ant species affect the spatial pattern of recruitment and establishment for four myrmecochorous plant species, including one invasive species. We measured the locations of dispersed seedlings relative to ant nests, adult plants, and other dispersed seedlings, as well as measured the effects of location on plant performance. The invasive ant, Myrmica rubra, secondarily dispersed seeds farther from its nests, creating a less clumped pattern of seedling recruitment compared to the native ant, Aphaenogaster rudis. Plant species responded differently to dispersal. Invasive seedlings recruited farther from adult plants than native seedlings, and had higher survival the farther they were from conspecifics. In contrast, native plants had higher survival and grew taller when dispersed farther from invasive plants. We show that seed-dispersing ant partners differ in mutualist quality creating differences in dispersal distance and deposition location that affects a plant’s competitive environment. Our results reveal the potential for long-term consequences on plant community structure with changing ant partner identity. We emphasize the need to examine dispersal quality in addition to quantity to uncover the importance of partner identity in structuring communities.
KeywordsAphaenogaster rudis Biological invasions Myrmecochory Myrmica rubra Seed dispersal Spatial patterns
We are grateful to G. Cho, L. Moretto, J. Robinson, M. Thompson, and T. Powell for their help in the field; and to S. Senthivasen, who assisted with the image analysis. We thank A. Weis, J. Stinchcombe, and S. Schneider for providing support at the Koffler Scientific Reserve at Joker’s Hill. We would also like to thank M. J. Fortin for statistical advice and guidance. Funding was provided by an NSERC Undergraduate Student Research Award (SAMD), an NSERC Canada Graduate Scholarship (SAMD), an EEB Postdoctoral Fellowship from the University of Toronto (KMP), the Ontario Ministry of Economic Development and Innovation (KMP and MEF), and an NSERC Discovery Grant (MEF).
Author contribution statement
SAMD, KMP, and MEF designed the research; SAMD and KMP carried out the fieldwork; SAMD analyzed the data with significant input from KMP and MEF; SAMD wrote the paper with help from KMP and MEF.
- Baker HG (1965) Characteristics and modes of origin of weeds. In: Baker HG, Stebbins GL (eds) The genetics of colonizing species. Academic Press, New York, pp 147–172Google Scholar
- Holway DA, Lach L, Suarez AV et al (2002) The causes and consequences of ant invasions. Annu Rev Ecol Syst 33:181–233. https://doi.org/10.1146/annurev.ecolsys.33.010802.150444 CrossRefGoogle Scholar
- Leal LC, Neto MCL, de Oliveira AFM et al (2014b) Myrmecochores can target high-quality disperser ants: variation in elaiosome traits and ant preferences for myrmecochorous Euphorbiaceae in Brazilian Caatinga. Oecologia 174:493–500. https://doi.org/10.1007/s00442-013-2789-2 CrossRefPubMedGoogle Scholar
- Lobstein MB, Rockwood LL (1993) Influence of elaiosome removal on germination in five ant-dispersed plant species. Va J Sci 44:59–72Google Scholar
- Ness JH, Bronstein JL (2004) The effects of invasive ants on prospective ant mutualists. Biol Invasions 6:445–461. https://doi.org/10.1023/B:BINV.0000041556.88920.dd CrossRefGoogle Scholar
- Suarez AV, McGlynn TP, Tsutsui ND (2010) Biogeographic and taxonomic patterns of introduced ants. In: Lach L, Parr CL, Abbott KL (eds) Ant ecology. Oxford University Press, New York, pp 233–244Google Scholar
- Wetterer JK, Radchenko AG (2011) Worldwide spread of the ruby ant, Myrmica rubra (Hymenoptera: Formicidae). Myrmecol News 14:87–96Google Scholar