, Volume 138, Issue 3, pp 448–454 | Cite as

Forest edges and fire ants alter the seed shadow of an ant-dispersed plant

  • J. H. NessEmail author
Community Ecology


Exotic species invade fragmented, edge-rich habitats readily, yet the distinct impacts of habitat edges and invaders on native biota are rarely distinguished. Both appear detrimental to ant-dispersed plants such as bloodroot, Sanguinaria canadensis. Working in northeastern Georgia (USA), an area characterized by a rich ant-dispersed flora, fragmented forests, and invasions by the red imported fire ant, Solenopsis invicta , I monitored the interactions between ants and S. canadensis seeds in uninvaded forest interiors, uninvaded forest edges, invaded forest interiors, and invaded forest edges. I observed 95% of the seed dispersal events that occurred within the 60-min observation intervals. Seed collection rates were similar among all four (habitat × invasion) groups. The presence of invasive ants had a strong effect on seed dispersal distance: S. invicta collected most seeds in invaded sites, but was a poorer disperser than four of five native ant taxa. Habitat type (interior versus edge) had no effect on seed dispersal distance, but it had a strong effect on seed dispersal direction. Dispersal towards the edge was disproportionately rare in uninvaded forest edges, and ants in those habitats moved the average dispersed seed approximately 70 cm away from that edge. Dispersal direction was also skewed away from the edge in uninvaded forest interiors and invaded forest edges, albeit non-significantly. This biased dispersal may help explain the rarity of myrmecochorous plants in younger forests and edges, and their poor ability to disperse between fragments. This is the first demonstration that forest edges and S. invicta invasion influence seed dispersal destination and distance, respectively. These forces act independently.


Disturbance Fragmentation Invasive species Mutualism Myrmecochory 



The comments of J. Bronstein, N. Holland, L. Whitlow, C. Apse and I. Giladi improved the manuscript. I. Giladi, C. Christopher, G. Barrett, and C. Gibson assisted in site selection. Research was facilitated by access to the University of Georgia Natural History Museum, University of Arizona Arthropod Collection, Horseshoe Bend Experimental Station, Whitehall Experimental Forest, the State Botanical Gardens of Georgia, Memorial Park, and the Helfmeyer homestead, for which I am grateful. While writing this manuscript, I received financial support from the Center for Insect Science through the National Institute of Health’s training grant No. 1K12GM00708.


  1. Andersen AN (1988) Dispersal distance as a benefit of myrmecochory. Oecologia 75:507–511Google Scholar
  2. Beattie AJ, Culver DC (1981) The guild of myrmecochores in the herbaceous flora of West Virginia forest. Ecology 62:107–115Google Scholar
  3. Beattie AJ, Culver DC, Pudlo RJ (1979) Interactions between ants and the diaspores of some common flowering herbs in West Virginia. Castanea: 44:177–186Google Scholar
  4. Bond W, Slingsby P (1984) Collapse of an ant-plant mutualism: the Argentine ant (Iridomyrmex humilis) and myrmecochorous Proteaceae. Ecology 65:1031–1037Google Scholar
  5. Boyd RS (2001) Ecological benefits of myrmecochory for the endangered chaparral shrub Fremontodendron decumbens (Sterculiaceae). Am J Bot 88:234–241PubMedGoogle Scholar
  6. Brunet J, Von Oheimb G (1998) Migration of vascular plants to secondary woodlands in southern Sweden. J Ecol 86:429–438CrossRefGoogle Scholar
  7. Butz Huryn VM (1997) Ecological impacts of introduced honeybees. Q Rev Biol 72:275–297Google Scholar
  8. Carney SE, Byerley MB, Holway DA (2003) Invasive Argentine ants (Linepithema humile) do not replace native ants as seed dispersers of Dendromecon rigida (Papaveraceae) in California, USA. Oecologia 135:576–582Google Scholar
  9. Carvalho KS, Vasconcelos HL (1999) Forest fragmentation in central Amazonia and its effects on litter-dwelling ants. Biol Conserv 91:151–157CrossRefGoogle Scholar
  10. Christian CE (2001) Consequences of a biological invasion reveal the importance of mutualism for plant communities. Nature 413:635–639CrossRefPubMedGoogle Scholar
  11. Ehrlen J, Eriksson O ( 2000) Dispersal limitation and patch occupancy in forest herbs. Ecology 81:1667–1674Google Scholar
  12. Gaddy LL (1986) Twelve new ant-dispersed species from the southern Appalachians. Bull Torrey Bot Club 113:247–251Google Scholar
  13. Garrido JL, Rey PJ, Cerda X, Herrera CM (2002) Geographical variation in diaspore traits of an ant-dispersed plant (Heliothis foetidus): are ant community composition and diaspore traits correlated? J Ecol 90:446–455CrossRefGoogle Scholar
  14. Gibson W (1993) Selective advantages to hemi-parasitic annuals, genus Melampyrum, of a seed-dispersal mutualism involving ants. II. Seed-predator avoidance. Oikos 67:345–350Google Scholar
  15. Gorchov DL, Cornejo F, Ascorra C, Jaramillo M (1993) The role of seed dispersal in the natural regeneration of rain forest after strip-cutting in the Peruvian Amazon. Vegetatio 107/108:339–349Google Scholar
  16. Gotelli NJ, Arnett AE (2000) Biogeographic effects of red fire ant invasion. Ecol Lett 3:257–261CrossRefGoogle Scholar
  17. Harrison S, Bruna E (1999) Habitat fragmentation and large scale conservation: what do we know for sure? Ecography 22:225–232Google Scholar
  18. Heithaus ER (1981) Seed predation by rodents on three ant-dispersed plants. Ecology 62:136–145Google Scholar
  19. Hobbs RJ (2001) Synergisms among habitat fragmentation, livestock grazing, and biotic invasions in southwestern Australia. Conserv Biol 15:1522–28CrossRefGoogle Scholar
  20. Holway DA, Lach L, Suarez AV, Tsutsui ND, Case TJ (2002) The causes and consequences of ant invasions. Annu Rev Ecol Syst 33:181–233CrossRefGoogle Scholar
  21. Ingle NR (2003) Seed dispersal by wind, birds, and bats between Philippine montane rainforest and successional vegetation. Oecologia 134:251–261PubMedGoogle Scholar
  22. Jules ES (2000) Habitat fragmentation and demographic change for a common plant: Trillium in old-growth forest. Ecology 79:1645–1656Google Scholar
  23. Jules ES, Rathcke BJ (1999) Mechanisms of reduced Trillium recruitment along edges of old-growth forest fragments. Conserv Biol 13:784–793CrossRefGoogle Scholar
  24. Kaspari M (1996) Worker size and seed size selection by harvester ants in a Neotropical forest. Oecologia 105:397–404Google Scholar
  25. Kjellsson G (1991) Seed fate in an ant-dispersed sedge, Carex pilulifera L.: recruitment and seedling survival in tests of models for spatial dispersion. Oecologia 88:435–443Google Scholar
  26. Majer JD (1985) Recolonization by ants of rehabilitated mineral sand mines on North Stradbroke Island, Queensland, with particular reference to seed removal. Aust J Ecol 10:31–48Google Scholar
  27. Majer JD (1994) Spread of Argentine ants (Linepithema humile), with special reference to western Australia. In: Williams DF (ed) Exotic ants: biology, impact and control of introduced species. Westview, Boulder, Colorado, USA, pp 163–173Google Scholar
  28. Majer JD, Delabie JHC, McKenzie NL (1997) Ant litter fauna of forest, forest edges, and adjacent grasslands in the Atlantic rain forest region of Bahia, Brazil. Insect Soc 44:255–266CrossRefGoogle Scholar
  29. Marino PC, Eisenberg RM, Cornell HV (1997) Influence of sunlight and soil nutrients on clonal growth and sexual reproduction of the understory herb Sanguinaria canadensis L. J Torrey Bot Club 124:219–227Google Scholar
  30. Matlack GR (1993) Microenvironment variation within and among forest edge sites in the eastern United States. Biol Conserv 66:185–194CrossRefGoogle Scholar
  31. Matlack GR (1994a) Vegetation dynamics of the forest edge—trends in space and successional time. J Ecol 82:113–123Google Scholar
  32. Matlack GR (1994b) Plant species migration in a mixed-history forest landscape in eastern North America. Ecology 75:1491–1502Google Scholar
  33. McLachlan SM, Bazely DR (2001) Recovery patterns of understory herbs and their use as indicators of deciduous forest regeneration. Conserv Biol 15:98–110CrossRefGoogle Scholar
  34. Murcia C (1995) Edge effects in fragmented forests: implications for conservation. Trends Ecol Evol 10:58–62Google Scholar
  35. Pearson SM, Smith AB, Turner MG (1998) Forest patch size, land use, and mesic forest herbs in the French Broad River Basin, North Carolina. Castanea 63:382–395Google Scholar
  36. Porter SD, Savignano DA (1990) Invasion by polygyne fire ants decimates native ants and disrupts arthropod community. Ecology 71:2095–2106Google Scholar
  37. Pudlo RJ, Beattie AJ, Culver DC (1980) Population consequences of changes in an ant-seed mutualism in Sanguinaria canadensis. Oecologia 146:32–37Google Scholar
  38. Quilichini A, Debussche M (2000) Seed dispersal and germination patterns in a rare Mediterranean island endemic (Anchusa crispa Viv, Boraginaceae). Acta Oecol 21:303–313CrossRefGoogle Scholar
  39. Schemske DW (1978) Sexual reproduction in an Illinois population of Sanguinaria canadensis (L). Am Midl Nat 100:261–268Google Scholar
  40. Smith BH, DeRivera CE, Bridgman CL, Woida JJ (1989) Frequency-dependent seed dispersal by ants of two deciduous forest herbs. Ecology 70:1645–1648Google Scholar
  41. Suarez AV, Bolger DT, Case TJ (1998) Effects of fragmentation and invasion on native ant communities in coastal southern California. Ecology 79:2041–2056Google Scholar
  42. Thomas DW, Cloutier D, Provencher M, Houle C (1988) The shape of bird- and bat-generated seed shadows around a tropical fruiting tree. Biotropica 20:347–348Google Scholar
  43. Zettler JA, Spira TP, Allen CR (2001) Ant seed mutualisms: can red imported fire ants sour the relationship? Biol Conserv 101:249–253CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  1. 1.Institute of EcologyUniversity of GeorgiaAthensUSA
  2. 2.Dept. of Ecology and Evolutionary BiologyUniversity of ArizonaTucsonUSA

Personalised recommendations