, Volume 45, Issue 7, pp 661–673 | Cite as

Population biology of figs: Applications for conservation

  • D. McKey


The flowering phenology typical of at least monoecious figs-intra-tree synchrony and inter-tree asynchrony-poses problems for persistence of the pollinator population, and hence of the fig population itself, when fig population size is small. Establishment and maintenance of a population of the short-lived, species-specific wasp pollinator require that the fig population include a critical minimum number of trees (critical population size: CPS). Below CPS, temporal gaps between flowering trees occur that are unbridgeable by the pollinator, leading to its local extinction. This has implications for conservation in two contexts: human-aided invasions of introduced fig/wasp pairs, in which initial populations of figs and/or wasps may be small, and the persistence of figs and wasps in fragmented forest, in which initially large populations may be drastically reduced. Long-distance range extension by fig/wasp pairs is problematical for two reasons: 1) the fig species must first attain CPS, most likely through repeated seed dispersal events, before the wasp can establish; and 2) long-distance transit should be difficult for the tiny, short-lived wasp pollinators. I review the biology of natural and human-aided range extension by figs and fig wasps, and show that in human-aided range extensions these two difficult steps are circumvented. Once introduced into an area where hosts are abundant, fig wasps should readily establish from a small number of initial colonists, since they mate before dispersal and are highly tolerant of inbreeding. They are thus less subject than many insects to the genetic and demographic hazards of small population size. Of 5–6 fig/wasp pairs that have performed human-aided long-distance range extensions, one Asian pair,Ficus microcarpa and its pollinatorParapristina verticillata, is established in numerous areas in the northern neotropics, and the plant may become a serious weed. In tropical forests, figs may provide keystone resources for frugivores, providing fruit during seasons when other resources are scarce. Figs pose difficult problems for conservation biology, since minimum viable populations appear to be large, and since many species of tropical rainforests occur at low densities. This means that minimum areas required for persistence of a fig population- and for those of other species that would be affected were figs to be removed from the system-may often be large.

Key words

Ficus fig biological invasion phenology minimum viable population conservation biology keystone resource 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Anonymous,Pleistodontes imperialis. Proc. Haw. ent. Soc.5 (1923) 200.Google Scholar
  2. 2.
    Anonymous,Pleistodontes imperialis Saund. Proc. Haw. ent. Soc.5 (1924) 343.Google Scholar
  3. 3.
    Anonymous,Pleistodontes froggatti Mayr;Pleistodontes imperialis Saund. Proc. Haw. ent. Soc.5 (1924) 348.Google Scholar
  4. 4.
    Anonymous,Pleistodontes imperialis Saund. Proc. Haw. ent. Soc.7 (1929) 218.Google Scholar
  5. 5.
    Anonymous, Fig-wasps established on Kauai. Proc. Haw. ent. Soc.8 (1934) 379.Google Scholar
  6. 6.
    Anonymous,Eupristina verticillata Waterst. Proc. Haw. ent. Soc.10 (1939) 182.Google Scholar
  7. 7.
    Anonymous,Eupristina verticillata Waterst. Proc. Haw. ent. Soc.10 (1939) 194.Google Scholar
  8. 8.
    Anonymous,Eupristina verticillata Waterst. Proc. Haw. ent. Soc.10 (1939) 195.Google Scholar
  9. 9.
    Anonymous, Recent records of the introduction of beneficial insects into the Hawaiian Islands. Proc. Haw. ent. Soc.10 (1939) 349–352.Google Scholar
  10. 10.
    Anonymous,Eupristina verticillata Waterst. Proc. Haw. ent. Soc.10 (1940) 361.Google Scholar
  11. 11.
    Anonymous,Eupristina verticillata Waterston. Proc. Haw. ent. Soc.10 (1940) 362.Google Scholar
  12. 12.
    Anonymous,Pleistodontes imperialis Saunders. Proc. Haw. ent. Soc.12 (1944) 17.Google Scholar
  13. 13.
    Backer, C. A., The problem of Krakatao as seen by a botanis. Visser & Co., Weltevreden, Java, and Martinus Nijhoff, The Hague 1929.Google Scholar
  14. 14.
    Baker, H. G., and Cox, P. A., Further thoughts on dioecism and islands. Ann. Missouri bot. Gard.71 (1984) 244–253.Google Scholar
  15. 15.
    Bazzaz, F. A., Life history of colonizing plants: some demographic, genetic, and physiological features, in: Ecology of Biological Invasions of North America and Hawaii, pp. 96–110. Eds H. A. Mooney and J. A. Drake. Springer-Verlag, New York 1986.Google Scholar
  16. 16.
    Beehler, B., Frugivory and polygamy in birds of paradise. Auk100 (1983) 1–12.Google Scholar
  17. 17.
    Berg, C. C., TheFicus species (Moraceae) of Madagascar and the Comoro Islands. Adansonia, 4e ser.,8 (1986) 17–55.Google Scholar
  18. 18.
    Berg, C. C., Hijman, M. E. E., and Weerdenburg, J. C. A., Flore du Cameroun 28. Moracées (incl. Cecropiacées). Ministère de l'Enseignement Superieur et de la Recherche Scientifique (MESRES), Yaoundé, Cameroun 1985.Google Scholar
  19. 19.
    Borgia, G., Evolution of haplodiploidy: models for inbred and outbred systems. Theoret. Pop. Biol.17 (1980) 103–128.Google Scholar
  20. 20.
    Bronstein, J. L., A mutualism at the edge of its range Experientia45 (1989) 622–637.Google Scholar
  21. 21.
    Bronstein, J. L., Gouyon, P.-H. Gliddon, C., Kjellberg, F., and Michaloud, G., The consequences of flowering asynchrony in monoecious figs: A simulation study. Ecology, submitted.Google Scholar
  22. 22.
    Condit, I. J.,Ficus: the exotic species. University of California Division of Agricultural Sciences, Berkeley 1969.Google Scholar
  23. 23.
    Corner, E. J. H., An introduction to the distribution ofFicus. Reinwardtia4 (1958) 325–355.Google Scholar
  24. 24.
    Corner, E. J. H.,Ficus in the Pacific region, in: Pacific Basin Biogeography; a Symposium, pp. 233–253. Ed. J. L. Gressitt. Bishop Museum Press, Honolulu 1963.Google Scholar
  25. 25.
    Corner, E. J. H.,Ficus (Moraceae) and Hymenoptera (Chalcidoidea): figs and their pollinators. Biol J. Linn. Soc.25 (1985) 187–195.Google Scholar
  26. 26.
    Dow, R. L., and Terceira, C., Indian laurel survey. Dept. Agr. Fisheries, Bermuda, Monthly Bull.56 7 (1985) 53.Google Scholar
  27. 27.
    Ehrlich, P. R., Which animal will invade?, in: Ecology of Biological Invasions of North America and Hawaii, pp. 79–95. Eds H. A. Mooney and J. A. Drake Springer-Verlag, New York 1986.Google Scholar
  28. 28.
    Florence, J., and Hladik, A., Catalogue des phanérogames et des ptéridophytes du nord-est du Gabon (sixième liste). Adansonia, sér. 2,20 (1980) 235–253.Google Scholar
  29. 29.
    Foster, R. B., Famine on Barro Colorado Island, in: The Ecology of a Tropical Forest, pp. 201–212. Eds E. G. Leigh, A. S. Rand and D. M. Windsor. Smithsonian Institution Press. Washington, D. C. 1982.Google Scholar
  30. 30.
    Galil, J.,Ficus religiosa L.-the tree-splitter. Bot. J. Linn. Soc.88 (1984) 185–203.Google Scholar
  31. 31.
    Galil, J., and Copland, J. W.,Odontofroggatia galili Wiebes in Israel, a primary fig wasp ofFicus microcarpa L. with a unique ovipositor mechanism (Epichrysomallinae, Chalcidoidea). Proc. K. Ned. Akad. Wet. (C)84 (1981) 183–195.Google Scholar
  32. 32.
    Galil, J., and Eisikowitch, D., On the pollination ecology ofFicus religiosa in Israe. Phytomorphology18 (1986) 356–363.Google Scholar
  33. 33.
    Gardner, R. O., AustralianFicus wild in Auckland. Auckland bot. Soc. Newsletter38 (1983) 2.Google Scholar
  34. 34.
    Gautier-Hion, A., and Michaloud, G., Figs: are they keystone resources for frugivorous vertebrates throughout the tropics? a test in Gabon. Ecology (1989) in press.Google Scholar
  35. 35.
    Gentry, A. H., Changes in plant community diversity and floristic composition on environmental and geographical gradients. Ann. Missouri bot. Gard.75 (1988) 1–34.Google Scholar
  36. 36.
    Gentry, A. H., ed. Four Neotropical Forests. Yale University Press, New Haven, Connecticut, in press.Google Scholar
  37. 37.
    Gressitt, J. L., ed. Pacific Basin Biogeography: a Symposium. Bishop Museum Press, Honolulu 1963.Google Scholar
  38. 38.
    Hamilton, W. D., Wingless and fighting males in fig wasps and other insects, in: Sexual Selection and Reproductive Competition in Insects, pp. 167–220. Eds M. S. Blum and N. A. Blum. Academic Press, New York 1979.Google Scholar
  39. 39.
    Herre, E. A., Coevolution of reproductive characteristics in 12 species of new world figs and their pollinator wasps. Experientia45 (1989) 637–647.Google Scholar
  40. 40.
    Hill, D. S., Figs (Ficus spp.) and fig-wasps (Chalcidoidea). J. nat. Hist.1 (1967) 413–434.Google Scholar
  41. 41.
    Hubbell, S. P., and Foster, R. B., Commonness and rarity in a neotropical forest: implications for tropical tree conservation, in: Conservation Biology. The Science of Scarcity and Diversity, pp. 205–231. Ed M. E. Soule. Sinauer, Sunderland, Mass. 1986.Google Scholar
  42. 42.
    Janzen, D. H., How to be a fig. A. Rev. Ecol. Syst.10 (1979) 13–51.Google Scholar
  43. 43.
    Janzen, D. H., No park is an island: increase in interference from outside as park size decreases. Oikos41 (1983) 402–410.Google Scholar
  44. 44.
    Janzen, D. H., The eternal external threat, in: Conservation Biology The Science of Scarcity and Diversity, pp. 286–303. Ed M. E. Soule. Sinauer, Sunderland, Mass. 1986.Google Scholar
  45. 45.
    Judd, C. S., Introducing fig wasps. Haw. Forester and Agriculturist18 (1921) 76–79.Google Scholar
  46. 46.
    Kjellberg, F., and Maurice, S., Seasonality in the reproductive phenology ofFicus: Its evolution and consequences. Experientia45 (1989) 653–660.Google Scholar
  47. 47.
    Kjellberg, F., and Valdeyron, G., Species-specific pollination: a help or a limitation to range extension?, in: Biological Invasions in Europe and the Mediterranean Basin. Eds F. di Castri and A. J. Hansen. Dr. W. Junk, Dordrecht, Netherlands, in press.Google Scholar
  48. 48.
    Kjellberg, F., Doumesche, B., and Bronstein, J., Longevity of a fig wasp (Blastophaga psenes). Proc. K. Ned. Akad. Wet. (C)91 (1988) 117–122.Google Scholar
  49. 49.
    Lambert, F., Fig eating and seed dispersal by birds in a Malaysian lowland rain forest. Trop. Biol. Newsletter (Aberdeen)54 (1988) 2–3.Google Scholar
  50. 50.
    Lande, R., Genetics and demography in biological conservation. Science241 (1988) 1455–1460.Google Scholar
  51. 51.
    Leighton, M., and Leighton, D. R., Vertebrate responses to fruiting seasonality within a Bornean rain forest, in: Tropical Rain Forest: Ecology and Management, pp. 181–196. Eds S. L. Sutton, T. C. Whitmore and A. C. Chadwick. Blackwell, Oxford 1983.Google Scholar
  52. 52.
    Lyon, H. L., Figs in Hawaiian Forestry. Haw. Planters' Rec.33 (1929) 83–97.Google Scholar
  53. 53.
    McKey, D.,Ceropia peltata is replacingMusanga cecropioides in southwestern Cameroon. Biotropica20 (1988) 262–264.Google Scholar
  54. 54.
    McKey, D., and Kaufmann, S., Naturalization of exoticFicus species (Moraceae) in south Florida. Proceedings of the symposium on exotic pest plants, Miami 1988; in press.Google Scholar
  55. 55.
    Michaloud, G., Aspects de la reproduction des figuires monoiques en forêt equatoriale africaine. Ph. D. Dissertation, Université des Sciences et Techniques du Languedoc, Montpellier, France 1988.Google Scholar
  56. 56.
    Michaloud, G., and Michaloud-Pelletier, S.,Ficus hemi-epiphytes (Moraceae) et arbres supports. Biotropica19 (1987) 125–136.Google Scholar
  57. 57.
    Milton, K., Windsor, D. M., Morrison, D. W., and Estribi, M., Fruiting phenologies of two neotropicalFicus species. Ecology63 (1982) 752–762.Google Scholar
  58. 58.
    Monkman, K. D., Rapid spread of the Indian laurel. Dept. Agric. Fisheries, Bermuda, Monthly Bull.55, 11 (1984) 84-85.Google Scholar
  59. 59.
    Morrison, D. W., Foraging ecology and energetics of the frugivorous batArtibeus jamaicensis. Ecology59 (1978) 716–723.Google Scholar
  60. 60.
    Myers, N., Tropical deforestation and a mega-extinction spasm, in: Conservation Biology. The Science of Scarcity and Diversity, pp. 394–409. Ed M. E. Soule. Sinauer, Sunderland, Mass. 1986.Google Scholar
  61. 61.
    Ng, F. S. P., Ecological principles of tropical lowland rain forest conservation, in Tropical Rain Forest: Ecology and Management, pp. 359–375. Eds S. L. Sutton, T. C. Whitmore and A. C. Chadwick. Blackwell, Oxford 1983.Google Scholar
  62. 62.
    Pemberton, C. E., The fig wasp in its relation to the development of fertile seed in the Moreton Bay fig. Haw, Planters' Rec.24 (1921) 297–319.Google Scholar
  63. 63.
    Poore, M. E. D., Studies in Malaysian rain forest. 1. The forest on triassic sediments in Jengka Jorest Reserve. J. Ecol.56 (1986) 143–196Google Scholar
  64. 64.
    Putz, F. E., and Holbrook, N. M., Notes on the natural history of hemiepiphytes. Selbyana9 (1986) 61–69.Google Scholar
  65. 65.
    Putz, F. E., and Holbrook, N. M., Further observations on the dissolution of mutualism betweenCecropia and its ants: the Malaysian case. Oikos53 (1988) 121–125.Google Scholar
  66. 66.
    Ramirez B., W., Host specificity of fig wasps (Agaonidae). Evolution24 (1970) 680–691.Google Scholar
  67. 67.
    Ramirez B., W., and Montero S. J.,Ficus microcarpa L. andF. benjamina L. and other species introduced in the New World, their pollinators (Agaonidae) and other fig wasps. Reta. Biol. trop., in press.Google Scholar
  68. 68.
    Ridley, H. N., The Dispersal of Plants Throughout the World. L. Reeve and Co., Ltd. Ashford, Kent 1930.Google Scholar
  69. 69.
    Sailer, R. I., Our immigrant insect fauna. Bull. ent. Soc. Am.24 (1978) 3–11.Google Scholar
  70. 70.
    Sailer, R. I., History of insect introductions, in: Exotic Plant Pests and North American Agriculture, pp. 15–38. Eds C. L. Wilson and C. L. Graham. Academic Press, New York 1983.Google Scholar
  71. 71.
    Sakimura, K., and Linford, M. B., An annotated list of insects from Lanai. Proc. Haw. ent. Soc.10 (1940) 451–454.Google Scholar
  72. 72.
    Shaffer, M. L., Minimum population sizes for species conservation. Bio Science31 (1981) 131–134.Google Scholar
  73. 73.
    Simberloff, D., Introduced insects: a biogeographic and systematic perspective, in: Ecology of biological Invasions of North America and Hawaii, pp. 3–26. Eds H. A. Mooney and J. A. Drake. Springer-Verlag, New York 1986.Google Scholar
  74. 74.
    Simberloff, D., The contribution of population and community biology to conservation science. A. Rev. Ecol. Syst.19 (1988) 473–511.Google Scholar
  75. 75.
    Soule, M. E., ed. Conservation Biology. The Science of Scarcity and Diversity. Sinauer, Sunderland, Mass. 1986.Google Scholar
  76. 76.
    Soule, M. E., ed. Viable Populations for Conservation. Cambridge University Press, New York 1987.Google Scholar
  77. 77.
    Soule, M. E., and Simberloff, D., What do genetics and ecology tell us about the design of nature reserves?. Biol. Conserv.35 (1986) 19–40.Google Scholar
  78. 78.
    Stange, L. A., and Knight, R. J. Jr. Fig pollinating wasps of Florida. Entomol. Circular No. 296 4 pp. Florida Dept. of Agric. and Consumer Services, Div. Plant Industry, Tallahassee, 1987.Google Scholar
  79. 79.
    Swezey, O. H., Records of introduction of beneficial insects into the Hawaiian Islands. Proc. Haw. ent. Soc.5 (1923) 299–304.Google Scholar
  80. 80.
    Terborgh, J., Five Neotropical Primates Princeton University Press, Princeton, New Jersey 1983.Google Scholar
  81. 81.
    Terborgh, J., Keystone plant resources in the tropical forest, in: Conservation Biology. The Science of Scarcity and Diversity. pp. 330–344. Ed. M. E. Soule. Sinauer, Sunderland, Mass. 1986.Google Scholar
  82. 82.
    Timberlake, P. H., Records of the introduced and immigrant chalcidflies of the Hawaiian Islands (Hymenoptera). Proc. Haw. ent. Soc.5 (1924) 418–449.Google Scholar
  83. 83.
    Timberlake, P. H., Biological control of insect pests in the Hawaiian Islands. Porc. Haw. ent. Soc.6 (1927) 529–566.Google Scholar
  84. 84.
    Todzia, C., Growth habits, host tree species, and density of hemiepiphytes on Barro Colorado Island, Panama. Biotropica18 (1986) 22–27.Google Scholar
  85. 85.
    Troth, R. G., Vegetational types on a ranch in the central llanos of Venezuela, in: Vertebrate Ecology in the Northern Neotropics, pp. 17–30. Ed. J. F. Eisenberg, Smithsonian Institution Press, Washington, D. C. 1979.Google Scholar
  86. 86.
    Valdeyron, G., Kjellberg, F., Ibrahim, M., Raymond, M., and Valizadeh M., A one species-one population plant: How does the common fig escape genetic diversification?, in: Genetic Differentiation and Dispersal in Plants, pp. 383–393. Eds P. Jacquard, G. Heim and J. Antonovics. Springer-Verlag, Berlin 1985.Google Scholar
  87. 87.
    Whitmore, T. C., Tropical Rain Forests of the Far East, Clarendon Press, Oxford 1975.Google Scholar
  88. 88.
    Windsor, D. M., Morrison, D. W., Estribi, M. A. and de Leon, B., Phenology of fruit and leaf production by ‘strangler’ figs on Barro Colorado Island, Panama, Experientia45 (1989) 647–653.Google Scholar
  89. 89.
    Wyatt-Smith, J., The vegetation of Jarak Island, Straits of Malacca. J. Ecol.41 (1953) 207–225.Google Scholar

Copyright information

© Birkhäuser Verlag Basel 1989

Authors and Affiliations

  • D. McKey
    • 1
  1. 1.Department of BiologyUniversity of MiamiCoral GablesUSA

Personalised recommendations