Antonovics, J., and Levin, D.A. 1980. The ecological and genetic consequences of density-dependent regulation in plants. Annu. Rev. Ecol. Syst. 11: 411-452.
Beattie, A.J. 1971. Pollination mechanisms in Viola. New Phytol. 70: 343-360.
Beijerinck, W. 1940. Calluna: a monograph on the Scotch heather. Verh. K. Ned. Akad. Wet. 38: 1-180.
Berry, P.E., and Calvo, R.N. 1989. Wind pollination, self-incompatibilty, and altitudinal shifts in pollination systems in the high Andean genus Espeletia (Asteraceae). Am. J. Bot. 76: 1602-1614.
Burd, M. 1994. Bateman's principle and plant reproduction: the role of pollen limitation in fruit and seed set. Bot. Rev. 60: 83-139.
Charlesworth, D. 1989a. Why do plants produce so many more ovules than seeds? Nature (London), 338: 21-22.
Charlesworth, D. 1989b. Evolution of low female fertilty in plants: pollen limitation, resource allocation and genetic load. Trends Ecol. Evol. 4: 289-292.
Dafni, A., and Dukas, R. 1986. Insect and wind pollination in Urginea maritima (Liliaceae). Plant Syst. Evol. 154: 1-10.
Ellis, W.N., and Ellis-Adam, A.C. 1993. To make a meadow it takes a clover and a bee: the entomophilous flora of N.W. Europe and its insects. Bijdr. Dierkd. 63: 193-220.
Faegri, K., and van der Pijl, L. 1980. The principles of pollination ecology. 3rd ed. Pergamon Press, Oxford, U.K.
Feldman, J.D.S., Hoffman, R., Gagnon, J., and Simpson, J. 1987. Statview SE+Graphics. Abacus Concept Inc., Berkeley, Calif.
Fishbein, M., and Venable, D.L. 1996. Diversity and temporal change in the effective pollinators of Asclepias tuberosa. Ecology, 77: 1061-1073.
Galen, C., Gregory, T., and Galloway, L.F. 1989. Costs of self-pollination in a self-incompatible plant, Polemonium viscosum. Am. J. Bot. 76: 1675-1680.
Gimingham, C.H. 1960. Biological flora of the British Isles: Calluna Salibs. J. Ecol. 48: 455-483.
Gomez, J.M., and Zamora, R. 1996. Wind pollination in high mountain populations of Hormathophylla spinosa (Cruciferae). Am. J. Bot. 83: 580-585.
Grane, E., Walker, P., and Day, R. 1984. Directory of important honey world sources. International Bee Research Association, London, U.K.
Hagerup, O. 1950. Thrip pollination in Calluna. K. Dan. Vidensk. Selsk. Biol. Medd. 18: 1-16.
Haslerud, H.D. 1974. Pollination of some Ericaceae in Norway. Nord. J. Bot. 21: 211-216.
Herrera, J. 1987. Biologia reproductiva del algunas especies del matorral de Donana. An. Jard. Bot. Madrid, 44: 483-497.
Herrera, J. 1988. Pollination relationships in southern Spanish Mediteranean shrublands. J. Ecol. 76: 274-287.
Herrera, C. 1989. Pollinator abundance, morphology, and flower visitation rate: analysis of the "quantity" components in a plant pollinator system. Oecologia, 80: 241-248.
Jacquemart, A.-L. 1993. Floral visitors of Vaccinium species in the High Ardennes, Belgium. Flora, 188: 263-273.
Jacquemart, A.-L., and Thompson, J.D. 1996. Floral and pollination biology of three sympatric Vaccinium (Ericaceae) species in the Upper Ardennes, Belgium. Can. J. Bot. 74: 210-221.
Kearns, C.A., and Inouye, D.W. 1993. Techniques for pollination biologists. University Press of Colorado, Boulder, Colo.
Kearns, C.A., and Inouye, D.W. 1994. Fly pollination of Linum lewisii (Linaceae). Am. J. Bot. 81: 1091-1095.
Kevan, P.G., and Baker, H.G. 1983. Insects as flower visitors and pollinators. Annu. Rev. Entomol. 28: 407-453.
Klinkhamer, P.G.L., deJong, T.J., and deBruyn, G.J. 1989. Plant size and pollinator visitation in Cynoglosum officinale. Oikos, 54: 201-204.
Knuth, P. 1908. Handbook of flower pollination. Vol. 2. Clarendon Press, Oxford, U.K.
Lindsey, A.H. 1984. Reproductive biology of Apiaceae. I. Floral visitors to Thaspium and Zizza and their importance in pollination. Am. J. Bot. 71: 375-387.
Mahy, G., and Jacquemart, A.L. 1998. Mating system of Calluna vulgaris: self-sterility and outcrossing rate estimations. Can. J. Bot. 76: 37-42.
Mahy, G., Vekemans, X., Jacquemart, A.-L., and DeSloover, J. 1997. Allozyme diversity and genetic structure in South-Western populations of heather, Calluna vulgaris. New Phytol. 137: 325-334.
Motten, A.F. 1983. Reproduction of Erythronium umbilicatum (Liliaceae): pollination success and pollinators effectiveness. Oecologia, 59: 351-359.
Motten, A.F., Campbell, D.R., and Alexander, D.F. 1981. Pollinator effectiveness of specialist and generalist visitors to a North Carolina population of Claytonia virginica. Ecology, 62: 1278-1287.
Ockendon, D.J., and Currah, L. 1977. Self-pollen reduces the number of cross-pollen tubes in the styles on Brassica oleracea L. New Phytol. 78: 675-680.
Ollerton, J. 1996. Reconciling ecological processess with phylogenetic patterns: the apparent paradox of plant-pollinator systems. J. Ecol. 84: 767-769.
Pellmyr, O. 1997. Stability of plant-animal mutualisms: keeping the benefactors at bay. Trends Plant Sci. 2: 408-409.
Proctor, M., Yeo, P., and Lack, A. 1996. The natural history of pollination. Harper Collins Publishers, London, U.K.
Sacchi, C.F., and Price, P.W. 1988. Pollination of the arroyo willow, Salix lasiolepis: role of insects and wind. Am. J. Bot. 75: 1387-1393.
SAS Institute Inc 1989. SAS user's guide, SAS Institute Inc., Cary, N.C.
Schemske, D.W., and Horvitz, C.C. 1984. Variation among floral visitors in pollination ability: a precondition for mutualism specialization. Science (Washington, D.C.), 225: 519-521.
Shore, J.S., and Barrett, S.C.H. 1984. The effect of pollination intensity and incompatible pollen on seed set in Turnera ulmifolia (Turneraceae). Can. J. Bot. 62: 1298-1303.
Thompson, D.B.A, MacDonald, A.J., Mardsen J.H., and Galbraith, C.A. 1995. Upland heather moorland in Great Britain: a review of international importance, vegetation change and some objectives for nature conservation. Biol. Conserv. 71: 163-178.
Waser, N.M., and Price, M.V. 1991. Reproductive costs of self-pollination in Ipomopsis aggregata (Polemoniaceae): are ovules usurped? Am. J. Bot. 78: 1036-1043.
Waser, N.W., Chittka, L., Price, M.V., Williams, N.M., and Ollerton, J. 1996. Generalization in pollination systems, and why it matters. Ecology, 77: 1043-1060.
Willis, J.C., and Burkill, I.H. 1895. Flowers and insects in Great Britain. Ann. Bot. (London), 17: 539-571.
