Dichogamy is the temporal separation of gender in hermaphroditic organisms (e.g., some gastropods and most angiosperms). In the context of angiosperms, there are two forms of dichogamy: protogyny and protandry. Protogyny is when female function precedes male function; protandry is the converse. Subclass Subclass Eogastropoda     Patellogastropoda Subclass Orthogastropoda   Superorder Cocculiniformia   Superorder Hot Vent Taxa     Neomphaolida   Superorder Vetigastropoda   Superorder Neritaemorphi     Neritopsina   Superorder Caenogastropoda     Architaenioglossa     Sorbeoconcha   Superorder Heterobranchia     Heterostropha     Opisthobranchia     Pulmonata The gastropods, or univalves, are the largest and most successful class of mollusks, with 60,000-75,000 species, and second largest class... Classes Magnoliopsida - Dicots Liliopsida - Monocots The flowering plants (also angiosperms or Magnoliophyta) are one of the major groups of modern plants, comprising those that produce seeds in specialized reproductive organs called flowers, where the ovulary or carpel is enclosed. ...

Historically, dichogamy has been interpreted as a mechanism for reducing inbreeding (e.g., Darwin, 1862). However, a survey of the angiosperms (Bertin, 1993) found that self-incompatible (SI) plants, which are incapable of inbreeding, were as likely to be dichogamous as were self-compatible (SC) plants. This led to the recent reinterpretation of dichogamy as a more general mechanism for reducing the impact of pollen-pistil interference on pollen import and export (reviewed in Lloyd & Webb, 1986, Barrett, 2002). Unlike the inbreeding-avoidance hypothesis, which focused on female function, this interference-avoidance hypothesis considers both gender functions. Inbreeding is breeding between close relatives. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... The Pistil is the part of the flower made up of one or more carpels. ...

In many hermaphroditic species, the close physical proximity of anthers and stigmas makes interference unavoidable, either within a flower or between flowers on an inflorescence. Within-flower interference, which occurs when either the pistil interrupts pollen removal or the anthers prevent pollen deposition, can result in autonomous or facilitated self-pollination (Lloyd & Webb, 1986; Lloyd & Schoen, 1992). Between-flower interference results from similar mechanisms, except that the interfering structures occur on different flowers within the same inflorescence and it requires pollinator activity. This results in geitonogamous pollination, the transfer of pollen between flowers of the same individual (Lloyd & Schoen, 1992; de Jong et al., 1993). In contrast to within-flower interference, geitonogamy necessarily involves the same processes as outcrossing: pollinator attraction, reward provisioning, and pollen removal. Therefore, between-flower interference not only carries the cost of self-fertilization (inbreeding depression; Charlesworth & Charlesworth, 1987; Husband & Schemske, 1996), but also reduces the amount of pollen available for export (pollen discounting; Harder & Wilson, 1998). Because pollen discounting diminishes outcross siring success, interference avoidance may be an important evolutionary force in floral biology (Harder & Barrett, 1995, 1996; Harder & Wilson, 1998; Barrett, 2002). Flower of the spider tree (Crateva religiosa) with its numerous conspicuous stamens The stamen is the male organ of a flower. ... A stigma is part of the female part of a flower; that part of a pistil which has no epidermis, and is fitted to receive the pollen. ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms ( flowering plants; Division Magnoliophyta). ... An inflorescence is a group or cluster of flowers on a branch of a plant. ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... A pollinator is the agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms ( flowering plants; Division Magnoliophyta). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... A pollinator is the agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... Inbreeding is breeding between close relatives. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ...

Dichogamy may reduce between-flower interference by minimizing the temporal overlap between stigmas and anthers within an inflorescence. Large inflorescences attract more pollinators, potentially enhancing reproductive success by increasing pollen import and export (Schemske, 1980; Queller, 1983; Bell, 1985; Geber, 1985; Schmid-Hempel & Speiser, 1988; Klinkhamer & de Jong, 1990). However, large inflorescences also increase the opportunities for both geitonogamy and pollen discounting, so that the opportunity for between-flower interference increases with inflorescence size (Harder & Barrett, 1996). Consequently, the evolution of floral display size may represent a compromise between maximizing pollinator visitation and minimizing geitonogamy and pollen discounting (Klinkhamer & de Jong, 1993; Barrett et al, 1994; Holsinger, 1996; Snow et al., 1996). Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... A stigma is part of the female part of a flower; that part of a pistil which has no epidermis, and is fitted to receive the pollen. ... Flower of the spider tree (Crateva religiosa) with its numerous conspicuous stamens The stamen is the male organ of a flower. ... An inflorescence is a group or cluster of flowers on a branch of a plant. ... An inflorescence is a group or cluster of flowers on a branch of a plant. ... A pollinator is the agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... An inflorescence is a group or cluster of flowers on a branch of a plant. ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... An inflorescence is a group or cluster of flowers on a branch of a plant. ... A pollinator is the agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. ...

Protandry may be particularly relevant to this compromise, because it often results in an inflorescence structure with female phase flowers positioned below male phase flowers (Bertin & Newman, 1993). Given the tendency of many insect pollinators to forage upwards through inflorescences (Galen & Plowright, 1988), protandry may enhance pollen export by reducing between-flower interference (Darwin, 1862; Harder et al, 2000). Furthermore, this enhanced pollen export should increase as floral display size increases, because between-flower interference should increase with floral display size. These effects of protandry on between-flower interference may decouple the benefits of large inflorescences from the consequences of geitonogamy and pollen discounting. Such a decoupling would provide a significant reproductive advantage through increased pollinator visitation and siring success. An inflorescence is a group or cluster of flowers on a branch of a plant. ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms ( flowering plants; Division Magnoliophyta). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms ( flowering plants; Division Magnoliophyta). ... A pollinator is the agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. ... An inflorescence is a group or cluster of flowers on a branch of a plant. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ... An inflorescence is a group or cluster of flowers on a branch of a plant. ... A pollinator is the agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. ...

Harder et al. (2000) demonstrated experimentally that dichogamy both reduced rates of self-fertilization and enhanced outcross siring success through reductions in geitonogamy and pollen discounting, respectively. Routley & Husband, (2003) examined the influence of inflorescence size on this siring advantage and found a bimodal distribution with increased siring success with both small and large display sizes. An inflorescence is a group or cluster of flowers on a branch of a plant. ...

See Griffin et al., (2000) for an experimental test of the adaptive significance of protogyny.

References

Bell G., 1985, On the function of flowers. Proc. R. Soc. Lond. B 224: 223–265. Wildflowers A flower is the reproductive organ of those plants classified as angiosperms ( flowering plants; Division Magnoliophyta). ...

Bertin R.I. & Newman C.M., 1993, Dichogamy in angiosperms. Bot. Rev. 59: 112–152.

de Jong T.J., Waser N.M. & Klinkhamer P.G.L., 1993, Geitonogamy: the neglected side of selfing. Trends Ecol. Evol. 8: 321–325.

Galen C. & Plowright R.C., 1988, Contrasting movement patterns of nectar-collecting and pollen-collecting bumble bees (Bombus terricola) on fireweed (Chamaenerion angustifolium) inflorescences. Ecol. Entomol. 10: 9–17. An inflorescence is a group or cluster of flowers on a branch of a plant. ...

Harder L.D. & Barrett S.C.H., 1996, Pollen dispersal and mating patterns in animal-pollinated plants. In: Floral Biology: Studies on Floral Evolution in Animal-Pollinated Plants (D.G. Lloyd & S.C.H. Barrett, eds.), Chapman and Hall, New York, New York, USA, pp. 140–190.

Holsinger K.E., 1996, Pollination biology and the evolution of mating systems in flowering plants. In: Evolutionary Biology (M.K. Hecht, ed.), Plenum Press, New York, pp. 107–149. Wildflowers A flower is the reproductive organ of those plants classified as angiosperms (flowering plants; Division Magnoliophyta). ...

Klinkhamer P.G.L. & de Jong T.J., 1990, Effects of plant size, plant density and sex differential nectar reward on pollinator visitation in the protandrous Echium vulgare. Oikos 57: 399–405. A pollinator is the agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. ...

Klinkhamer P.G.L. & de Jong T.J., 1993, Attractiveness to pollinators: a plant’s dilemma. Oikos 66: 180–184. A pollinator is the agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain. ...

Lloyd D.G. & Webb C.J., 1986, The avoidance of interference between the presentation of pollen and stigmas in angiosperms: I. Dichogamy. New Zeal. J. Bot. 24: 135–162. A stigma is part of the female part of a flower; that part of a pistil which has no epidermis, and is fitted to receive the pollen. ...

Queller D.C., 1983, Sexual selection in a hermaphroditic plant. Nature 305: 706–707.

Schemske D.W., 1980, Evolution of floral display in the orchid Brassavola nodosa. Evolution 34: 489–491.

Schmid-Hempel P. & Speiser B., 1988, Effects of inflorescence size on pollination in Epilobium angustifolium. Oikos 53: 98–104. An inflorescence is a group or cluster of flowers on a branch of a plant. ...

Snow A.A., Spira T.P., Simpson R. & Klips R.A., 1996, The ecology of geitonogamous pollination. In: Floral Biology: Studies on Floral Evolution in Animal-Pollinated Plants (D.G. Lloyd & S.C.H. Barrett, eds.), Chapman and Hall, New York, New York, USA, pp. 191–216.