Nectar guide
Nectar guides are markings or patterns seen in flowers of some angiosperm species, that guide pollinators to their rewards. These markings may appear as lines, spots, or "blotches".[1] Such patterns are also known as "pollen guides" and "honey guides", though some authorities argue for the abandonment of such terms in favour of floral guides (see, for example, Dinkel & Lunau[2]).
Pollination
[edit]Nectar guides serve as an interspecific signal that the flower contains a reward. Rewards commonly take the form of nectar, pollen, or both; however, plants may also produce oil,[3] resins,[4] scents,[5] or waxes. Pollinator visitation can select for various floral traits, including nectar guides, through a process called pollinator-mediated selection. For example, nectar guides are thought to increase pollinator foraging efficiency by reducing handling time.[6] These guides may also decrease nectar robbing, which leads more pollen to be transferred and ultimately increases plant fitness.[7]
Visibility
[edit]_Vis_UV_IR_comparison.jpg)
Nectar guides are sometimes visible to humans; for instance, the Dalmatian toadflax (Linaria genistifolia) has yellow flowers with orange nectar guides.[8] However, in some plants, such as the meadow buttercup (pictured to the right), they are visible only when viewed in ultraviolet light. Under ultraviolet, the flowers have a darker center, where the nectaries are located, and often specific patterns upon the petals as well. This is believed to make the flowers more attractive to pollinators such as honey bees and other insects that can see ultraviolet light. This page on butterflies shows an animated comparison of black-eyed Susan (Rudbeckia hirta) flowers in visible and UV light.[9]
The ultraviolet color, invisible to humans, has been referred to as bee violet, and mixtures of greenish (yellow) wavelengths (roughly 540 nm[10]) with ultraviolet are called bee purple by analogy with purple in human vision.[11]
References
[edit]- ^ Free, JB.: "Effect of Flower Shapes and Nectar Guides on the Behaviour of Foraging Honeybees". Behaviour Volume 37, Issue 3–4, January 1970, Pages 269–285
- ^ Dinkel T., Lunau K.: "How drone flies (Eristalis tenax L., Syrphidae, Diptera) use floral guides to locate food sources". Journal of Insect Physiology Volume 47, Issue 10, September 2001, Pages 1111–1118
- ^ Buchmann, SL.: "The ecology of oil flowers and their bees". Annual Review of Ecology and Systematics Volume 18, Issue 1, 2000, Pages 343–370
- ^ Reis Mariza G.; de Faria, AD.; Bittrich, V; do Carmo, M.; Amaral E.; Marsaioli, AJ. "The Chemistry of Flower Rewards". Journal of the Brazilian Chemical Society, Volume 11, Issue 6, 2000, Pages 600–608,
- ^ Teichert, Holger; "Pollination biology of cantharophilous and melittophilous Annonaceae and Cyclanthaceae in French Guiana"; Doctoral dissertation at University of Ulm, 2008
- ^ Hansen, DM.; Van der Niet, T.; Johnson, SD: "Floral signposts: testing the Significance of visual ‘nectar guides’ for pollinator behaviour and plant fitness". Proceedings of the Royal Society B: Biological Sciences, Volume 279, Issue 1729, 2011, Pages 634–639
- ^ Leonard, AS.; Brent, J.; Papaj, DR.; Dornhaus, A.: "Floral Nectar Guide Patterns Discourage Nectar Robbing by Bumble Bees". PLOS One, Volume 8, Issue 2, 2013.
- ^ "Dalmatian Toadflax (Internet Archive)" (PDF). Archived from the original (PDF) on 2007-03-17.
- ^ "Butterfly Color Vision". Web Exhibits. Retrieved 28 April 2025.
- ^ Briscoe, Adriana D.; Chittka, Lars. "The Evolution of Color Vision in Insects". Annual Review of Entomology. 2001. 46:471–510
- ^ Charles D. Michener (1974). The Social Behavior of the Bees: A Comparative Study. Harvard University Press. ISBN 0-674-81175-5.
External links
[edit]- Dalmatian Toadflax from the Southwest Exotic Plant Information Clearinghouse.
(See archived version on the Internet Archive -- accessed on 2009-03-17). - UltravioletPhotography.com Online library of ultraviolet floral signatures.
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