Flower continuity

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Most insects are constant in bloom and quickly decide which form of flower to visit, even with a larger selection.

The flower constancy (English flower constancy ) pollinating insects is the learned preference for the flowers of a plant, recently, around the beginning of the search for food, a reward in the form of nectar or pollen has commanded. This behavior was already described by Aristotle for the honey bee and later examined by Charles Darwin. Today it is assumed that depending on the situation, flower continuity occurs more or less pronounced in most flower-visiting insects.

Ecological importance

Flower continuity increases the likelihood of successful pollination for the affected plants because the pollinating insect transfers pollen of the same species to the stigma of a flower. If the flowers are not steady, the stigmas are increasingly blocked by pollen from other species, so that the reproductive success of the plants decreases. For the insects, the flower continuity means that on the way to the preferred flowers they sometimes ignore other flowers that provide more nectar or pollen.

Variability and cause of flower continuity

It could be shown that honey bees, which show strong flower continuity in the wild, are less able to flower under controlled test conditions: If bees were offered a sufficient amount of nectar on a flower, they preferred to visit flowers of the same type. Flower continuity was lower when the bees received little nectar on the first or second visit to a particular flower. That is, after one or two initial failures, the bees increasingly looked for nectar on different flowers. A reduced flower continuity was not observed when the lowest amount of nectar exceeded a threshold value.

Flower continuity is maintained as long as the preferred flowers provide enough nectar. A prerequisite for flower continuity is that the insects can tell the flowers of the different species apart (based on shape, size, color or fragrance) and that the preferred flowers are not too far away. The alternative to flower continuity is to collect nectar from different flowers. A greater success is uncertain because the insects cannot estimate the nectar content, which varies within a species, when a flower approaches. In addition, switching to other types of flowers requires time-consuming relearning in nectar collection.

Determination and description of flower continuity

The studies of flower continuity are rarely carried out directly on natural meadows, but are mostly carried out with artificial flowers in a precise arrangement in order to ensure controlled test conditions. Different colored centrifuge tubes, which contain a sucrose solution as nectar, can play the role of different flowers.

A constancy index (CI) was used in various studies based on the following formula to enable precise comparisons of the flower continuity of an individual insect with other species:

CI = (c − e) / ((c + e) ​​- (2ce))

c relates to a single insect and corresponds to the ratio of successive visits to a flower form to all flower visits.

e is the ratio of the average value of all determined c-values ​​to the c-value of an individual insect.

Example: When choosing between type A and type B, a certain bee only visits the flowers of type A (c = 1), while a large number of other bees visit type A and type B without preference (e = 0.5 ). In this case, a CI of 1 results for the examined bee and species A, which means complete constancy . In relation to type B, the result is a CI of −1, equivalent to complete inconstancy . If the examined bee visits flowers just as randomly as the other tested conspecifics (c = e = 0.5), then CI = 0 ( random foraging ).

Individual evidence

  1. ↑ D. Goulson: Are insects flower constant because they use search images to find flowers? In: Oikos. 88, 2000, pp. 547-552.
  2. ↑ C. Grüter, FLW Ratnieks: Flower constancy in insect pollinators: Adaptive foraging behavior orcognitive limitation? In: Commun Integr Biol. 4, 2011, p. 633.
  3. ↑ C. Grüter, H. Moore, N. Firmin, H. Helanterä, FLW Ratnieks: Flower constancy in honeybees (Apis mellifera) depends on ecologically realistic rewards. In: Journal of Experimental Biology. 214, 2011, pp. 1397-1402.
  4. ↑ CE Sanderson, BS Orozco, PSM Hill, H. Wells: Honeybee (Apis mellifera ligustica) response to differences in handling time, rewards and flower colors. In: Ethology. 112, 2006, pp. 937-946.
  5. ↑ L. Chittka, JD Thomson, NM Waser: Flower constancy, insect psychology, and plant evolution. In: Natural Sciences. 86, 1999, pp. 361-377.
  6. ↑ a b M. C. Otterstatter, RJ Gegear, SR Colla, JD Thomson: Effects of parasitic mites and protozoa on the flower constancy and foraging rate of bumble bees. In: Behavioral Ecology and Sociobiology. 58, 2005, pp. 383-389.
  7. ^ NM Waser: Flower constancy: definition, cause and measurement. In: The American Naturalist. 127 (5), 1986, pp. 596-603.