AOBPreview originally published online on May 8, 2009
Annals of Botany 2009 103(9):1529-1545; doi:10.1093/aob/mcp095
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
This article appears in the following Annals of Botany issue: Special Issue: Plant-Pollinator Interactions [View the issue table of contents]
The adaptive accuracy of flowers: measurement and microevolutionary patterns
1 School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK
2 Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA
3 Department of Biology, NTNU, NO-7491, Trondheim, Norway
4 Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, PO Box 1050, N-0316 Oslo, Norway
* For correspondence. E-mail scott.armbruster{at}port.ac.uk
Received: 11 November 2008 Returned for revision: 29 January 2009 Accepted: 24 March 2009 Published electronically: 8 May 2009
Background and Aims: From Darwin's time onward, biologists have thought about adaptation as evolution toward optimal trait values, but they have not usually assessed the relative importance of the distinct causes of deviations from optima. This problem is investigated here by measuring adaptive inaccuracy (phenotypic deviation from the optimum), using flower pollination as an adaptive system.
Methods: Adaptive accuracy is shown to have at least three distinct components, two of which are optimality (deviation of the mean from the optimum) and precision (trait variance). We then describe adaptive accuracy of both individuals and populations. Individual inaccuracy comprises the deviation of the genotypic target (the mean phenotype of a genotype grown in a range of environments) from the optimum and the phenotypic variation around that genotypic target (phenotypic imprecision). Population inaccuracy has three basic components: deviation of the population mean from the optimum, variance in the genotypic targets and phenotypic imprecision. In addition, a fourth component is proposed, namely within-population variation in the optimum. These components are directly estimable, have additive relationships, and allow exploration of the causes of adaptive inaccuracy of both individuals and populations. Adaptive accuracy of a sample of flowers is estimated, relating floral phenotypes controlling pollen deposition on pollinators to adaptive optima defined as the site most likely to get pollen onto stigmas (male inaccuracy). Female inaccuracy is defined as the deviation of the position of stigma contact from the expected location of pollen on pollinators.
Key Results: A surprising amount of variation in estimated accuracy within and among similar species is found. Some of this variation is generated by developmental changes in positions of stigmas or anthers during anthesis (the floral receptive period), which can cause dramatic change in accuracy estimates. There seem to be trends for higher precision and accuracy in flowers with higher levels of integration and dichogamy (temporal separation of sexual functions), and in those that have pollinators that are immobile (or immobilized) during pollen transfer. Large deviations from putative adaptive optima were observed, and these may be related to the effects of conflicting selective pressures on flowers, such as selection against self-pollination promoting herkogamy (spatial separation of pollen and stigmas).
Conclusions: Adaptive accuracy is a useful concept for understanding the adaptive significance of phenotypic means and variances of floral morphology within and among populations and species. Estimating and comparing the various components of adaptive accuracy can be particularly helpful for identifying the causes of inaccuracy, such as conflicting selective pressures, low environmental canalization and developmental instability.
Key words: Adaptive accuracy, Collinsia, Dalechampia, fitness, floral precision, Linum, optimality, pollination, Stylidium
Present address: Plant Ecology, Department of Ecology and Evolution, Uppsala University, Villavägen 14, SE-75236 Uppsala, Sweden.
CiteULike 
Connotea 
Del.icio.us What's this?
Related articles in Ann Bot:
- ContentSnapshots
Ann Bot 2009 103: i.[Extract] [Full Text]
This article has been cited by other articles:
|
|
 |
|
  D. L. Marshall, J. J. Avritt, S. Maliakal-Witt, J. S. Medeiros, and M. G. M. Shaner The impact of plant and flower age on mating patterns Ann. Bot., October 29, 2009; (2009) mcp260v1. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. S. Armbruster, J. Lee, and B. G. Baldwin Plant and Insect Biodiversity Special Feature: Macroevolutionary patterns of defense and pollination in Dalechampia vines: Adaptation, exaptation, and evolutionary novelty PNAS, October 27, 2009; 106(43): 18085 - 18090. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. J. Mitchell, R. E. Irwin, R. J. Flanagan, and J. D. Karron Ecology and evolution of plant-pollinator interactions Ann. Bot., June 1, 2009; 103(9): 1355 - 1363. [Abstract] [Full Text] [PDF]
|
|