Floral Integration
Friday, July 11, 2003
Unrelated to my “official” thesis work, I have been thinking about floral form and its influence on plant fitness. As an excuse to start a discussion with anyone interested, I’ve posted this overview of what I hope to work on next.
Plant mating systems control the transmission of genes between generations and, therefore, are a fundamental characteristic of populations. Since flowers are the reproductive organs of plants, floral form fundamentally influences plant mating systems. However, research into floral evolution has traditionally “atomized” flowers into conspicuous traits that are then investigated independently. Despite the undeniable success of this reductionist approach, an alternate research strategy called phenotypic integration, found at the intersection of morphometrics, quantitative genetics, reproductive ecology, and plant evolution, offers a unique perspective. Floral integration, in particular, asserts that the variance-covariance structure of entire flowers, rather than mean values of individual traits, may be an important target for selection. This is especially relevant for animal-pollinated, hermaphroditic flowers (i.e., most angiosperms) in which the male and female sexual organs must be positioned precisely within the path of pollen movement. Consequently, I expect high integration for anther and stigma placement relative to, for example, vegetative characters. After a long period of neglect, floral integration is beginning to receive more attention. To date, most of this research has focussed on quantifying the magnitude of integration, whereas the evolutionary significance of variation in floral integration remains an open question.