The relative lability of floral vs. non-floral characters and a morphological phylogenetic analysis of Cobaea (Polemoniaceae) |
| |
Authors: | L ALAN PRATHER |
| |
Institution: | Michigan State University Herbarium, Department of Botany &Plant Pathology, Michigan State University, East Lansing, MI 48824–1312, USA. |
| |
Abstract: | The relative levels of lability in floral vs. vegetative characters have been suggested to give insight into the mechanisms of adaptation and speciation. Cobaea (Polemoniaceae) exhibits a remarkable diversity in floral form. A morphology-based phylogeny was constructed and is congruent in most regards with a previously published molecular phylogeny, but significant incongruence was found in the placement of two taxa. A combined analysis was performed, excluding C. aquatoriensis and C. lutea, and was nearly identical to the molecular analysis. The phylogenies are compatible with a recently published classification. Incongruencies between the phylogenies within section Rosenbergia may have profound implications for floral evolution. A simple method for testing the levels of homoplasy, as an indicator of lability between two classes of data, is developed and used to test for differences between floral and non-floral classes of characters. The method is based on repeated randomization of the data into partitions and recalculation of a test statistic defined as the difference between consistency index (CI) values of the data in each partition over a given tree. The null hypothesis that the floral characters are no more homoplasious than the non-floral characters cannot be rejected (P=0.09). |
| |
Keywords: | adaptation - cladistics classification evolution homoplasy morphology parallel evolution pollination |
|
|