Evolution concepts and mechanisms

Clarkia Unguiculata: Onagraceae

Evolutionary (Pollination Ecology))

This study conducted by the department of ecology and marine biology of the University of California analyses the factors that contribute to the reproductive success of the plant CLARKIA UNGUICULATA. The purpose of the study was to research the possibility of the allelic variations affecting the male and female reproductive functions. For the study the researchers took pollen donors homozygous for C. And B. alleles. The researchers used both selfed and out- crossed pollination using different homozygous pollen donors.

The tests were performed under both competitive (more pollen) and non-competitive conditions with mixed pollination. The amount of pollen used was also varied (high, medium and low) so as to discern the pre-fertilization performance of the pollens from their post fertilization performance. (Viability, abortion). All the plants used in the study were selected from the same place and the seedlings were germinated under same conditions. The difference in genotypes between the seedlings can be identified by CAGE. (Cellulose acetate electrophoresis). Pgi genotypes of the resulting seeds will help identify the pollen donor. From the study it was found that for the same genotypes there was not a significant difference in the siring success using either self or outcrossing pollination.

In C.unguiculata. The gametophytic competition basically revolves around the different Pgi genotypes. This indicates that the individual reproductive ability is directly influenced by Allozyme variations of Pgi. The male reproductive ability is a measure of the siring success under competing conditions while the female reproductive success is measured as the number of viable seeds in the maternal plant. The CC allele was found to have a higher siring rate than the BB donor type (particularly under high load of pollens) and also the nature of pollination did not have a significant effect on the siring ratio between CC and BB.

The main finding of the research is that it is the nature of genotype rather than the type of pollination that directly affects the reproductive success of C. unguiculata. It is also inferred that the rate of metabolism affects reproductive success as reflected in the form of speedy pollen tube development in the case of CC allele. However the positive effects of the increased metabolic rate can be offset by the negative effects as in the case of reduced ovule fertilization time. (Leading to fewer seeds). In short the counterbalancing effects of the rate of metabolism on the male and female reproductive systems creates a kind of equilibrium.