Question

3. You are working in a temperate rainforest that has small patches of sandy soil spread throughout the area. This soil has a unique chemistry, different from the soil of the neighboring clay-rich areas of the forest, and results in a different composition of plants. In particular, you notice one shrub that occurs only on the small sandy patches.

1. Briefly describe three factors that you hypothesize may explain the patchy distribution of the shrub.
   
2. How would you determine the sexual system of the shrub and whether it varies?
   
3. If you determine the shrub species is a hermaphrodite, how would you determine its selfing rate and whether it varies?
   
4. Explain, how this shrub species’ distribution might affect its mating system.

Answer 1

A. Climte and soil are among the most important factors and drivers of shrubs distribution.Soil aeration is also important factor for patchy distribution of shrubs.Presence of minerals,nutrients in sandy soil effects the salinity of soil which help them in their biological cycle.The soil does not only influence species composition,but species also effect soil properties such as nutrient status, mainly by species specific litter input.The bidirectional link between plant soil create composition of species in temeprate rainforest.

B. Natural regeneration by the shrub in sandy soil is potentially limited by the absence of clonal regeneration,low seedling emergence, and incidence of dead shoots in mature plants.For sexual reproduction, the soil seed bank density was not a limiting factor in natural regeneration in stabilized sandy soil.Overall seedling survival in mobile and stabilized sandy soil was relatively low.,which suggests that at particular stages of seedling survival and seedling growth could also be limited factors in the natural regenration of this shrub.Additionally, clonal reproductive and clonal growth may be the most important ways for population expansion.

C.The selfing rate of hermaphroditicc shrubs could be estimated on 12 families produced by focal hermaphroditic shrubs in FB patch and 23 families in the HB patch.We found hermaphroditic experiencing a high local female frequency self - pollinated at a significantly higher rate that the other group.Fianlly the number of outcrossed seeds was significantly higher in the HB compared to the FB patch, but it was only marginally affected by shrubs gender and it did not depend on the interaction between the two factors.

D.The proportion of seeds fertilized by self and outcross pollen varies widely among species , ranging from predominant self fertilization to exclusive outcrossing.The extent to which individual and population are outcrossing or mating system   can influence the genetic structure of populations, the extent of gene flow ,effective populaltion size and expression for inbreeding depression.