Question

1. You are conducting an experiment to examine genetic variation and local adaptation in populations of Cypripedium montanum (Mountain Lady’s Slipper, Orchidaceae), which occur at high elevation in open woods in the Northwest US and Canada. You have two sites: one is in Oregon near Three Sisters and the other is in the North Cascades in Washington State.

1. How might you determine the extent of gene flow between your populations across latitude and whether one population has been through a bottleneck? Explain your answer.
   
2. How might you determine whether local adaptation has occurred, and what does this mean in terms of evolutionary ecology?
   
3. If you found that local adaptation occurred, nutrient availability might influence plant fitness, potentially causing this local adaption. Explain what types of nutrient availability are most likely to affect your plants and how you might test for nutrient limitation.

Answer 1

1.

a.

If gene flow occurs between two populations, we can see some new phenotypes. This is because the two populations are too far and must have adapted to their environmental conditions and hence have slightly different phenotypes. So, when some of the animals reach the other population, those genes are addaed to the population and new phenotypes can be seen. This disturbs the allele frequency of the original population. Any time such gene flow happens, allele frequency is disturbed.The population is said to be evolving due to change in allele frequencies. More alleles in a population for a particular gene there will be more variety in the population. Increased variety will help in the survival of the organisms and prevent it from getting extinct.

Genetic bottle neck is the phenomenon when there is vary little diversity in the organisms and very few individuals are also present which might have occured due to some environmental reasons. If the population survives from such a bottle neck, the resulting individuals will be having very less variability in the population as most of their alleles must have got destroyed due to the death of the organisms.

So, if the population is having less variability, we can say that the population has undergone genetic variability. AFter genetic bottle neck, the composition of the population will be very different from that of the original population.

b. Local adaptations help the organism to survive and reproduce efficiently in the surroundings. Adaptations are due to natural selection of the already existing variant in the population. New variants arise due to mutations of the DNA. These mutations bring new phenotypes and if they give survival advatage to the organism, they get selected during the course of time leading to adaptations. Adaptations can be understood by comparing the phenotypes of the two populations in their original location. If they differ in certain traits and are present only in one of the populations and giving the population the survival advatage, we can consider that the adaptations have occurred in the population.

c. At high altitudes certain nutrients will be limited because fo the flow of water or snow which might carry the nutrients from the soil away. It is found that the the soils are deficient in important nutrient su ch as Nitrogen. This limits the plant growth in high altitudes. Nitrogen is available abundantly in the air. But plants can take only solid nitrogen in the form of Nitrates and ammonia. The solid nutrients which are solble can get carried away due to rain and deplete the soil of the nutrient. Reduced plant growth in the region can be tested by supplying higher amounts of the nutrient and studying the growth of the plant.