Monday, September 2, 2019
Niche Wars David Scott Smith-3/27/2013 Introduction: This report discusses an experiment to study the relationship between the ecological niche and competition. The hypothesis formulated states that if competition traits are identical and resources are abundant than multiple species will be able to coexist, and if one species has an advantage over the others than this species will be more likely to out compete another species for resources. The objective of this experiment is to use a simulation model of a rabbit pen containing four different Ã¢â¬Å"speciesÃ¢â¬ of rabbits.The model establishes rules for each species that are based on a number of important characteristics reflecting their ecological niches and their competitive abilities. These characteristics include how far rabbits can see (to find food), how fast they can hop (to acquire food), how much energy they use each day just to stay alive, how much energy they must accumulate before reproducing, and how much energy they absorb from each type of food they eat. This simulation model is Ã¢â¬Å"parameterizedÃ¢â¬ by assigning values to the variables for the rules.This experiment relates very closely to the competitive exclusion principle sometimes referred to as Gause's Law of competitive exclusion or just Gause's Law, which states that two species that compete for the exact same resources cannot stably coexist. One of the two competitors will always have an ever so slight advantage over the other that leads to extinction of the second competitor in the long run. Methods: In this experiment, there was 4 different rabbit species (black, white, red, brown) that were competing over 1 resource (lettuce).The species had different characteristic settings that could be adjusted in the attempt to have all 4 species coexisting together. These characteristics include how far rabbits can see (to find food), how fast they can hop (to acquire food), how much energy they use each day just to stay alive, how much e nergy they must accumulate before reproducing, and how much energy they absorb from each type of food they eat. Also there was parameter setting determining how much food was grown and the location of the food.The first step of this exercise was determining how competitive exclusion affected the species when a critical resource is limited in the environment. The modification to increase/decrease the amount of lettuce (the limiting resource) available each week was ran 3 different times set on (2,4,8). Next changing the characteristic settings for each species was looked at to determine what would account for the best coexistence to exist. The white species energy level for black rabbits was changed to 4. The black rabbitÃ¢â¬â¢s energy level for white was also changed to 4.The brown rabbitÃ¢â¬â¢s energy level for red rabbits was changed to 4. The red rabbitÃ¢â¬â¢s energy level for brown rabbits was also changed to 4. By making certain rabbits predators on other rabbits it allow s for 2 species to coexist with one another once the preyed upon species went extinct. The amount of lettuce per week was also doubled than tripled and finally quadrupled to see how this change affected the species. Results/Discussion: Changing the species characteristic settings allowed for 2 species to coexist with one another but that is the best I could achieve.When using the predation characteristic it helped the species stay near their carrying capacity which allowed them to be able to coexist. The predation characteristic is highly likely in nature and is most likely one of the key factors contributing to the selection of certain habitats and niches. When competition traits were all identical and resources were increased to be abundant than multiple species were not able to coexist and most went extinct because they over shot their carrying capacities which disproved part of the initial hypothesis.When all four species were biologically identical, it was impossible to correct ly predict which species would survive competition but when one or two species were given an advantage you could predict which species would survive the longest. Conclusion: Different characteristics of species allows for the types of niches that can be occupied and whether or not they can be coexisted for example a food specialist will have anatomical and physiological adaptations that allow it to acquire and extract energy and nutrients from one food source extremely well, but will be at a disadvantage if that food source runs low.A food generalist may not acquire as much energy from the specialistÃ¢â¬â¢s preferred food, but will be able to make up for that by consuming other kinds of food. We can easily envision circumstances in which either species might outcompete the other. To achieve coexistence of species the carrying capacities of certain species must not be overshot and remain constant.