Intraspecific competition among Tribolium castaneum in response to crowding

Topics: Interspecific competition, Wheat, Population growth Pages: 8 (863 words) Published: April 27, 2014
Introduction
Competition is an important interaction that occurs between living organisms that co-exist in an environment. All living organisms need certain resources in order to survive and reproduce. These resources include but are not limited to nutrients, food, water, and a space to live in. When these resources become limited in a shared area, organisms are forced to compete with each other for the resources that they need. This competition can occur among individuals belonging to the same species, called intraspecific competition, and also among organisms belonging to different species which is called interspecific competition. At times competition will be direct and obvious but often it can also be subtle and unrecognized without further experimentation. With this study we intend to achieve a greater understanding of the effects of abiotic factors on intraspecific competition of the flour beetles. The effects of competition on these organisms have often led to interesting discoveries of their behavior. In one study, conducted by Sonleitner and Guthrie (1991), they determined that limited resources in a crowded space effects the ovipostion rate of the flour beetles. When beetle population densities become too high for their area, the female beetles respond by lowering their oviposition rates. These condition changes include nutrition depletion, accumulation of dead beetle skin and feces, and the presence of quinone, an irritating substance secreted by adult beetles (Sonleiitner & Guthrie, 1991). This study also mentions the tendency of females to participate in delayed reproduction, where they increase their egg production at a later date when their living space is less crowded and their offspring will have a better chance of surviving. This decrease in ovipostion rate is an important behavior that displays the effects of intraspecific competition on the flour beetles and may be applied to other insects. In another experiment done by Yan and Stevens (1995), the effects of a tapeworm, Hymenolepis diminuta on the beetles was found to have a negative effect on their fitness. Under high-stress conditions it was found that these tapeworms significantly reduced the fitness of both male and female flour beetles by increasing adult cannibalism and therefore decreasing fecundity. Under low stress the parasites did not seem to significantly affect the fitness of their beetle hosts (Yan and Stevens, 1995). This parasitism shows that the susceptibility to parasites was increased when the beetles were under stress, displaying yet another effect of intraspecific competition to look out for in our study. In this particular experiment the objective was to determine whether food limitation and temperature affected population growth dynamics of the flour beetles. These dynamics include fecundity, survival, and population growth rates. We hypothesized that the beetles, under more stress (ambient temperature and limited food), would spend more of their energy on competition for survival than the beetles under less stress (warm temperature and plenty of food). Spending more of their energy on competition would leave less energy to spend on reproduction and therefore, we predicted that the stressed beetle population would decrease over time. The unstressed beetles, however, would have plenty of resources, resulting in less competition and more energy to spend on reproduction. Taking this into account we predicted that the unstressed beetle population would increase over time. To achieve our objectives for this experiment we first set up four groups of beetles and treated each group with a different combination of food availability and temperature conditions. After seven and ten weeks we assessed the beetle populations to measure the beetles’ reactions. Methods

To begin the experiment we separated eighty flour beetles into four groups of twenty. We treated two out of the four groups with high food resources and the other two...
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