20 October 2014
Introduction Species that lack a lot of genetic variation are thought to be more vulnerable to extinction from natural or human-caused changes in their environment. Awareness of global environmental change gives some priority to the study of biodiversity and its maintenance. “Biodiversity typically refers to the number and variety of distinct organisms living on the Earth even though individual species are just one level of organization living in nature” (Gibbs 2006). In the evaluation of biodiversity, invertebrates take an important role. Spiders can be used to provide an interesting model to represent invertebrates. They are predators, they are taxonomically diverse, they are easy to catch, and can inhabit a variety of ecological conditions. With that said, spiders can be used to help understand the concept of biological diversity as it occurs at various taxonomic levels through the classification of different life forms. Biodiversity is a measure that combines species richness and evenness across a species. It is often measured because diversity is observed as proportional to ecosystem health (Magurran 2004). In general, diverse communities are believed to have increased stability, increased productivity, and resistance to invasion and other disturbances. Species richness is a measure of the number of different kinds of organisms present in a particular area. For example, the number of species per sample is a measure of richness. The more species present in a sample, the richer the sample. However, diversity depends not only on richness, but also evenness. Species evenness compares the similarity of the population size of each of the species present. It’s a measure of the relative abundance of the different species making up the richness of an area. A community dominated by one or two species is considered to be less diverse than one in which several different species have a similar abundance. As species richness and evenness increase, the diversity within a community will increase. Once species richness and evenness are taken into account, the Simpson’s Diversity Index can be used to quantify the biodiversity of a habitat. The Simpson’s Reciprocal Index measures the probability that two individuals randomly selected from a sample will belong to the same species. The higher the value, the greater the diversity. In order to analyze community distinctiveness, the Jaccard coefficient of community similarity is used to contrast and compare uniqueness between pairs of sites.
In order to manage habitats, a study was conducted using spider collections to understand how organisms are affected by their environment, distinctions between different species, the concepts of species richness and diversity, and how to measure biodiversity. I believe that the species found across the different areas will not be equally common because their environment and surroundings have an effect on how they live. The findings from the study will allow a decision to be made about conservation priorities in order to successfully manage a habitat.
Materials and Methods
The principle of this method is to compare knowledge of the distribution of species with the composition of the community desired to test. The study took place in a woodland area located near West Rock at Southern Connecticut State University, where many spider webs were found hanging from bushes and tree branches. The study was conducted on August 8th, 2014 at 4pm. The air was muggy and the temperature was 75 degrees Fahrenheit. For collecting spiders, several methods were used. The first is known as the sweeping and beating method. A sweeping net was used to sweep through grass and plants to pick up spiders. A beating net was used to beat branches of trees and bushy areas in order to knock down spiders and then collect any resulting ground dwellers. (Filmer) A hand-to-jar method was also used to gather spiders. A