Learning to Measure Biodiversity: Two Agent-Based Models That Simulate Sampling Methods & Provide Data for Calculating Diversity Indices

Abstract

[ILLUSTRATION OMITTED] There is certainly no substitute for experiencing firsthand. Nothing could be more effective than a wilderness experience to demonstrate the importance of conserving biodiversity. That said, computer models have several features that are helpful in understanding how is measured. For one, they are easily used when natural resources, transportation, and time constraints limit the use of field laboratories. Moreover, computer models can generate realistic data, in large quantities, that can be used to calculate different indices of diversity. Here we provide background on concepts and measures of biodiversity, and present two agent-based simulation models that can be accessed from the Internet. One model simulates stream sampling for invertebrate biodiversity, while the other simulates sampling for plant diversity. The stream sampling model is simpler, and effective as a demonstration as well as for generating data for analysis. It is designed to be used at the high school and college levels. The plant sampling model is more advanced, and is useful in teaching experimental design and to generate data for advanced analyses. It is appropriate for the college level, or AP biology. * Background on Biodiversity It is common to hear ecologists talking about biodiversity, particularly in terms of conservation biology. Biodiversity is a frequently used term, and is considered to refer to something important, yet, it is often unclear exactly what is being discussed. In fact, biodiversity can refer to many things, and has man?, specific definitions. The most common definition of biodiversity, sometimes called species diversity, refers to the number of different species in a given area. The greatest by this measure would he the number of different species found in tropical rainforests, and is estimated to be in the millions. Biologists sometimes refer to the diversity within a particular group or taxon. For example, the southern Appalachians are a world hotspot for salamander diversity. Several indices of species diversity are discussed below. Biodiversity, in the broad sense, can also refer to variation within species, or among populations. Many species have populations which can be differentiated by gene frequencies, morphology, or behavior. Typically this occurs within species having large ranges. Consider, for example, the extraordinary differences among human populations across the globe. This variation reflects underlying differences in allele proportions among populations and is called genetic diversity. Genetic diversity is of special concern regarding endangered species because small populations tend to lose genetic diversity rapidly through random genetic drift or bottlenecks. Without genetic diversity, populations lose their ability to adapt to changing environments. An extreme example of a species with low genetic diversity is the cheetah. Cheetahs are so genetically similar that many can accept skin grafts from unrelated individuals without tissue rejection (O'Brien et al., 1985). On a larger scale, we can consider ecosystem diversity. In this case, we are not considering individual species, but rather a species assemblage in a particular habitat. Ecosystem diversity is a broad concept, encompassing levels of ecological organization above species (e.g., habitat, community, or ecosystem). An example of a major threat to ecosystem diversity in the U.S. is the loss of wetlands to development. It is difficult to quantify ecosystem diversity, because the edges of habitat patches and communities are difficult to define. However, it can be argued that the most natural way to preserve all levels of is to protect as much and as varied habitat as possible, and then let nature take care of the rest. * Measures of Biodiversity Though is a conceptually broad subject, there are numerous quantitative indices of biodiversity. …