Study Questions Weeks 5-10 Weeks 5-6 1. During what time of year did fires occur in the US Southeast previous to widespread European settlement, and why was this so? From the standpoint of 1) burning practice and 2) vegetation management, why is it important to burn longleaf pine forests at this time of year? Natural fires due to lighting striking trees occurred primarily during the growing season before European settlement and the development of fire suppression as a standard practice. Current burning practices refrain from burning during the growing season in order to minimize risk of human associated damage. Fires instead are burned low and cool during the winter months between growing seasons. These small winter fires are not sufficient to reduce shrubbery overgrowth and therefore allow buildup and overcrowding of the forest floor. This reduces the amount of herbaceous species diversity, limits habitat for a number of other species (i.e. gopher tortoises, reticulated salamanders), and affects the overall species composition of the forest. To maintain the natural species composition and the grass dominated floor of long-leaf pine forests, growing season burns are necessary to reduce shrub overgrowth. 2. Briefly describe the approaches and essential findings of two experimental tests of Island Biogeography Theory. Do the findings support or challenge the theory? A. Experimental Zoogeography of Islands: Effects of Island Size- Daniel Simberloff - Studied variably sized mangrove islands of the coast of Florida and demonstrated that the species number increases with island size and that equilibrium was obtained after conditions were altered. It was also demonstrated that consistent with Equilibrium Theory of Island Biogeography (ETIB), smaller islands exhibited faster turnover rates. Done by removal of species from islands and observance of species re-colonization and also by inducing saturated conditions to the islands and observance of extinction rates. B. A survey of national park habitat and deforestation of surrounding areas by William Newmark in the 1980s showed that fragmentation of habitat into “habitat islands” leads to increased extinction rates and a decreased colonization rate that results in a reduction of species diversity. This is directly consistent with the predictions of ETIB. 3. What is meant by SLOSS? How do the predictions of Island Biogeography Theory bear on the SLOSS debate? Briefly describe the empirical data from habitat reserves in North America which were presented in class as non-experimental support for IBT and its SLOSS recommendation. SLOSS stands for Single Large Or Several Small. The ETIB posits that a single large area of habitat will support more species than a single small area. This has been supported by such studies as discussed in question 2 part A. However, what is a better conservation investment, one large area of habitat or several small areas that add up to the same amount of total area as the single large area? This is the SLOSS debate. The ETIB leans toward the single large area based on the fact that as stated above large areas can support more species. In the case where multiple small areas overlap to form one large area (nestedness), it is often the consensus that this type of single large area would be a better conservation investment because itcontains the species present in the several small areas as well as other species that are ONLY found in larger areas. Empirical data from both sides was presented in class: Single large: The occurrence of small mammal species in montane habitats of the southern Rocky Mountains - These data provide evidence that in a nested area of high species richness you get both the species found in less rich areas (several small) plus more just as described in the previous paragraph. Several small: Data from surveys on the Hawaiian and Galapagos archipelagos. - These data show that in both archipelagos collections of smaller islands contain more total species than a single large island of equal area. 4. Briefly describe one argument for each side (a total of 2 arguments) of the SLOSS debate which turns on information about species identities not taken into account by IBT, as well as the empirical data described in class as supporting each argument. Single Large: - The nested argument is probably the best argument but there is also decreased edge effects due to less edges present in one big area as opposed to more edge length present in many smaller reserves. Several Small: - Overall more species found in several small areas when compared to one large area. Less overlap could possibly separate species from detrimental factors such as disease, predation. 5. Provide formulae for the area and circumference or total edge length of a circle or square, respectively. Derive a formula for the ratio of edge to area and graph this ratio as a function of size. Briefly explain the conservation implications of your graph: how does it relate to SLOSS? Area of a circle: π r2 Circumference of a circle: 2 π r Circumference(c)/unit of area(a): 2π(r)/π(r)2= 2/r r c/a small reserve large reserveArea of a square: s=side length: s2 Edge length of a square: 4s Edge length(e)/unit area(a): 4s/s2= 4/s These equations and the resultant graphs show that for a square or rectangular reserve there is much more edge length per unit area than present in a circle at any relative size. This has to be taken into account when designing protected areas because of edge effects that can alter the effectiveness of a protected area by affecting individuals that live close to the edges with factors such as increased exposure to changing climate and potentially increased vulnerability to fire, predation, parasitism, human contact, etc. Several small protected areas have much greater vulnerability to edge effects because there is logically more edge habitat in several small areas as opposed to a single large area. 6. What is a metapopulation? Describe the dynamics of a metapopulation, in plain English (avoiding scientific jargon). What is the primary commonality with the dynamics of species on oceanic islands? What are two crucial differences? The definition of a metapopulation is: A collection of spatially isolated subpopulations of the same species that interact at some level. In a metapopulation there is a continual dynamic of losses and gains of