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Reasoning about the factors underlying habitat connectivity and the inter-habitat movement of species is essential to many areas of biological inquiry. In order to better describe and understand the ways in which the landscape may support species movement, an increasing amount of research has focused on identification of paths or corridors that may be important in providing connectivity among habitat. The least-cost path problem has proven to be an instrumental analytical tool in this sense. A complicating aspect of such path identification methods is how to best reconcile and integrate the array of criteria or objectives that species may consider in traversal of a landscape. In cases where habitat connectivity is thought to be influenced or guided by multiple objectives, numerous solutions to least-cost path problems can exist, representing tradeoffs between the objectives. In practice though, identification of these solutions can be very challenging and as such, only a small proportion of them are typically examined leading to a weak characterization of habitat connectivity. To address this computational challenge, a multiobjective optimization framework is proposed. A generalizable multiobjective least-cost path model is first detailed. A non-inferior set estimation (MONISE) algorithm for identifying supported efficient solutions to the multiobjective least-cost path model is then described. However, it is well known that unsupported efficient solutions (which are equally important) can also exist, but are typically ignored given that they are more difficult to identify. Thus, to enable the identification of the full set of efficient solutions (supported and unsupported) to the multiobjective model, a multi-criteria labeling algorithm is then proposed. The developed framework is applied to assess different conceptualizations of habitat connectivity supporting amphibian movement in a wetland system. The results highlight the range of tradeoffs in characterizations of connectivity that can exist when multiple objectives are thought to contribute to movement decisions and that the number of unsupported efficient solutions (which are typically ignored) can vastly outweigh that of the supported efficient solutions., Competing Interests: The authors have declared that no competing interests exist.

Aquatic habitat features can directly influence the abundance, species richness, and quality of juvenile amphibians recruited into adult populations. We examined the influences of within-wetland slope, vegetation, and stocked mosquito fish (Gambusia affinis) on amphibian metamorph production and species richness during the first two years post-construction at 18 experimental wetlands in northeast Missouri (U.S.A.) grasslands. We used an information theoretic approach (AICc) to rank regression models representing total amphibian metamorph production, individual amphibian species metamorph production, and larval amphibian species richness. Total amphibian metamorph production was greatest at shallow-sloped, fish-free wetlands during the first year, but shallow-sloped wetlands with high vegetation cover were best the second year. Species richness was negatively associated with fish and positively associated with vegetation in both survey years. Leopard frog (Rana blairi/sphenocephala complex) metamorph quality, based on average metamorph size, was influenced by slope and the number of cohorts in the wetland. However, the tested variables had little influence on the size of American toads (Bufo americanus) or boreal chorus frogs (Pseudacris maculata). Our results indicate that wetlands designed to act as functional reproductive habitat for amphibians should incorporate shallows, high amounts of planted or naturally established vegetation cover, and should be fish-free.

Waste sorts were conducted during each of the four quarters (or seasons) of 1996 at the City of Columbia Sanitary Landfill. A detailed physical sampling protocol was outlined. Weight fractions of 32 waste components were quantified from all geographic areas that contribute to the Columbia Sanitary Landfill using a two-way stratification method, which accounted for variations in geographical regions and seasons. Comparisons of solid waste generated between locations and seasons were conducted at the 80% confidence level. The composition of the entire waste stream was 41% paper, 21% organic, 16% plastic, 6% metal, 3% glass and 13% other waste. Paper was the largest composition and glass was the smallest composition for all geographical regions. The result of this study was also compared with a 1987 Columbia, Missouri study conducted by EIERA (1987), with studies conducted in other states such as Minnesota, Wisconsin, Oregon and with national study conducted by the USEPA (USEPA 530-R-96-001, PB96-152 160. US Environmental Protection Agency, Office of Solid Waste, Washington, DC). The results of studies from other states are different from this study due to different local conditions, different methodologies and a different scope. There was a small (5%) increase in per capita weight from 1987 to 1996. The total per capita weight in the present study was 60% greater than the national per capita weight reported by the USEPA (1996) due to that the USEPA report excluded industrial, construction and certain commercial waste. The total per capita weight agrees with the national per capita weight for municipal waste reported by Tchobanoglous (1993), which included industrial, construction and commercial sources. The geographical and seasonal effects on the waste composition are evaluated and discussed. Statistical analysis indicates that waste characteristics are different among geographical regions and seasons. The potential for waste recovery and reduction is also discussed.