We quantified the sensitivity of predicted rates of growth and consumption to parameter variation for models of yellow perch (Perca flavescens), largemouth bass (Micropterus salmoides), and alewife (Alosa pseudoharengus). We used statistical analyses of the results of Monte Carlo simulations to rank parameter importance. The order of parameter importance was model specific, although the results emphasized the need for accurate estimation of the realized fraction of maximum consumption rate (P) and allometric parameters for consumption (a1, b1) and respiration (a2, b2). Excretion and egestion parameters contributed little to prediction errors. The Monte Carlo methods were used to examine the relative importance of parameter variation and diet composition, an external forcing function, on forecasts of alewife growth. If standard deviations of model parameters were known within 2% of their expected values, uncertainty in diet composition could contribute as much as 47% of the variance in predicted alewife weight. When standard deviations of model parameters are realistically defined, diet uncertainty contributed less than 10% of the variance in predicted weight.

SynopsisWe compared ecological and morphological patterns among cichlid faunas from three different biotic regions : the Rfo Tortuguero/Rio Sarapiquf in Costa Rica, the Rfo Apure drainage in Venezuela, and the Upper Zambezi drainage in Zambia . Cichlids comprise 19 percent of the fish fauna in the Tortuguero and Upper Zambezi drainages and 6 .5 percent in the Apure drainage. Cichlid faunas exhibited similar patterns of habitat and food resource utilization, although vegetation-dwelling is more common and detritivory and herbivory are rarer in the Apure fauna . We hypothesize that South American ostariophysan fishes were more preadapted than cichlids to exploit detritivore and herbivore niches . The Zambezi cichlid fauna shows less ecomorphological diversification than the other two faunas, even though the degree of dietary diversification is similar among faunas . Chaetobranchus flavescens from the Venezuelan fauna is the only species that specializes on zooplankton as an adult, and algae grazing (Neetroplus nematopus) and specialized fruit feeding ('Cichlasoma' tuba) were represented only in the Costa Rican fauna. Based on the most recent hypothesized phylogeny for the family Cichlidae, we identified numerous interfaunal ecomorphological and feeding niche convergences . Patterns of ecomorphological divergence in relation to cladogenesis indicate a faster rate of evolutionary niche diversification in Central American cichlids compared with the two other faunas .

The vulnerability of India and Indian states to climate change was assessed using the Vulnerability-Resilience Indicator Prototype (VRIP). The model was adapted from the global/country version to account for Indian dietary practices and data availability with regard to freshwater resources. Results (scaled to world values) show nine Indian states to be moderately resilient to climate change, principally because of low sulfur emissions and a relatively large percentage of unmanaged land. Six states are more vulnerable than India as a whole, attributable largely to sensitivity to sea storm surges. Analyses of results at the state level (Orissa, and comparisons between Maharashtra and Kerala, and Andhra Pradesh and Himachal Pradesh) demonstrate the value of VRIP analyses used in conjunction with other socio-economic information to address initial questions about the sources of vulnerability in particular places. The modeling framework allows analysts and stakeholders to systematically evaluate individual and sets of indicators and to indicate where the likely vulnerabilities are in the area being assessed.

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The interaction of large—scale fire, vegetation, and ungulates is an important management issue in Yellowstone National Park. A spatially explicit individual—based simulation model was developed to explore the effects of fire scale and pattern on the winter foraging dynamics and survival of free—ranging elk (Cervus elaphus) and bison (Bison bison) in northern Yellowstone National Park. The Northern Yellowstone Park (NOYELP) model simulates the search, movement, and foraging activities of individuals or small groups of elk and bison. The 77 020—ha landscape is represented as a gridded irregular polygon with a spatial resolution of 1 ha. Forage intake is a function of an animal's initial body mass, the absolute amount of forage available on a site, and the depth and density of snow. When the energy expenditures of an animal exceed the energy gained during a day, the animal's endogenous reserves are reduced to offset the deficits. Simulations are conducted with a 1—d time step for a duration of 180 d, °1 November through the end of April. Simulated elk survival for three winters (1987—1988; 1988—1989; 1990—1991) agreed with observed data. A factorial simulation experiment was conducted to explore the effects on ungulate survival of fire size, fire pattern, and winter severity during an initial postfire winter (when no forage is available in burned areas) and a later postfire winter (when forage is enhanced in burned areas). Initial ungulate population sizes were held constant at 18 000 elk and 600 bison. Winter severity played a dominant role in ungulate survival. When winter conditions were extremely mild, even fires that affected 60% of the landscape had no effect on ungulate survival during the initial postfire winter. The effects of fire on ungulate survival become important when winter conditions were average to severe, and effects were apparent in both the initial and later postfire winters. The spatial patterning of fire influenced ungulate survival if fires covered small to moderate proportions of the landscape (e.g., 15% or 30%) and if winter snow conditions were moderate to severe. Ungulate survival was higher with a clumped than with a fragmented fire pattern,suggesting that a single, large fire is not equivalent to a group of smaller disconnected fires. The interaction between fire scale and spatial pattern suggests that knowledge of fire size alone is not always sufficient to predict ungulate survival.