Browsing by Subject "species distribution model"

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    Grasshopper Sparrow Distribution, Habitat Associations, and Use as an Indicator Species for Grassland Birds in Southwestern Minnesota
    (2016-02) Elliott, Lisa
    Reductions in grassland habitat due to agricultural conversion have caused severe declines in populations of many grassland bird species. Effective grassland bird conservation requires efficient use of limited funding. Techniques advocated by conservationists include: 1) focusing management activities on a single indicator species that represents the habitat and management requirements of other species, 2) managing existing preserved habitat for appropriate vegetation structure to ensure desired population responses, and 3) identifying areas of high value for species of interest through remotely sensed data. In Minnesota, the Grasshopper Sparrow (Ammodramus savannarum) has been identified as a species of conservation interest and potential management indicator species. My objectives were to: 1) assess the extent to which the Grasshopper Sparrow and seven other passerines might serve as grassland bird indicators, 2) identify local-scale habitat associations of these species, and 3) develop and assess the suitability of landscape-scale species distribution models for the Grasshopper Sparrow. To address these objectives I conducted bird and vegetation surveys on 71 grassland sites in southwestern Minnesota during 2013–2014, examined patterns of community composition and species-specific habitat associations, and modeled Grasshopper Sparrow density. I found that the Grasshopper Sparrow could reasonably be used as a management indicator for five of seven grassland species. Inclusion of a second indicator species could improve representation of the entire group of species. Grasshopper Sparrow density was positively associated with distance to trees and negatively associated with vegetation height, vegetation density, and percent tree cover. Grasshopper Sparrow density also exhibited nonlinear relationships with litter and percentages of shrub, dead vegetation, and bare ground cover. Judicious selection of explanatory variables offered an efficient approach to determination of species’ habitat requirements and predicting their occurrences. Finally, using both local-scale habitat and remotely sensed landscape variables produced a better model than using variables at either scale alone.
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    History, dispersal limitation, and environment shape the current and future ranges of forest herbs of the Southern Appalachians
    (2018-08) Erlandson, Stephanie
    As climate changes, favorable climatic conditions for some species might cease to overlap with their current geographic ranges, due to low dispersal rates, barriers to dispersal, or lack of microhabitats, among others. Here, we focus on herbaceous paleoendemics plants in the Southern Appalachian Mountains, possibly threatened by climate change. We developed species distribution models to identify areas of predicted current suitable habitat, both inside and outside of ranges, and evaluated the extent to which these areas shift or move northwards under various future climate scenarios. We discovered predicted suitable habitat in northern areas disjunct from current ranges, suggesting dispersal limitation. We also found severe reductions in predicted suitable habitat under future climate scenarios, both in geographic extent and in percent suitability. Results from models created using more widespread species reinforced these results. Thus, it is imperative to employ conservation efforts in order to prevent species declines or extinctions.
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    The rise and fall of the Ruffe (Gymnocephalus cernua) empire in Lake Superior
    (2017-12) Gutsch, Michelle
    Invasive species are a global problem, impacting property, habitats, ecosystem function, and native species. Our ability to predict future habitat and spread of aquatic invasive species is limited because it is challenging to collect and integrate information regarding life history, movement, and habitat, especially across continents. Ruffe (Gymnocephalus cernua), a demersal, invasive fish, has caused substantial ecological damage. Given the potential for ecological impacts, such as native fish declines, ongoing concern regarding the spread of Ruffe in the Laurentian Great Lakes is warranted. But there are significant research gaps regarding life history, movement, and Ruffe distribution in the native and non-native range. Therefore, the overall goals of my dissertation were to acquire life stage-specific data for Ruffe, including dispersal, seasonal, and spawning movements and characterize their life cycle and to develop a lake-scale species distribution model at 30-m resolution. Regarding the first goal, I found that Ruffe has characteristics that allow them to adapt to a range of environments, including rapid maturation, relatively long life and large size, batch spawning, genotypic and phenotypic plasticity, tolerance to a wide range of environmental conditions, broad diet, and multiple dispersal periods. To address the second goal, I developed a species distribution model for Lake Superior because Ruffe has established in the lake but is not yet widespread. I found that a variety of species distribution models constructed to predict Ruffe suitable habitat based on environmental data resolved to a variety of scales all performed similarly but varied substantially in the area of habitat predicted, particularly the offshore habitat area classified as suitable. I conclude that to interpret the outputs of the Ruffe species distribution models, both model performance and the ecology of Ruffe must be considered to better characterize its fundamental niche. Broadly, I demonstrate the importance of synthesizing the life stage-specific biology and distribution of an invasive species with species distribution models to advance our ability to predict the future habitat of an invasive species.