| The Role of Interspecific Interactions in Determining the Winter Distribution and Abundance of Emberizid Sparrows (2009) | |||||||||||||
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| Species ranges are influenced by interactions with both the abiotic and biotic environment. Biotic interactions may be positive, in which one individual benefits from the interaction, or negative, in which one individual is harmed by the interaction. Biotic interactions have been shown to influence species distributions at small scales, but their importance at larger scales is not well understood. The purpose of this study was to determine whether interactions between closely-related species influence species distributions at large (continental) scales. I looked at the relationships between abundances of closely-related species of emberizid sparrows in their eastern North American winter ranges between the years 1996 and 2007. Based on the hypothesis that ecologically-similar species should compete for resources, assuming that closely-related species are ecologically similar, I predicted that there would be a negative relationship between closely-related species. Contrary to my predictions, I found a positive relationship between the abundances of closely-related species. These positive relations suggest that negative interactions among species may not cause segregation of wintering ranges among closely-related species, at least at the spatial scale I examined. Instead, the positive relationship between closely-related species, after statistically controlling for environmental variables, suggests either a positive association between the species which could be due to anti-predator benefits or increased foraging efficiency, or an attraction of closely-related species to similar habitats or resources which may be due to recent ancestry and shared ecological traits. | |||||||||||||
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