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Previous work on gradients of human-altered landscapes has identified golf courses as potentially valuable areas for wildlife conservation. We assessed 6 golf courses in and around Oxford, Ohio that were surrounded by varying degrees of land-use intensity and studied bird communities within these courses to identify factors that promote diverse bird assemblages. We used a Geographic Information System (GIS) and aerial photography to estimate percentages of different land-cover types sur- rounding each course using buffers at scales of 100-1,000 m. We also measured on- site vegetation characteristics within 50 m of the same points used for bird sampling. We used simple linear regressions between each environmental variable and bird community statistics (abundance, species richness, Shannon diversity, and evenness) to determine which variables had the most influence on bird communities. We found that landscapes surrounding golf courses were the most important determinants of bird diversity and on-site variables were relatively unimportant. Specifically, natural land-cover buffers (forests, riparian areas, and open water) promote bird diversity and residential cover reduces diversity, especially in small buffers immediately surrounding courses. Results were similar when we limited the bird data set to Neotropical migrants or to birds with declining population trends. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that area represents the primary explanation for the latitudinal diversity gradient using breeding terrestrial birds of North America, the northern Palearctic, Australia and the Afrotropics as our focal group. We tested two propositions inherent to the area hypothesis: (1) tropical biomes are larger than extra-tropical biomes, and (2) there is a significant species-area relationship for birds at the biome scale of resolution. Using a more realistic definition of biomes which incorporates the effects of both energy and water, we find no support for either proposition, leading us to conclude that the area per se does not explain terrestrial latitudinal diversity gradients. [ABSTRACT FROM AUTHOR]

It is often claimed that we do not understand the forces driving the global diversity gradient. However, an extensive literature suggests that contemporary climate constrains terrestrial taxonomic richness over broad geographic extents. Here, we review the empirical literature to examine the nature and form of the relationship between climate and richness. Our goals were to document the support for the climatically based energy hypothesis, and within the constraints imposed by correlative analyses, to evaluate two versions of the hypothesis: the productivity and ambient energy hypotheses. Focusing on studies extending over 800 km, we found that measures of energy, water, or water-energy balance explain spatial variation in richness better than other climatic and non-climatic variables in 82 of 85 cases. Even when considered individually and in isolation, water! energy variables explain on average over 60% of the variation in the richness of a wide range of plant and animal groups. Further, water variables usually represent the strongest predictors in the tropics, subtropics, and warm temperate zones, whereas energy variables (for animals) or water-energy variables (for plants) dominate in high latitudes. We conclude that the interaction between water and energy, either directly or indirectly (via plant productivity), provides a strong explanation for globally extensive plant and animal diversity gradients, but for animals there also is a latitudinal shift in the relative importance of ambient energy vs. water moving from the poles to the equator. Although contemporary climate is not the only factor influencing species richness and may not explain the diversity pattern for all taxonomic groups, it is clear that understanding water-energy dynamics is critical to future biodiversity research. Analyses that do not include water-energy variables are missing a key component for explaining broad-scale patterns of diversity. [ABSTRACT FROM AUTHOR]