Local ecology and geographic ranges of plants in the Bishop Creek watershed of the eastern Sierra Nevada, California, USA

All species have ecophysiological requirements and tolerances, and both their local niche occupancy and their geographic distribution depend on the availability of suitable habitat (Gaston, 1990). Range sizes have been correlated with a number of variables, including niche breadth, local abundance, body size, growth form, pollination syndrome, and dispersal mode (Bock & Ricklefs, 1983; Brown, 1984; Gaston & Lawton, 1990; Novotny, 1991; Gaston, 1996; Kelly & Woodward, 1996; Pyron, 1999). Most studies have demonstrated a positive relationship between local abundance and geographic range (Bock & Ricklefs, 1983; Gaston, 1990; Pyron, 1999). This correlation may depend on niche breadth, with species that are able to withstand a diversity of environments being successful at achieving high densities in many sites and at occurring throughout a large geographic area (Brown, 1984). Gaston & Lawton (1990) suggest that the correlation between local density and range size depends on the degree to which the habitat sampled, ‘the reference habitat’, resembles the habitat of the surrounding geographic area. Thus, it would be interesting to determine the degree to which physiologically important aspects of the reference habitat are correlated with characterizations of species’ ranges. The characteristics of the geographic range of a species are partially determined by macrotopography and climate. The Department of Biology, California State University, Northridge, CA, USA