How does the pattern of sampling influence the species-area relationship for datasets spanning a wide range of scales

Background/Question/Methods

In is well known that the spatial arrangement of species strongly influences the shape of the species area relationship (SAR); however, it is not as well documented that the pattern of sample accumulation also can have dramatic effects on the SAR. The purpose of this study was to compare the SAR that was constructed from nested samples and those constructed from linear transects for a wide range of spatial extents. We predicted that the method of construction would have a greater influence on SARs documented at larger extents due to stronger environmental gradients and geographic barriers encountered at large scales. We utilized a collection of small scale quadrat data and large scale survey data (USDA county list of vascular plants and the USGS breeding bird survey) to test our hypothesis.
Results/Conclusions

Species-area relationships constructed using continuous transects accumulate species more rapidly than nested sampling of adjacent areas.  Furthermore, this difference between the two methods of curve construction was greatest for the larger scale survey data.  Our results suggest that the spatial arrangement of sampling is an important element to consider when comparing diversity patterns between studies.