Brian, I agree that the approach you described is circular and troublesome.
For what its worth, I recently published an article (Brewer and Menzel, 2009. A method for evaluating outcomes of restoration when no reference sites exist. Restoration Ecology 17:4-11) that might be of some interest to you. It uses multivariate statistics to convert presence/absence data of plant species in communities listed and described in flora manuals for a given region to quantitative habitat fidelity or indicator scores. These indicator scores can then be used to calculate weighted averages of abundance or occurrence within given localities to determine the extent to which the community at a given site given contains species indicative of a given habitat interest (e.g., mature forest, anthropogenically disturbed communities, etc.).
One potential problem I've encountered in recommending this approach to animal ecologists is that plant manuals tend to be more precise in the description of the plant communities in which each species occurs (e.g., calcareous hardwood forests, longleaf pine savannas, etc. as opposed to "fields, "forests", "open areas"). At least that's what I've been told by bird and arthropod biologists. This may be because many animal species tend to cue in on structural characteristics of the habitat as opposed to precise compositional characteristics. Also, with birds (and some arthropods), you have the additional complicating factor of migration.
Steve Brewer At 4:18 PM -0500 1/29/09, Brian D. Campbell wrote:
Dear listserv members: I've been reading a lot of literature recently on the effects of fragmentation and land-use conversion from forests to agroforests and have been really troubled by what seems a pervasive issue (at least in my mind); defining the biodiversity value of a human-modified habitat type (e.g. either fragment or agroforest). Almost all studies I've reviewed partition bird communities into categories of "forest species", "rainforest specialists", "agricultural generalists", among others, and proceed to compare these among different land-uses. This is not my issue per se, but rather, I find it very circular if one uses the data/observations they collected in a study to define these groups; e.g. all species encountered in a "control" site of extensive forest were defined as forest species. These make useful and note-worthy observations but if one then proceed to include control sites in a statistical comparison then I think there is major issue with circularity. This also seems to me a very different approach than having defined a priori (e.g. from distribution lists or other literature) a set of forest-candidate species which may or may not be present in any given site surveyed. Have others here found similar issues when reviewing papers dealing with the biodiversity values of secondary forest and agricultural habitats? Brian Campbell
-- Department of Biology PO Box 1848 University of Mississippi University, Mississippi 38677-1848 Brewer web page - http://home.olemiss.edu/~jbrewer/ FAX - 662-915-5144 Phone - 662-915-1077
