Brian, I think this is part of the larger problem generated by trying to determine habitat preferences by where you find organisms. Distributions are where organisms persist, not where they prefer to be or where their fitness is highest; they are the outcome of the interactions between species-environment, as well as intraspecific and interspecific, interactions. This goes back to Fretwell and Lucas and the ideal free distribution, and is supported by a growing body of experimental work on habitat selection that demonstrates how important species interactions are in determining habitat selection. Habitat suitability is not determined solely by habitat type, but to large extent by who else is there. Assuming that current distributions define a species preferred or critical habitat is potentially hazardous, especially when dealing with conservation or restoration.
William J. Resetarits Program Director Ecological Biology Cluster Division of Environmental Biology National Science Foundation 4201 Wilson Blvd., Suite 635 wrese...@nsf.gov Voice (703) 292-7184 Fax (703) 292-9064 -----Original Message----- From: Ecological Society of America: grants, jobs, news [mailto:ecolo...@listserv.umd.edu] On Behalf Of Brian D. Campbell Sent: Thursday, January 29, 2009 4:18 PM To: ECOLOG-L@LISTSERV.UMD.EDU Subject: [ECOLOG-L] Analysis of habitat specificity and circular logic 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
