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Introduction
One of the major objectives of the National GAP program is to document the representation of native vertebrate species in regional assessments. In order to meet this objective, we are developing a spatial database of predicted species distributions throughout the state. While we don't have the resources to conduct a complete survey for every species, we do have access to a tremendous knowledge base that allows us to model distributions based on known range and habitat relationships. Currently the analysis includes terrestrial vertebrates, but the long-term goal is to expand the species of interest as time and resources allow.
The composition and structure of the dominant vegetation is an important and easily described measure of habitat for animals (Scott et al. 1993) and has long been used as an indirect indicator of animal distributions (Austin 1991). Other biotic and abiotic factors (i.e. elevation, wetland type, and distance from standing water) can also play a major role in defining a particular species' habitat. Many studies of vertebrate species have been conducted over the years documenting this type of information. In addition, data on known ranges for vertebrate species has also been collected. This includes not only survey data records, but also the cumulative field experiences of biologists who work with these species on a daily basis. If we take a habitat description, break it down into vegetative communities and other environmental factors (e.g. elevation, riparian, edges used, wetland type, etc.), and then identified those areas within a known range, we would be creating a predicted distribution map. That is essentially what we are doing for each terrestrial vertebrate species in Illinois. The final step is to overlay those maps together to get a representation of biodiversity.
Why are we modeling only terrestrial vertebrates? Again, it’s a matter of resources. Realistically, we can only model a subset of all species. Terrestrial vertebrates are a logical choice because we generally know more about their habitat relationships and range extents than those of other taxa. Even so, there are over 400 terrestrial vertebrates to be modeled. The key to filling in the 'gaps' in the documented data is to have a thorough review by experts at every stage.
Species Modeled
The first step is to develop the list of species to be modeled. We used the following criteria to develop a list and then had our reviewers make arguments to either drop or add individual species.
"Terrestrial vertebrates (birds, mammals, reptiles and amphibians) that are known to breed (5 of the last 10 years) and that are regularly occurring non-accidentals in the state of Illinois"
The result is a list of 485 individual species which include:
- 41 amphibians (View List)
- 323 individual birds (48 year round residents, 152 summer residents, 111 winter residents, and 278 migrants) (View List)
- 60 mammals (View List)
- 61 reptiles (View List)
Vertebrate
Distribution Models
To access individual IL-GAP vertebrate distributions, please choose a group below:
Last updated Monday, 08/08/2005 9:48 AM