A vast number of grassland ecosystem types have become rare in recent years because of urban and suburban expansion, agricultural conversion, exotic flora and fauna, fire suppression, soil stabilization, and natural succession. The State of Nebraska recognizes 69 ecological community types which contain approximately 1,470 plant species and are home to 60 amphibians and reptiles, 80 fish, 400 birds, and 95 mammal species. These ecological communities are also home to tens of thousands of invertebrates including poorly known and even undescribed species. Among these species are twenty-four insects on Nebraska’s Natural Heritage Elements list including the American burying beetle, Nebraska’s only federally endangered insect, four species of tiger beetles, and 18 species of butterflies.
Despite their importance in food webs and their importance as indicators of habitat degradation invertebrates have received relatively little study in Nebraska. Unfortunately this situation is unlikely to change because of invertebrate diversity and abundance, it is both too time consuming and costly to attempt the cataloguing of all species in Nebraska.
In the past twenty years, there has been an increasing focus on using biological indicator species (a subset of taxa which are sensitive to environmental change) not only for the purpose of judging habitat quality, but also to locate discrete areas of unique habitat types. By using biological indicator species as clues to the presence of a unique habitat type, it is easily possible to make surveys for unique ecosystems more efficient and cost-effective. Species associations are particularly important in the assessment of rare habitat types, and once these are known, it is often possible to predict the presence or absence of a given species by the presence or absence of other better-known species.
Several groups of insects include many members which serve as excellent biological indicator species. Of particular interest among these are the butterflies, Order Lepidoptera and beetles, Order Coleoptera.
Among the butterflies are specialist herbivores, which feed exclusively on one or two plant species. These butterflies are useful as indicator species because their presence or absence most often reflects the presence or absence of the host species.
Predaceous beetles, particularly the tiger beetles (Family Cicindelidae), are generalist predators, but often require very strict microhabitats. In addition most of the tiger beetles require disturbance to maintain suitable habitat, and this group can thus be very useful in assessing disturbance frequencies. One advantage in using tiger beetles as indicator species is their occurrence at the predator trophic level, which makes them especially sensitive to habitat change.
Also within the Coleoptera several groups contain small numbers of species which play important roles in the ecosystem. One such group, the carrion beetles (Family Silphidae) are important recyclers which are sensitive to habitat degradation including invasion of exotic plants species and changes in small mammal fauna which they use for feeding and reproduction.
Finally, among the bees and wasps, Order Hymenoptera, ants have become model organisms for assessing biological diversity and habitat changes. Ants are favored because they form long-lived colonies which are very habitat specific.