Bugs, maps, and math...

Landscape ecology of insects in disturbed habitats

Our research in landscape ecology focuses on the effects of human and natural disturbances that modify large scale terrestrial landscapes on both the viability of individual insect species and on overall insect biodiversity. We are particularly interested in examining how movement of invertebrate species affects their ability to maintain populations in disturbed habitats. An important part of this research is determining how different types or intensities of activities within non-habitat areas affect the probability of mortality for different species. Another facet of this research is examining the effects that such large-scale habitat alterations have on the spread of invasive insect species. We are currently using field work on wood-boring beetles (Coleoptera: Buprestidae, Cerambycidae) to look at these effects of disturbance, however, many different insects in different systems could also be used profitably.

Scale and empirical studies

Another major aspect of our research consists of examining the role that spatial scale has in affecting the results of empirical studies. Species respond to their environment at different spatial scales. This suggests that the results of empirical studies are greatly influenced by the scale at which the study is carried out. We use a combination of field work, geographical information systems (GIS) and scaling software to examine the influence of spatial scale on results of empirical studies to understand the influence of scale, examine differences in species' responses, and to inform future empirical studies. Most studies in our lab use these techniques to tune in to the 'signal' or response of the study organism and avoid inappropriate Type II error probabilities. We are also interested in looking at the causes of multiple peaks in response strength to habitat to determine the ecological causes of each peak. The scaling software FOCUS can be found here.

Habitat fragmentation and insect movement

As habitat becomes more fragmented due to habitat loss, organisms may face an increased risk of extinction if recolonization cannot offset local extirpations. The hostility or resistance of non-habitat areas then becomes an important factor influencing future biodiversity in human-disturbed landscapes. We are interested in ways that non-habitat areas influence insect movement between habitats, and how it may influence species extinctions by acting as a selective filter. An important part of such studies is the development of technologies for tracking, or statistics for inferring, the movement of insects across landscapes.

Spatial dynamics of live-tree borer populations

Most ecological studies involve a very brief (1 to several years) snapshot of an ecological system. Animal populations are influenced by a huge number of factors, some of which may not be measured, and most of which probably operate on scales (temporal and spatial) other than the study scales. There is a need for data on animal populations over long time periods in order to better understand the impacts of land use and changes to habitat on species. One way to do this is to survey a given population or set of populations each year for several decades. We are working on another way to accomplish this that we like to refer to as 'larval time travel.' We are using standard dendrochronology techniques to date larval scars of species of longhorned beetles on living trees. The scars of some species are easily recognizable and assignable to the species, and remain visible for up to 60 years or more. We are therefore able to determine the exact year that a species was within a given tree. By combining this information with detailed studies of the trees, forest habitat, and forest maps collected over the same period by other Purdue University researchers, we are able to correlate changes in the borer prevalence and occurrence with changes to the forest habitat.