Many living organisms, including plants, invertebrates, birds, mammals, fishes, amphibians and reptiles, have been employed effectively as indicator species (IS) for monitoring ecosystem dynamics and environmental changes. Recently, the use of IS has been criticized for lacking robust methods to quantify their effectiveness in achieving monitoring goals. In addition, the Indicator Value index (IndVal), one of the most widely-used techniques for identifying appropriate IS does not account for detection or occupancy probabilities, or consider the association between proposed indicators and monitoring context.
I introduce a multi-metrics index that I call Indicator Species Potential (ISP). The ISP quantifies the efficacy of indicator species in classifying sites, monitoring ecological changes, and assessing desired management conditions. The ISP is the average of three metrics including occupancy probability, abundance specificity, and detection probability. I suggest that the ISP provides a reasonable way to assess the effectiveness of an indicator species for monitoring environmental change. Through simulation and an application to real data, I illustrate the use of the ISP.
Results/Conclusions:
Simulated data on response of small mammals to habitat restoration shows differences between species chosen by ISP and by IndVal. When applied to salamanders as potential indicators of changes in forests in Massachusetts, ISP suggests that Plethodon cinerus is a reasonable IS for ecological change in hemlock stands whereas Notopthalmus viridescens is a potential IS in mixed hardwoods.
Overall, the ISP shows promise as a method for summarizing ecological and statistical information (i.e. multi-metrics) about potential IS in a single value. In particular I showed the theoretical ecological and methodological criteria these describe the best indicator species that ecologists and conservation biologists can use to guide their decisions in monitoring habitat changes but also I demonstrated the importance of having quantitative, multidimensional, cost-effective measure to evaluate the potential of any selected indicator species. Finally, these findings are expected to provide ecologists and conservation biologists with a protocol to improve the application of indicator species method in ecological monitoring in general as well as promote and encourage the use of multimetrics to better evaluate indicators potential to reflect changes in such complex ecosystems.