The ability to use monitoring data to answer questions about how butterflies are impacted by a changing environment is a critical component of NAB-Net. Most groups monitor for two key reasons: 1) to educate and recruit more people into the ranks of butterfly enthusiasts and 2) to track changes in butterfly populations over space and time.
To achieve this second goal, we need the ability to answer specific questions like: Are population sizes changing over time? Do specific human activities influece butterfly population levels? Can we link changing populations to specific changes in the environment? Monitoring data is the only source to be able to answer these questions on large scales and over long time periods. However, the fact that protocols tend to be more casual, survey placement less "random" (or at least stratified), and experience levels more variable - adds substantial noise to data that is already noisy from the natural fluctuations of butterfly populations. Further - the sheer volume of data, while a goldmine for answering questions, can be difficult to handle.
We work with a wide range of scientists to continue development of rigorous methods to better understand the biological patterns underlying these data sets. As the field of statistics grows and changes along with the questions of the highest priority to researchers, conservationsists and land managers - the analytical challenges are always shifting as well.
In 2022, our network began collaborating with the USGS sponsored Status of Butterflies in the United States working group, contributing our valuable monitoring data to a nationwide assessment of butterfly diversity trends.
Some analytical projects we have engaged with include:
Developing yearly indices and identifying population trends across time
Accounting for asynchrony in population counts
Incorporating temperature dependence into phenological models
References:
Baskerville, G. L., & Emin, P. (1969). Rapid estimation of heat accumulation from maximum and minimum temperatures. Ecology, 514-517.
Calabrese, J. M. (2012). How emergence and death assumptions affect count-based estimates of butterfly abundance and lifespan. Population ecology, 54(3), 431-442.
Matechou, E., Dennis, E. B., Freeman, S. N., & Brereton, T. (2014). Monitoring abundance and phenology in (multivoltine) butterfly species: a novel mixture model. Journal of Applied Ecology. doi: 10.1111/1365-2664.12208
Soulsby, R. L., & Thomas, J. A. (2012). Insect population curves: modelling and application to butterfly transect data. Methods in Ecology and Evolution, 3(5), 832-841.
Zalucki, M. P. (1982). Temperature and rate of development in Danaus plexippus L. and D. chrysippus L.(Lepidoptera: Nymphalidae). Australian Journal of Entomology, 21(4), 241-246.
Zonneveld, C. (1991). Estimating death rates from transect counts. Ecological Entomology, 16(1), 115-121.