Impacts of projected climate change on the evolution of behavior and life history in seed beetles

The latest assessment report from the Intergovernmental Panel on Climate Change (IPCC WGI, 2013) states that: “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.”

Although it is now widely accepted that anthropogenic green house gas emissions are driving many of these observed climate changes, the impacts of projected climate change on biological systems is notoriously difficult to measure. Ecosystem dynamics are highly non-linear and multidimensional, and communities that may appear stable in the face of temperature change or shifts in precipitation may suddenly crash. To make matters worse, regional climate change may come in the form of slight changes in the temperature or precipitation means, or as increased occurrences of their extreme high or low values, or as changes in the timing of seasonal phenomena, or as unanticipated statistically subtle changes which, nevertheless, may have significant impacts on individual communities within a larger ecosystem. This highlights the need for carefully controlled climate change impact experiments, conducted in closely monitored laboratory settings.

In the second experiment to be conducted at the Environmental Science Research Laboratory at AUP, Professors Berg and Piani will investigate the impact of daily and seasonal temperature shifts on the behavior, life history, and evolution of seed beetles (Callosobruchus maculatus). The seed beetle is an excellent model system in which to test the potential effects of climate change on wildlife. C. maculatus is a common pest of stored legumes, and the laboratory environment represents a close approximation of this beetle’s natural habitat (Fox et al. 2003). We already know a huge amount about C. maculatus behavior and life history (for example, see the many publications of Professor Charles Fox, University of Kentucky). Males and females are easy to tell apart, hatch success is high, and generation time is short – a mere 3 weeks (Beck & Blumer 2014). All the beetles need to thrive is a jar with some host beans (for example, mung beans) and a controlled environment. The lab is equipped with two state-of-the-art climate chambers that we can program to different temperatures, humidities, and light cycles.

For several months, we will maintain communities of seed beetles in two different chambers. The “control” chamber will be set to a constant and universally accepted baseline for lab populations of this species (29°C, 50% relative humidity, and a 12 hour light:dark cycle). For the first part of the experiment, the second “experimental” chamber will be set to diurnal temperature and light cycles that are representative of the current base climate of this species’ native environment of southern India. After several generations we will change these conditions to reflect a slightly altered climate representative of the projected changes over southern India presented in the IPCC’s 5th Assessment Report (2013). These changes will include increases in diurnal temperature cycles. Changes in temperature cycles are relatively stronger, and far more relevant to ecosystems, than changes in temperature means. No changes will be made to the humidity settings since the values during the Indian wet season are fairly constant.

At different points throughout the experiment we will monitor the effects of the different chamber environments on beetle mating behavior, hatch success, and lifespan of males and females. This experimental design will allow us to assess not only which behaviors and life history traits these temperature shifts affect, but how quickly and effectively they are able to adapt to projected future climate changes.

References:

  • Beck, C.W. & Blumer, L.S. 2014. A handbook on bean beetles, Callosobruchus maculatus. Downloaded fromwww.beanbeetles.org
  • Fox, C.W., Bush, M.L. & Wallin, W.G. 2003 Maternal age affects offspring lifespan of the seed beetle, Callosobruchus maculatus. Functional Ecology 17, 811-820.
  • IPCC, 2013: Climate Change 2013: The Physical Science Basis. [Stocker, T.F., et al.]. Cambridge University Press, Cambridge, United Kingdom.
  • IPCC, 2014: Summary for Policymakers. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1-32. TS