Microclimate variation and butterflies

Kronängen is a fenced off area 3 km north of the Tovetorp research station. Its heterogeneous environment – including managed meadows, mixed forests and lakes – together with its size of roughly 0.25 km2, makes Kronängen an excellent site for studying microclimate variation. The area is also suitable for field experiments – like transplantation of animals – as the fence protects against, among other things, interference from passers-by.

The infrastructure
We have established a dense network of 120+ temperature loggers (whereof many also measure relative humidity) at Kronängen. These loggers collect data every hour, which means that we have access to microclimate measurements with a very high resolution, both spatially and temporally.  The maintenance of this network is also relatively easy, as the fence protects the loggers from animals like wild boar.

The butterflies
One aim is to use the microclimate data to investigate the effects of microclimate variation on insect populations. Continuing a long tradition within the Department of Zoology at Stockholm University, we use the green-veined white butterfly (Pieris napi) as our ecological model organism. As a strong natural population of green-veined whites exist at Kronängen, the species is particularly suitable for the area as this population can be sampled for both lab and field experiments.

Our work include field studies, like transplantation of overwintering pupae across Kronängen to investigate the effects of winter microclimate variation on overwintering success, but also lab experiments where we test the physiological temperature boundaries of the species. As we gain increased knowledge about the effect of temperature things such as development rate and mortality,
we can relate this to the observed microclimate variation in field settings.

Other goals
We are currently planning to develop a microclimate model over Kronängen using vegetational and topographical predictors. The end goal is to integrate this model with thermal performance models to create a complex, but verifiable, model describing the population dynamics of the green-veined white butterfly in the area. The combination of the temperature logger infrastructure and a locally abundant study species provides a unique opportunity to gain insight in how microclimate variation might be influencing the population dynamics of insects. Perhaps we can also broaden our scope and investigate other matters, such as the importance of microclimate variation for mitigating the ecological effects of climate change, e.g. through providing thermal microrefugia.

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Text (c) 2019 Loke von Schmalensee