My research interests include bioenergetics of butterfly flight, life-history responses to environmental variation, and ageing.
Bioenergetics of butterfly flight
Flight is extremely important to many insects, yet flight is an energetically costly activity, and flying insects have remarkably high metabolic rates. In the context of life-history evolution, energetically expensive processes are expected to result in trade-offs among different traits, such as reproduction, somatic maintenance, and lifespan.
I am interested in factors that affect variation in individual flight capacity, and consequences of individual variation. For example, we have shown that in the Glanville fritillary butterfly, flight metabolic rate is affected by environmental temperature and molecular variation at the phosphoglucose isomerase (Pgi) locus (Niitepõld 2010, JExB ; Niitepõld et al 2009, Ecology). Molecular variation at Pgi has been shown to be connected to a a whole suite of life-history traits and even population dynamics at the landscape scale (reviewed in Niitepõld & Saastamoinen 2017).
Ageing and lifespan
There is a huge amount of variation in lifespan among species and also within species. Despite years of study, our understanding of the mechanistic underpinnings of ageing and the determination of lifespan is still limited. Even though some animals seem to follow a “live fast, die young” strategy, the so-called “rate-of-living” theory has been largely discredited. We too have shown that in the Glanville fritillary butterfly (Melitaea cinxia), individuals with high peak metabolic rates were the ones with the longest lifespans (Niitepõld & Hanski 2013).
Free radicals and reactive oxygen species (ROS) are believed to serve a role in various ageing processes (and diseases), but their exact contribution to ageing is heavily debated. We now know that ROS carry signalling functions and that ageing may be a more controlled process than previously thought, but the jury is still out. Nevertheless, there is clear evidence pointing to mitochondria as central components of biological ageing.
My current research focuses on mitochondrial function and involves comparative approaches to understand ageing processes in birds, mammals, and butterflies.
Physiological and biochemical costs of migration
I’m interested in the processes that shape the evolution of migration. In particular, I focus on costs of long-distance flight. For example, we found that flight metabolic rate was lower in monarch butterflies that perform long-distance migration compared to non-migratory monarchs (Zhan et al 2014, Nature). Studying the best endurance athletes of the animal world helps us to pinpoint adaptations that make migratory flight possible.
In Europe, a perhaps even more impressive migration takes place annually when red admirals and painted ladies re-colonise Northern Europe from the Mediterranean. As red admirals and painted ladies cannot overwinter in the north, they fly south in the autumn. Painted ladies apparently venture deep into Africa. Much of this African-European migration system is still unknown.
Responses to environmental variation
How do wild animals respond to environmental change? We have used butterfly study systems to examine how species with different life-history strategies react to conditions that induce stress. For example, we showed that conditions that mimic reduced food availability can lower the number of eggs a female can lay, but species differ in how sensitive they are to food restriction (Niitepõld, Perez and Boggs 2014, PBZ). Interestingly, butterflies appear to retain their flight capacity even when experiencing semi-starvation. Experimental flight treatments, however, may have positive effects on egg production (Niitepõld & Boggs 2015, PLOS One).