The curved tusks of tusked-weevils, the elongated heads of giraffe weevils, the miniature antlers of antlered flies, and enlarged hind-legs of leaf-footed bugs are all examples of sexually selected traits. Competition for reproductive opportunities drives the evolution of many of these extreme structures, yet it has long been a mystery how animals bear the costs of such large and conspicuous morphology. In no other group of organisms have these weapons diversified more or grown disproportionately large as in the insects. These structures can account for more than a third of body mass in some insects, and understanding how these elaborated structures are used, how they grow and develop provides a window into understanding many aspects of physiology and behaviour.
Sexually selected traits are often tied to energetics and metabolism in fundamental ways - and new findings from the field of metabolic ecology and sub-cellular energetics provide insight into the shared processes that shape trait exaggeration and diversification. My research integrates research from mitochondrial respiration, natural history, animal behaviour and evolutionary biology to shed new light on long-standing questions in biology:
1) How do these structures grow and develop during ontogeny?
2) What are the selective mechanisms that lead to, and sustain trait exaggeration?
3) What are the physiological processes that allow animals to pay the energetic costs of bearing and maintaining these extreme structures?
4) How are these extreme structures shaped by their evolutionary history across a phylogeny?
My research program focuses on non-model insect systems that often bear exaggerated morphology to provide new perspectives on the factors that may be important in shaping the evolution of these structures. I examine allocation trade-offs during trait growth and development, measure selection in wild populations, measure the muscle, oxygen transport, and mitochondrial properties of animals bearing this extreme morphology. I aim to understand the mechanisms by which different species develop shared or unique pathways to grow, use and maintain weapons and ornaments.
Somjee U (2021) Positive allometry of sexually selected traits: do energetic costs play an important role? BioEssays: Problems and Paradigms. DOI: 10.1002/bies.202000183. *Wiley Top Cited Article 2021-2022
Somjee U, Powell E, Hickey AJ & Painting CJ (2021) Exaggerated sexually selected weapons maintained with disproportionately low metabolic costs in a single species with extreme size variation. Functional Ecology DOI: 10.1111/1365-2435.13888 *Shortlisted for the Haldane Prize
Somjee U, Woods HA, Duell M. and Miller CW. 2018. The hidden cost of sexually selected traits: the metabolic expense of maintaining a sexually selected weapon. Proceedings of the Royal Society B: Biology 285, 10–12. *Cover image
Somjee U, Miller CW, Tatarnic N, Simmons LS. 2017. Experimental manipulation reveals a trade-off in weapons and testes. Journal of Evolutionary Biology. DOI: 10.1111/jeb.13193