What unites this research group is a fascination with the evolution of animal shapes and behaviors. Together, we have worked topics ranging from weapon biomechanics and trade-offs, to context-dependent mate choice, and to phenotypic plasticity in feeding morphology. Right now we are thinking a lot about sexual selection, especially male-male competition. With grant funding from the National Science Foundation, we are asking the question of why sexually selected weapons (for example, deer antlers) are often so easily damaged in contests. More generally, we are studying the influence of nutrition on the construction and maintenance of a sturdy animal body, ready for combat. We also are actively studying trade-offs between traits involved in sexual selection, including weapons and testes. We use the incredible insect superfamily Coreoidea, the Leaf-footed bugs and allies, to address our broad research questions. Below you'll see some information on two of our major research directions. See the Publications page for a more complete picture of what we are up to!

Dynamic environments and the biomechanics of animal weapons

A trip to the Rocky Mountains can reveal male elk sparing with their antlers, pronghorn trying to edge out other males, and dung flies competing for mates on bison dung. In fact, any trip to the wilderness easily shows us many examples of male-male competition, or, in some cases, female-female competition over access to mates. People have been fascinated by animal weapons and their fighting behaviors for centuries.  In spite of the interest, we still do not know why there is such amazing weapon diversity. Why do some species use tusks to fight over females, while others use their legs? Why do even closely-related species often have such striking differences in their weapons? And, why when a trait is this important, does it so easily break? We tackle these problems using the striking diversity of weapons in the leaf-footed bugs and their relatives (Superfamily Coreoidea).  Working together with David Labonte at Imperial College in London and Walter Federle at the University of Cambridge, we are studying how biomechanics shape weapon diversification.  Together with Michael Forthman, former postdoc in the lab, we have reconstructed the phylogeny of these insects so that we can map their amazing weapons and trace the evolutionary process. Our research takes us to Panama, Kenya, Swaziland, South Africa, Australia, Singapore, and across the insect-rich state of Florida. This work has been funded by multiple NSF grants, including a NSF CAREER Award.

FEATURED PAPERS
Miller CW, Kimball RT & Forthman M (in review). The evolution of multi-component weapons in the superfamily of leaf-footed bugs. Available preprint.

Woodman TE, Chen S, Emberts Z, Wilner D, Federle W & Miller CW.  (2021) Developmental nutrition affects the structural integrity of a sexually selected weapon. Integrative and Comparative Biology. PDF

Trade-offs between weapons and ejaculates

Males in many species use weapons such as horns, antlers, and spurs to compete with other males for access to females. Larger weapons often allow males to win high-quality territories and mating opportunities. However, many of these weapons are costly to produce and maintain, competing for a limited supply of resources within the body. Through experimentation, we have discovered weapons-testes trade-offs in the leaf-footed bugs. Interestingly, such trade-offs are not limited to males; we have found leg-ovary trade-offs in females. The female trade-offs provide insights into the nature of resource allocation within the bodies of individual animals. 

FEATURED PAPERS
Miller CW, Joseph PN & Emberts Z (2021). Trade-offs between weapons and testes do not manifest at high social densities.  Journal of Evolutionary Biology. 34: 726-735. ​PDF

Cavender K, Ricker T, Lyon M, Shelby E, Miller CW & Moore PJ (2021) The trade-off between investment in weapons and fertility is mediated through spermatogenesis in the leaf-footed cactus bug Narnia femorata. Ecology & Evolution. DOI: 10.1002/ece3.7686. PDF
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Miller CW, Joseph PN, Kilner RM, Emberts Z (2019). A weapons–testes trade-off in males is amplified in female traits. Proceedings of the Royal Society of London (B). 286: 20190906. PDF​

Joseph PN, Emberts Z, Sasson DA, & Miller CW (2018). Males that drop a sexually-selected weapon grow larger testes. Evolution. 72: 113–122. DOI: 10.1111/evo.13387.  PDF 

Somjee U, Miller CW, Tatarnic NJ, & Simmons LW (2018). Experimental manipulation reveals a trade-off between weapons and testes. Journal of Evolutionary Biology. 31: 57–65. DOI: 10.1111/jeb.13193. PDF 

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​The Superfamily Coreoidea: There are more than 3300 species of these insects worldwide, and male hind legs are impressively diverse in shape. Males in many species (but not all) use their hind legs as weapons to wrestle over plant territories where females visit to mate, feed, and lay eggs. 

Here are two male leaf-footed cactus bugs, Narnia femorata, wrestling over a territory on a nearby cactus. Males fight in intense bursts, use a variety of fighting maneuvers, and they obtain numerous  injuries. Their combat behavior is a lot like mixed martial arts fighting in humans. And, below you can see the variety of shapes, sizes, and colors  in this insect superfamily.

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