Research in the Miller Lab
We live in a time of massive global change. Understanding the consequences for life on this planet requires knowledge of the factors leading to diversification of animals and plants and the resilience of this biodiversity to further change. Understanding the processes of evolution has arguably never before been more exciting nor more important.
We work on the evolution of morphology, function, and behavior. We focus on sexual selection in insects, examining the importance of environmental variability both for the expression of sexually-selected traits and for the process of selection itself. Most of our research is conducted with Hemipterans in the Superfamily Coreoidae.
We work on the evolution of morphology, function, and behavior. We focus on sexual selection in insects, examining the importance of environmental variability both for the expression of sexually-selected traits and for the process of selection itself. Most of our research is conducted with Hemipterans in the Superfamily Coreoidae.
The Superfamily Coreoidea: There are more than 3000 species of these insects worldwide, and male hind femurs (a sexually-selected weapon) are impressively diverse in size and shape. Males in many species (but not all) use their hind legs as weapons to wrestle over access to females and territories. Males with larger legs are often more likely to win male-male contests and have greater mating success.
Florida is a haven for coreoid researchers! We have dozens of local species, each with its own unique fighting style and weapon shape.
Florida is a haven for coreoid researchers! We have dozens of local species, each with its own unique fighting style and weapon shape.
Functional performance and diversity in the weapons of sexual selection: Most species of animal possess some type of weapon, but the most extreme weapons found in the natural world are those used by males competing over access to females. These astonishing structures have fascinated people for centuries. In fact, the earliest known human paintings depict the horns of buffalo and rhinoceros, the antlers of stags, and the tusks of mastodons. In spite of the interest these structures have attracted, 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? My students and I are fascinated by the striking diversity of weapons in the leaf-footed bugs and relatives (Superfamily Coreoidea). We are currently beginning new research into the effects of fighting style on the evolution of weapon shape and the potential for mate-monopolization potential on the evolution of weapon size (with Ph.D. student, Ummat Somjee). We are capitalizing on the numerous species of leaf-footed bugs here in Florida, and we also study insects in Panama, Kenya, Singapore, and Australia.
Photo: A hind leg of one of our local species, Acanthocephala femorata. Males in this species wrestle on plants such as sunflower, pressing that prominent spine into the abdomen of their opponents. Successful males become territory holders and interact with females visiting the plants. Weapon reconstruction image courtesy of Dr. Josh Yarrow, UF.
Environmental effects on sexual selection: Within species of animals, the size and shape of the ornaments and weapons of sexual selection are influenced by nutrition, social environment, and genetics. The environmental context even influences the processes of sexual selection directly. Using multiple species of coreid bugs, we have discovered that sexually-selected traits can vary in expression over both space and time in the wild (Miller & Emlen 2010). Juvenile diet affects adult expression of male weapons (Miller & Emlen 2010, Gillespie et al. 2014), testes (Ummat, Allen, & Miller 2015), copulatory courtship behaviors, and mating receptivity (Miller 2008). We have found that females change their mating decisions based on their context, and these effects translate into differences in selection on male traits (Addesso et al. 2014, Gillespie et al. 2014). We measured sexual selection via male-male competitions and found that selection was stronger in the presence of females (Procter et al. 2012). The social environment matters in many ways Exotic species can create a whole host of problems in natural communities, and we have identified an example of reproductive interference where males of an exotic squash bug attempt to mate with native squash bug (Hamel, Nease, and Miller 2015).
On the right, two male leaf-footed cactus bugs, Narnia femorata, compete over a territory on blooming cacti. When males have an escalated competition, they turn around and wrestle with their hind legs. One of the real strengths of working with N. femorata is that we can examine variation in sexual selection under realistic environmental conditions. Narnia lives on cholla and prickly pear cactus from the Southern U.S. to Central America. Cactus nutritional quality for these insects is seasonal and highly variable. Some juveniles have access to green cactus fruits for growth and development, others feed on red, ripe cactus fruits, and some unlucky individuals only have access to cactus pads. Insects that develop with fruit develop faster (Nageon de Lestang & Miller 2009), grow larger, and are more competitively successful as adults (Gillespie et al. 2014).
