Overview
Work in my lab addresses a fundamental question in biology: how do major, novel traits originate and diversify in nature? What are the genetic, developmental, and ecological mechanisms, and the interactions between them, that underlie the genesis of novel traits and their subsequent diversification? Addressing these questions requires a multi-disciplinary, integrative approach. Research in my lab therefore uses approaches ranging from molecular developmental genetics and genomics to quantitative genetics, comparative endocrinology, morphometrics and behavioral ecology. Most of our work focuses on the origin and diversification of beetle horns, in particular in the genus Onthophagus (examples of our study organisms can be seen on the right). We have also begun to address related questions in other organisms, in particular ants, termites, and fireflies, and are open to add additional organisms to our repertoire. Below is a brief description of the major themes currently addressed in my lab.
Evolutionary developmental genetics & genomics of beetle horns
Beetle horns are a phenotypic novelty without obvious homology to any other trait outside beetles. However, the development of beetle horns resembles in certain aspects that of conventional insect appendages such as legs, antennae or mouthparts. We have shown that the development of horns is instructed by a subset of the same patterning mechanisms. At the same time, our results suggest the existence of a wide diversity of modifier mechanisms that modulate horn expression at very different time points during horn development in different species, sexes, morphs, or even tissue regions of the same individual. Beetle horns therefore provide an outstanding opportunity to study how patterning mechanisms and their interactions have become re-organized in the origin and diversification of a major phenotypic novelty. Current research is completing the first characterization of the gene network underlying horn expression and diversification using a combination of comparative gene expression studies, genome-wide expression profiling (in collaboration with Justen Andrews, IU), and functional analysis of candidate genes via RNAinterference.
Behavioral ecology and sexual selection in beetles
Beetle horns and male horn dimorphisms function in the context of alternative reproductive tactics. Horned males fight, whereas hornless males sneak to gain access to females. Using recently established exotic populations we have shown that changes in ecological factors (such as the intensity of competition between males or species) can cause populations to rapidly diverge in patterns of morph expression. Current research contrasts divergences between these populations to divergences observed between natural species pairs to investigate the early stages in the evolution of reproductive isolation.
A second project focuses on female reproductive behavior. Specifically, we have recently documented that females facultatively brood parasitize conspecific females, and are now exploring the degree to which female competition and aggression have shaped morphological diversity within the genus. Here we have expanded our tool box to include species with reversed sexual dimorphisms (females express much larger horns then males), which we examine through a combination of laboratory and field studies.
Endocrine mechanisms of developmental evolution
Our past work has shown that a common and well-studied insect hormone (called juvenile hormone or JH) is an important endocrine regulator of horn development in beetles. We have also shown that changes in the way JH acts represents an important mechanism for evolutionary diversification in horned beetles. Current research explores how JH and regulatory genes interact in the development of beetle horns and how changes in the nature of these interactions have mediated the diversification of horned beetles on different levels. Furthermore, in collaboration with MaryAnn Rankin (UT Austin) we have begun to document titer profiles of JH and JH-Esterase (the major JH degrading enzyme) within and between sexes, populations, and species of horned beetles to begin integrating micro- and macroevolutionary perspectives on endocrine evolution.
Trade-offs in horned beetle development and physiology
Beetle horns grow mainly during late larval development at a time when the organism itself is no longer taking in any resources. During this time many physiological processes (including growth of appendages, muscles and internal structures) share, and compete for, a limited pool of resources. The resulting resource allocation tradeoffs can influence the final size of adult structures and may limit the types and magnitude of evolutionary change that development can accommodate. In collaboration with Fred Nijhout (Duke) we have found evidence for trade-offs between head horns and male genitalia, even though both structures develop on opposite ends of the animal. In collaboration with Allen Gibbs (UNLV) we have also found evidence in another species that the growth of horns occurs at the expense of flight muscles, causing measurable reduction of respiratory performances in horned males. Current research is exploring these and related phenomena in more detail, using a variety of approaches such as tissue ablations and RNAinterference.
Invasive species as model systems in evolution, ecology, and development
Several of our approaches use exotic and rapidly evolving beetle populations as a study system. These populations have developed into extremely valuable tools to investigate the early stages of between-population divergence, and we have begun to expand towards other taxa to address related questions. In particular, in collaboration with Claudia Husseneder (LSU) we have begun to explore post-invasion evolution of scaling relationships in the Formosan termite Coptotermes formosanus. Apart from using invasive species as tools for ecological and evolutionary studies research in my lab also explores how insights into post-invasion evolution can inform and benefit conservation and protection efforts.
(* = undergraduate co-author)
Parzer HF, Moczek AP 2008. Rapid antagonistic coevolution between primary and secondary sexual characters in horned beetles. Evolution 62-9: 2423-2428.
Moczek AP 2008. On the origin of novelty in development and evolution. Bioessays 5: 432-447.
Moczek AP 2008. Developmental plasticity and the origins of diversity: a case study on horned beetles. In: Phenotypic plasticity in insects: mechanisms and consequences. Edited by: TN Ananthakrishnan & D Whitman. Science Publishers, Inc. Plymouth, UK. in press.
Shepherd BL*, Prange HD, Moczek AP 2008. Some like it hot: body and weapon size affect thermoregulation in horned beetles. Journal of Insect Physiology 54: 604-611.
Pizzo A, Roggero A, Palestrini C, Moczek AP, Rolando A 2008. Rapid shape divergences between natural and introduced populations of a horned beetle partly mirror divergences between species. Evolution and Development 10: 166-175.
Moczek AP 2007. Pupal remodeling and the evolution and development of alternative male morphologies in horned beetles. BMC Evolutionary Biology 7: 151.
Moczek AP, Andrews J, Kijimoto T, Yerushalmi Y, Rose D 2007. Emerging model systems in evo-devo: horned beetles and the origins of diversity. Evolution and Development 9: 323-328.
Moczek AP 2007. Developmental capacitance, genetic accommodation, and adaptive evolution. Evolution and Development 9: 299-305.
Shelby JA*, Madewell R*, Moczek AP 2007. Juvenile hormone mediates sexual dimorphism in horned beetles. Journal of Experimental Zoology B, Molecular and Developmental Evolution 308B: 417-427.
Moczek AP, Cruickshank, TE, Shelby JA* 2006. When ontogeny reveals what phylogeny hides: gain and loss of horns during development and evolution of horned beetles. Evolution 60: 2329-2341.
Moczek AP 2006. Integrating micro- and macroevolution of development through the study of horned beetles. Heredity 97: 168-178.
