Faculty Member - Division of Biological Sciences University of Missouri-Columbia

A) Host shifts can lead to divergent natural selection between populations on novel and ancestral hosts, and to assortative mating as a consequence of changes in life history timing. Host shifts also have the potential to profoundly alter the evolutionary trajectory of mate communication systems. This graphical model illustrates our approach to exploring the cause-and-effect relationships between host shifts and the evolution of communication. B) We are exploring the causes of evolutionary divergence in signals in the Enchenopa binotata species complex of treehoppers. This panel shows the divergence in female preferences for signal frequency; change in preferences appears to have been an important source of divergent selection on male signals.

Research description

Research in my laboratory focuses on the relationship between the evolution of communication and speciation. What role do mate communication systems play in assortative mating between diverging populations? And how do the ecological changes that accompany diversification shape the communication systems used in mating and other social interactions?

We currently have two main areas of research. The Enchenopa binotata species complex of treehoppers is one of the most widely cited examples of sympatric speciation in plant-feeding insects. The eleven species in this clade are host plant specialists that may have diversified as a consequence of host shifts. We are investigating the patterns and processes of divergence in mating signals in the E. binotata complex, focusing on the consequences of signal evolution for assortative mating and sympatric divergence. Our approaches include comparative behavioral studies of signals, preferences, and mating systems; investigation of how signaling environments differ among host plants; ecological experiments to assess local adaptation and developmental plasticity; and molecular phylogeny and phylogeography to estimate species relationships and the evolutionary history of host plant shifts. This research was initiated in collaboration with the late Tom Wood and continues in collaboration with Randy Hunt (at Indiana University Southeast).

A second focus of research in the lab is the evolution of social behavior and social communication systems. Our study species here are also treehoppers, which are well known for their diversity of social behavior. Our research approaches include broad comparative analyses of the relationship between ecology, social behavior and communication; investigation of how maternal care influences the availability of nutritional resources for offspring; and detailed behavioral experiments to assess signal function and the interplay of cooperation and competition within social groups.

The insects we are studying communicate by means of substrate-borne vibrations, and we are also studying aspects of this communication modality. These include studies of localization of vibrational signals; study of ecological sources of selection on vibrational communication systems, including characterization of vibrational environments and the vibration-transmitting properties of plants; and the development of more accurate methods of measuring and characterizing vibrational signals.

Selected publications

Ramaswamy, K & Cocroft, RB. In press. Collective signals in treehopper broods provide predator localization cues to the defending mother. Animal Behaviour.

Cocroft, RB, Rodriguez, RL & Hunt, RE. 2008. Host shifts, the evolution of communication and speciation in the Enchenopa binotata species complex of treehoppers. Pp. 88-100 in: Tilmon, KJ (ed.), Specialization, Speciation and Radiation: The Evolutionary Biology of Herbivorous Insects. University of California Press, Berkeley, CA.

McNett, GD & Cocroft, RB. 2008. Host shifts favor vibrational signal divergence in Enchenopa binotata treehoppers. Behavioral Ecology 19:650-656.