Collaborative Research: Origins of Diversity in Animal Communication: Habitat-Dependent Adaptive Change in Lizard Visual Displays

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For animals to communicate efficiently, they must produce signals that are obvious to receivers in the environment. Animals are therefore expected to evolve signal forms, which are tailored to be conspicuous within the habitats in which they live. The notion that signals need to 'stand out' in the environment in which they are used has interesting implications for evolutionary biology. For instance, if the members of a species using visual signals move into a new environment, with different visual characteristics from their previous environment, one would expect their signals to evolve to become more conspicuous in that new environment. On the other hand, we also know from comparative studies that there are constraints on the evolution of signals, and that the evolutionary history of a species may affect the ways in which it adjusts its signals to suit the conditions in its current environment. At this point, however, it is unclear how environmental conditions and phylogeny interact to affect the diversity of signal forms that are observed in groups of animals whose members currently live in a wide array of different environments. This study examines how properties of the signal environment and phylogenetic effects explain variation in the elaborate visual displays of Jamaican and Puerto Rican Anolis lizards. Anole displays consist of stereotyped up/down movements of the head - 'head-bob' - and a retractable throat fan - 'dewlap' - and are used to maintain and defend territories. The investigators will record and analyze the displays produced under natural conditions in the field by a number of different species, living in environments with different visual characteristics. These data will be used to determine the extent to which the display characteristics of distantly-related species are similar for species living in comparable environments (convergence in display behavior), and the extent to which display characteristics are affected by evolutionary history, i.e., whether closely-related species have similar display characteristics, even though they live in different environments. Based on the data collected from free-living lizards, a programmable robot lizard will be used to present alternative signal patterns to lizards in the field and test causal links between displays, habitat characteristics and phylogeny. The research involves the participation of a number of undergraduate students, who will be given hands-on experience in conducting research under field conditions, data processing/analysis, and communicating science with their peers and at professional meetings. Video footage of lizard displays collected in the field will also provide the basis for a new introductory biology lab designed to teach undergraduates general principles of evolution. This lab will be expanded into a more advanced web-based module for upper level behavioral ecology and evolution courses, which will ultimately be released to other educators over the Internet. The video library and motion analysis data compiled during the study will represent the most detailed survey of dynamic visual displays conducted for any taxonomic group. At the project's completion, this database will be made freely available to other researchers through a web-based public repository of behavioral information.