Evolutionary Interactions Between Visual and Chemical Signals: Chemosignals Compensate for the Loss of a Visual Signal in Male Sceloporus Lizards
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Animals rely on multimodal signals to obtain information from conspecifics through alternative sensory systems, and the evolutionary loss of a signal in one modality may lead to compensation through increased use of signals in an alternative modality. We investigated associations between chemical signaling and evolutionary loss of abdominal color patches in males of four species (two plain-bellied and two colorful-bellied) of Sceloporus lizards. We conducted field trials to compare behavioral responses of male lizards to swabs with femoral gland (FG) secretions from conspecific males and control swabs (clean paper). We also analyzed the volatile organic compound (VOC) composition of male FG secretions by stir bar extraction and gas chromatography-mass spectrometry (GC-MS) to test the hypothesis that loss of the visual signal is associated with elaboration of the chemical signal. Males of plain-bellied, but not colorful-bellied species exhibited different rates of visual displays when exposed to swabs of conspecific FG secretions relative to control swabs. The VOC composition of male Sceloporus FG secretions was similar across all four species, and no clear association between relative abundances of VOCs and evolutionary loss of abdominal color patches was observed. The emerging pattern is that behavioral responses to conspecific chemical signals are species- and context-specific in male Sceloporus, and compensatory changes in receivers, but not signalers may be involved in mediating increased responsiveness to chemical signals in males of plain-bellied species.
KeywordsMultimodal communication Chemical signals Femoral glands Volatile organic compounds Stir bar extraction Sceloporus
We thank Patrick Cain, Alison Ossip-Klein, and José Oyola Morales for assistance in the field. We thank Ryan Seddon, Savannah Price, and Lindsay Forrette for providing comments on a previous version of the manuscript. Permission to conduct this work was granted by the Texas Parks and Wildlife Department (S. merriami: SPR-0511-129) and the Secretaría de Medio Ambiente y Recursos Naturales of México (SEMARNAT; S. siniferus: 09/O1-0557/12/13; S. cozumelae and S. parvus: 09/k50904/01/13). We thank Big Bend Ranch State Park and El Parque Nacional Huatulco for granting access to public lands, and Carolyn Ohl-Johnson for granting access to private land. This material is based upon work supported by the National Science Foundation under grant numbers IOS-1050274 to EPM and IOS-1052247 to DKH, and while serving at the National Science Foundation (EPM). All procedures were approved by the Indiana State University Institutional Animal Care and Use Committee.
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