title: Evolution of vocal patterns: tuning hindbrain circuits during species divergence.
abstract: The neural circuits underlying divergent courtship behaviors of closely related species provide a framework for insight into the evolution of motor patterns. In frogs, male advertisement calls serve as unique species identifiers and females prefer conspecific to heterospecific calls. Advertisement calls of three relatively recently (∼8.5 Mya) diverged species -Xenopus laevis,X. petersiiandX. victorianus- include rapid trains of sound pulses (fast trills). We show that while fast trills are similar in pulse rate (∼60 pulses s-1) across the three species, they differ in call duration and period (time from the onset of one call to the onset of the following call). Previous studies of call production inX. laevisused an isolated brain preparation in which the laryngeal nerve produces compound action potentials that correspond to the advertisement call pattern (fictive calling). Here, we show that serotonin evokes fictive calling inX. petersiiandX. victorianusas it does inX. laevisAs inX. laevis, fictive fast trill inX. petersiiandX. victorianusis accompanied by anN-methyl-d-aspartate receptor-dependent local field potential wave in a rostral hindbrain nucleus, DTAM. Across the three species, wave duration and period are strongly correlated with species-specific fast trill duration and period, respectively. When DTAM is isolated from the more rostral forebrain and midbrain and/or more caudal laryngeal motor nucleus, the wave persists at species-typical durations and periods. Thus, intrinsic differences within DTAM could be responsible for the evolutionary divergence of call patterns across these related species.
authors.affiliation: Doctoral Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA.
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Barkan
authors.affiliation: Biology Department, Reed College, Portland, OR 97202, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Zornik
authors.affiliation: Doctoral Program in Neurobiology and Behavior, Columbia University, New York, NY 10032, USA dbk3@columbia.edu.|Department of Biological Sciences, Columbia University, New York, NY 10025, USA.
authors.forename: Darcy B
authors.identifier: 0000-0003-4736-4939
authors.initials: DB
authors.lastname: Kelley
mesh_terms: D000200:Action Potentials; D000818:Animals; D005075:Biological Evolution; D005260:Female; D007823:Laryngeal Nerves / Q000502:physiology; D008297:Male; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012249:Rhombencephalon / Q000502:physiology; D012701:Serotonin / Q000378:metabolism; D013045:Species Specificity; D014828:Vocalization, Animal; D014981:Xenopus / Q000502:physiology*; D029867:Xenopus Proteins / Q000378:metabolism
chemical_list: D016194:Receptors, N-Methyl-D-Aspartate; D029867:Xenopus Proteins; D012701:Serotonin
keywords: Central pattern generator; Communication; Evolution; Motor; Vocalization; Xenopus