Evolution of the vocal anatomy associated with the acoustic diversity in Bokermannohyla Faivovich, Haddad, Garcia, Frost, Campbell & Wheeler, 2005 (Anura, Hylidae, Cophomantini)

Author(s)

Davi Lee Bang

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC)
• Defense date: 2023-08-01

Examining board members

Flávio Alicino Bockmann; Roberta Azeredo Murta da Fonseca; Felipe Sá Fortes Leite; Renato Christensen Nali; Thiago Ribeiro de Carvalho Tavares; Katyuscia de Araujo Vieira

• Advisor: Flávio Alicino Bockmann

Abstract

The diversity of phenotypic patterns has been increasingly studied from a comparative and phylogenetic perspective. Vocal communication in anurans is a behavioral phenotype that shows great diversity. Vocalizations result from phonation, which occurs primarily through the vibration of the vocal cords in the larynx. The larynx is composed of cartilages and associated muscles that can modulate the characteristics of vocalizations. This vocal anatomy allows for the production of diverse vocal repertoires, the advertisement call being the main vocalization, as it is species-specific, used for attracting females, and consequently serves as a mechanism for reproductive isolation. Variation in the advertisement call is therefore under selective pressures such as sexual selection. These pressures may lead to evolutionary modifications in advertisement calls among species to be correlated with changes in the larynx, as acoustic traits can be underpinned by the vocal anatomy. Thus, the hypothesis arises that the diversity of calls reflects the diversity of anatomical forms of the larynx, especially in Bokermannohyla, a neotropical genus of anurans that exhibits great acoustic diversity. The present project aims to characterize in detail the vocal apparatus and associated advertisement calls in this genus and, based on that, test hypotheses about evolutionary patterns (e.g., phylogenetic signal and ancestral state reconstruction) to evaluate whether differences or similarities in the vocal apparatus reflect correlated evolutionary changes or conservatism in advertisement calls throughout the phylogeny of Bokermannohyla, while also assessing the degree of constraint of these two phenotypes by body size. Anatomical and acoustic descriptions were performed for 28 out of 31 Bokermannohyla species. Anatomical characterizations revealed that, contrary to the acoustic diversity within the genus, all species share the same overall plan and structure of the larynx, although there is considerable variation in quantitative measurements such as larynx length, vocal cord area, and muscular architecture measures among species. Some notable cases of allometry in these measurements relative to body size were seen. Characterization of the advertisement calls within Bokermannohyla revealed five vocal patterns, recognized based on discrete temporal characteristics such as structure, number of note types, and the manner in which they are emitted, as well as three patterns in spectral structure. Complex patterns of evolutionary changes were observed both in anatomical characteristics of the larynx and advertisement call traits, including multiple instances of phenotype homoplasy throughout the phylogeny (e.g., larynx length) or clear patterns of single origin of phenotypes (e.g., note structure) among groups. Finally, the evolutionary correlations between laryngeal anatomy and advertisement calls provided insights into possible anatomical structures of the larynx involved in the biomechanics of call production. One of the correlations that allowed to delineate clear hypotheses was the relationship between body size or laryngeal anatomy characteristics and the dominant frequency of calls. On the other hand, the absence of correlations, for example, between anatomical characteristics of the larynx and discrete acoustic traits, suggests that the control of the larynx and the vocal apparatus for call production involves a more complex biomechanical process than previously thought. This study has contributed to the formulation of a series of hypotheses and biological questions to be addressed in the future regarding the possible underlying processes behind the observed phenotypic patterns, both for laryngeal anatomy and advertisement calls in the genus. Therefore, Bokermannohyla, given the observed phenotypic diversity, has proven to be a promising biological model for understanding acoustic communication and the underlying biomechanical processes in anurans in general. (AU)

• FAPESP's process: 17/27137-7 - Vocal anatomy evolution associated with the acoustic diversity in Bokermannohyla Faivovich, Haddad, Garcia, Frost, Campbell & Wheeller, 2005 (Anura, Hylidae, Cophomantini)
• Grantee: Davi Lee Bang
• Support Opportunities: Scholarships in Brazil - Doctorate