DOI: 10.5061/dryad.qnk98sfd5
title: Ecological and evolutionary drivers of geographic variation in songs of a Neotropical suboscine bird: The Drab-breasted Bamboo Tyrant (Hemitriccus diops, Rhynchocyclidae)

description: Understanding the evolutionary and ecological mechanisms that shape the
 spatial divergence of signals involved in reproductive isolation is a
 central goal in studies of speciation. For birds with innate songs, such
 as the suboscine passerine birds, the integration and comparison of both
 genetic and ecological factors in explaining song variation at the
 microevolutionary scale is rare. Here we evaluated the evolutionary and
 ecological processes underlying the variation in the songs of the Atlantic
 Forest endemic Drab-breasted Bamboo Tyrant (Hemitriccus diops), testing
 the effects of both stochastic and adaptive processes, namely the
 Stochastic and Adaptation Acoustic Hypotheses, respectively. We combined
 vocal, genetic and ecological (climate and forest cover) data across the
 species’ range. To this end, we analyzed 89 samples of long and short
 songs. We performed analyses on raw and synthetic data song variables with
 linear mixed models and multivariate statistics. Our results show that
 both song types differ in spectral features between the two extant
 phylogeographic lineages of this species, but such vocal divergence is
 weak and subtle in both song types. Overall, there is a positive
 relationship of acoustic distances with the amount of forest cover in long
 songs. Our results suggest that there is cryptic geographical variation in
 both song types and that this variation is associated with low levels of
 genetic divergence in both songs and with ecological factors in long
 songs.
description: Songs of <i>H.</i> <i>diops</i> were
 obtained from our field work, other researchers’ private collections and
 public libraries. Public online libraries from which songs were obtained
 included Xenocanto (http://www.xeno-canto.org), Wikiaves
 (http://www.wikiaves.com/), Macaulay Library
 (https://www.macaulaylibrary.org/) and the Jacques Vielliard Neotropical
 Music Library of the State University of Campinas (FNJV). The vocal
 sampling corresponds to most of the species range in the Brazilian
 Atlantic Forest.  First, we evaluated the vocal
 repertoire of <i>H.</i> <i>diops</i> with
 sonograms generated in Raven Pro 1.4 (www.birds.cornell.edu/raven, Charif
 et al. 2010). After inspecting all available recordings and based on our
 field experience, a long and a short song were identified based on their
 acoustic structure. The long song of <i>H.</i>
 <i>diops</i> is a harmonic trill with a duration of
 <i>ca</i>. 1 second and with a high number of fast delivered
 notes . The short song is a harmonic trill with a duration of ca. 0.2
 seconds and with a small number of fast delivered notes. 
 This data set contains 19 acoustic variables and 8 ecological
 variables. Also, we included the genetic distances between
 populations. For more details view: Ecological and
 evolutionary drivers of geographic variation in songs of a Neotropical
 suboscine bird: The Drab-breasted Bamboo Tyrant (Hemitriccus diops,
 Rhynchocyclidae). The Auk: Ornithological Advances.