Molecular sexing and intersexual differences in the morphometry of the Hangnest Tody-Tyrant Hemitriccus nidipendulus (Passeriformes: Rhynchocyclidae)

Abstract

Variation in the morphometry of individuals in a population may result from natural or sexual selection. In the present study we investigated morphometric differences between males and females of a bird species endemic to the Brazilian Atlantic Forest, the Hangnest Tody-Tyrant, Hemitriccus nidipendulus (Wied, 1831), with no apparent sexual dimorphism. All individuals (n = 56) were sexed by PCR amplification of the intronic fragments of the CHDZ/CHDW alleles obtained from blood samples, and 12 morphometric measurements were recorded. The molecular configuration was similar to that described for other species of Passeriformes, with males presenting a single band of approximately 360 base pairs (bp), and females with two bands of 360 and 400 bp. Males had significantly larger tarsi and wings than the females, while the females had two larger beak measurements. This indicates that differential selection pressures may be modeling the morphometry of the Hangnest Tody-Tyrant. In the males, larger tarsi and wings may be beneficial for the exploration of the habitat or the acquisition of potential mates, while females with larger beaks may be able to exploit larger food items and forage more efficiently. However, these hypotheses need to be tested empirically in future studies.

Long‐term stability of sex chromosome gene content allows accurate qPCR‐based molecular sexing across birds

“…Accurate sex identification is necessary for research (e.g., developmental, population, and evolutionary studies), management of wildlife species, and improvement of captive breeding programmes both for conservation and poultry (Morinha et al, 2012). Several methods have been developed to identify the sex of birds, based on cytogenetic markers (Griffiths & Phil, 2000; Harris & Walters, 1982), identification of sex‐specific differences in morphometric characters (Reynolds et al, 2008; Cappello & Boersma, 2018; Medeiros et al, 2019; Alonso et al, 2019; Seyer et al, 2020) and behaviour (Gray & Hamer, 2001), including vocalization (Volodin et al, 2009), measurement of hormone levels (Bercovitz et al, 1978) and laparoscopy for gonad inspection (Richner, 1989). However, many of these methods have limited applications, because they are time‐consuming, technically demanding (e.g., cytogenetics, morphometrics), potentially harmful (e.g., laparoscopy), or error‐prone.…”