Contents lists available at ScienceDirect Zoology journal homepage: www.elsevier.com/locate/zool Coevolution between male and female genitalia in Belostoma angustum Lauck, 1964 (Insecta, Heteroptera, Belostomatidae): disentangling size and shape José Ricardo Inacio Ribeiro a, ⁎, Fabiano Stefanello a,1 , Cristhian Bugs a , Cristina Stenert b , Leonardo Maltchik b , Eric Guilbert c a Laboratório de Estudos da Biodiversidade do Pampa (LEBIP), Universidade Federal do Pampa, Campus São Gabriel, 97307–020, São Gabriel, Rio Grande do Sul State, Brazil b Laboratório de Ecologia e Conservação de Ecossistemas Aquáticos, Universidade do Vale do Rio dos Sinos, Av. Unisinos, 950, 93022–000, Cristo Rei, São Leopoldo, Rio Grande do Sul State, Brazil c Muséum national d'Histoire naturelle, MECADEV - UMR 7179 MNHN/CNRS, CP50-57, rue Cuvier, 75005, Paris, France ARTICLEINFO Keywords: aquatic insects geometric morphometrics semi-landmarks sexual selection southern South America ABSTRACT Sexual and natural selection mechanisms might drive variation in the genitalia of male animals. All afore- mentioned mechanisms are known to predict the coevolution of male and female genital morphology. Belostoma angustum is known to have subtle variation in the male and female genitalia of its members. In this species, phallosoma with dorsal arms and ventral diverticulum are assumed to be intromittent male genital traits that interact with the female genital chamber. We thus evaluated the existence of variation after disentangling the size from the shape of male genitalia in B. angustum. Body and genitalia dimensions and photographs of phal- losoma with dorsal arms, ventral diverticulum and lateral views of the right paramere (the non-intromittent part) were obtained. Semi-landmarks and landmarks were used to capture phenotypic variation, by eliminating all non-shape variation with a Procrustes superimposition. Male and female specimens collected from the same location or immediate vicinity were grouped, and 12 groups originating from 12 locations were used to conduct two block-Partial Least Squares analyses (PLS). Group structures were also taken into account by adopting a multilevel approach. The male and female genital traits had similarly shallow static allometry slopes, as well as the dispersion values around the mean (i.e. coefcient of variation) and the standard error of the estimate. The correlation between the pooled within-locality covariance matrix of the symmetric component of phallosoma with dorsal arms and the female genital chamber was signifcant (r-PLS = 0.37), as well as that with male body dimensions (r-PLS = 0.36), even after controlling for allometry. Specimens with lower PLS shape scores had narrower phallosoma with dorsal arms, with poorly curved outer margins of the dorsal arms, whereas specimens with higher PLS shape scores had slightly shorter dorsal arms, with strongly curved outer margins. Lower shape scores were associated with narrower and especially shorter and narrower female genital chambers. Similar shallow allometric curves among sexes and the correlation between intromittent male parts and the female genital chamber, as well as male dimensions, suggest the coevolution of these contact structures in size and in shape. 1. Introduction Continuous sexual selection and natural selection through “lock- and-key” mechanisms might drive variation in the genitalia of male animals (Arnqvist, 1998; Simmons and García-González, 2008; Kameda et al., 2009). Genital structures can vary in size and shape throughout a species population, and the diversity of male genitalia is signifcantly higher within polyandrous species, where opportunities for post- copulatory sexual selection can be strong (Arnqvist, 1998). The size and shape of a male’s genitalia can infuence his ability to engage the female https://doi.org/10.1016/j.zool.2019.125711 Received 3 March 2019; Received in revised form 3 August 2019; Accepted 22 September 2019 ⁎ Corresponding author at: Universidade Federal do Pampa, Campus São Gabriel, Av. Antônio Trilha, 1847, 97300–000 São Gabriel, Rio Grande do Sul State, Brazil. E-mail addresses: joseribeiro@unipampa.edu.br (J.R.I. Ribeiro), stefanellof@yahoo.com.br (F. Stefanello), cristhianbugs@unipampa.edu.br (C. Bugs), cstenert@unisinos.br (C. Stenert), maltchik@unisinos.br (L. Maltchik), guilbert@mnhn.fr (E. Guilbert). 1 Permanent address: Laboratório de Biologia Comparada e Abelhas (LBCA), Departamento de Biologia, Faculdade de Filosofa, Ciências e Letras de Ribeirão Preto (FFCLRP), Universidade de São Paulo, Av. Bandeirantes, 3900, 14040–901, Ribeirão Preto, São Paulo State, Brazil. Zoology 137 (2019) 125711 Available online 25 September 2019 0944-2006/ © 2019 Elsevier GmbH. All rights reserved. T