Factors Driving Sexual Dimorphism and Colour Variability In
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Canadian Journal of Zoology Factors driving sexual dimorphism and colour variability in Achala Copper Lizard (Pristidactylus achalensis), an endemic species to the highland mountains in Central Argentina Journal: Canadian Journal of Zoology Manuscript ID cjz-2019-0293.R1 Manuscript Type: Article Date Submitted by the 01-Feb-2020 Author: Complete List of Authors: Naretto, Sergio; Universidad Nacional de Cordoba Facultad de Ciencias Exactas Fisicas y Naturales, Biologia del Comportamiento; Consejo Nacional deDraft Investigaciones Cientificas y Tecnicas, Instituto de Diversidad y Ecologia Animal (IDEA) Chiaraviglio, Margarita; Universidad Nacional de Córdoba Facultad de Ciencias Exactas Físicas y Naturales, Biología del Comportamiento; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Instituto de Diversidad y Ecologia Animal (IDEA) Is your manuscript invited for consideration in a Special Not applicable (regular submission) Issue?: REPRODUCTION < Discipline, SEX DIFFERENCES < Discipline, SEX Keyword: RATIO < Discipline, REPTILIA < Taxon, SEXUAL SELECTION, COLOUR https://mc06.manuscriptcentral.com/cjz-pubs Page 1 of 46 Canadian Journal of Zoology 1 Title Page Title: Factors driving sexual dimorphism and colour variability in Achala Copper Lizard (Pristidactylus achalensis), an endemic species to the highland mountains in Central Argentina Author names: S. Naretto1,2 and M. Chiaraviglio1,2 Affiliations and addresses: 1: Universidad Nacional de Córdoba, Facultad de Ciencias Exactas, Físicas y Naturales. Laboratorio de Biología del Comportamiento. Córdoba, Argentina. 2: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Diversidad y Ecología Animal (IDEA). Córdoba, Argentina.Draft Postal address: Laboratorio de Biología del Comportamiento, Facultad de Ciencias Exactas Físicas y Naturales, Universidad Nacional de Córdoba, Vélez Sársfield 299, Córdoba, Argentina. CP X5000JJC. Email addresses: [email protected] , [email protected] Corresponding author: Sergio Naretto Postal address: Vélez Sársfield 299, Córdoba, Argentina. CP X5000JJC Telephone number: +54 9 351 5939815 . +54 351 4332100 (247) Email address: [email protected] https://mc06.manuscriptcentral.com/cjz-pubs Canadian Journal of Zoology Page 2 of 46 2 Title: Factors driving sexual dimorphism and colour variability in Achala Copper Lizard (Pristidactylus achalensis), an endemic species to the highland mountains in Central Argentina Author names: S. Naretto and M. Chiaraviglio Abstract The intensity of mating competition varies according to the temporal and spatial distribution of individuals. Measuring sexual dimorphism over time and interpreting the association between individuals is therefore important if we aim to understand how sexual traits are influenced. We examined sex differences in Pristidactylus achalensis (Gallardo 1964), an endemic species from the highest part of mountains of central Argentina. Over four years, we explored sex-specific variation in body size, head size, interlimb length, and body colouration. Further, we evaluated how these traits varied temporally, and we also explored whether the spatial distribution of individuals is explained by variation in these traits. We found that P. achalensis is a species withDraft sexual dimorphism in multiple characters, including body size, head size, and colouration. Interestingly, some traits related to mating, such as head width, show a temporal variability in both sexes, whereas other traits, such as colouration, varies seasonally only in males. Our results underline the intriguing possibility of seasonal morphological changes related to mating, and more broadly that sex differences are influenced by sexual selection pressures mediated by temporal variation in mate competition. Keywords: sexual selection, secondary sexual traits, competition, endemism, colouration, Pristidactylus achalensis, Achala Copper Lizard https://mc06.manuscriptcentral.com/cjz-pubs Page 3 of 46 Canadian Journal of Zoology 3 Introduction Differentiation in morphology, performance, behaviour and colouration between males and females has long been a paradigm for evolutionary biologists (Darwin 1871; Andersson 1994). An integrative approach of different sexual traits provides an opportunity to increase our understanding of trait evolution because they result from selection forces that act differentially on each sex (Irschick et al. 2006; Kvarnemo and Merilaita 2006; Corl et al. 2009; Naretto et al. 2014). The intensity of mating competition could be characterized by the temporal and spatial distribution of partners (Clutton-Brock and Vincent 1991). Variation in the number of relative partners may generate more intense competition between some individuals, affecting their reproductive tactics (Kvarnemo and Merilaita 2006). It is essential to highlight that sexual dimorphism is a commonly addressed aspect, but this framework is still open to new ideas about which factors promote the differences between sexes and their relative importance on different traits (Friesen et al. 2017; Vanburen et al. 2018; Corbalán et al. 2019; Boscaini et al. 2019). Moreover, information about the intensity of sexual selectionDraft is necessary to understand the mechanisms driving the evolution of sexual traits (Baeckens et al. 2018). Secondary sexual traits evolve through the process of sexual selection, either via mate choice, intrasexual competition or a combination of both (Berglund et al. 1996). Although sexual body size dimorphism is common in reptiles (Schoener 1977; Fitch 1981; Stamps 1983), the relative size of different body parts can be very informative of the selective pressures posed on each sex (Cooper and Vitt 1989; Anderson and Vitt 1990; Braña 1996; Butler and Losos 2002; Kratochvil et al. 2003; Scharf and Meiri 2013). For example, an increased head size may affect the outcome of intrasexual interactions increasing, increasing the chances of winning a contest (Herrel et al. 1996; Herrel et al. 1999; Herrel et al. 2001), and increasing the chances of being selected by a sexual partner (Fitch 1981; Vitt and Cooper 1985; Bull and Pamula 1996; Pough et al. 2001). In species with seasonal reproduction, the strength of selective forces may vary at different moments in time (Irschick et al. 2006; Naretto et al. 2014; Ortiz et al. 2016) for example through the relative availability of partners and competitors (Grant and Foam 2002). Therefore, measuring traits over time and interpreting it as a dynamic trait is decisive to understand how the sexual traits are influenced (Heuring and Hughes 2019). https://mc06.manuscriptcentral.com/cjz-pubs Canadian Journal of Zoology Page 4 of 46 4 Sexual selection pressures can act on visual signalling, and species with conspicuous colouration often shows males more colourful than females, resulting in sexual dichromatism (Kodric-Brown 1998; Owens and Hartley 1998; Oxford and Gillespie 1998; Badyaev and Hill 2003; Pérez i de Lanuza et al. 2013). As morphological traits, the colouration could be more intense in species subject to intense sexual selection, whereby the degree of dichromatism could be positively associated with sexual size dimorphism (Figuerola and Green 2000; Stuart–Fox and Ord 2004; Mays et al. 2006; Chen et al. 2012; Pérez i de Lanuza et al. 2013). Conspicuously coloured individuals can obtain more mates (Sætre et al. 1994; Sundberg 1995; Kwiatkowski and Sullivan 2002), and often achieve higher social status or/and greater access to resources (Gerald 2001; Pryke et al. 2002; Zamudio and Sinervo 2003; Hamilton et al. 2013). Selection acts on not only the complete body colouration but also certain body parts are subject to selective pressures; for example, ventral colours in lizard can act as social signals (Ábalos et al. 2016) whereas dorsal colours are more relevant to avoid predators (Stuart-Fox and Ord 2004). The strength of sexual selection could predict the dichromatism in those body regions useful for intraspecific communication (Stuart-Fox and Ord 2004).Draft In addition, some discrete patches have ultraviolet colour and may be involved in signalling functions in species with UV receptors (Fleishman et al. 1993; Stapley and Whiting 2006; Whiting et al. 2006; Bajer et al. 2010; Pérez i de Lanuza and Font 2011; Bajer et al. 2011; Bohórquez-Alonso et al. 2018). Studies on the visual system of diurnal lizards suggest that lizards are capable of perceive the UV reflectance, which is a requisite for their role as communicative signals (Loew et al. 2002; Fleishman et al. 2011; Pérez i de Lanuza and Font 2014). Thus, sexual selection can operate on a range of body parts along the colour spectrum modulating sexual dichromatism. Understanding the mechanisms that promote variation in any phenotype first requires defining the dimension and properties of the trait in question. The range of colour variation between sexes tells about the functional significance as a signal. There is a huge amount of literature about sexual dimorphic traits in lizards from several points of views, such as prey-predator interaction (Stuart-Fox et al. 2003; Macedonia et al. 2009; Marshall and Stevens 2014), intraspecific variability (Macedonia et al. 2002; Stuart-Fox et al. 2006; Rossi et al. 2019) and overall the colouration as a factor that define reproductive strategies (Bastians et al. 2013; Fernández et al. 2018; Bruinjé et al. 2019). In addition to using signals, lizards can have physical contact in mating competition. An important role of bite lies in determining