The effect of sex ratio on size-assortative mating in two explosively breeding anurans

Abstract

Size-assortative mating (SAM) is a widespread phenomenon related to individual fitness. In our study, we examined: (i) the appearance of SAM, and (ii) the effect of sex ratio on intensity of SAM in wild populations of two explosively breeding anurans, common frogs,Rana temporaria, and common toads,Bufo bufo. Despite a higher male-biased operational sex ratio (OSR) in toads, the body lengths of the paired males and females were significantly correlated only in frogs. Increasing male-male competition, assessed via the OSR, resulted in a stronger correlation also in frogs only. Thus, great variability in the presence and intensity of SAM has been observed within both studied species.

Assortative mating in space and time: patterns and biases

“…It is important to make data available for critical evaluation by the referees and readers. For example, researchers should compare the distribution of body size in their samples from multiple populations and multiple breeding periods to ensure that they are consistent (Schwartz 2013;Vojar et al 2015;Moura & Gonzaga 2017;Schweiger et al 2018). An alternative approach is to explicitly incorporate the spatial and/or temporal dimension in the statistical analytical models.…”

“…Hence, assortative mating patterns can emerge as the result of the interaction between mate competition and mate choice particularly when there are large individual advantage in intrasexual competition and a variation in body size of mates, in which large, preferred partners are more fecund or fertile (Crespi 1989). Some authors have argued that mate competition can intensify mate choice effects or even promote assortative mating in the absence of mate choice (Qvarnstr öm et al 2012;Vojar et al 2015;Moura & Gonzaga 2017, 2019Tinghitella et al 2018). This is an on-going field with the potential to improve our comprehension of causal mechanisms promoting assortative mating.…”

“…The influence of assortative mating patterns on gene flow and genetic variation depends on its consistency among populations and across breeding seasons (Johannesson et al 1995;Schwartz 2013;Nonaka et al 2014;Gauthey et al 2016). In fact, several studies have reported strong spatial and temporal variation in the occurrence and strength of mate assortments (Schwartz 2013;Vojar et al 2015;Moura & Gonzaga 2017;Schweiger et al 2018). However, most studies on mate assortment overlook the potential effects of temporal and spatial variation in ecological conditions on the patterns reported and the conclusions derived.…”

“…In fact, several studies have reported strong spatial and temporal variation in the occurrence and strength of mate assortments (Schwartz 2013; Vojar et al . 2015; Moura & Gonzaga 2017; Schweiger et al . 2018).…”

Temporal migration patterns and mating tactics influence size-assortative mating in Rana temporaria

“…Assortment can also be incidental, due to spatial or temporal segregation ( Jiang et al 2013 ). Examples for such incidents causing assortative mating include spatial and/or temporal separation in birds ( Bearhop et al 2005 ), temporal segregation of Drosophila strains ( Tauber et al 2003 ), or differences in flowering periods in plants ( Devaux and Lande 2008 ; Weis et al 2014 ).…”