Female northern grass lizards judge mates by body shape to reinforce local adaptation

Abstract

Background: Identifying the factors that contribute to divergence among populations in mate preferences is important for understanding of the manner in which premating reproductive isolation might arise and how this isolation may in turn contribute to the evolutionary process of population divergence. Here, we offered female northern grass lizards (Takydromus septentrionalis) a choice of males between their own population and another four populations to test whether the preferences that females display in the mating trials correlate with phenotypic adaptation to local environments, or to the neutral genetic distance measured by divergence of mitochondrial DNA sequence loci. Results: Females showed a strong preference for native over foreign males. Females that mated with native versus foreign males did not differ from each other in mating latency, or copulation duration. From results of the structural equation modelling we knew that: 1) geographical distance directly contributed to genetic differentiation and environmental dissimilarity; 2) genetic differentiation and environmental dissimilarity indirectly contributed to female mate preference, largely through their effects on morphological divergence; and 3) females judged mates by body shape (appearance) and discriminated more strongly against morphologically less familiar allopatric males. Conclusions: Local adaptation rather than neutral genetic distance influences female mate preference in T. septentrionalis. The tendency to avoid mating with foreign males may indicate that, in T. septentrionalis, local adaptations are more valuable than genetic novelties. Our results highlight the importance of comprehensive studies integrating ecological, molecular and behavioral approaches to understand population divergence in female mate preferences as the consequence of local adaptations.

Sexual size monomorphism may evolve in lizards with a body size maximizing reproductive performance for both sexes

“…Takydromus septentrionalis is not among lizard species displaying evident male–male agonistic behavior ( Ji et al 1994 ; Du and Yao 2007 ; Guo et al 2020 ). Evidence from field observations reveals that northern grass lizards are active in relatively stable home ranges, of which the mean size is greater in males than in females of the same SVL and greater in larger individuals than in smaller ones of the same sex, and that males increase mating opportunities primarily by increasing their home range (and thus the number of females encountered) rather than male–male competition ( Ji et al 1994 ).…”

“…We collected 253 lizards (122 males and 131 females) larger than 50 mm snout–vent length (SVL) in early April 2017 from a previous studied population ( Ji et al 2007 ; Cai et al 2012 ; Guo et al 2020 ) in Lishui (28°46ʹN, 119°92ʹE), East China. Lizards were transported to our laboratory in Hangzhou, where they were weighed, measured (for SVL and tail length), and numbered via unique combinations of clipped toes.…”

“…Adults are sexually dimorphic in head size but not in body size ( Ji et al 1998 ). Male–male combat is rare even if existing in T. septentrionalis , females reproduce frequently and can lay up to 9 clutches per breeding season from early April to late August, and larger females generally produce more and heavier clutches than smaller ones ( Ji et al 1994 ; Du et al 2005 ; Ji et al 2007 ; Luo et al 2010 ; Guo et al 2020 ). Here, we used T. septentrionalis as a model animal to test the hypothesis that sexual size monomorphism may evolve in species where reproductive performance is maximized at a similar body size in both sexes.…”

Climate warming will increase chances of hybridization and introgression between two Takydromus lizards (Lacertidae)

“…Female T. septentrionalis can lay up to 9 clutches with 1-5 eggs each per breeding season from April to August (Ji et al, 2007;Luo et al, 2010); female T. sexlineatus can lay up to 5 clutches with 1-4 eggs each per breeding season also from April to August (Xu & Ji, 2000;Zhang & Ji, 2004). Evidence from T. septentrionalis has shown that males are the less choosy sex and can mate at extreme phylogenetic distances, either with conspecific females from distant populations, or even with heterospecific but congeneric females (Guo et al, 2020).…”