Latitudinal variation in sexual dimorphism in a freshwater fish group

Abstract

Tropical animals are characterized by showy ornaments and conspicuous body colours as compared with their temperate relatives. Some recent studies have hypothesized that sexual selection pressures are stronger in the tropics than in the temperate zone. Although negative correlations between latitude and the degree of sexual dimorphism would support this hypothesis, phylogeny should be taken into account in such comparative studies. Comparisons of the degree of sexual dimorphism in body size and fin lengths among species of the Adrianichthyidae, a freshwater fish family having a wide geographical range throughout Southeast and East Asia, revealed that lower latitude species are sexually more dimorphic in all characters than higher latitude species. Phylogenetic generalized least squares analyses using a mitochondrial DNA phylogeny demonstrated that the negative correlations between latitude and the degree of sexual dimorphism become non-significant when phylogeny is considered, but that the variance in the degree of sexual dimorphism is explained not only by phylogeny but also almost equally by latitude. Ancestral state reconstruction indicated that sexual dimorphisms have evolved independently even within major clades. These findings are consistent with the view that tropical species are exposed to stronger sexual selection pressures than temperate species. We discuss possible causes of the latitudinal variation in sexual selection pressure.

Sexual size and shape dimorphism in Turkish common toads (Bufo bufo Linnaeus 1758)

“…Although we have revealed sexual dimorphic differences between sexes, the study has some limitations due to not considering geographic variation of the SSD and SShD. The dataset is covering a very large area and has very limited sample size from some locations, but geographic variation related to body size and other characters is a common phenomenon in amphibians (Baraquet et al, 2018; Bidau et al, 2011; Yu et al, 2010) and other animal groups (Kwiatkowski & Sullivan, 2002; Roulin, 2003; Stillwell & Fox, 2009; Sumarto et al, 2020). For instance, Hemelaar (1988) compared five populations of common toads from different altitudes and latitudes in Europe and he reported that the populations from the northern latitudes and high altitudes have maximal sizes than the rest of populations.…”

Diversity of sex chromosomes in Sulawesian medaka fishes

“…Since DMY gene was discovered as a sex-determination gene (Matsuda et al, 2002), a total of 3 sex-determining genes have been identified and 8 chromosomes have been reported to be sex-linked thus far (Myosho et al, 2015(Myosho et al, , 2012Nagai et al, 2008;Takehana et al, 2014Takehana et al, , 2008Takehana et al, , 2007. Furthermore, medaka fishes, particularly in Sulawesi Island, Indonesia, show great diversity in sexual dimorphism in body coloration and fin shapes (Mokodongan and Yamahira, 2015;Sumarto et al, 2020). These fishes enable us to test whether the sex chromosome evolution is associated with the evolution of sexually dimorphic traits.…”

Diversity of sex chromosomes in Sulawesian medaka fishes

“…Furthermore, despite the fact that Sulawesi Island, Indonesia, contains more than 20 medaka species and a hotspot of diversity in the medaka fishes (Mokodongan & Yamahira, 2015), the information of sex chromosomes in Sulawesiam medakas is limited. Because Sulawesiam medakas show great diversity in sexual dimorphism, such as prominent nuptial colorations and longer fins in the males (Mokodongan & Yamahira, 2015; Sumarto et al, 2020), these medaka fishes will provide us an excellent opportunity to test the link between the evolution of sex chromosome and sexual dimorphism.…”

“…Because Sulawesiam medakas show great diversity in sexual dimorphism, such as prominent nuptial colorations and longer fins in the males (Mokodongan & Yamahira, 2015;Sumarto et al, 2020), these medaka fishes will provide us an excellent opportunity to test the link between the evolution of sex chromosome and sexual dimorphism.…”