Sexual size and shape evolution in European newts (Amphibia: Caudata: Salamandridae) on the Balkan Peninsula

Abstract

We used a phylogenetic perspective in an examination of the direction and extent of sexual dimorphism in body size and body shape in European newts from the Balkan Peninsula (alpine newts, Mesotriton alpestris; crested newts, Triturus cristatus superspecies; smooth newts, Lissotriton vulgaris). We found a strong, female-biased sexual size dimorphism (SSD) in the analysed clades of alpine newt, whereas within crested newts we found a less stringent female-biased SSD in Triturus carnifex, Triturus macedonicus and Triturus karelinii, and no significant SSD in T. cristatus or Triturus dobrogicus. Among the smooth newts, we found male-biased SSD in Lissotriton vulgaris vularis and Lissotriton vulgaris greacus and no SSD in Lissotriton vulgaris meridionalis. Most of these newts also exhibit a significant sexual dimorphism in body shape, which varied more randomly than body size, regardless of SSD level. Female and male body size as well as the degree of SSD displayed statistically significant phylogenetic signal, while sexual dimorphism in body shape was phylogenetically independent. The relationship between independent contrast data for female size and male size indicated that SSD in European newts could be driven by a disproportionate increase in female size as increase in female size was not accompanied by a proportional increase in male size.

Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

“…We cannot say whether this result is due to the different phylogenetic history of the Triturus genus. One of the main cause of nonsignificant differences in digit ratio between sexes can be small sexual size dimorphism in T. cristatus (Ivanović et al, 2008). Another reason could be that crested newts spend more time in water than Lissotriton and Mesostriton.…”

“…T. cristatus is more aquatic than other European newt species; moreover, immature crested newts can sometimes be found in water (Jehle et al, 2011;Sparreboom, 2014). In this species differences in body-size between sexes are D2:D4 IN CAUDATA nonsignificant (Ivanović et al, 2008). M. alpestris (the alpine newt), is a medium-sized newt with an unspotted orange belly and throat.…”

“…The alpine newt occurs in a variety of habitats such as large water ponds, temporary ponds, or forested areas (Sparreboom, 2014). In this species a strong female-biased sexual size dimorphism is well expressed (Ivanović et al, 2008).…”

Sexual dimorphism in the skull geometry of newt species of Ichthyosaura, Triturus and Lissotriton (Salamandridae, Caudata, Amphibia)

“…Previous studies revealed that the sexual differences in body size range from female-biased (females larger than males) sexual dimorphism in Ichthyosaura alpestris, more labile SSD in Triturus newts and even male-biased SSD in Lissotriton vulgaris (Malmgrem and Thollesson 1999;Ivanović et al 2008a). In these newts, the relationship between body size and the level of sexual size dimorphism does not follow Rensh's rule (Ivanović et al 2008a), which states that in groups with male-biased SSDs, the sexual dimorphism increases in larger groups (species, races or populations) and on the contrary, in the cases of femalebiased SSD, the intersexual difference diminishes in larger groups (e.g.…”

“…In these newts, the relationship between body size and the level of sexual size dimorphism does not follow Rensh's rule (Ivanović et al 2008a), which states that in groups with male-biased SSDs, the sexual dimorphism increases in larger groups (species, races or populations) and on the contrary, in the cases of femalebiased SSD, the intersexual difference diminishes in larger groups (e.g. Abouheif and Fairbairn 1997).…”