Female‐biased dimorphism in size and age at maturity is reduced at higher latitudes in lake whitefish Coregonus clupeaformis

Abstract

Female-biased sexual dimorphism in size at maturity is a common pattern observed in freshwater fishes with indeterminate growth, yet can vary in magnitude among populations for reasons that are not well understood. According to sex-specific optimization models, female-biased sexual size dimorphism can evolve due to sexual selection favouring earlier maturation by males, even when sexes are otherwise similar in their growth and mortality regimes. The magnitude of sexual size dimorphism is expected to depend on mortality rate. When mortality rates are low, both males and females are expected to mature at older ages and larger sizes, with size determined by the von Bertalanffy growth equation. The difference between size at maturity in males and females becomes reduced when maturing at older ages, closer to asymptotic size. This phenomenon is called von Bertalanffy buffering. The predicted relationship between the magnitude of female-biased sexual dimorphism in age and size at maturity and mortality rate was tested in a comparative analysis of lake whitefish Coregonus clupeaformis from 26 populations across a broad latitudinal range in North America. Most C. clupeaformis populations displayed female-biased sexual dimorphism in size and age at 50% maturity. As predicted, female-biased sexual size dimorphism was less extreme among lower mortality, high-latitude populations.

General patterns of sexual dimorphism in graylings (Thymallus), with a comparison to other salmonid species

“…In female graylings, the commonly observed female-biased dimorphism in size among other salmonid species (e.g. Tamate and Maekawa 2004;Morbey 2018) is not supported in our analysis, although length dimensions of the abdomen and distances between fins were generally longer in females. However, these differences may be a secondary effect of the position of the fins perhaps in relation to the extended dorsal and anal fin bases in males.…”

The gill-oxygen limitation theory (GOLT) and its critics

“…Similarly, regarding item (ii), in over 80% of fish families where females and males look alike, it is the females that eventually reach larger sizes (Fig. 3B), even if this growth dimorphism can become attenuated in certain circumstances (81). This strong female dimorphism should lead to a rethink of the notion that the cost of reproduction causes growth to decline.…”

Morphological Characterization of Lithognathus mormyrus (Linnaeus, 1758) Populations in the Southern Black Sea (Turkey)

“…and DFBL, and this situation showed that head and fin length might differ by sex. Similarly, Morbey (2018) reported that sexual differences were generally seen in fin size and head morphology. It may occur because aquatic environments present different characteristics, habitats, or diets (Delariva & Agostinho, 2001).…”

“…Geographic and different environmental components can vary in single morphological characteristics, growth patterns, and body shape within and among populations (Firmat, Schliewen, Losseau, & Alibert, 2012). For fish, sexual dimorphism, generally, has been recorded in body size, fin size and shape, color pattern, and head morphology (Morbey, 2018). Females are usually larger than males of the same age, while males are larger than females for some species (Mann, 1980).…”