Sexual dimorphism of fish
Sexual selection is considered the major cause of sexual dimorphism, but recent observations suggest that natural selection may play a more important role in the evolution of sex differentiation than previously recognized. Therefore, studying the trade-offs between natural selection and sexual selection is crucial to a better understanding of the ecology underlying the evolution of sexual dimorphism. The freshwater blenny Salaria fluviatilis , a fish inhabiting lakes and rivers around the Mediterranean Sea, displays strong sexual dimorphism in size, shape, and behavior i. We tested for differences in sexual dimorphism in size and shape between the populations from lake and river habitats with the goal of identifying the trade-offs between natural and sexual selection that underlie variations in sexual dimorphism in this species. Together, this suggests that the different environmental conditions between lake and river habitats e. This study highlights the importance of considering the environmental conditions to which populations are exposed to better understand the ecology underlying the evolution of sexual dimorphism.
Sexual dimorphism - Wikipedia
Sexual dimorphism is common across the animal kingdom, but the contribution of environmental factors shaping differences between the sexes remains controversial. We further anticipated that this gender difference would progressively decrease with the increasingly harsh environmental conditions toward higher latitude. Growth of both sexes decreased with increase in latitude, and the female latitudinal clines were steeper than those of males. One prominent macroecological pattern is the Rensch's rule Rensch, , which states that the magnitude of SSD tends to increase with increase in body size when males are the larger sex and to decrease with increase in size when females are larger Fairbairn, Consequently, male body size varies more than female body size, irrespective of which sex is larger.
Latitudinal variation in sexual dimorphism in life‐history traits of a freshwater fish
Fish samples were collected between July and December Fourteen morphometric variables, including body weight, total length, standard length, body depth, cheek depth, pre-orbital length, postorbital length, pectoral fin length right and left , pelvic fin length right and left , head length, gonad weight, eye diameter and four meristic variables, including number of pectoral fins right and left and number of pelvic fins right and left , were taken using standard methods. Size-adjusted morphometric measurements subjected to step-wise discriminant function analysis were used to determine predictor variables to morphologically differentiate sexes for both species; magnitude of dimorphism between sexes was estimated using percentage classification accuracy of the discriminant function analysis. Overall, our results indicate that the different magnitude of sexual dimorphism between the two species could be attributable to the type and functional role of sexual dimorphic traits. Alfaro M.
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