Sexually mediated phenotypic variation within and between sexes as a continuum structured by ecology: The mosaic nature of skeletal variation across body regions in Threespine stickleback (Gasterosteus aculeatus L.). Issue 10 (13th October 2022)

• Record Type: Journal Article
• Authors: Schutz, Heidi; Anderson, Rebecca J.; Warwick, Ethan G.; Barry, Tegan N.; Jamniczky, Heather A.
• Is Part Of: Ecology and evolution. Volume 12:Issue 10(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-10-13
• Subjects: morphological evolution -- morphometrics -- mosaic phenotypic variation -- sexual variation -- skeleton -- stickleback; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.9367
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Ecological character displacement between the sexes, and sexual selection, integrate into a convergent set of factors that produce sexual variation. Ecologically modulated, sexually mediated variation within and between sexes may be a major contributor to the amount of total variation that selection can act on in species. Threespine stickleback ( Gasterosteus aculeatus ) display rapid adaptive responses and sexual variation in many phenotypic traits. We examined phenotypic variation in the skull, pectoral and pelvic girdles of threespine stickleback from two freshwater and two coastal marine sites on the Sunshine Coast of British Columbia, Canada, using an approach that avoids a priori assumptions about bimodal patterns of variation. We quantified shape and size of the cranial, pectoral and pelvic regions of sticklebacks in marine and freshwater habitats using 3D geometric morphometrics and an index of sexually mediated variation. We show that the expression of phenotypic variation is structured in part by the effects of both habitat marine vs freshwater and the effects of individual sites within each habitat. Relative size exerts variable influence, and patterns of phenotypic variation associated with sex vary among body regions. This fine‐grained quantification of sexually mediated variation in the context of habitat difference and different anatomical structures indicates a complex relationship between genetically inferred sex and environmental factors, demonstrating that the interplay between shared genetic background and sexually mediated, ecologically based selective pressures structures the phenotypic expression of complex traits. Abstract : This study was designed to examine the relative importance of sex in structuring phenotypic variation in stickleback fish. We used replicate examples of two habitat types (marine and freshwater) as a means of testing the hypothesis that the interplay between shared genetic background and sexually‐mediated selective pressures structures phenotypic expression of complex traits in a mosaic fashion. We found that sexual variation in the skull and girdles of sticklebacks does not manifest in a clear and uniform pattern of binary sexual dimorphism. Rather, it is a continuum of variation differing across structural units and reflecting the interacting effects of genetic sex and ecology on phenotypic variation.