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.)

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.

Characterizing contemporary evolutionary change in a recently isolated population of threespine stickleback (Gasterosteus aculeatus L.)

“…This divergence suggests that this axis of variation may be capturing variation that is partly driven by sex. Several previous studies have observed sexually mediated variation in morphological traits in stickleback (e.g., Aguirre et al 2008;Aguirre and Akinpelu 2010;Leinonen et al 2011a;Kitano et al 2012), including between individuals from the comparative localities described here (Schutz et al 2022). Interestingly, while there is a significant effect of sex on shape in Lost Lagoon (Table 1), the nature of this variation is not clearly captured along either of the two largest principal components of variation within this group (Fig.…”

“…3). Sexually mediated variation in stickleback is known to vary in expression across habitats (Spoljaric and Reimchen 2008) and may be obscured by habitat-associated differences in body shape (Schutz et al 2022). In the Lost Lagoon population documented here, which is in the process of adapting to fresh water, changing Eda allele frequencies are likely driving gradual body shape change that is obscuring the nature of any sexually mediated variation in body shape within the Lost Lagoon sample.…”

Classifying high-dimensional phenotypes with ensemble learning

“…(1) (Schutz et al, 2022), Gasterosteidae (2) (Fraser & El-Sabaawi, 2022), Hominidae (Krenn et al, 2022), Hynobiidae (Jia et al, 2022), Muridae (a/b) (Devine et al, 2022), Poeciliidae (Riesch et al, 2016), Serranidae (Alós et al, 2014), Cichlidae (Ronco et al, 2020), Colubridae+ (Head & Polly, 2015), Crocodylidae (Watanabe & Slice, 2014), Formicidae (Kennedy et al, 2014), Ocypodidae (Hopkins et al, 2016), Percidae (Martin & Mendelson, 2014), Vespidae (Perrard et al, 2014), andViviparidae (Van Bocxlaer &Hunt, 2013). Dataset details are listed in Table S1.…”