Evol Ecol Res 20: 27-50 (2019)     Full PDF if your library subscribes.

The role of genetic and environmental background driving ontogenetic trajectories of skeletal variation in the Threespine stickleback (Gasterosteus aculeatus L.)

Alexandra E. Pistore¹, Tegan N. Barry², Stevi L. Vanderzwan²,

Heidi Schutz³, Sean M. Rogers² and Heather A. Jamniczky¹

¹Department of Cell Biology and Anatomy, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada,  ²Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada and ³Biology Department, Pacific Lutheran University, Tacoma, Washington, USA

Correspondence: H.A. Jamniczky, Department of Cell Biology and Anatomy, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada. email: hajamnic@ucalgary.ca

ABSTRACT

Background: Despite their prominence as an evolutionary model, little is known about the developmental trajectories that produce phenotypic differences among Threespine stickleback (Gasterosteus aculeatus) occupying different habitats. The relationship between shape and size over ontogeny is known to provide an important context for the study of rapid adaptive change.

Objective: Quantify phenotypic variation in skeletal shape and the relationship between shape and size across ontogenetic stages from 90 days post-fertilization to reproductive maturity in stickleback occupying representative habitats.

Methods: We collected wild, reproductively mature fish from marine and freshwater habitats in coastal British Columbia. These were crossed and raised in the laboratory and sampled sequentially for one year. We used 3D geometric morphometrics to quantify the shape of the cranial and postcranial skeleton and to compare ontogenetic trajectories.

Results: Skeletal phenotypes are already distinct by 90 days post-fertilization and remain so throughout ontogeny. The greatest differences occur between freshwater and protected marine habitats. The relationship between shape and size is different for each habitat at each point in time. Ontogenetic trajectories differ among all three habitats, with marine individuals forming more similar trajectories than the those from the freshwater habitat. Our results indicate that genetic differences contribute more strongly to the divergence of freshwater forms from marine forms, while stratification between marine phenotypes is produced by the contribution of developmental timing changes and functional constraints.

Keywords: development, Gasterosteus aculeatus, geometric morphometrics, ontogeny, phenotype, skeleton, Threespine stickleback.

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