Quantification of Phenotypic Variation in populations of Newfoundland Threespine Stickleback (Gasterosteus aculeatus)

Date of Award


Degree Type


Degree Name

Master of Science in Biology



Chief Instructor

John A. Baker

Second Reader

Susan A. Foster

Third Reader

John A. Baker


Phenotypic variation in morphology driven by ecological factors has been well characterized in Alaskan and British Columbian populations of threespine stickleback, with studies demonstrating that the variation is extensive in a wide variety of anti-predator traits and body shape. In contrast, the limited published studies of stickleback in eastern North America suggest that there is relatively little among-population phenotypic variation in anti-predatory armor and body shape. Recent samples obtained from 30 populations of stickleback in Newfoundland, from a wide array of habitats, indicate that the earlier suggestion of relatively limited phenotypic diversity may need to be reevaluated. Using geomorphic morphometrics plus more traditional measures of specific body parts (for body shape), and linear measurements and counts of armor features (for anti-predator aspects), I quantified the degree of variation both within and across populations. Using summary metrics, I then compared the variation in effective body depth (a holistic measure which accounts for body depth and extension of all functional spines) between Newfoundland populations to that of Alaskan populations, to more rigorously test the original suggestion of more limited variation. Data acquisition and results suggest that this region on average has more coverage and prominent armor features than documented in other regions. The degree of variation is easily appreciated in armor features with the magnitude of divergence extending several standard deviations in some components. Variation of body shape in Newfoundland populations is also extensive. Discrepancies between the marine form and freshwater forms is described along with the first documentation of ecological niche specializers, ecotypes in Newfoundland.

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