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Determining the Role of Morphology in Reproductive Isolation between Two Related Species

Fossberg, Sydnie
Very closely related species are ideal candidates for studying the finer mechanisms of evolution. This study aims to determine the role of ecologically valuable physical traits in maintaining reproductive isolation between two recently diverged species, the Red-naped Sapsucker ( Sphyrapicus nuchalis ) and the Red-breasted Sapsucker ( S. ruber ), by analyzing the morphological differences in a collection of specimens taken from an area in which they interbreed. I measured and recorded the mass, dimensions of the bill, length of the wing chord, and length of the tarsus for each of the specimens, then described how these traits vary by ancestry and sex. I found that the males of two species differed significantly in the length of the wing chord, the length of the tarsus, and in mass, but that any differences involving females were negligible. Of the traits that differed between the two parental species, we found evidence that only mass and wing chord are contributing to reproductive isolation between the subspecies. These findings show that traits that are not traditionally considered important to sexual selection still play a role in the early divergence of species.
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University of Wyoming. Libraries
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speciation , hybrid zones , reproductive isolation , species divergence , evolution
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