Graduation Year

2014

Document Type

Open Access Senior Thesis

Department

W.M. Keck Science Department

Second Department

Biology

Reader 1

Lars Schmitz

Reader 2

Donald A. McFarlane

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© 2014 Amanda YL Jacobs

Abstract

Common ancestry prevents scientists from using traditional statistical tests in dimensional comparisons that span entire clades. Data in these cases are non-independent, so a variety of special statistical methods have been developed specifically for phylogenetic comparative analyses. A phylogenetic least squares method was used to re-examine four published datasets detailing structural correlates of eyes while factoring in the different ways the phylogeny was expected to affect the covariance in trait values. All analyses were carried out in a strict phylogenetic context, using published time-calibrated phylogenies and the statistical platform R. Specifically, Pagel’s lambda was used to determine how much of an influence phylogeny had on each pair of traits. In all tested soft and hard tissue correlations, the phylogeny of the species slightly altered the trend lines of the measurements, compared to lines that did not take phylogenetic relationship into consideration. These results do not contradict previous results, but further work needs to be done to determine the implications that significant phylogenetic signal has on subsequent analyses. Future studies should account for phylogenetic relationships which have been shown to influence the relationship between traits.

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