Spectral breakdown of morphometric chronoclines—A Paleogenetic problem
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Data on Nigerian Paleogene marine ostracodes are used to demonstrate that morphologic characters of species of the same group tend to vary parallelly through time in response to environmental stimuli. A model for the spectral breakdown of total morphometric variability into components of variation, possibly identifiable with environmental and genetic effects, by means of principal components analysis is tested on the ostracodes. In this model, the total variation is partitioned according to the equation
wheret stands for size variation in the phenotype supposedly of environmental origin,u represents variation of supposedly genetic origin, ande represents the residual variation. The results obtained for the ostracodes suggest that time series of the first principal component (“size”) vary, similar to the pattern shown by the original means. The second component follows another pattern, seemingly haphazard in nature and distinct from the first. The practical biostratigraphic significance of the results is reviewed.
$$x = t + u + e$$
KeywordsTime Series Principal Component Analysis Total Variation Genetic Effect Morphologic Character
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