Research Training Program

Erik Martin
Los Angeles Valley College
Van Nuys, CA

William A. DiMichele, Ph.D.
Supervising Scientist
Department of Paleobiology

"This summer has been an all encompassing experience. Kudos to everyone involved. Viva RTP"

A study of the character variance and correlations of Neuropteris ovata through its existence in the fossil record was conducted. This study attempted to prove the hypothesis of the German paleontologist, Otto Schindewolf that species lineages will go through a three-part cycle of youth, maturity, and old age. In the 1940's, Schindewolf proposed that this theory, which he called typostrophism, was the main factor in determining how long a species would last before it went extinct. We proposed that due to the action of natural selection, the species over time will become more and more specialized at occupying an ever-narrowing range. This overspecialization will at some point in the plants' existence no longer be advantageous, and in fact, will leave the species vulnerable to extinction. This hypothesis should be testable by measuring various morphological characteristics of the species, and plotting the variance and correlation between those characteristics over time. If selection is indeed reducing the natural variability of the species then the variance should go down over time. On the other hand, as the variability of the species goes down one could assume that the character correlations would in turn go up over time as the species becomes more uniform. In this study several characteristics of N. ovata leaf pinnules were measured at six different intervals in the fossil record. These characteristics were length, width, distance between pinnules, length of the midvein, number of veins per millimeter of margin, and number of times the veins branched from the midvein to the margin. The results of this study were, for the most part, inconclusive. This is due probably to the fact that many of the fossils in the collections were not well enough preserved in a fashion conducive to gathering the data required. Another possibility is that the evidence for the species decreasing variance is not present on the pinnules, but rather in some other part of the plant that is not well represented in the fossil record.