EFFECT OF POPULATION DENSITY ON SEX RATIO OF HETERODERA ROSTOCHIENSIS . A 2 DIMENSIONAL MODEL

A model was based on the hypothesis that the second stage larvae of H. rostochiensis arrive at their feeding sites within the host plant roots at random, and become female only when they have room to produce a large enough group of giant cells. The circumference of the stele of 1 cm of root was represented as a rectangle in which larvae formed groups of giant cells at random. The size of the giant-cell group that a larva needed to become a female was changed in different tests. A larva arriving in an unoccupied space large enough to accomodate such a group was designated female, whereas one whose giant cells overlapped one or more already present was designated male. Results calculated from the model agreed reasonably with those from experiments. To simplify the relationship between population density and the number of females produced, an exponential curve was fitted to the results. © 1969 BRILL.