GEOGRAPHICAL VARIATION IN MALE COURTSHIP BEHAVIOR AND SEXUAL ISOLATION IN WOLF SPIDERS OF THE GENUS SCHIZOCOSA

We surveyed 12 populations of the wolf spider Schizocosa crassipes (Wa lckenaer) and S. nr. crassipes in Tennessee, Mississippi, Louisiana an d Florida, in the U.S, to determine the extent of variation in male co urtship behaviour when observed in standard laboratory conditions. We observed variation in both the frequency of occurrence and the sequenc e of the four principal male courtship behaviours and, when compared s tatistically, most of these behaviours differed between populations. A lthough there was no clinal pattern in the frequency of courtship beha viour, we observed geographically consistent patterns in the sequence in which male courtship behaviours are displayed. We conducted two sub sequent studies to determine whether sexual isolation among selected p opulations existed. In the first study, we performed male-female recip rocal crosses of brush-legged spiders (S. nr. crassipes) between two p opulations from the Yazoo-Mississippi Delta physiographical region and one population from the Loess Bluff region of Mississippi and measure d mating success, number of matings that produced egg sacs, and the nu mber of egg sacs that hatched young. The results of that experiment su ggest that sexual isolation occurs among populations in different phys iographical regions but not between populations within regions of the state. In a second crossing study, we paired the brush-legged spiders from one of the Mississippi physiographical regions (Yazoo-Mississippi Delta) with Schizocosa ocreata (Hentz) from Ohio. The results of that cross suggest that the Mississippi Delta population is more similar t o the northern S. ocreata populations than to S. crassipes. We discuss the results of the crossing experiments in terms of what was revealed about geographical patterns in male courtship behaviour. (C) 1998 The Association for the Study of Animal Behaviour.