Geographic variation in the territorial success of Drosophila melanogaster males.

Drosophila melanogaster males defend food against other males to increase their access to females on food. The territorial behavior of stocks collected from Townsville, Corindi, and Melbourne on the east coast of Australia were compared. Males from these stocks showed the same incidence of territorial encounters. However, Melbourne males were more successful at obtaining territories in competition with Townsville or Corindi males. This difference could be accounted for largely by variation in body weight, although territorial success was also determined by other factors because Townsville and Corindi males that held territories were not heavier than Melbourne males. In reciprocal crosses between the populations there was directional dominance for increased territorial success. F1 males were of intermediate weight and F1 males that held territories tended to be lighter than territorial Melbourne males. Melbourne males were more successful than Townsville males because they tended to win escalated encounters, resulting in displacement of territory residents.