Signal efficacy and the evolution of male dimorphism in the jumping spider, Maevia inclemens.

An extreme form of male dimorphism occurs in the jumping spider, Maevia inclemens, where two male morphs differ dramatically in both morphology and behavior. We examined the visual signals transmitted to females by the two different morphs during courtship display. Even though the display of each male is different, as a function of behavior and courtship distance, the males present females with images that are almost identical in height and visual target area. By substituting live males with computer-animated sequences of male courtship behavior, the male morphs were superimposed upon each other, and females were determined to have two distinct male-recognition templates. We hypothesize that the dimorphic males of this species evolved through sensory exploitation and selection for alternative male strategies that stimulate different fields of the female visual range. IMAGES: