Intra-specific competition in the sex communication channel : a selective force in the evolution of moth pheromones?

• A model for mate competition in moths sexually signalling with pheromones is presented. The model has four variables. N is the number of individuals of each sex per area unit. r is the length of the female odour plume as detected by a responding male. ε is a parameter increasing with male ability to discriminate between concentrations. r-ε becomes the competitive part of the female pheromone plume, i.e. the distance at which an upwind female is able to distract males from downwind plumes. Assuming a random distribution of males and females the number of matings in a generation can be calculated. Introducing a fourth parameter, B = surviving offspring of each sex from a mating, the population dynamics of the population can be described. Two special cases are analysed; (1) ε = r, and (2) ε = 0. In case (1) mating success increases with population density towards unity. In case (2) interference between the pheromone plumes of different females will lower the mating success at higher population densities. The stability of the communicating population decreases with increasing ε and B. We conclude that there should be a strong selection pressure for male ability to discriminate between odour plumes under natural circumstances and for individually distinguishable pheromone plumes.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

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