LEK SIZE, MALE MATING SKEW AND THE EVOLUTION OF LEKKING

DESPITE extensive theoretical effort(1,8), the evolution of lekking as a mating system remains a controversial issue(9,10). Leks are nonreso urce-based matins aggregations(2), but may also be regarded as patches differing in female encounter rate(2,3,5,7). We report here a new dis tribution model that incorporates variation in male mating skew with l ek size. The model predicts that, under specified conditions, high-ran king males have smaller optimal lek sizes than low-ranking males. All males benefit from initial clustering, but only low-ranking males gain from large aggregations. This generates progressive clustering around high-ranking males at hotspots determined by female spatial distribut ions. The predictions of our model were validated in two ways using em pirical data on lekking ruffs, Philomachus pugnax. Our model integrate s the basic elements of the previously competing hotspot(2,3) and hots hot(4) models of lek evolution by a simple mechanism, and could explai n the evolution of lekking.