The flexible lek: Phymatopus hecta the gold swift demonstrates the evolution of leking and male swarming via a hotspot (Lepidoptera: Hepialidae)

Leking moths present an evolutionary problem in their apparently simultaneous reversal of male-female attraction. The mating system of Phymatopus (or Hepialus) hecta embraces an unusually wide range of procedures. Both males and females use medium-range olfactory attractants (also probably visual signals), and both sexes will lure, and both will approach, the other, either when flying or perched. This produces an infinite variety' which includes the classic moth mating procedure (males fly to sessile female); a typical lek procedure (female flies to sessile male); a mating swarm (hovering male follows passing female); and intermediates such as a mutual courtship dance. Male behaviour includes a flying display, two sessile displays, and an escalating war of attrition. The system is versatile, persistent, and probably evolutionarily stable. The lek site has a high density of perches suitable for copulation which facilitate predator-escape by means of a dead drop. The whole supports a model for the evolution of resource-based leks which commence with a concentration of females on a hotspot, leading to a concentration of males; and then an escalating process of sexual selection as males become increasingly attractive over a distance to females, and females use the males as a way of locating the resource. The main stabilizing pressure may be selection for efficient mate acquisition, and as with grouse leking systems, the precondition for evolution was probably having travelling females that actively sought a reproductive resource or a predator free space.(c) 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114, 184-201.