Lek mating

A lek is an aggregation of male animals gathered to engage in competitive displays, lekking, to entice visiting females which are surveying prospective partners for copulation. Leks are commonly formed before or during the breeding season. A lekking species is characterised by male displays, strong female mate choice, and the conferring of indirect benefits to males. Although most prevalent among birds such as black grouse, lekking is also found in insects including paper wasps, crustaceans, fishes, amphibians, reptiles and mammals.The term derives from the Swedish lek, a noun which typically denotes pleasurable and less rule-bound games and activities ('play', as by children). English use of lek dates to the 1860s. Llewelyn Lloyd's The Game birds and wild fowl of Sweden and Norway (1867) introduces it (capitalised and in single quotes, as 'Lek') explicitly as a Swedish term.The term was originally used most commonly for black grouse (Swedish: 'orrlek') and for capercaillie (Swedish: 'tjäderlek'), and lekking behavior is quite common in birds of this type, such as sage grouse, prairie chicken, great bustard and sharp-tailed grouse. However, lekking is also found in birds of other families, such as the ruff, great snipe, Guianan cock-of-the-rock, musk ducks, hermit hummingbirds, manakins, birds-of-paradise, screaming pihas and the kakapo. Lekking is seen in some mammals such as fallow deer, Ugandan kob (a waterbuck), some pinnipeds, some bats, and the topi antelope. Lekking is found in amphibians such as moor frogs and bullfrogs, reptiles such as marine iguanas and some species of fish (e.g., Atlantic cod, desert pupfish, and the cichlid Astatotilapia burtoni). Even insects like the midge, ghost moth, and lesser wax moth demonstrate lekking behavior. Lekking is also found in some paper wasp species such as Polistes dominula, the orchid bee Eulaema meriana, in some butterfly species like the black swallowtail (Papilio polyxenes), and in tarantula hawks like Hemipepsis ustulata.There are two types of lekking arrangements: classical and exploded. In the classic lekking system, male territories are in visual and auditory range of their neighbours. In an exploded lek, males are further away from one another than they would be in a classic lek. Males in an exploded lek are outside of visual range of one another, but they stay within earshot. Exploded lek territories are much more expansive than classic systems and are known to exhibit more variation. A well-known example of exploded leks is the 'booming' call of the kakapo, the males of which position themselves many kilometres apart from one another to signal to potential mates.The main benefit for both sexes is mating success. For males, the costs stem from females’ preferences. The traits that are selected for may be energetically costly to maintain and may cause increased predation. For example, increased vocalization rate caused a decrease in the mass of male great snipes. Other costs can derive from male combat. For example, male great snipes regularly fight to display dominance or defend their territory, with females preferring victorious males. Aggressive male black grouse are preferred over non-aggressive males and when the males fight they tear feathers from each other's tails.A meta analysis of 27 species found that qualities such as lekking size, male display rate, and the rate of male aggression exhibit positive correlation with male success rates. A positive correlation was also found between attendance, magnitude of exaggerated traits, age, frequency of fights, and mating success. This female preference leads to mating skew, with some males being more successful at copulating with females. The variation in mating success is quite large in lek mating systems with 70-80 percent of matings being attributed to only 10%-20% of the males present.Since sexual selection by females for specific male trait values should erode genetic diversity, the maintenance of genetic variation in lekking species constitutes a paradox in evolutionary biology. Many attempts have been made to explain it away, but the paradox remains. There are two conditions in which the lek paradox arises. The first is that males contribute only genes and the second is that female preference does not affect fecundity. Female choice should lead to directional runaway selection, resulting in a greater prevalence for the selected traits. Stronger selection should lead to impaired survival, as it decreases genetic variance and ensures that more offspring have similar traits. However, lekking species do not exhibit runaway selection. In a lekking reproductive system, what male sexual characteristics can signal to females is limited, as the males provide no resources to females or parental care to their offspring. This implies that females gain indirect benefits from her choice in the form of 'good genes' for her offspring. Amotz Zahavi argued that male sexual characteristics only convey useful information to the females if these traits confer a handicap on the male. The handicap principle may be a resolution to the lek paradox, for if females select for the condition of male ornaments, then their offspring have better fitness. One potential resolution to the lek paradox is Rowe and Houle's theory that sexually selected traits depend on physical condition, which might in turn, summarize many genetic loci. This is the genic capture hypothesis, which describes how a significant amount of the genome is involved in shaping the traits that are sexually selected. There are two assumptions in the genic capture hypothesis: the first is that sexually selected traits are dependent upon condition and the second is that general condition is attributable to high genetic variance. In addition, W. D. Hamilton and M. Zuk proposed that sexually selected traits might signal resistance to parasites. One resolution to the lek paradox involves female preferences and how preference alone does not cause a drastic enough directional selection to diminish the genetic variance in fitness. Another conclusion is that the preferred trait is not naturally selected for or against and the trait is maintained because it implies increased attractiveness to the male.There have been several hypotheses proposed as to why males cluster into leks. The hotshot hypothesis is the only model that attributes males as the driving force behind aggregation. The hotshot model hypothesizes that attractive males, known as hotshots, garner both female and male attention. Females go to the hotshots because they are attracted to these males. Other males form leks around these hotshots as a way to lure females away from the hotshot. A manipulative experiment using the little bustard, Tetrax tetrax, was done to test the various lek evolution models. The experiment involved varying the size and sex ratio of leks using decoys. To test whether or not the presence of a hotshot determined lek formation, a hotshot little bustard decoy was placed within a lek. After the fake hotshot was added to the lek, both male and female visitation to the lek increased.