On the maintenance and origin of alternative strategies in the Ruff Philomachus pugnax

Abstract

This paper has tried to answer the question of how the independent and the satellite strategy of the Ruff originated and has been maintained during evolution. It is not intended as a report of a piece of completed research but gives a number of tentative, but testable hypotheses. Data are presented that independent males and satellites are equally successful in copulating, provided that almost all copulations occur on leks, and independent males and satellites spend an equal proportion of their time on leks. The extent that males with the different strategies are attached to leks is analysed. Within the group of independent males, considerable differences exist: a resident male is strongly attached to only one particular lek and a marginal male seems to sample many leks. A satellite male behaves intermediately: he is attached to a limited number of leks. The mechanism for the maintenance of both strategies could not be explained by competition for resources (copulations). Contests between independent males and satellites are asymmetric, the satellite being the weaker contestant. The mechanism seems to be due to enlarging the accessibility of the resource by cooperation between both strategies. The ideas on the origin of the system are based mainly on the behaviour of females. There is no relation between the distribution of leks and the size of a female's foraging area, except that most leks are situated along the migration route. It further seems that the number of copulating females in the Netherlands is larger than the number of males on leks, but the number of breeding females is much lower. It is suggested that many females copulate on migration, which is related to extreme breeding conditions in the north of the range. Apart from a change in the sex ratio from south to north, a change in the proportion of satellites is also predicted. The origin of the system is ascribed to the incompatibility between favourable food conditions for chicks and further possibilities for inter‐male competition on leks in the same area. The satellite strategy is considered as being derived from a non‐competitive strategy accompanying females on migration. In the phase of cooperation between resident and satellite males, individual recognition became important. This could be the factor underlying the evolution of white plumages in satellites and the extreme plumage diversity in independent males.

Diversity of Nuptial Plumages in Male RuffsPhilomachus pugnax

“…Our results are consistent with earlier findings (Dobrinskij 1969, van Rhijn 1983, Höglund & Lundberg 1989) that body size in males with white plumages tends to be smaller than in dark males. Yet, the differences, especially in wing length, were considerably smaller than in earlier studies (about 1 mm or less than 1% of the total, compared to about 4 mm or 2% of the total in earlier studies).…”

“…Satellite males on leks are slightly smaller than independent males (van Rhijn 1983). Female mimics are considerably smaller than other males (Jukema & Piersma 2006).…”

Genetic variation in nuclear and mitochondrial markers supports a large sex difference in lifetime reproductive skew in a lekking species

“…The 97% reduction in nuclear genetic variation is empirical support for the assumed stronger interindividual variance in lifetime reproductive success (LRS) of male ruffs relative to females. This result confirms the intuition of previous field researchers who observed the large investments by some males in dominating the lek (Hogan‐Warburg ; van Rhijn , ). Males may display so intensively that they refrain from eating and drinking, and lose mass throughout the breeding season (Widemo ; Bachman and Widemo ).…”

A dominant allele controls development into female mimic male and diminutive female ruffs

“…Previous considerations of the relative fitnesses of ruff morphs have only considered the mating success of ornamented males [6,10,24,25]. Although a female's Satellite -locus genotype can be inferred from male behaviour induced by administration of testosterone [17], there is no obvious reason to expect differential selection on the alternative Satellite alleles in females.…”