English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Open

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

In lekking sage grouse (Centrocercus urophasianus), females exhibit relatively unanimous mate choice for particular males, but a satisfactory explanation for this unanimity has been elusive. We present analyses of mating distributions from two leks over 4 years that provide evidence for female choice based on differences in vocal display performance of males, the locations at which hens mated in the previous year, and the choices of other females (copying). The unanimity of female choice varied markedly among leks and years in correlation with changes in the mean numbers of hens that mated at the same time and hence the opportunity to copy. The results confirm that hens assess phenotypic traits of males directly but also indicate that the secondary tactics of site fidelity and copying are often important components of female choice. The occurrence of these secondary tactics has three implications: the variance in mating success among lek males will be a poor predictor of the intensity of sexual selection on specific traits; female preferences may generate more clustered dispersions of displaying males than predicted by hotspot settlement models; and direct assessment of males by females may be difficult or costly, a conclusion that supports adaptive models of sexual selection over a nonadaptive Fisherian process. In lekking birds and mammals, almost all matings are performed by a small minority of the males at the lek. Although in some species, the skew in male mating success may be largely due to aggressive dominance by a few males (Beehler and Foster, 1988), most observers concur that in the majority of lek species, the skew is a result of relatively unanimous female mate choice (for review, see Bradbury and Gibson, 1983; Wiley, 1991). G I B S O N , B R A D B U R Y , A N D V E H R E N C A M P , B E H A V I O R A L E C O L O G Y 2 (1 9 9 1 ) 2 Unfortunately, a satisfactory explanation of the processes that generate this degree of female unanimity has been elusive. The question is interesting because the answer promises to shed light both on the problem of lek evolution (Beehler and Foster, 1988; Höglund and Robertson, 1990; Warner, 1988) and on the central issue of why females should choose mates in nonresource-based mating systems (Heisler et al., 1988). In this paper we present data that show how unanimity of choice is generated in the sage grouse (Centrocercus urophasianus), a bird that exhibits classic lekking behavior. At least three mechanisms for the evolution of unanimous female choice on leks have been proposed. First, females may base choices on phenotypic or social traits exhibited by male courtship. Such preferences might have evolved by a Fisher process with no adaptive benefit to the females expressing them (Kirkpatrick, 1982; Lande, 1981), by good-genes sexual selection in populations with persistent heritability of overall fitness (Pomiankowski, 1988), or by direct selection on females to reduce intrasexual interference (Trail, 1985; Trail and Adams, 1989), reduce disease transmission (Borgia and Collis, 1990), or increase fertility (Avery, 1984). Female choice for behavioral or morphological traits of males appears to be common in lekking species, despite the uncertainty about its adaptive basis. Although several early studies failed to find phenotypic correlates of male mating success (for review, see Bradbury and Gibson, 1983), more recent work has identified clear correlations in 8 of 10 species of birds and mammals (Andersson, 1989; Balmford, 1990; Clutton-Brock et al., 1988; Gibson and Bradbury, 1985; Gratson, 1989; Höglund and Lundberg, 1987; Landel, 1989; McDonald, 1989; Petrie et al., 1991; Pruett-Jones and Pruett-Jones, 1990; Trail, 1984). Data from correlational studies are open to a variety of alternative interpretations. The most common is that some unmeasured factor, such as attractiveness of a male’s territory or male dominance, is the true determinant of female choice and that phenotypic traits are correlated with mate choice only because they are also linked to the critical trait (Wiley, in press). One way to resolve causation is direct manipulation of the possible factors. In several instances, this has been done, and the results have confirmed that individual identity or specific components of display or morphology affect mate choice independently of other factors such as territory location and aggressive interactions among males (Clutton-Brock et al., 1989; Gibson, 1989; Höglund et al., 1990). A second mechanism that could generate unanimity is a female preference for males in particular territories within the lek. Female site specificity might arise in short-lived insects in which a preference for some conspicuous topographic landmark would allow the sexes to meet with minimal search costs (Alcock, 1987). For longer-lived species (e.g., most vertebrates), fidelity of females to sites in which they had previously mated might be favored because mate choice was risky or costly in time (Warner, 1987, 1988). Once females favor males in certain sites, adaptive sexual selection (assuming male competition for sites reliably links male quality with location) might further favor the preference. The usual evidence cited for female site specificity is a correlation between proximity of a male to a lek “center” and mating success (Bradbury and Gibson, 1983; Gosling and Petrie, 1990; Kermott, 1982; Landel, 1989; Trail, 1984). Unfortunately, such a correlation can also be generated by the centripetal clustering of less successful males around successful ones (Gibson and Bradbury, 1986; Höglund and Robertson, 1990; Landel, 1989). A better G I B S O N , B R A D B U R Y , A N D V E H R E N C A M P , B E H A V I O R A L E C O L O G Y 2 (1 9 9 1 ) 3 approach is to monitor the success of specific lek territories through successive owners. Balmford (1990) has used this approach to demonstrate that previous history of a territory does affect subsequent mating success in Uganda kob. The third mechanism for unanimity is female copying of the choices of others. As suggested by theoretical analyses of resource assessment, copying may be advantageous where assessment of males is difficult and/or where sampling is costly (Boyd and Richerson, 1985; Clark and Mangel, 1984; Kiester and Slatkin, 1974; Losey et al., 1986; Shields et al., 1988; Stamps, 1988). However, the benefit of copying requires that some individuals assess males directly. When a high proportion of individuals copy, copying may yield a male far from the preferred phenotype because there is a risk of copying others that have not assessed males directly (Losey et al., 1986). Opportunities for copying at leks arise when a female can observe the choices of other females that mate before her, either because several females mate within the duration of single lek visit or because a female makes more than one visit to a lek before mating, as is typical of lekking birds (Gibson and Bradbury, 1986; Landel, 1989; Lill, 1974; Pruett-Jones and Pruett-Jones, 1990; Trail and Adams, 1989). The copying hypothesis is appealing because it could explain why mate choice is highly unanimous even where, as is often the case, correlations with phenotypic or spatial cues are low or absent (Wade and Pruett-Jones, 1990). This point is underscored by computer simulations which show that, unlike copying, independent female choice based on either phenotypic or spatial cues is unlikely to generate such an extreme mating skew as is observed in most field studies (Bradbury et al., 1985). Clutton-Brock et al. (1988) found that female fallow deer entered a lek harem at higher rates when the male began to mount an estrous female. The rate at which females entered harems also increased with harem size in both fallow deer (Clutton-Brock et al., 1989) and Uganda kob (Balmford, 1990). These observations are highly suggestive of copying, but they might also have arisen because both harem size and arrival rates were related to a third variable such as male display rate (see also Jamieson and Colgan, 1989; Ridley and Rechten, 1981). Among lekking birds, sage grouse are well suited for investigating mate choice. Leks are large and are easily observed due to the species’ large size, open habitat, and the predictable timing and location of display (a few hours at dawn and dusk during a 2–3-month period in the early spring). Males typically defend individual mating territories, and females are able to exert choice by entering a male’s territory and soliciting copulation. Except where territoriality has broken down, levels of intrasexual interference in courtship and copulation are low (Gibson and Bradbury, 198 7), so that differences in mating success must primarily reflect female choice. In a previous study, we showed that differences in mating success at a lek in one season were correlated with male lek attendance (as one might expect) and with differences in the rate and vocal performance of the stereotyped strut display. These results suggest that females base choice on display performance of those males present on the lek they visit (Gibson and Bradbury, 1985). Boyce (1990) has suggested that ectoparasitic lesions may also contribute to male phenotypic differences discerned by females, but such lesions were rare in our population and hence unlikely cues. Although sage hens appear to use male phenotype to some degree, it remains possible that they also use nonphenotypic cues. Wiley (1973) suggested that spatial cues play an G I B S O N , B R A D B U R Y , A N D V E H R E N C A M P , B E H A V I O R A L E C O L O G Y 2 (1 9 9 1 ) 4 important role in this species. We were unable to confirm his suggestion that hens prefer centrally located males (Gibson and Bradbury, 1985), but whether hens base choice on topographic cues or exhibit mating-site fidelity has not been adequately tested (but see Hartzler and Jenni, 1988). The possibility of copying was also raised in previous studies

Mate choice in lekking sage grouse revisited: the roles of vocal display, female site fidelity, and copying