Does female plumage coloration signal parental quality? A male removal experiment with the bluethroat (Luscinia s. svecica)

Females in several sexually dimorphic species with conventional sex roles possess ornamental traits that resemble those found in males. The evolution of such traits, however, is still poorly understood. Bluethroats (Luscinia s. svecica) are socially monogamous, sexually dichromatic passerine birds, in which female throat patch coloration varies from near absence to near full expression of male-like coloration. A recent study, demonstrating that male bluethroats prefer colourful females, suggests that female coloration is subject to sexual selection through male choice. However, the benefits males may gain from mating with colourful females have not yet been identified. In this study we tested the hypothesis that female coloration signals parental quality (the good-parent hypothesis). During the course of the same day, we recorded female care both in the presence and the absence of the male mate. The latter was done to eliminate the confounding effect of variable male care by removing the male temporarily. Female coloration did not correlate with female feeding rates either in the presence or in the absence of the male. Female feeding rates in the absence and the presence of the male were positively, although weakly, correlated. Female coloration did not correlate with female ability to compensate for the loss of male care, or with the change in brood mass during male removal. Therefore, there is no evidence for the good-parent hypothesis to explain female plumage coloration in bluethroats. Received: 4 March 1999 / Received in revised form: 14 October 1999 / Accepted: 23 October 1999     

装饰不锈钢管抛光粉尘的治理

通过装饰不锈钢管抛光粉尘治理实例，介绍除尘系统密闭罩设计、除尘以及装置的降噪、防腐、防磨。     

Indirect genetic benefits of polyandry in a spider with direct costs of mating

The search for the evolutionary explanation of polyandry is increasingly focused on direct and indirect selection on female resistance. In a polyandrous spider Stegodyphus lineatus, males do not provide material benefits and females are resistant to remating. Nevertheless, polyandrous females may obtain indirect genetic benefits that offset the costs associated with multiple mating. We manipulated the opportunity for females to select between different partners and examined the effect of female mating history (mated once, mated twice, or rejected the second male) on offspring body mass, size, condition, and survival under high- and low-food rearing regimens. We found that multiple mating, not female choice, results in increased female offspring body mass and condition. However, these effects were present only in low-food regimen. We did not find any effects of female mating history on male offspring variables. Thus, the benefits of polyandry depend not only on sex, but also on offspring environment. Furthermore, the observed patterns suggest that indirect genetic benefits cannot explain the evolution of female resistance in this system.     

Female resistance and duration of mate-guarding in three aquatic peracarids (Crustacea)

Both theoretical and empirical studies have treated mate-guarding in aquatic Crustacea purely as a male decision problem. However, male and female interests are rarely identical, as implied by observations of female resistance against guarding attempts. We tested experimentally the occurrence of sexual conflict over guarding duration in three crustacean species: Idotea baltica, Asellus aquaticus (Isopoda), and Gammarus zaddachi (Amphipoda). Specifically, we manipulated, by osmotic stress or a neuromuscular blocking agent, the female's ability to resist guarding attempts. Female manipulation, by both methods, roughly doubled precopula duration in I. baltica (Figs. 1 and 2) showing that female resistance effectively diminishes guarding duration. However, in A. aquaticus and G. zaddachi female manipulation had no effect on guarding duration, which also was longer than in I. baltica (Fig. 2). This implies either that male and female interests are equal or that the conflict is resolved according to the male interest in these species. The lack of female resistance in such species allows long precopulatory guarding. In I. baltica we also manipulated, by osmotic stress and by clipping nails, male ability to hold the female. These treatments had no effect on guarding duration (Figs. 1 and 2). Male size tended to correlate positively with guarding duration in control groups, but not in female manipulation groups (Fig. 3). Thus, conflict is mainly resolved according to the female interest in I. baltica. Results in this species also suggest that female resistance selects for large male size. Consequently, mechanisms of sexual selection may differ considerably between species with otherwise comparable mating patterns.     

Foraging costs of a tail ornament: Experimental evidence from two populations of barn swallows Hirundo rustica with different degrees of sexual size dimorphism

Secondary sexual characters are assumed to be costly to produce or maintain. A test of this assumption was performed using the sexually exaggerated outermost tail feathers of male barn swallows Hirundo rustica, a trait currently subject of a directional female mate preference. A possible cost of sexual signalling in male barn swallows arises from increased flight cost during foraging in this aerially insectivorous species. A longer tail may impose a greater drag during flight and thereby affect foraging ability. This was tested by determining the relationship between experimentally modified male tail lengths and number and size of prey delivered to offspring in Spain, where sexual size dimorphism in tail length is small, compared to Denmark, where dimorphism is large. Food boluses contained significantly fewer small insects in Spain than in Denmark. Males with elongated tails captured more and smaller insects while males with shortened tails captured fewer and larger prey items at both sites. Males with naturally long tails were less affected by experimental treatment in terms of effects on the number and the size of prey delivered to their offspring, a finding consistent with a long tail being a condition-dependent viability indicator. The effect of a given degree of tail manipulation on prey size and number of prey per bolus was larger in Spain than in Denmark. These results demonstrate that (1) tail length in male barn swallows affects foraging, and (2) larger sexual size dimorphism occurs where the foraging cost of an increment in ornament size is smallest.Communicated by M. Zuk     

Elaborately ornamented males avoid costly parental care in the house finch (<Emphasis Type="Italic">Carpodacus mexicanus</Emphasis>): a proximate perspective

Selection should favor flexibility in reproductive tactics when the combination of sexual traits and reproductive behaviors that achieve the highest fitness differs between males within a population. Understanding the functional significance of variation in male reproductive tactics can provide insight into their evolution. Male house finches (Carpodacus mexicanus) in a Montana population display continuous variation in parental tactics: males with more elaborated (redder) plumage color provide little or no parental care compared to less elaborated (dull) males. Here, we first determined whether elevation of prolactin (a pituitary hormone) was related to variation in male parental tactics and, second, we used the relationship between prolactin levels and parental behavior to investigate why redder males avoid a high investment in parental care. We found that prolactin elevation was closely associated with paternal care. In addition, males with redder plumage color had low prolactin levels, whereas dull males, which provision twice as frequently, had high levels of prolactin. We also found that male condition was unrelated to plumage color but negatively related to prolactin levels. These results suggest that the low provisioning of redder males was not due to physiological constraints, but instead reflected a tactic to avoid the costs associated with parental care. The condition benefits accrued by redder males may explain their higher post-breeding survival compared to dull males. Moreover, dull males were previously shown to have higher pairing success than redder males, suggesting that the relationship between male plumage color and parental care may reflect individually optimized parental tactics.Communicated by H. Kokko     

Assessments and decisions in Metellina segmentata (Araneae: Metidae): evidence of a pheromone involved in mate guarding

Assessments and decision-making underlying the initiation of mate guarding in a common web-building spider, Metellina segmentata, are examined in a series of field and laboratory studies. Adult males do not build webs but wander in search of females and mating opportunities. Adult males then wait at the edge of the webs of females and guard them prior to courtship and mating. Guarded females were heavier, larger and carried more mature eggs than solitary females. An active process of information gathering is apparent from introductions of males to the webs of females. Males make accurate assessments about female quality, even in the absence of the resident female. Cues involving web architecture are not used. Males may assess pheromonal cues on the web of the female in deciding whether to guard or abandon a female.     

A conspicuous courtship signal in the fiddler crab Uca perplexa: female choice based on display structure

The fiddler crab Uca perplexa has a conspicuous male courtship signal that is directed at females to attract them to the male’s burrow for mating. The signal involves waving the unflexed large claw up and down. To determine whether the spatiotemporal structure of the wave is under selection by female choice, we examined whether females had a preference for any particular features of the wave. Females respond to a waving display by either visiting the male’s burrow entrance or by electing to pass without visiting the burrow. We filmed mate-searching females and the waving males that they visited or passed. We documented the wave structure of these males using frame-by-frame analysis. Males produce a two-part wave with component A preceding component B. Both components have an upstroke, a pause at the apex and a downstroke. The tip of the claw was raised much higher in B than in A. Visited males had a shorter delay between the two wave components than did males that the females passed without visiting. Visited males also produced component B waves that had a slower upstroke than those of passed males. There was a significant correlation between the relative height of the raised claw and the duration of the upstroke of component B. Females were selecting males that raised their major claw to the highest position (two to three times as high as the carapace width). Passed males brought down their major claw earlier and from a lower position than did visited males. The data suggests that wave structure has evolved through female choice. Male display rate and body size were not female choice cues. An earlier study showed that display duration was also not used by females in selecting mates.     

Consensus among females in their choice of males in the guppy Poecilia reticulata

We studied female guppies from two populations (Trinidad and Jemez Springs, New Mexico) to determine their mating preferences, the degree of consensus among females for particular male phenotypes, and the variation among females for the types of traits they prefer. We recorded the visual responses of 68 Trinidad and 10 Jemez females in paired male trials. The three sexually-selected male traits quantified were the area of orange color and iridescence on the body, and display behavior. Females from the Trinidad population agreed in their choice of males in three of the eight replicates, and this agreement was based on display rate rather than male color patterns. Females from the Jemez population showed no agreement in their preferences of males. Mating preferences of females varied both between populations and among females of a population. In both populations, female preferences were based primarily on courtship intensity and only secondarily on color pattern. However, females from both populations differed in the relative importance of orange color and iridescence. The fact that females differ in criteria for evaluating males has important implications for selection and maintenance of color polymorphisms and for the interactions among multiple secondary sexual traits of males in the guppy. Received: 5 December 1995/Accepted after revision: 7 June 1996     

Genetic evidence for the “good genes” process of sexual selection

The adaptive nature of female mate choice remains one of the most contentious issues in the study of sexual selection. Here, I provide evidence that mate choice by females of the ovoviviparous cockroach Nauphoeta cinerea influences the rate at which offspring develop and provides both direct and indirect benefits to the female. Males that are more attractive to females produce offspring with shorter development times than less preferred males. Development time is heritable and apparently unconstrained by antagonistic pleiotropy. Male attractiveness and rate of offspring development are genetically correlated. Offspring gain an indirect benefit from their mother's mate choice because, on average, individuals that hatch faster reach sexual maturity more quickly. Females that discriminate among males gain a direct benefit because N. cinerea is ovoviviparous and the time between clutches is decreased by producing offspring with shorter development. In addition to providing evidence for beneficial consequences of mate choice, this study highlights how genetic data provide insights into the process of sexual selection not gained in a purely phenotypic study.Communicated by P. Pamilo