Female preference and sexual selection for male coloration in the guppy (Poecilia reticulata)

Summary Experiments were designed to determine the effects of male pigmentation patterns on female choice in guppies. When presented with a series of variably-colored males, females of different genetic strain consistently exhibited similar preferences (Tables 1 and 2), preferring those males with the greatest development of both carotenoid and iridescent pigments (Table 3). A partial rank correlation analysis of pigments of males indicates positive correlations between the iridescent and carotenoid pigments and also between melanins and showiness (Table 4). Only when either the carotenoid or iridescent pigments were held constant was there any effect of the other pigments on the ranking order of males by the females. Other pigments appear to be relatively unimportant in influencing female choice of males. These results indicate that females discriminate among males on the basis of color and that females of different strains prefer the same male colors rather than those characteristics of males of their own strain. The results support those models of sexual selection that hold that sexually selected traits honestly advertise the phenotypic and genetic qualities of males; they do not support models of runaway selection for particular male traits, such as first proposed by Fisher (1930).     

Persistence of individually distinctive display patterns in fatigued side-blotched lizards ( Uta stansburiana)

Iguanian lizards perform conspicuous species-typical push-up displays, which are used in territory advertisement, threat, and courtship contexts. Subtle individually distinctive differences in push-up characteristics have been suggested to play a role in the recognition of social partners. However, if the structure of push-ups is responsive to changing physiological states then their capacity to promote recognition may be limited. The current study evaluated whether the push-ups performed while in an experimentally imposed state of fatigue by male side-blotched lizards (Uta stansburiana), retain the individually distinctive characteristics apparent in rested lizards. We found repeatable among-individual differences in the duration and the relative height of push-up components. Repeatability values did not change consistently between the rested and fatigued conditions, nor when both conditions were pooled, indicating that these push-up characteristics do not change with fatigue. Similarly, discriminant functions that were generated using push-ups from one state assigned push-ups performed in an alternate state to the correct individuals. Furthermore, when analyzed independently of individual identity, the values of display parameters examined in the current study did not change significantly between states, and discriminant function analysis could not reliably classify push-ups to the correct state. Taken together the results show that individually distinctive push-up characteristics are robust to effects of fatigue, consistent with their suggested role in social recognition. In the future, video playback experiments can test whether lizards utilize the signature-like characteristics of push-ups to discriminate among individuals.Communicated by T. Czeschlik     

Age-dependent association between testosterone and crown UV coloration in male blue tits (Parus caeruleus)

The proximate basis of sexual traits can suggest mechanisms maintaining honesty in signalling. A central role hereby has been attributed to testosterone, although its importance for brightly coloured plumage has been questioned. We determined circulating testosterone levels in male blue tits captured at the start of breeding and demonstrated an age-dependent relationship between testosterone and male crown UV/blue coloration. In yearling males, testosterone increases with increasing ornamentation (higher UV chroma, higher chroma, more UV-shifted hue), whereas in older males, this relationship is negative, with less UV-ornamented males having higher testosterone. This pattern is robust since it occurred in 2 years, before and after egg laying, and in males sampled during the day and during the night, despite a tenfold difference in testosterone levels. Since more UV-ornamented young males gain higher within-pair paternity, while less UV-ornamented older males achieve more extra-pair matings, the results imply that higher testosterone is associated with reproductive success and attractiveness in both age classes. We hypothesise that this relationship could result from causal effects of testosterone on coloration or through associations with behaviour and suggest ways to test these hypotheses. Our results caution against premature dismissal of a potential role for testosterone in maintaining honesty of plumage signals.     

Male remating and female fitness in the wolf spider Pardosa astrigera: the role of male mating history

Although the effects of male mating history on female reproductive output and longevity have been studied in insects, few such studies have been carried out in spiders. In a mating system in which females are monandrous while males are polygynous, females may incur the risk by mating with successful males that have experienced consecutive matings and suffer from the possible depletion of sperm and/or associated ejaculates. Here, we examine the effects of male mating history on male courtship and copulation duration, female reproductive fitness, and female adult longevity of the wolf spider, Pardosa astrigera. Results indicated that male mating frequency had little effect on their subsequent copulation success, and of 35 males tested, about half of the males were able to copulate with five virgin females successively at an interval of 24 h. Male mating history had little effect on their courtship duration. However, male mating history significantly affected male copulation duration, female adult longevity, and reproductive output. Males that mated more frequently copulated longer and more likely failed to cause their mates to produce a clutch, although there was no significant difference in the number of eggs laid and the number of eggs hatched regardless of the first clutch or the second one. Multiple mating of male P. astrigera resulted in significant reduction in female adult longevity. Our results indicate that monandrous females mating with multiple-mated males may incur substantial fitness costs.     

Chemical polymorphism in male femoral gland secretions matches polymorphic coloration in common wall lizards (Podarcis muralis)

Previous studies showed that common wall lizards (Podarcis muralis) are polymorphic in colour, both sexes showing three main ventral morphs (white, yellow and red) within the same population and that the three morphs correlate with many life-history traits, including a positive assortative mating according to colour. Chemical communication plays a key role in intra-specific recognition and in social organization of lizards; thus chemical cues might be involved in morph recognition and mate choice. We used gas chromatography–mass spectrometry (GC–MS) to investigate possible differences in the lipophilic fraction of femoral gland secretions between size/age classes and to explore whether chemical secretions match male colour morphs. As expected, most males shared the same compounds, but smaller males showed significantly higher proportions of aldehydes, alcohols and ketones and significantly lower proportions of tocopherols than larger males. Interestingly, inter-morph differences in the proportion of some compounds (especially tocopherols and furanones) matched ventral colour polymorphism. Pairwise comparisons showed that white lizards had significantly different chemical profiles than both the yellow and red ones, whereas differences between yellow and red males were only marginal. A further canonical analysis of principal coordinates correctly classified 67.2 % on average of the chemical profiles according to colour morph (white 85.0 %, red 60.9 %, yellow 57.1 %). We hypothesized that chemical differences associated with colour polymorphism may play a central role in intra-specific communication and even in sexual selection, allowing individuals to choose their partners according to their age, and more interestingly according to their colour morph, in a non-random mating population system.     

The effects of testosterone on antibody production and plumage coloration in male house sparrows (Passer domesticus)

Many bird species have patches of colour in their plumage, contrasting with their basic coloration, which are used to display and signal status to conspecifics. These are called ’badges of status’, because they are believed to be low-cost signals of social status. For a signalling system to be evolutionarily stable, cheating must be controlled. The conventional view is that there is frequent testing, which uncovers cheats. Recently, the immunocompetence handicap hypothesis (ICHH) suggested that signals may be dependent on testosterone for their development, with a cost being imposed through immune suppression. We report experiments on house sparrows (Passer domesticus) which show that testosterone significantly influences the size of the bib (a ’badge of status’). The ultimate effect of the testosterone manipulation was to impair antibody production, as predicted by the ICHH. However, testosterone manipulations also changed the levels of the ’stress hormone’ corticosterone. The level of corticosterone was also related to the degree of immunosuppression. After controlling for the effect of corticosterone, testosterone enhanced the birds’ ability to produce antibodies, counter to the ICHH. The hypothesis therefore must be modified. We suggest that testosterone has a dual effect: it leads to immunosuppression through a mechanism involving corticosterone but, conversely, leads to increased immunocompetence probably via dominance influencing access to resources. Received: 5 March 1999 / Received in revised form: 1 October 1999 / Accepted: 16 October 1999     

Leg ornamentation and the efficacy of courtship display in four species of wolf spider (Araneae: Lycosidae)

This study used both correlative and experimental video playback methods to test the hypothesis that the secondary sexual traits of male wolf spiders act to increase the efficacy of visual courtship displays. Direct observations of courtship of several lycosid genera and a review of the literature revealed a significant association between ornamentation and visual courtship displays. This suggests that the ornamentation may be playing the role of amplifier for a visual display. To test this hypothesis, male courtship behaviors of four Schizocosa species were experimentally manipulated using video-imaging techniques. Females of species with non-visually displaying, non-ornamented males (Schizocosa duplex and S. uetzi) did not increase in frequency of receptivity when tufts were added to conspecific males. In a species with a visual display and foreleg pigmentation (S. stridulans), the addition of foreleg tufts increased female receptivity. In a tufted species (S. crassipes), females tended to decrease their receptivity when male ornamentation was completely removed. In visually displaying species, ornamentation acts to increase female receptivity, supporting its role as an amplifier of a visual display. Received: 29 December 1997 / Received in revised form: 23 October 1999 / Accepted: 13 December 1999     

Storage and display of odour by male Saccopteryx bilineata (Chiroptera, Emballonuridae)

Males of the sac-winged bat, Saccopteryx bilineata, actively fill their propatagial sacs with secretions from the genital region, the gular gland, urine and saliva. From our observations and those of Starck we deduce that propatagial sacs in S. bilineata do not have a glandular function, but are instead organs for the storage and display of odours. In addition to the already known “salting” and hovering behaviour of male S. bilineata, we describe in detail how odour is fanned to roosting individuals during the complex, stereotypic hovering displays. S. bilineata males also coat the fur of their backs with saliva using the wing tip and might scent-mark territory boundaries. “Yawning” may represent a visual as well as an olfactory cue. Odour seems to play an important role in the social communication of S. bilineata and in other emballonurids, as revealed by the broad distribution of wing sacs in this family. S. bilineata males display odour during energetically costly hovering flights in front of females. We demonstrate that the number of hovering displays increases with harem size. The mating effort of S. bilineata males comprises a multimodal signalling behaviour. Although males defend harem territories in which females gather, females seem to be able to choose the father of their progeny freely among the males of a colony. This may have led to the evolution of the complex mating displays by male S. bilineata. Received: 9 December 1998 / Received in revised form: 6 May 1999 / Accepted: 13 June 1999     

The effect of male coloration on female mate choice in closely related Lake Victoria cichlids (Haplochromis nyererei complex)

We studied the effect of male coloration on interspecific female mate choice in two closely related species of haplochromine cichlids from Lake Victoria. The species differ primarily in male coloration. Males of one species are red, those of the other are blue. We recorded the behavioral responses of females to males of both species in paired male trials under white light and under monochromatic light, under which the interspecific differences in coloration were masked. Females of both species exhibited species-assortative mate choice when colour differences were visible, but chose non-assortatively when colour differences were masked by light conditions. Neither male behaviour nor overall female response frequencies differed between light treatments. That female preferences could be altered by manipulating the perceived colour pattern implies that the colour itself is used in interspecific mate choice, rather than other characters. Hence, male coloration in haplochromine cichlids does underlie sexual selection by direct mate choice, involving the capacity for individual assessment of potential mates by the female. Females of both species responded more frequently to blue males under monochromatic light. Blue males were larger and displayed more than red males. This implies a hierarchy of choice criteria. Females may use male display rates, size, or both when colour is unavailable. Where available, colour has gained dominance over other criteria. This may explain rapid speciation by sexual selection on male coloration, as proposed in a recent mathematical model. Received: 11 April 1997 / Accepted after revision: 27 July 1997     

Courtship in fast water currents by a male stream goby ( Rhinogobius brunneus) communicates the parental quality honestly

The stream goby Rhinogobius sp. DA (dark color type) shows exclusive paternal care of the eggs. Males court females in the stream current and previous field observations suggest that females favor males that perform their courtship display in faster water currents, and that such males may have high parental ability because of good physical condition. To validate these observations we examined female choice under controlled laboratory conditions. Mate choice experiments indicated clearly that females preferred males that courted in the faster currents, whereas neither sexually different morphological traits, such as body size, nor the water current alone were important. The experiments with food supply treatments indicated that only males of high physical condition are able to court in the fast currents. Furthermore, males that courted in the fast currents achieved good egg survival, whereas males that were unable to court in the currents did not, due to cannibalism of their egg clutch. Thus, the maximum speed of the water current in which a male courts should be indicative of his quality and of the subsequent survival of eggs under his care. We conclude that Rhinogobius sp. DA females utilize the male courtship display in the water current as an honest indicator of parental quality.Communicated by K. LindströmAn erratum to this article can be found at     

Sensory ecology of a semi-aquatic spider (Dolomedes triton)

Summary Preferred ambush sites of fishing spiders Dolomedes triton (Pisauridae) were investigated, primarily with respect to aquatic vegetation and wave action, at five locations differing in these variables along the shore of Dow Lake (near Athens, Ohio). The linear density of spiders correlated positively with the presence of aquatic vegetation. D. triton most often stood at a distance from shore proportional to the width of the zone of floating and emergent vegetation (Fig. 2). Usually they positioned their bodies in the horizontal plane on floating living or dead plant parts. Spider density was negatively correlated with the amplitude of wind-generated waves (Fig. 4). The maximum energy of these waves measured on breezy days was at a frequency of 1.4 Hz, with no components exceeding 10 Hz (Fig. 5). Spiders could discriminate high-amplitude (up to 40 mm) wind waves from prey waves, probably since the latter have substantially higher frequencies (Figs. 3, 5).     

Prior encounters with the opposite sex affect male and female mating behavior in a wolf spider (Araneae,Lycosidae)

Mate availability can vary widely in nature depending upon population density and sex ratio and can affect the ability of individuals to be selective in mate choice. We tested the effects of prior encounters with the opposite sex (i.e., exposure to the opposite sex either with or without mating) on subsequent mating behavior in two experiments that manipulated mate availability for both males and females in the wolf spider, Hogna helluo. The probability of mating in the experimental trial depended upon whether the prior encounter involved mating or not, and males and females responded in opposite directions. Exposure without mating resulted in a higher subsequent frequency of mating for females and a lower subsequent frequency of mating for males, while prior mating experience resulted in a lower frequency of female remating and a higher frequency of male remating. Prior exposure without mating did not affect female aggression. However, mated females engaged in precopulatory cannibalism more frequently than virgins. Mated males escaped postcopulatory cannibalism more frequently than virgins. Our results show that males respond to exposure without mating in the expected manner. However, prior mating (1 week earlier) had unexpected effects on males, which may be due to mated males being of higher quality. There were little or no effects of the size of the prior exposure individual or mate on subsequent mating behaviors. Further research is needed to determine why different species use different degrees of prior information in mate choice.     

Female-enhanced male competition determines the first mate and principal sire in the spider Linyphia litigiosa (Linyphiidae)

Summary Two to five days before sexual maturation, female sierra dome spiders (Linyphia litigiosa: Linyphiidae) undergo a transformation in their behavior toward males that visit their webs. During this latter part of their penultimate instar, females change from consistently positioning themselves far away from males to actively maintaining close proximity, reactions I call avoidant and associative behavior, respectively. Consistent associative behavior ceases after the female's first mating and thus is limited to soon-to-mature penultimate females. When a mate-seeking male fords an associative female, he attempts to guard her until she matures; this is often a multi-day affair. In contrast, males guard immature avoidant and mature mated females for only a single day. This dichotomy in male guarding times can be understood by the fact that associative behavior signals that the female will soon develop peak reproductive value. Upon completion of their final molt, 98% of females immediately mate with the current guarding male. Secondary suitors are not as likely to achieve mating. Moreover, first mates father 1.8 times more offspring, on average, than secondary mates. Whenever they meet on any female's web, males fight until one of the contestants withdraws. Fights typically are intensive, occasionally deadly, and often result in usurpation of the web by the newly arriving male. Larger males win more fights, but other qualities (e.g., vigor and persistence) appear to be important when contestants differ by less than 10–20% in body weight. Prolonged (i.e., multi-day) guarding of associative females enhances the intrasexual selection process by ensuring that every male that arrives at the web finds it already guarded. Therefore every male that finds the web becomes a participant in a series of male-male conflicts and web usurpations which span the period between the resident female's commencement of associative behavior and her sexual maturation. Since unforced male departures from the webs of associative females are rare, victors are retained on the web until they themselves lose a fight. This facilitates a steady increase in the fighting ability of sequential guards throughout the associative period, up until female maturation and mating. On my study site, first mates represented the final winners in a combative sorting process based on a minimum average of 2 fights; they were heavier and larger than secondary mates and randomly sampled males. The combination of (1) associative behavior by nearly mature females, (2) high mating propensity of newly mature females, and (3) first male sperm priority, constitutes a system whereby females enhance male-male competition and boost the expected fighting prowess of the principal sire of their progeny. Since males appear to make no material contribution toward progeny, the female's behavior probably functions to improve the genetic constitution of the offspring. In addition, the timing of associative behavior may limit prolonged guarding by food-stealing males to a period (1) encompassing the female's pre-molt fast and (2) before the heavy yolking of eggs, thereby ameliorating the nutritional costs of intrasexual selection.     

Female choice in the guppy (Poecilia reticulata): the interaction between male color and display

The effect of two components of male courtship, color and display behavior, on female choice of mates was investigated in the guppy (Poecilia reticulata). Computer-modified videos were constructed to determine the relative importance of a static trait, the presence or absence of carotenoid pigment (C and NC), and a dynamic trait, high and low display rate (HD and LD), on female response. Females were given a choice between all combinations of male display and color in a binary choice design. Preference was determined by the time females spent visually inspecting the animation. Females preferred animations with high display rates when both animations displayed color (CHD vs CLD), but not in the absence of color (NCHD vs NCLD). Equal numbers of females chose the color/low-display animation and the no-color/high-display animation when the two were paired. Conversely, color became a criterion of choice when both animations showed a low display rate (CLD vs NCLD), but not when both displayed at a high rate (CHD vs NCHD). These results suggest that females use both static and dynamic traits to evaluate males, but their rankings are affected by the choices available. Results of these experiments provide insights into how females use multiple traits to assess males.     

Linking male qualities to multiple display traits: an example in a fish with exclusive male care

Recent theoretical models predict that the relative allocation to advertisement and parental care depends on whether paternal care is necessary for offspring survival: In species with exclusive male care, male investment in attraction is expected to reliably indicate paternal care effort and male phenotypic quality. Previous research, yielding contrasting results, has considered how one trait involved in mate attraction interacts with parental care or a specific aspect of male quality. In the blenny Salaria pavo, we perform a comprehensive analysis of the interplay between overall male attractiveness and male quality, the latter in terms of fertility, condition, and parental care. In this fish, males are larger than females, exhibit two sexually dimorphic traits (head crest and anal glands), and solely care for eggs. We generated a male attractiveness index through principal component analyses of morphological traits and quantified parental effort as the total time spent in egg care. In addition, we analyzed the relationships between specific components of attractiveness and male qualities. In agreement with theory predictions, we found that male overall attractiveness is a reliable indicator of fertility, in terms of sperm number, but is unrelated to body condition and parental care effort, with males able to perform high levels of care regardless of their level of advertisement. However, the relative expression of head crest area appears positively related to sperm number but is traded-off with parental care effort. These findings underline the need, in addressing real patterns, to consider interactions between multiple aspects of male display and quality.     

Acquisition of breeding coloration depends on badge size in male house sparrows Passer domesticus

Summary The black throat badge of the male house sparrow Passer domesticus, which functions as a status signal of dominance rank, changes in size during late winter because light feather tips gradually wear off. Males change the size of their visible badge earlier if their final badge size is large. The differential timing of the change from winter to breeding coloration in relation to badge size is partially controlled by the behaviour of the individual male. Feather abrasion of the badge is mainly due to preening and dust bathing. During late winter, male house sparrows preen the badge area more than females preen the homologous area, and males with large badges preen more than males with small badges. The seasonal change in size of the visible badge of male house sparrows may reflect the balance of different selection pressures. A large badge size signals dominance status in autumn and winter while predation by visually searching avian predators may constitute the main opposing selection pressure. Sexual selection causes a stronger selection pressure for a large badge in spring and summer. Correspondence to: A.P. Moller     

Biparental defence in a spider mite (Acari: Tetranychidae) infesting Sasa bamboo

Summary Field observations on the nesting pattern of Schizotetranychus celarius (Banks) (Acari: Tetranychidae) revealed that many individuals live gregariously in a united nest. Behavioural experiments recorded on video tape recorder and 16 mm film showed that adult males and females can effectively defend their nest and offspring from a phytoseiid predator, larvae of Typhlodromus bambusae Ehara (Acari: Phytoseiidae), through counterattacks. The male spider mite often killed the predator's larva and succeeded in defending offspring and nest completely. Comparison of the behaviour patterns recorded between a nest owner parent S. celarius and two kinds of intruders (predators and conspecific males or females) revealed conspicuous differences. I suggest that there is a kind of biparental care in S. celarius, and that the life-pattern of this species therefore fits the definition of subsociality originally framed for insects.