Meadow Voles (Microtus pennsylvanicus, Arvicolidae) Over-mark and Adjacent-mark the Scent Marks of Same-sex Conspecifics

Scent over-marking occurs when an animal deposits its scent mark on top of the scent mark of a conspecific; adjacent-marking occurs when an animal deposits its scent mark next to the scent mark of a conspecific. Given that male rodents usually scent mark more than females and that animals spend more time investigating the odor of the top-scent donor of an over-mark, I tested the following three hypotheses. First, male meadow voles deposit more scent marks than female meadow voles. Second, male meadow voles will deposit more over-marks and adjacent-marks in response to the scent marks of a same-sex conspecific than females would. Third, meadow voles spend more time investigating the odor of the second vole placed in the arena than that of the first vole placed in the arena. To test these hypotheses, two age-matched, like-sex conspecifics (first vole and second vole) were placed successively into an arena in which they were allowed to freely explore and scent mark for 15 min. The first hypothesis was not supported. The first and second vole, independently of sex, deposited a similar number of scent marks. The second hypothesis was also not supported by the data: more conspecific scent marks were over-marked by the second female than by the second male. The third hypothesis was supported by the data. After investigating a scented arena, males and females spent more time investigating the odor of the second vole than that of the first vole. Sex differences in scent-marking behaviors of meadow voles are unlike those reported for other species of rodents.     

Age Affects Over-Marking of Opposite-Sex Scent Marks in Meadow Voles, Microtus pennsylvanicus

Models of age-related effects on behavior predict that among short-lived species younger adults are more attractive and attracted to opposite-sex conspecifics than are older adults, whereas the converse is predicted for long-lived species. Although most studies of age-related effects on behavior support these predictions, they are not supported by many studies of scent marking, a behavior used in mate attraction. Over-marking, a form of scent marking, is a tactic used by many terrestrial mammals to convey information about themselves to opposite-sex conspecifics. The present study tested the hypothesis that the age of meadow voles, Microtus pennsylvanicus ; a microtine rodent, affects their over- and scent-marking behaviors when they encounter the marks of opposite-sex conspecifics. Sex differences existed in the over-marking behavior of adult voles among the three different age groups that were tested. Male voles that were 5–7 and 10–12 mo olds over-marked a higher proportion of the marks of females than did 2–3 mo old male voles. Female voles that were 2–3, 5–7, and 10–12 mo old over-marked a similar number of marks deposited by male voles. Overall, the data were not consistent with models predicting the behavior of short-lived animals such as rodents when they encounter the opposite sex. The differences in over-marking displayed by older and younger adult male voles may be associated with life history tradeoffs, the likelihood that they will encounter sexually receptive females, and being selected as mates.     

Scent Marking in Female Prairie Voles: a Test of Alternative Hypotheses

We conducted three experiments with females in different stages of reproductive condition to test alternative hypotheses for the function of scent marking in female prairie voles, Microtus ochrogaster . The three reproductive categories were isolated females prior to sexual stimulation (anoestrous), sexually stimulated (oestrous) and lactating. Females in different reproductive condition were given the opportunity to scent mark clean unmarked substrate or areas that had previously been marked by adult females or adult males. The numbers of scent marks deposited by females did not differ statistically for females in different reproductive condition. However, there was a trend for anoestrous females to mark the most, oestrous females less, and lactating females the least. The lack of scent marking by lactating females might be to reduce conspicuousness to conspecifics or predators. Oestrous females tended to mark the most in the area marked previously by males, although the difference was not statistically significant.
Our results provide some support for a mate-attraction hypothesis and a territorial-defense hypothesis, but were most consistent with a self-advertisement hypothesis. Over marking was uncommon and did not differ by experiment or sex of previous donor. Our results suggest that the number and placement of scent marks by females are highly variable and function primarily to convey individual identity.     

Diurnal Variation in Scent Marking Behavior in Captive Male and Female Common Marmosets,Callithrix jacchus

Chemical communication by scent-marking behavior in New World primates is used to prevent the access of potential competitors to a territory, to identify food resources and the reproductive condition of mates, among others. In common marmosets, primates of the Callitrichidae family, this behavior also occurs as olfactory identification of an individual or of the reproductive status of females. Despite this information, the diurnal variation and gender differences in the profile of this behavior remain to be investigated. The aims of this study were to establish the diurnal profile of the distribution of this behavior and the influence of the sex of markers. We used 18 adult common marmosets, Callithrix jacchus, 10 males and 8 females from 6 family groups (6 fathers and 4 sons; 4 mothers and 4 daughters). The frequency of scent-marking behavior was recorded for each animal over a period of 8 days, twice a week, for 4 weeks, starting when the animals left the nest box (approximately at 05:00 a.m.) until the end of the photophase, at about 05:00 p.m. A MANOVA test was performed to compare the frequency of scent-marking behavior at 2 hour intervals using pooled data for males and females. The results showed that significantly higher levels of scent-marking behavior occurred during the 03:00–05:00 p.m. interval compared to all other intervals. Lower values were recorded during the 11:00–13:00 interval and an effect of the sex factor was also found, with the values being higher for females than for males, although a significant difference was recorded only for the 07:00–09:00 interval. Minimal values for males were recorded during the 07:00–09:00 interval, whereas minimum values for females were recorded during the 11:00–13:00 interval. However, the highest values for both sexes continued to occur during the 15:00–17:00 interval. These results suggest that scent marking behavior in common marmosets has a preferential incidence at the end of the day and this might be occurring in association with feeding behavior. At this time these animals usually forage more to prepare for the night's fast. Since these animals can discriminate chemical clues as long as 24 hours after they have been left, the higher incidence of this behavior at this time probably will assure that the animals will localize feeding resources used on the preceding day. Significant elevation of scent marking behavior in females in relation to males was found only at 07:00–09:00 interval and seems to be associated with signalizing of reproductive status, preferential access to foraging or both.     

Diurnal Variation in Scent Marking Behavior in Captive Male and Female Common Marmosets, Callithrix jacchus

Chemical communication by scent-marking behavior in New World primates is used to prevent the access of potential competitors to a territory, to identify food resources and the reproductive condition of mates, among others. In common marmosets, primates of the Callitrichidae family, this behavior also occurs as olfactory identification of an individual or of the reproductive status of females. Despite this information, the diurnal variation and gender differences in the profile of this behavior remain to be investigated. The aims of this study were to establish the diurnal profile of the distribution of this behavior and the influence of the sex of markers. We used 18 adult common marmosets, Callithrix jacchus, 10 males and 8 females from 6 family groups (6 fathers and 4 sons; 4 mothers and 4 daughters). The frequency of scent-marking behavior was recorded for each animal over a period of 8 days, twice a week, for 4 weeks, starting when the animals left the nest box (approximately at 05:00 a.m.) until the end of the photophase, at about 05:00 p.m. A MANOVA test was performed to compare the frequency of scent-marking behavior at 2 hour intervals using pooled data for males and females. The results showed that significantly higher levels of scent-marking behavior occurred during the 03:00-05:00 p.m. interval compared to all other intervals. Lower values were recorded during the 11:00-13:00 interval and an effect of the sex factor was also found, with the values being higher for females than for males, although a significant difference was recorded only for the 07:00-09:00 interval. Minimal values for males were recorded during the 07:00-09:00 interval, whereas minimum values for females were recorded during the 11:00-13:00 interval. However, the highest values for both sexes continued to occur during the 15:00-17:00 interval. These results suggest that scent marking behavior in common marmosets has a preferential incidence at the end of the day and this might be occurring in association with feeding behavior. At this time these animals usually forage more to prepare for the night's fast. Since these animals can discriminate chemical clues as long as 24 hours after they have been left, the higher incidence of this behavior at this time probably will assure that the animals will localize feeding resources used on the preceding day. Significant elevation of scent marking behavior in females in relation to males was found only at 07:00-09:00 interval and seems to be associated with signalizing of reproductive status, preferential access to foraging or both.     

Male and Female Meadow Voles,Microtus pennsylvanicus,Differ in Their Responses to Heterospecific/Conspecific Over‐Marks

Voles use runways, paths, and trails that may also be used by rabbits and mink. These shared areas could contain the scent marks of conspecifics and heterospecifics. Thus, it is likely that the scent marks of heterospecifics may overlap or be overlapped by those of voles, forming over‐marks. Much is known about how voles respond to over‐marks of two different conspecifics. However, we do not know how they would respond to an opposite‐sex conspecific whose scent marks are in an over‐mark with the scent marks of predator or the scent marks of a non‐predator heterospecifics. We tested the hypothesis that meadow voles, Microtus pennsylvanicus, differ in their response to the scent mark of the opposite‐sex conspecific if the scent mark was overlapped by that of a mink, a vole predator, or rabbit, a vole non‐predator. We found that female but not male voles showed a preference for the scent marks of the opposite‐sex conspecifics that were part of the mink‐vole over‐mark when compared to those of opposite‐sex conspecifics that were not part of the over‐mark. This preference by female voles was independent of whether the male vole was the top‐scent donor or bottom‐scent donor of the over‐mark. Male and female voles showed no preference between the scent marks of the opposite‐sex conspecifics whose marks were part of or not part of the rabbit‐vole over‐mark. Sex differences in the manner that meadow voles respond to rabbit‐vole and mink‐vole over‐marks are discussed.     

Scent Marking in Voles: A Reassessment of Over Marking, Counter Marking, and Self-Advertisement

We conducted a series of experiments to discern among the counter-marking, over-marking, and self-advertisement hypotheses for secondary marking in male prairie voles, Microtus ochrogaster , and meadow voles, M. pennsylvanicus . Secondary scent marks (those placed in an area that has already been marked by a conspecific) were not significantly greater than initial marks placed on clean substrate (a substrate without any previous scent marks) for either species and thus did not support a counter-marking hypothesis. Similarly, overlapping of initial scent marks with secondary marks occurred less often than expected by chance and did not support an over-marking hypothesis. Secondary marks tended to avoid overlap with scent marks previously deposited by a potential competitor. Our results suggest that secondary scent marking functions to self-advertise by maximizing individual identity and avoiding masking or blending with previous donors. Future studies on secondary marking should be designed to quantify the observed and expected frequency and placement of original and secondary marks to discern among alternative hypotheses for the adaptive significance of secondary marking.     

圈养条件下黑麂雄性标记行为与雌性化学信息存留位置的关系

化学物质被认为是哺乳动物标记行为信息传递的主要载体,而标记在鹿科动物的竞争雌性资源中具有重要的作用,因此本文重点对雄性黑麂的化学标记与雌性化学信息存留点的关系进行了行为学研究。观察发现面腺标记(利用额腺和眶下腺)是雌雄黑麂共有的化学标记行为,而行为性排尿和刨地行为(利用蹄腺)则仅为雄性具有的标记行为;躺卧不具有化学标记作用,而排粪在化学标记上的作用则难以确定。同时分析表明,雄性黑麂更倾向于在靠近雌性化学信息存留区的区域进行化学标记,且可能会因竞争压力的增大而扩大领域范围。     

Olfactory Experience Affects the Response of Meadow Voles to the Opposite‐Sex Scent Donor of Mixed‐Sex Over‐Marks

Scent marking and over‐marking are important forms of communication between the sexes for many terrestrial mammals. Over the course of three experiments, we determined whether the amount of time individuals investigate the scent marks of opposite‐sex conspecifics is affected by 4 d of olfactory experience with those conspecifics. In Experiment 1, female meadow voles, Microtus pennsylvanicus, spent more time investigating the scent mark of the novel male conspecific than that of the familiar male donor, whereas male voles spent similar amounts of time investigating the scent mark of the familiar female and a novel female conspecific. In Experiment 2, voles were exposed to a mixed‐sex over‐mark in which subjects did not have 4 d of olfactory experience with either the top‐scent donor or the bottom‐scent donor. During the test phase, male and female voles spent more time investigating the scent mark of the opposite‐sex conspecific that provided the top‐scent mark than that of a novel, opposite‐sex conspecific. Male and female voles spent similar amounts of time investigating the scent mark of the bottom‐scent donor and that of a novel opposite‐sex conspecific. In Experiment 3, voles were exposed to a mixed‐sex over‐mark that contained the scent mark of an opposite‐sex conspecific with which they had 4 d of olfactory experience. During the test phase, male voles spent more time investigating the mark of the familiar, top‐scent female than the scent mark of a novel female donor but spent similar amounts of time investigating the mark of the familiar, bottom‐scent female and that of a novel female donor. In contrast, female voles spent more time investigating the mark of a novel male donor than that of either the familiar, top‐scent male or that of the familiar, bottom‐scent male. The sex differences in the responses of voles to scent marks and mixed‐sex over‐marks are discussed in relation to the natural history and non‐monogamous mating system of meadow voles.     

不同雄雌配比对SPF级布氏田鼠繁殖性能的影响

目的 探讨不同雄雌配比对SPF级布氏田鼠产仔数、成活率等繁殖性能的影响.方法 设置4种配对繁殖方式:1♂:1♀、1♂:2♀、2 ♂:2♀和3♂:2♀,经过2年的试验,期间记录各组SPF级布氏田鼠的产仔数和成活率等繁殖性能指标.结果 4种配比方式雌鼠产仔率分别为97.69％、62.47％、59.24％和28.3％,成活率为96.98％、96.14％、94.57％和91.22％,平均产仔数为6.48、7.87、6.16和6.14.结论 在屏障环境中饲养的布氏田鼠封闭群采用1♂:2♀的配比方式,其繁殖性能和经济效益最理想.     

Scent Marking, Sexual Behavior and Aggression in Male Gerbils: Comparative Analysis of Endocrine Control

SYNOPSIS. The aggressive, sexual, and scent marking behaviorsof male gerbils (Meriones unguiculatus) are sensitive to gonadalandrogens, but androgens are not equally important in the controlof each behavior. In this species, territorial residency, prioraggressive experience, and unidentified factors that contributeto large individual differences in aggressiveness, influencethe aggressive behavior of males at least as much as androgensdo. To the extent that androgens affect aggression between malegerbils, they act partially by altering aggressiveness and partiallyby altering production of aggression-eliciting cues. The natureof these cues is unknown. Understanding the role of androgensin aggression in this species is further complicated by theobservation that castration can either increase or decreaseaggression depending on the age at which the surgery is performed.In contrast, androgens play aprimary role in the control ofsexual behavior and scent marking. Both behaviors consistentlydecline following castration despite prior experience of themales. Both behaviors are also controlled by the medial preopticarea-anterior hypothalamus, an area of the brain often implicatedin the control of male sociosexual behaviors. It appears, though,that the sites, and possibly the mechanisms, of hormone actionunderlying scent marking and sexual behavior differ. Studyingboth behaviors in the same species, and whenever possible inthe same individuals, is proving to be a useful technique foridentifying such differences between behaviors as their sensitivityto steroids and to brain lesions.     

Behavioural Responses to Scent Marks of Increasing Age in Klipspringer Oreotragus oreotragus

Klipspringers Oreotragus oreotragus are small antelopes which use scent marks to demarcate and defend their territory. The strength of behavioural response to the introduction of unfamiliar scent was measured in order to estimate the effective lifespan of scent secretion. The total number of scent marks deposited during the experiment was higher than control levels when fresh scent was introduced, but not when older scent was introduced. However, the proportion of marks deposited on introduced twigs remained higher than control levels until scent was aged at least 7d. The probability of licking twigs immediately before scent-marking was much higher than control levels when scent aged up to 3d was introduced, but not when scent was aged 7d or more. These results indicate that preorbital gland scent retains at least some degree of efficacy for up to 7d. The decreasing level of response to scent aged 0-7d is most likely to be due to decay of the scent signal. However, in contrast to the total number of marks deposited and the probability of licking before scent-marking, which both consistently decreased in response to older scent, the proportion of marks deposited on scent aged 3d was higher than over fresh scent. It is suggested that, in view of the role that scent-marking plays in territory defence, this difference in the timing of peak response between the three variables may represent an adaptive response to the perceived threat of encounter with an adversary, which is mediated by the age of the scent marks.     

Female Scent Signals Enhance the Resistance of Male Mice to Influenza

Background

The scent from receptive female mice functions as a signal, which stimulates male mice to search for potential mating partners. This searching behavior is coupled with infection risk due to sniffing both scent marks as well as nasal and anogenital areas of females, which harbor bacteria and viruses. Consideration of host evolution under unavoidable parasitic pressures, including helminthes, bacteria, viruses, etc., predicts adaptations that help protect hosts against the parasites associated with mating.

Methods and Findings

We propose that the perception of female signals by BALB/c male mice leads to adaptive redistribution of the immune defense directed to protection against respiratory infection risks. Our results demonstrate migration of macrophages and neutrophils to the upper airways upon exposure to female odor stimuli, which results in an increased resistance of the males to experimental influenza virus infection. This moderate leukocyte intervention had no negative effect on the aerobic performance in male mice.

Conclusions

Our data provide the first demonstration of the adaptive immunological response to female odor stimuli through induction of nonspecific immune responses in the upper respiratory tract.     

Meadow Voles (Microtus pennsylvanicus) and Prairie Voles (M. ochrogaster) Differ in Their Responses to Over-Marks from Opposite- and Same-Sex Conspecifics

Over‐marking occurs when one individual deposits its scent mark on the scent mark of a conspecific. Previous studies have shown that meadow voles (Microtus pennsylvanicus) and prairie voles (M. ochrogaster) that were exposed to an over‐mark of two same‐sex conspecifics, later responded similarly to the top‐scent mark but differed in their response to the bottom‐scent mark. In the present study, we examined the responses of meadow voles and prairie voles to same‐sex and mixed‐sex over‐marks to ascertain whether their responses reflect the different tactics which males and females in promiscuous (meadow voles) and monogamous (prairie voles) species use to attract opposite‐sex conspecifics and to compete with same‐sex conspecifics. Males and females of both species spent more time investigating the mark of the top‐scent donor than that of the bottom‐scent donor of an over‐mark. Meadow voles exposed to a mixed‐sex over‐mark spent more time investigating the mark of the opposite‐sex conspecific independently of whether it was from the top‐ or bottom‐scent donor. In contrast, prairie voles spent more time investigating the mark of the opposite‐sex donor if it was from the top‐scent donor. These results suggest that: (i) over‐marking serves a competitive function; (ii) the scent marks of individuals attract multiple mates in promiscuous species such as the meadow vole; and (iii) the scent marks of individuals establish and maintain pair bonds between familiar opposite‐sex conspecifics in monogamous species such as the prairie vole.     

Temporal and Spatial Distribution of Male Scent Marks in the Polygynous Greater Sac-Winged Bat

Scent marks are relatively long-lived signals that can be perceived by conspecifics when the producer is absent. Therefore, it is often not obvious to whom the signal is directed. In daytime roosts of the polygynous greater sac-winged bat, males scent mark territories with facial gland secretions. Territories are a valuable resource for males, as they offer exclusive courtship opportunities, which results in increased male reproductive success and, consequently, increased male–male competition over territories. The information encoded in male scent marks could, therefore, be either directed at females as part of an olfactory courtship display or at male competitors as part of territorial behaviour. We expected territorial males to scent mark in the morning, shortly before females return to the territory and close to female roosting sites, if scent marks are directed at females as part of the courtship display. And we expected harem males to scent mark at the territory boundaries, where male–male encounters are most likely to occur, if scent marks are directed at male competitors. We found that males marked more frequently in the afternoon, at a time when all females have already left the territory, and harem males marked at the territory boundaries and not inside their territory in the area where females roost. At boundaries males fan volatiles from specialised wing sacs towards competitors outside the territory. Scent marking of male Saccopteryx bilineata might therefore be congruent with the assessment-hypothesis, which states that scent marks offer intruders the possibility to make an olfactory assessment of the territory owner without direct physical interaction. Thus, scent marks of male S. bilineata are most likely influenced by male–male competition and not by female choice.     

Responses of Male and Female Black Grouse to Male Vocal Display

The evolution of leks may be explained by several hypotheses. The ‘female preference’ hypothesis, which states that females favour males that have aggregated, has recently gained some empirical support. Low-quality, unattractive males may, however, settle near attractive males, as predicted by the ‘hotshot’ hypothesis. We tested whether black grouse Tetrao tetrix females use auditory cues to find the preferred leks, and whether males respond to vocal display emitted on leks. We conducted a playback experiment with male vocal display (rookooing) on leks, where the visiting females and displaying males were counted. The number of males tended to increase more on playback leks. Specifically, the number of 1-year-old males was greater on playback sites than on control sites. Also, the number of females, in relation to the lek size before the start of the experiment tended to increase. In addition, we used aviary playback trials to test whether females distinguish between single-male and multi-male displays. In a choice test, females showed greater preference for the ‘multi-male’ tape. The tendency for increased male numbers on playback leks resulted from increased visits of young, mobile males which were attracted to leks that they perceived to be large. This suggests a ‘hotshot’-type mechanism in the settlement of young males. Because females also responded to the supplemented auditory advertisement, or directly to the increased number of males, the ‘female preference’ hypothesis is also supported. Females may, at least in part, base their decision of which lek to visit on auditory cues, but visual contact to males may be also needed.     

Hot or Not: The Effects of Exogenous Testosterone on Female Attractiveness to Male Conspecifics in the Budgerigar

An increasing number of studies indicate that not only females but also males can be selective when choosing a mate. In species exhibiting male or mutual mate choice, females may benefit from being attractive. While male attractiveness is often positively influenced by higher plasma levels of the androgenic hormone testosterone, it has been shown that testosterone can masculinise female behavior and morphology in several bird species, potentially rendering them less attractive. In this study, we investigated whether female budgerigars, Melopsittacusundulatus, suffer from increased plasma testosterone levels through a negative effect on their attractiveness to males. We experimentally increased plasma testosterone levels in testosterone-treated females (T-females) compared to controls (C-females) and allowed males to choose between a T- and a C-female in a two-way choice situation. Although testosterone treatment significantly affected female behavioral and morphological characteristics, males did not show a significant difference in preference between T- and C-females. These results suggest that experimentally increasing testosterone levels in females does not appear to influence male preference during initial mate choice. Our findings indicate that selection for higher levels of testosterone in male budgerigars is probably not constrained by a correlated response to selection causing negative effects on female attractiveness during initial mate choice. Evaluating whether or not a potential constraint may arise from negative testosterone-induced effects on other fitness related traits in females requires further work.     

Response of Prairie Voles, Microtus ochrogaster (Rodentia, Arvicolidae), to Scent Over-marks of Two Same-sex Conspecifics: A Test of the Scent-masking Hypothesis

Previous work shows that after investigating a same-sex over-mark, two nonmonogamous species, meadow voles and golden hamsters, preferred the odor of the top-scent donor to that of the bottom-scent donor, and behaved as the odor of the bottom-scent donor was not familiar. This finding supported the scent-masking hypothesis; one of three hypotheses suggested previously to account for how an animal responds to the overlapping scent marks of two same-sex conspecifics. The present experiments tested whether one of these hypotheses, either scent-masking, scent-bulletin-board, or scent-blending, predicts how a monogamous species, the prairie vole, responds to such over-marks. Our data show that none of the three hypotheses adequately describes the way in which prairie voles respond to conspecific over-marks. Although prairie voles preferred the top scent to the bottom scent, they behaved as if the latter scent was familiar and less important than a novel scent (a scent not part of the over-mark). Overall, the data suggest that the manner in which males and females respond to same-sex over-marks reflects the different tactics they may use to attract and compete with conspecifics in monogamous and nonmonogamous species.     

The Role of Scent Marking in Mate Selection by Female Pumas (Puma concolor)

Mate selection influences individual fitness, is often based on complex cues and behaviours, and can be difficult to study in solitary species including carnivores. We used motion-triggered cameras at 29 community scrapes (i.e. scent marking locations used by multiple individuals) and home range data from 39 GPS-collared pumas (Puma concolor) to assess the relevance of communication behaviours for mate selection by female pumas in California. Female pumas visited community scrapes irregularly and visitation bouts appeared to be correlated with oestrus. Female pumas on average selected from 1.7 collared males, and selection was based on multiple cues that varied among the different time periods measured (i.e. the female’s visitation bout and in 90 days previous to the consorting event). Female mate selection over the course of a visitation bout was based on frequency of the male visitation, mass, and age. In the 90 days previous to consorting, the number of scrapes a male created was the most important contributor to selection, which was likely related to his residency status. We also found that at least 14% of females mated with multiple males, thus possibly confusing paternity. Our findings provide a mechanistic understanding of how female pumas use scent and auditory communication at community scrapes to select dominant resident males to mate with.     

Sex-linked Correlated Responses in Female Reproductive Traits to Selection on Male Eye Span in Stalk-eyed Flies

Coevolution between male and female traits can result from correlatedresponses to selection or correlated selection on geneticallyindependent traits. This study examines the possibility thattraits involved in precopulatory sexual selection may influencethe evolution of traits involved in postcopulatory sexual selectiondue to the existence of correlated selection or correlated responsesto selection. Artificial selection on male eye span in Cyrtodiopsisdalmanni, a sexually dimorphic stalk-eyed fly, is used to testfor correlated changes in reproductive traits of male and femaleflies. Flies from replicate lines that had been under selectionfor 57 generations were matched for age and genotyped at fourX-linked microsatellite loci. Egg number and testis size increasedwith age, but did not differ among lines. Spermathecal areasand duct lengths differed among replicates, but not among selectiontreatments. Female relative eye span, size of the ventral receptacleand egg size exhibited significant correlated responses to selectionon male relative eye span. The absence of any change in spermlength or testis size between lines indicates that changes infemale traits are unlikely due to correlated selection mediatedby sperm competition. Significant effects of X-linked microsatellitegenotypes indicate instead that the correlated responses toselection were due, in part, to X-linked genes in linkage disequilibriumor that exhibit pleiotropy. The presence of nonadditive alleliceffects on genetically correlated female traits combined withadditive allelic effects on a male ornament provides a previouslyunrecognized mechanism by which genetic variation could be maintaineddespite strong sexual selection.