MATE CHOICE IN THE SAILFIN MOLLY,POECILIA LATIPINNA

We examined both female and male mate choice in the sailfín molly, Poecilia latipinna. Female mollies preferred larger males over smaller ones when comparing males from their own populations. Although the expression of this preference depends on a female's receptive state, the level of female preference does not appear to be associated with any other attribute of the female or of the males. When presented with males of the same size from different populations, females preferred native over foreign males in some but not all population combinations. These results cannot be explained by a bias for higher size-specific rates of courtship displays that is shared by all females. Males preferred larger over smaller females; larger males exhibited stronger preferences, and preference for the larger female also increased as the disparity in size between the two object females increased. We found no evidence that males preferred native over foreign females when encountered singly or in size-matched combinations. These results indicate that discrimination among populations arises because females exercise divergent directional preferences for size-specific trait values that are associated with differences among males in these values. This result implies an active role for sexual selection in contributing to the maintenance of the behavioral or morphological distinctions among males observed within and among populations.     

Female Preferences Based on Male Quality in House Mice: Interaction between Male Dominance Rank and t-Complex Genotype

Considerable evidence indicates that female house mice (Mus domesticus) prefer dominant over subordinate males as mates. In addition, male genotype at the t-complex seems to be an important characteristic used by females in mate choice. Specifically, female mice that carry a t-haplotype at the t-complex prefer +/+ over +/t males as mates. The purpose of the present study was to examine the relative contributions of male dominance rank and male t-complex genotype to female mating preference when both factors were systematically varied. We tested females of three genotypes (+/+, +/t, and t/t) in a preference apparatus using pairs of stimulus males varying in relative dominance status and t-complex genotype. In general, when given the choice, females preferred dominant over subordinate males regardless of the male's t-complex genotype. The preference for dominant males was manifested when both stimulus males were of the same t-complex genotype but differed in dominance rank. In addition, when forced to choose between a dominant +/+ and subordinate +/t or between a dominant +/t and subordinate +/+, females continued to prefer the dominant male. Preference for dominant males was independent of female genotype. Only when both males were dominant but differed in t-complex genotype (i.e. one male was +/+ and the other +/t) or when males were unranked (i.e. had not been used in aggressive encounters to determine dominance rank) did females carrying t-haplotypes manifest preferences for +/+ males. Quite unexpectedly, when both males were subordinate but differed in t-complex genotype, preferences of all females shifted in the direction of the +/t male. It is not clear from present data whether the propensity of females to give greater weight to male dominance rank than to t-complex genotype in choosing mates results in greater fitness. However, if these trends are found in natural populations, it would indicate that the role of mating preference in regulating the frequency of t-haplotypes in wild populations is less straightforward than had been previously thought.     

INTERSPECIFIC RECOGNITION AND DISCRIMINATION BASED UPON OLFACTORY CUES IN NORTHERN SWORDTAILS

Female Xiphophorus montezumae were attracted to olfactory cues from conspecific and heterospecific (X. cortezi and X. nigrensis) males when given a choice between the stimulus and water. When given a choice between conspecific and heterospecific cues, females only demonstrated a strong preference for the conspecific stimulus when it was matched against X. nigrensis. Female X. nigrensis were attracted to olfactory cues from their close relative, X. cortezi, but did not respond to cues from the more distantly related X. montezumae. They preferred the scent of their own males to the olfactory cues of both heterospecific species. Our results indicate that X. cortezi and X. nigrensis share an apomorphic change in some aspect of their olfactory cue-receiver system that is not shared with X. montezumae. We also uncovered an asymmetry in response based on olfactory stimuli in these fishes: X. montezumae is moderately attracted to the cue from X. nigrensis, whereas X. nigrensis does not respond to the cue from X. montezumae at all.     

Female assessment of male functional fertility during mate choice in a promiscuous fish

Sexual selection should favour females that can assess the functional fertility of available sexual partners and avoid mating with recently mated, sperm‐depleted males. Our current understanding of the sensory mechanism(s) underlying female assessment of males based on their functional fertility and avoidance of sperm‐depleted males is incomplete. Female Trinidadian guppies (Poecilia reticulata) are known to avoid mating with males that they had previously observed mating with other females. Here, we investigated experimentally the proximate sensory cues that they use to distinguish between paired size‐ and colour‐matched mated and unmated males in the absence of visual public information on their prior mating histories. When only water‐borne chemical cues from the males were available, females avoided the previously mated male and preferred the unmated one, but they chose randomly when only male visual cues (and no chemical cues) were available. They also preferred unmated over mated males when freely swimming with them in a more sensorially complex environment with multiple male cues (i.e., visual, chemical and mechanical cues) concurrently available. Females exhibited no preference for either stimulus males when both were unmated, irrespectively of the sensory environment. These novel results suggest that, in the absence of prior visual public information on the recent mating histories of males, female guppies use olfactory cues putatively emitted by mated males to avoid mating with them. The source and nature of the implicated olfactory cues and the fitness benefits gained by female guppies in sexually preferring males that have not recently mated remain unknown and warrant further research.     

Sex differences in dogfish behaviour: alternative activity patterns and habitat choice

Guppies are highly sexually dimorphic and females have been shown to mate preferentially with males with various visible traits. Guppies, however, have been shown to respond behaviourally to odour cues from conspecifics. Using a specially designed olfactory choice tank, we tested whether females (1) could detect other guppies on the basis of their olfactory cues alone, (2) preferred to associate with males or with females and (3) could distinguish between different males. Female guppies were found to associate preferentially with other guppies when given a choice between water containing cues from another fish and water containing no cues. When females were presented with olfactory cues from a male or a female, they preferred the female initially but most then reversed their decision and swam to the male. Females associated preferentially with certain males based upon olfactory cues alone. Males, however, preferred on the basis of olfactory cues were the least preferred for visual cues.     

Cross-Fostering of Male Mice Subtly Affects Female Olfactory Preferences

The maternal environment has been shown to influence female olfactory preferences through early chemosensory experience. However, little is known about the influence of the maternal environment on chemosignals. In this study, we used two inbred mouse strains, C57BL/6 (C57) and BALB/c (BALB), and explored whether adoption could alter male chemosignals and thus influence female olfactory preferences. In Experiment 1, C57 pups were placed with BALB dams. Adult BALB females then served as the subjects in binary choice tests between paired male urine odours (BALB vs. C57, BALB vs. adopted C57 and C57 vs. adopted C57). In Experiment 2, BALB pups were placed with C57 dams, and C57 females served as the subjects in binary choice tests between paired male urine odours (C57 vs. BALB, C57 vs. adopted BALB, and BALB vs. adopted BALB). In both experiments, we found that females preferred the urine of males from different genetic backgrounds, suggesting that female olfactory preferences may be driven by genetic compatibility. Cross-fostering had subtle effects on female olfactory preferences. Although the females showed no preference between the urine odours of adopted and non-adopted males of the other strain, the BALB females preferred the urine odour of BALB males to that of adopted C57 males, whereas the C57 females showed no preference between the urine odour of C57 and adopted BALB males. Using gas chromatography-mass spectrometry (GC-MS) and stepwise discriminant analysis, we found that the ratios of volatile chemicals from urine and preputial gland secretions were altered in the fostered male mice; these changes may have resulted in the behavioural changes observed in the females. Overall, the results suggest that female mice prefer urine odours from males with different genetic backgrounds; this preference may be driven by genetic compatibility. The early maternal environment influences the chemosignals of males and thus may influence the olfactory preferences of females. Our study provides additional evidence in support of genotype-dependent maternal influences on phenotypic variability in adulthood.     

To change or not to change sex: A comparison between twoOphryotrocha species (Polychaeta)

Summary The polychaeteOphryotrocha puerilis is a male-to-female sex-changer, whereasO. labronica has separate sexes throughout life. In other respects the two species are remarkably similar: they occur in the same habitat, they look the same, they eat the same things, and in someO. labronica populations sex-changers can actually be found. The size-advantage hypothesis predicts that inO. puerilis males should not benefit reproductively from a size increase as much as males inO. labronica: henceO. puerilis but notO. labronica males should change to the female sex at a certain size. I experimentally compared reproductive success at different body sizes between the two species. In isolated male-female pairs reproductive rate increased significantly with female body size but not with male body size, and this pattern was the same in both species. Hence male fecundityper se cannot account for the difference in reproductive type between the two species. In other experiments I investigated if larger males gained access to more females because they were superior competitors for mates or were preferred by females, compared to small males. InO. puerilis the combined effect of these two factors conferred no size advantage to the males, whereas inO. labronica larger males acquired more females than did smaller males. Hence interactions among males and females, in accordance with the size-advantage hypothesis, can explain why sex change is maintained inO. puerilis, and why separate sexes are maintained inO. labronica.     

Female preferences based on olfactory cues in the guppy (Poecilia reticulata)

Guppies are highly sexually dimorphic and females have been shown to mate preferentially with males with various visible traits. Guppies, however, have been shown to respond behaviourally to odour cues from conspecifics. Using a specially designed olfactory choice tank, we tested whether females (1) could detect other guppies on the basis of their olfactory cues alone, (2) preferred to associate with males or with females and (3) could distinguish between different males. Female guppies were found to associate preferentially with other guppies when given a choice between water containing cues from another fish and water containing no cues. When females were presented with olfactory cues from a male or a female, they preferred the female initially but most then reversed their decision and swam to the male. Females associated preferentially with certain males based upon olfactory cues alone. Males, however, preferred on the basis of olfactory cues were the least preferred for visual cues.     

Validation of a Method for Quantifying Male Mating Preferences in the Guppy (Poecilia reticulata)

Male and female mating preferences are commonly inferred from association times spent with potential mates in a dichotomous‐choice test. However, this assessment method is rarely validated, particularly so for male mating preferences. Using the Trinidadian guppy (Poecilia reticulata), an important model species in the study of sexual selection, we tested whether a male’s mating preference for either of two stimulus females in a dichotomous‐choice test predicted his mating behaviours directed at the preferred female when he was allowed to swim freely with both females. First, we presented individual males with two females that differed in body length in a dichotomous‐choice apparatus in which the male could only use visual cues to assess the paired females. We quantified male mating preference as the duration of time a focal male spent associating with each female. Immediately following this test, the focal male was allowed to swim freely with both females, and we quantified the time he spent sexually pursuing each female and the number of courtship sigmoid displays and copulation attempts he directed at each female. On average, males did not significantly prefer either of the two stimulus females in either of the two tests; however, the magnitude of male preference for the larger female tended to increase as the size difference between the paired females increased. More importantly, there was a significant positive relationship between male association time in the dichotomous‐choice test and both the time spent sexually pursuing and the number of courtship sigmoid displays directed at the same female initially preferred in the dichotomous‐choice test. Collectively, these results confirm that association time measured in a dichotomous‐choice test is a reliable predictor of male mating preferences in the Trinidadian guppy.     

Pre-copulatory isolation in sympatric Melolontha species (Coleoptera: Scarabaeidae)

1 The two most abundant cockchafer species in Europe, the forest cockchafer Melolontha hippocastani Fabr. and the European cockchafer Melolontha melolontha L., tend to form calamitous mass breedings with casual reports on sympatric and simultaneous occurrence. 2 Both species are known to use feeding‐induced green leaf volatiles (GLV) as primary attractants (sexual kairomones) for mate finding. The attractiveness of GLV is enhanced by the sex pheromones 1,4‐benzoquinone in M. hippocastani and toluquinone in M. melolontha. Phenol attracts males from both species. All three compounds are present in females of both species. 3 In the present study, it is confirmed that only male M. melolontha perform the typical swarming flight at dusk, as has already been shown for M. hippocastani. Furthermore, whether swarming Melolontha males were cross‐attracted to heterospecific females, and whether males could discriminate olfactorily between conspecific and heterospecific females, was tested in the field. 4 Males of both species preferred females when given the choice between females and males of the other species. However, they preferred conspecific females when females from both species were offered simultaneously. 5 The results suggest that species‐specific pheromone blends contribute to precopulatory reproductive isolation in sympatric populations of M. melolontha and M. hippocastani, but are not mutually exclusive or indispensable prerequisites for mate finding as in other insects.     

Sex recognition in zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>)

We investigated sex recognition in female zebrafish (Danio rerio) to better understand the underlying sensory mechanisms and identify male secondary sexual traits. Females were simultaneously presented with two fish, a male and a female, in a flow-chamber apparatus, and females’ relative attraction towards males was observed under different conditions. With domesticated fish, females were more attracted to males when presented with both visual and chemosensory cues from stimulus fish. They still discriminated the sexes when only visual cues were provided, but not when white ambient light was changed to yellow, indicating that colour plays a role. Sex discrimination under yellow light was improved when chemosensory cues were also provided. Surprisingly, females’ attraction to males was not more pronounced in the morning when mating occurs. Domesticated females discriminated the sexes when presented with wild-derived, as well as domesticated fish, whereas wild-derived females did not show any biases for domesticated or wild-derived males. Behavioural observations indicated that the wild-derived females were distressed, which explains their lack of attraction to males. In summary, domesticated female zebrafish discriminated the sexes using both visual (body colour) and olfactory cues; however, wild-derived zebrafish were too distressed for behavioural experiments under these laboratory conditions.     

Male courtship preferences demonstrate discrimination against allopatric colour morphs in a cichlid fish

Whether premating isolation is achieved by male‐specific, female‐specific or sex‐independent assortative preferences often depends on the underlying evolutionary processes. Here we test mate preferences of males presented with females of different allopatric colour variants of the cichlid fish Tropheus sp., a Lake Tanganyika endemic with rich geographical colour pattern variation, in which the strength of sexual isolation varies between populations. We conducted two‐way mate choice experiments to compare behaviour of males of a red‐bodied morph (population Moliro) towards females from their own population with behaviour towards females from four allopatric populations at different stages of phylogenetic and phenotypic divergence. Males courted same‐population females significantly more intensely than females of other populations, and reduced their heteromorphic courtship efforts both with increasing genetic and increasing phenotypic distinctness of the females. In particular, females of a closely related red‐bodied population received significantly more courtship than either genetically distinct, similarly coloured females (‘Kirschfleck’ morph) or genetically related, differently coloured females (‘yellow‐blotch’ morph), both of which were courted similarly. Genetically and phenotypically distinct females (Tropheus polli) were not courted at all. Consistent with previous female‐choice experiments, female courtship activity also decreased with increasing genetic distance from the males’ population. Given successful experimental and natural introgression between colour morphs and the pervasive allopatry of related variants, we consider it unlikely that assortative preferences of both sexes were driven by direct selection during periods of secondary contact or, in turn, drove colour pattern differentiation in allopatry. Rather, we suggest that sexual isolation evolved as by‐product of allopatric divergence.     

Widespread reliance on olfactory sex and species identification by lyssomanine and spartaeine jumping spiders

Jumping spiders (Salticidae) are renowned for their exceptional vision, but this does not preclude use of other senses. Here we provide evidence that olfactory pheromones are widespread in the Spartaeinae and Lyssomaninae, two subfamilies regarded as basal clades within the Salticidae. Pheromone use by salticids was tested in a series of experiments: males were tested with the odour of conspecific females, heterospecific females, and conspecific males, and females were tested with the odour of conspecific males. With seven of the 29 species tested, we also tested males using the draglines of conspecific females (spider absent) as the odour source. Males of all species tested were attracted to the odour of conspecific females and to the odour of the draglines of conspecific females. There was no evidence of males responding to the odour of heterospecific females or conspecific males, or of females responding to the odour of conspecific males. These findings suggest that it is primarily males that respond to olfactory sex pheromones, consistent with the apparent trend within spiders of males more actively searching for females and females placing greater emphasis on mate‐choice decisions. Compared with most salticid groups, lyssomanines and spartaeines are unusually sedentary and this lifestyle may favour olfactory mate searching. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107 , 664–677.     

Female mate preference based on male orange spot patterns in the feral guppy <Emphasis Type="Italic">Poecilia reticulata</Emphasis> in Japan

It is known that females prefer males with larger and/or brighter orange spots in many populations of the guppy Poecilia reticulata. However, female preference for male orange spots varies among populations and changes within several years when they are introduced into new habitats with different environment. Guppies were introduced into Okinawa, Japan, more than 20 years ago and were subjected to natural and sexual selection for a long period. The female preference for orange spot patterns of males was examined by the dichotomous choice experiment for a feral guppy population of the Hiji River, Okinawa. We chose full-sibling males as a pair of stimulus males that were simultaneously presented to a test female, because sibling males should resemble each other. To create different orange spot patterns between stimulus males, one male of the stimulus male pair was fed carotenoid-supplement food such as algae and another male was fed low-carotenoid food. High-carotenoid-treatment males showed not only brighter coloration of orange spots but also larger spots than other males as a result of this dietary-manipulation. In the dichotomous choice experiment, females preferred the high-carotenoid-treatment males. In addition, logistic regression analysis clarified that brighter coloration of male orange spots was the most important factor for female mate preference. This finding suggests indirect benefits of female preference for male orange spot patterns if the male foraging ability for algae were heritable.     

Mate Choice Copying in Female Humpback Limia (Limia nigrofasciata, Family Poeciliidae)

Mate choice copying is a mechanism of non‐independent mate choice that has important implications for models of evolution and sexual selection. In this study, we examined copying behavior in female humpback limia (Limia nigrofasciata). In three experiments, we allowed a focal female to choose between two males on opposite sides of an aquarium, then repeated the choice trial with the following modifications: (i) with no model female, (ii) with a model female added adjacent to the initially non‐preferred male, or (iii) with the model female adjacent to the initially preferred male. In the absence of other females, focal females displayed consistent mate preferences, measured as a significantly higher amount of time spent near the preferred male in both parts of the trial. When a model female was added adjacent to the initially non‐preferred male, focal females spent significantly more time near that male than they had in the first part of the trial, and significantly less time near the male they had initially preferred. When we placed the model female next to an initially preferred male as a control, the time spent by the focal female with the initially preferred or initially non‐preferred male did not change significantly. We conclude that female mate choice copying may be important in humpback limia, causing focal females to spend more time in preference zones of males they had not at first preferred.     

Sexual Isolation Between Drosophila Melanogaster, D. Simulans and D. Mauritiana: Sex and Species Specific Discrimination

The sexual isolation among the related species Drosophila melanogaster, D. simulans and D. mauritiana is asymmetrical. While D. mauritiana males mate well with both D. melanogaster and D. simulans females, females of D. mauritiana discriminate strongly against males of these two species. Similarly, D. simulans males mate with D. melanogaster females but the reciprocal cross is difficult. Interspecific crosses between several populations of the three species were performed to determine if (i) males and females of the same species share a common sexual isolation genetic system, and (ii) males (or females) use the same genetic system to discriminate against females (or males) of the other two species. Results indicate that although differences in male and female isolation depend on the populations tested, the isolation behaviour between a pair of species is highly correlated despite the variations. However, the rank order of the isolation level along the populations was not correlated in both sexes, which suggests that different genes act in male and female sexual isolation. Neither for males nor for females, the isolation behaviour of one species was paralleled in the other two species, which indicates that the genetic systems involved in this trait are species-pair specific. The implications of these results are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Differential mating success of virgin female katydidsRequena verticalis (Orthoptera: Tettigoniidae)

Male katydids (Orthoptera: Tettigoniidae) invest in offspring through nutrients provided in a large spermatophore. Previous research with Requena verticalishad shown that almost all of the investment of males mating with recently mated (4 days previously) females is in eggs fertilized by the female's previous mate. Thus males are predicted to discriminate against such females as mates. In experiments placing males with both a virgin and a female mated 4–5 days previously, virgin females obtained almost all matings. Although male discrimination of mates was noted in the experiments, there was no evidence that such discrimination was against nonvirgins in both this experiment and one in which a single virgin or mated female was placed with a male. Instead, the results suggest that the differential mating was a result of interfemale competition. The mating advantage held by virgin females over nonvirgins appeared to be lost once the latter had oviposited. Finally, there was no evidence from both single- and paired-female experiments that males preferred larger females as mates.     

Sexual reproduction of Daphnia pulex in a temporary habitat

Species of Daphnia (Crustacea: Cladocera) typically reproduce by cyclical parthenogenesis, in which a period of all-female parthenogenetic reproduction is followed by sexual reproduction. Sex in Daphnia is determined by the environment, with factors such as temperature, photoperiod and crowding stimulating the production of males and sexual females. Previous studies on Daphnia pulex from temporary pond habitats demonstrated the coexistence of male-producing and non-male-producing (NMP) females, as determined under crowding in the laboratory. A strong genetic component to this sex allocation variation suggested that sex expression in D. pulex is better described as a result of genotype-environment interaction. The present study examined the switch from parthenogenetic to sexual reproduction in two temporary-pond populations of D. pulex. Both populations showed a very early investment in sexual reproduction, independent of population density, by producing males very soon after the populations were reestablished from resting eggs in the early spring. Approximately 40% of the initial broods were male. Additional evidence for gender specialization was obtained by observing the sex of two or three successive broods for 85 individual females. Fifty-eight females produced successive broods of females, 13 females produced successive broods of males and 14 females produced successive broods which included both male and female broods. Females that produced successive female broods under natural conditions included a higher frequency of NMP females compared to a random sample of females, confirming the existence of NMP females. Sexual females were observed in both populations after the first appearence of males, suggesting that the presence of males may stimulate the production of sexual females. For D. pulex populations in a temporary environment, there appears to be an increased emphasis on sexual reproduction and a decreased influence of the environment on sex determination, compared to Daphnia populations in more permanent habitats. Received: 19 February 1996 / Accepted: 20 January 1997     

Behavioral and physiological responses of Diaeretiella rapae to semiochemicals

Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae) parasitizes many aphid species, including cabbage aphids on cruciferous crops and Russian wheat aphids on cereal crops. We investigated the olfactory perception of D. rapae to semiochemicals that may be encountered in these two environments while searching for hosts or for mates. We conducted electroantennogram and flight-tunnel experiments on male and female D. rapae and found marked differences between sexes. Cruciferous volatiles elicited physiological and behavioral responses by females but not by males. Males and females responded similarly to (Z)-3-hexen-1-ol, a component of green-leaf volatiles, in both electroantennogram and flight-tunnel assays. Female wasps responded similarly regardless of prior oviposition experience or population origin. Likewise, mating history and aphid presence did not increase responsiveness toward these semiochemicals.     

根田鼠的熟悉性及其自然动情下的配偶选择

报道了在室内雌鼠自然动情条件下根田鼠两性个体配偶选择的3种熟悉性效应的5组实验结果,包括雌性对熟悉和陌生雄鼠、配偶和陌生雄鼠、配偶和熟悉雄鼠的择偶行为实验 , 雄性对熟悉和陌生雌鼠、配偶和陌生雌鼠的择偶行为实验。在实验前, 将1对性成熟的雌雄鼠 (非亲缘关系) 每天关养8 h 共8 d 建立熟悉性; 配对雌雄鼠至少生育1胎则为配偶关系。在 Y 形迷宫内的30 min 实验中, 两个被选择鼠分别以项链拴在横跨选择箱顶端中央的一根铁丝上, 限制它们在各自箱内活动; 而允许异性选择鼠从中立箱自由进入两个选择箱。记录选择鼠对异性被选择鼠的访问、社会探究、攻击、交配和友好行为的频次和时间。经Wilcoxon 关联样本 T 检验发现, 除交配行为不显著外, 雌性根田鼠均选择熟悉性较高的雄鼠; 而雄鼠不具这种选择性。该结果提示雌雄根田鼠的不同择偶行为也许就是反映该种婚配制度特征的直接行为过程。因此, 在择偶行为中, 雌性根田鼠表现的单配性倾向和雄鼠的多配性倾向, 只能以其婚配制度为一雄多雌制的假设来解释。我们的实验还说明在多配制田鼠中, 一雄多雌制与混交制在雌鼠择偶行为上是不同的, 而与单配制的相似或相近, 故简单地比较多配制与单配制则不能反映田鼠亚科动物婚配制度的多样性。