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PubMed1998

Influence of mating frequency on sow reproductive performance.

Gilts and sows were bred one, two, or three times during a single estrous period in a commercial herd for evaluating the effect of mating frequency on reproductive performance. Estrus detection started at approximately 0630 daily by applying back pressure to females with the presence of a mature boar. Natural mating was used. Gilts detected in estrus were mated in the morning of d 1 (AM), the morning of d 1 and 2 (AM-AM), and the morning and afternoon of d 1 and morning of d 2 (AM-PM-AM) for mating frequencies 1, 2, and 3, respectively. Sows were bred in the AM, AM-AM, AM-PM-AM (1), and morning of d 1 and morning and afternoon of d 2 [AM-AM-PM (2)] for mating frequency 1, 2, 3 (1), and 3 (2), respectively. Breeding events in the morning and afternoon started at approximately 0730 and 1530. Females were randomly assigned to a mating frequency. Boars were randomly assigned to each breeding event. In total, 256 gilts and 766 sows were involved in the study. Gilts with a single mating (76.5%, P = .06) and triple matings (80.4%, P < .05) had higher farrowing rates than those with double matings (65.3%). No differences (P > .1) in the farrowing rates of sows were observed between mating frequencies 1, 2, 3 (1), and 3 (2). Double-mated gilts had more (P < .03) total born (9.7 vs 8.6) and pigs born alive (9.3 vs 8.2) than did single-mated gilts. There were no differences (P > .3) in total born and pigs born alive in sows between mating frequencies. We concluded that triple-mating gilts and sows did not improve farrowing rate and litter size compared with single and double matings. There were no differences in farrowing rate and litter size between double- and single-mated sows. Gilts with double matings had a larger litter size than those with a single mating.

Animals↗

PubMed1999

Male mating patterns in wild multimale mountain gorilla groups.

Although mountain gorillas, Gorilla gorilla beringei, are classified as having a one-male mating system, approximately 40% of the social units are multimale groups. I observed two multimale groups of mountain gorillas at the Karisoke Research Center, Rwanda, Africa, for 17 months to determine male mating patterns and male-male mating harassment in relation to both male dominance rank and female reproductive status. Dominant males mated significantly more than did individual subordinate males, and dominant males mated more with cycling adult and pregnant females. The dominant males participated in 47 and 83% of observed matings in the two groups. Subordinate males were more likely than dominant males to mate with subadult females. Eleven of 14 females were observed to mate with more than one male, and multiple males mated with three of the five females observed at the probable time of conception. Mating harassment was initiated and received by both dominant and subordinate males. Mating harassment occurred infrequently (during 30 and 22% of matings in each group), usually consisted of mild aggression, and usually terminated copulations by subordinate males, but not those by dominant males. These results suggest that multimale mountain gorilla groups can be favourable environments for subordinate males to obtain mating opportunities. Dominant males may be unable or unwilling to prevent subordinate males from mating. Based on behavioural observations, mountain gorillas can have a multimale mating system but further research on the role of females in male mating success and paternity determination is needed to understand fully this species' mating system. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed2005

Impact of male mating history on the temporal sperm dynamics of Choristoneura rosaceana and C. fumiferana females.

In the oblique-banded leafroller, Choristoneura rosaceana, and the spruce budworm, C. fumiferana, male reproductive performance decreases with consecutive matings. While the onset time of mating did not vary, the time spent mating was longer in mated than in virgin males. Furthermore, a decline observed in the spermatophore mass with successive matings was associated with a concomitant decline in its apyrene and eupyrene spermatozoa content. In the hours following mating, spermatozoa migrate from the spermatophore, located in the bursa copulatrix, to the spermatheca. Regardless of the male's previous mating history, the number of apyrene sperm dropped rapidly in the days following mating whereas the number of eupyrene spermatozoa declined gradually. As the temporal pattern of sperm movement was similar in all treatments, females mated with previously-mated males would suffer from sperm shortage sooner than those mated with virgins. Large C. rosaceana females stored more apyrene spermatozoa in their spermatheca than small ones, irrespective of the time after mating or male mating history, while only large females mated with once-mated males received more apyrene sperm and accessory gland secretions than small ones mated with virgin or twice-mated males. The results obtained in this study are discussed in relation with their potential impact on the reproductive success of both sexes.

Animals↗

PubMed2005

Alternative male mating behaviors dependent on relative body size in captive oval squid Sepioteuthis lessoniana (Cephalopoda, Loliginidae).

We observed the reproductive behavior of the oval squid Sepioteuthis lessoniana in captivity. The male used three different mating behaviors: male-parallel (MP), male-upturned (MU) and sneaking. Male competition over females frequently occurred before and during the female egg-laying period, and the outcome of most fights depended on male body size. Larger males guarded their partners from other males and performed MP mating during the egg-laying period of the paired females. In contrast, there was no pairing and mate guarding in MU mating and sneaking, which were adopted by smaller subordinate males as alternative tactics outside female egg-laying period and during the period, respectively. MP matings were 95% successful, but more than half of MU matings were unsuccessful. Higher mating success in MP mating was achieved through pairing, whereas males in MU mating were less successful because mating attempts without pair formation were often foiled by escape of the female. Sneaking was successful in all cases but occurred less frequently. Spermatophores were attached at the opening of the oviduct in MP mating, whereas they were attached around the female buccal membrane in MU mating and sneaking. Considering the route of egg transportation, higher fertilization success can be expected in MP mating because of the advantageous location of the attached spermatophores. Our results suggest that MP mating is used by larger, paired males during the female egg-laying period, and that MU mating and sneaking are alternative tactics adopted by smaller, subordinate males. These alternative mating behaviors would be conditional strategy dependent on relative body size, because some individual males displayed both MP and MU mating behaviors.

Aggression↗

PubMed2004

The effect of individual liveweight and condition scores of ewes at mating on reproductive and scanning performance.

AIMS: To determine the effects of liveweight (LW) and condition score (CS) of ewes at mating on both mating performance and scanning percentage, and to determine if effects of CS were independent of LW. METHODS: Two groups of ewes, comprising 1,780 mixed-aged Romney (Rom MA) and 692 composite two-tooth (1/8 East Friesian 1/16 Finn 13/16 Romney, Comp TT) ewes were grazed separately with harnessed rams for two reproductive cycles. Romney rams were used for the first 17 days of mating and then replaced on the morning of Day 18 by Suffolk rams. Ewes were weighed and CS assessed on a scale of 0-5 before the introduction of the rams. Ewes were identified as having been mated during the first cycle only, during both cycles, during the second cycle only, or not mated. All mated ewes were scanned using ultrasound, 50 days after the end of mating, and identified as being either non pregnant, single-, twin- or triplet-bearing. RESULTS: Linear relationships (R2=0.99) between mean LW and CS at mating were evident for both Rom MA and Comp TT ewes and the mean increase in LW per unit increase in CS was greater in the Rom MA ewes (7.88 kg) than the Comp TT (4.78 kg) ewes (p<0.05). Ewes mated in the second cycle only were significantly (p<0.05) lighter than those mated in the first cycle only. In Rom MA ewes, a greater proportion were mated in the first cycle only if CS was >/=2.0 than if CS was <2.0, and the proportions of ewes mated in the first cycle only or in both cycles did not differ if CS was >/=2.5. In Comp TT ewes, there was no difference in the proportions mated in the first cycle or both cycles, if CS was >/=2.0. Triplet-bearing ewes were heavier than twin-bearing ewes, which were in turn heavier than both singleton-bearing and non pregnant ewes. Twin-bearing ewes had higher CS than both single-bearing and non pregnant ewes (p<0.05) but differences were not significant if LW was included as a covariate. In both Rom MA and Comp TT ewes, greater proportions were non pregnant and lower proportions had twins if CS was <2.0 than if CS was >/=2.0. In Rom MA ewes only, a greater proportion again had twins and a lower proportion had singletons if CS was >/=3.0 than if CS was <3.0. In Comp TT ewes, the proportion that were non pregnant or twin-bearing did not vary with CS if CS was >/=2.0. Reproductive performance was maximal for Rom MA and Comp TT ewes that had CS at mating >/=3.0 and >/=2.0, respectively, equating to LW of 62.6 and 48.5 kg, respectively. CONCLUSIONS: In both groups of ewes, CS and LW at mating positively affected reproductive performance measured at the time of mating and at scanning, however, no reproductive advantage was evident above a minimum CS of 3.0 and 2.0, equating to LW of 62.6 and 48.5 kg, for Rom MA and Comp TT ewes, respectively. Sheep farmers should direct management to ensure that no ewes are below these minimum targets rather than ensuring high average LW and/or CS of a mob.

Journal Article↗

PubMed2005

The effect of individual liveweight and use of teaser rams prior to mating on the reproductive performance of ewe hoggets.

AIM: To determine the effects of liveweight (LW) and use of teaser rams prior to mating on both the mating performance and pregnancy rate of ewe hoggets. METHODS: Romney hoggets (n=841) were weighed and randomly assigned to one of two treatment groups; either exposed to seven harnessed, vasectomised (teaser) rams for 17 days prior to the breeding period (n=283); or not exposed to teaser rams (unteased, n=558). Harnessed Perendale rams were then introduced for two oestrous cycles. Using crayon marks, hoggets were identified as having been mated during the first 17 days only, during the second 17 days only, during both periods, or not mated. All mated hoggets were then scanned for pregnancy using ultrasound, 48 days after the end of the breeding period, and identified as being either non-pregnant, or as single-, twin or triplet-bearing. RESULTS: Hoggets mated in either the first 17 days only or in both the first and second 17-day periods were heavier than those mated in the second period only (p<0.001). Those mated in the first or second 17-day period only, and those mated in both periods were all heavier prior to mating than those not mated at all (p<0.001). Twin-bearing hoggets were heavier than both their single-bearing and non-pregnant counterparts (p<0.001). A greater proportion of the teased hoggets were mated in the first 17 days only compared with unteased hoggets (62.6 vs 32.1%; p<0.001). In contrast, more of the unteased hoggets were marked in the second 17-day period only (p<0.001). A greater proportion of mated, unteased hoggets were found to be non-pregnant in comparison to their teased counterparts (17.8 vs 11.2%; p=0.02). CONCLUSIONS: Heavier hoggets at breeding were more likely to be mated in the first 17 days of the breeding period and more likely to be twin-bearing. Use of teaser rams for 17 days prior to the breeding period increased the proportion of hoggets mated in the first 17 days, increased conception rates, and thus increased the proportion of pregnant hoggets. These results indicate that farmers should utilise teasers for 17 days prior to commencement of the breeding period and avoid mating hoggets that weigh below 36 kg.

Animals↗

PubMed2004

The role of male age, sperm age and mating history on fecundity and fertilization success in the hide beetle.

Models of age-related mate choice predict female preference for older males as they have proven survival ability. However, these models rarely address differences in sperm age and male mating history when evaluating the potential benefits to females from older partners. We used a novel experimental design to assess simultaneously the relative importance of these three parameters in the hide beetle, Dermestes maculatus. In a two-part experiment we first explored age-related male mating success and subsequently examined the consequences of male age, sperm age and male mating history on female fecundity and fertilization success. In a competitive mating environment, intermediate-age males gained significantly higher mating success than younger or older males. To test the consequences for females of aged-related male mating success, a second set of females were mated to males varying in age (young, intermediate-age and old), in numbers of matings and in timing of the most recent mating. We found that male age had a significant impact on female fecundity and fertilization success. Females mated to intermediate-age males laid more eggs and attained consistently higher levels of fertilization success than females with young and old mates. A male's previous mating history determined his current reproductive effort; virgin males spent longer in copula than males with prior mating opportunities. However, differences in copulation duration did not translate into increased fecundity or fertilization success. There was also little evidence to suggest that fertilization success was dependent on the age of a male's sperm. The experiment highlights the potential direct benefits accrued by females through mating with particular aged males. Such benefits are largely ignored by traditional viability models of age-related male mating success.

Age Factors↗

PubMed1983

Age correlation between mates and average consanguinity in age-structured human populations.

When population geneticists wish to determine the genetic consequences of some aspect of mating behavior, it is often necessary to compare observed levels of consanguinity to the level expected when mating is random with respect to the factor being studied. Expectations under random mating are often derived from discrete generation models that ignore age structure. Observed frequencies of consanguineous matings are due to processes that are continuous in time and are affected by variables that are functions of age structure. The extent to which this discrepancy between the models and reality might distort conclusions drawn from comparisons of observed and expected behavior has received insufficient attention. One potential source of error is the tendency for people to choose mates whose ages differ from their own by a certain amount; this tendency influences the frequency of consanguineous matings. Age correlation between mates should therefore also affect average consanguinity between mates and average inbreeding in the population. Expected levels of consanguinity might then differ depending on whether or not age structure has been taken into account. Hajnal developed a model that predicts the frequencies of consanguineous matings in age-structured populations. Hajnal's model is extended here to include relationships that are defined by lineal descent as well as by common ancestry, and to allow calculation of the frequencies of consanguineous matings in the absence of age correlation between mates. The extended model is then used to determine the effect of age correlation between mates on average consanguinity under various sets of conditions. The magnitude of this effect depends on the degree to which the increased frequency of some types of consanguineous matings is offset by the decrease in other types of matings. There is a fairly wide range of conditions under which this compensation is nearly complete and therefore under which the overall effect of age correlation is small. But the size of this effect is sensitive to many factors, especially the distribution of age differences between mates and the variances of ages at maternity and paternity. Under some conditions, age correlation between mates will have a substantial effect on average consanguinity.

Age Factors↗

PubMed1990

Population structure of the Jirels: patterns of mate choice.

The influence of mating practices on genetic structure has been an area of great interest for anthropologists. In this paper, the techniques of potential mates analysis are employed to explore the mating patterns observed among the Jirels, a tribal population of eastern Nepal. Genealogical, anthropometric, dermatoglyphic, and demographic data for members of seven Jirel villages are used. Potential mate pools for a sample of 268 females are enumerated by village. Age structure and the Jirel restriction against clan endogamy are found to severely limit the number of males who are potential mates for a given female. The mating structure of the population is illuminated by statistical analysis of the characteristics of 160 actual mate pairs and all corresponding potential mate pairs. Using this approach several general mate choice practices were verified: 1) biological kin tend to be avoided as mates, 2) members of the same clan are excluded as potential mates, 3) mate exchange between clans is nonrandom, 4) individuals similar in age tend to be selected as mates, and 5) mates are drawn from the natal village more often than random expectation. A multivariate phenotypic distance measure between individuals did not reveal any evidence for assortative mating for either anthropometric or dermatoglyphic characters.

Age Factors↗

PubMed2004

The closely related species Candida albicans and Candida dubliniensis can mate.

Because Candida dubliniensis is closely related to Candida albicans, we tested whether it underwent white-opaque switching and mating and whether white-opaque switching depended on MTL homozygosity and mating depended on switching, as they do in C. albicans. We also tested whether C. dubliniensis could mate with C. albicans. Sequencing revealed that the MTLalpha locus of C. dubliniensis was highly similar to that of C. albicans. Hybridization with the MTLa1, MTLa2, MTLalpha1, and MTLalpha2 open reading frames of C. albicans further revealed that, as in C. albicans, natural strains of C. dubliniensis exist as a/alpha, a/a, and alpha/alpha, but the proportion of MTL homozygotes is 33%, 10 times the frequency of natural C. albicans strains. C. dubliniensis underwent white-opaque switching, and, as in C. albicans, the switching was dependent on MTL homozygosis. C. dubliniensis a/a and alpha/alpha cells also mated, and, as in C. albicans, mating was dependent on a switch from white to opaque. However, white-opaque switching occurred at unusually high frequencies, opaque cell growth was frequently aberrant, and white-opaque switching in many strains was camouflaged by an additional switching system. Mating of C. dubliniensis was far less frequent in suspension cultures, due to the absence of mating-dependent clumping. Mating did occur, however, at higher frequencies on agar or on the skin of newborn mice. The increases in MTL homozygosity, the increase in switching frequencies, the decrease in the quality of switching, and the decrease in mating efficiency all reflected a general deterioration in the regulation of developmental processes, very probably due to the very high frequency of recombination and genomic reorganization characteristic of C. dubliniensis. Finally, interspecies mating readily occurred between opaque C. dubliniensis and C. albicans strains of opposite mating type in suspension, on agar, and on mouse skin. Remarkably, the efficiency of interspecies mating was higher than intraspecies C. dubliniensis mating, and interspecies karyogamy occurred readily with apparently the same sequence of nuclear migration, fusion, and division steps observed during intraspecies C. albicans and C. dubliniensis mating and Saccharomyces cerevisiae mating.

Animals↗

PubMed2005

Direct and indirect mate choice on leks.

Indirect mate choice is any behavior that restricts the individual's set of potential mates without discrimination of mate attributes directly, for example, by having preferences about where to mate. We analyzed a 14-year data set from great snipe (Gallinago media) leks for evidence of indirect mate choice based on relative and absolute position of lek territories. We found little or no effect of the centrality of territories on mating and no between-year consistency in the spatial distribution of matings within leks. Instead, the probability of matings occurring at a particular site increased if the current territory owner had mated the previous year. Furthermore, individual females returned in later seasons to mate with the same male as previously rather than at the same site. Previous work found that male interactions and dominance do not control matings and that females are very choosy about which territory they mate in. Here we show that this is because of the male occupying the territory rather than its position. We therefore conclude that direct female mate choice is the main behavioral process affecting variation in mating success among great snipe males, unlike in some lekking mammals where male competition and/or indirect mate choice appears more important.

Animals↗

PubMed2005

Effect of seminal fluids in mating between M and S forms of Anopheles gambiae.

Previous studies have shown that sympatric populations of M and S molecular forms of Anopheles gambiae sensu stricto exhibit strong assortative mating. In the few documented cases of cross-mating between M and S forms, females that mated with amale of the alternative form were often also mated with a male of their own form. A potential explanation for the association between cross-mating and double mating could be that male accessory gland or sperm proteins that are responsible for inducing refractoriness to further mating by females have diverged between the M and S forms. This mechanism of postmating reproductive isolation would have important implications for our understanding of the speciation processes in the An. gambiae complex. We tested for this mechanism, by comparing the likelihood of mating, feeding, and laying eggs, as well as the fertility of females presented with males of their own form or the alternate form in the laboratory. We also compared the likelihood of remating in cross-mated and assortatively-mated females, and we analyzed their progeny to unravel patterns of sperm precedence. We found that cross-mated females differed from assortatively-mated females only in terms of egg-hatching rate and larval survival but that these effects could be attributed to hybrid vigor rather than differential response to seminal products. Cross-mating between forms was not associated with remating behavior. These results indicate that the sex proteins responsible for inhibiting further insemination and triggering the gonotrophic cycle in females have not diverged between these M and S populations. We discuss alternative explanations for the patterns of cross-mating and multiple mating observed in the field.

Animals↗

PubMed1998

A novel quantitative mating assay for the fungal pathogen Cryptococcus neoformans provides insight into signalling pathways responding to nutrients and temperature.

Cryptococcus neoformans is a fungal pathogen that causes a lethal meningitis in immunocompromised individuals. Several factors are associated with virulence of this fungus, including its mating type; however, the mechanism by which mating type affects virulence is unknown. C. neoformans is a basidiomycete that exists in two mating types called a and alpha that can fuse to form an a/alpha dikaryon. A mating assay was developed that allowed a quantitative analysis of cryptococcal mating physiology. Interestingly, the efficiency of mating appeared to be dependent on temperature, being highest at 30 degrees C and almost completely absent at 37 degrees C. Thus, while mating type itself may be associated with virulence (which must occur at 37 degrees C), the ability to mate is probably not a virulence factor. Mating efficiency was increased by altering the carbon or nitrogen sources to give so-called starvation media. The addition of various drugs also seemed to alter the frequency of mating, depending on the composition of mating medium. The data suggested that cAMP, 8-bromo-cAMP and caffeine increased mating on starvation medium but only cAMP and 8-bromo-cAMP stimulated mating on rich medium; caffeine was unable to stimulate mating on rich medium. Aluminium fluoride, an activator of heterotrimeric GTP-binding proteins (G-proteins), was also found to stimulate mating, suggesting the involvement of a G-protein that may regulate the level of cAMP.

Cryptococcus neoformans↗

PubMed2003

The evolution of wing color: male mate choice opposes adaptive wing color divergence in Colias butterflies.

Correlated evolution of mate signals and mate preference may be constrained if selection pressures acting on mate preference differ from those acting on mate signals. In particular, opposing selection pressures may act on mate preference and signals when traits have sexual as well as nonsexual functions. In the butterfly Colias philodice eriphyle, divergent selection on wing color across an elevational gradient in response to the thermal environment has led to increasing wing melanization at higher elevations. Wing color is also a long-range signal used by males in mate searching. We conducted experiments to test whether sexual selection on wing melanization via male mate choice acts in the same direction as natural selection on mate signals due to the thermal environment. We performed controlled mate choice experiments in the field over an elevational range of 1500 meters using decoy butterflies with different melanization levels. Also, we obtained a more direct estimate of the relation between wing color and sexual selection by measuring mating success in wild-caught females. Both our experiments showed that wing melanization is an important determinant of female mating success in C. p. eriphyle. However, a lack of elevational variation in male mate preference prevents coevolution of mate signals and mate preference, as males at all elevations prefer less-melanized females. We suggest that this apparently maladaptive mate choice may be maintained by differences in detectability between the morphs or by preservation of species recognition.

Animals↗

PubMed1998

Male traits, mating tactics and reproductive success in the buff-breasted sandpiper, Tryngites subruficollis.

Buff-breasted sandpipers use a variety of mating tactics to acquire mates, including remaining at a single lek for most of the breeding season, attending multiple leks during the season, displaying solitarily or displaying both on leks and solitarily. We found that differences in body size, body condition, fluctuating asymmetry scores, wing coloration, territory location and behaviour (attraction, solicitation and agonistic) did not explain the observed variation in mating tactics used by males. Which males abandoned versus returned to leks was also not related to morphology or behaviour, and there was no tendency for males to join leks that were larger or smaller than the lek they abandoned. These results suggest that male desertion of leks was not dependent on a male's characteristics nor on the size of the lek he was presently attending. Males did join leks with larger males than their previous lek, perhaps to mate with females attracted to these larger 'hotshot' males. Males at both leks and solitary sites successfully mated. Lek tenure did not affect mating success, although lekking males appeared to mate more frequently than solitary males. Courtship disruption and to a lesser extent, female mimicry, were effective at preventing females from mating at leks, and may offer a partial explanation for female mating off leks. Our analysis that combined all males together within a year (regardless of mating tactic) indicated that males that attended leks for longer periods of time and that had fewer wing spots were significantly more likely to mate. Given some evidence that wing spotting declines with age, and that females inspect male underwings during courtship, the latter result suggests that female choice may play some role in determining male success. We suggest that male buff-breasted sandpipers may use alternative mating tactics more readily than males in other 'classic' lek-breeding species because: (1) unpredictable breeding conditions in this species' high arctic breeding range leads to low lek stability, which in turn hinders mate selection mechanisms mediated by male dominance and female choice; and (2) males are not constrained by morphological markings that indicate status or sex. Both characteristics may reduce the reproductive benefits associated with males adopting one mating tactic and result in a sort of scramble competition in which males switch between tactics as local conditions change.Copyright 1998 The Association for the Study of Animal Behaviour

Journal Article↗

PubMed2006

Experimental evolution of mating discrimination in budding yeast.

Assortative mating, when individuals of similar phenotypes mate, likely plays a key role in preventing gene flow during speciation. Reinforcement occurs when two previously geographically separated (allopatric) groups meet after having evolved partial postzygotic isolation; they are selected to evolve or enhance assortative mating to prevent costly intergroup matings that produce only maladaptive or sterile hybrids. Studies in Drosophila have shown that the genetic architectures of mating discrimination could differ significantly with or without reinforcement, suggesting that the evolution of assortative mating may be more complicated than expected. To study the evolution of assortative mating, we evolved mating discrimination in populations of the budding yeast, Saccharomyces cerevisiae. After 36 cycles of selection, these cells are five times more likely to mate with each other than to their ancestors, despite detectable one-way gene flow between the selected and reference populations. Several individual cultures evolved mating discrimination by changing their mating kinetics, with some mating more rapidly and others more slowly than the ancestral population. Genetic analysis indicates that multiple mutations have accumulated to produce the altered mating preference. Our results show that subtle details of mating behavior can play an important role in the evolution of reproductive isolation.

Biological Evolution↗

PubMed1999

Female mating behaviour, sexual selection and chromosome I inversion karyotype in the seaweed fly, coelopa frigida

Previous studies of the seaweed fly, Coelopa frigida, have revealed the operation of several different forces of sexual selection. The overall pattern of mate choice seen in natural populations is not consistent with the predictions of indirect sexual selection as females do not express preferences that maximize the fitness of their offspring, even though the benefits from such choice are relatively large in this species. Thus, the maintenance of female mate choice for large male size must instead either be a result of a direct benefit to the female of mating with large males, or a side-effect of the evolution of another character, in other words pleiotropy. In order to separate these two alternatives the genetical basis of female mating behaviour needs to be studied. Previous studies have revealed associations between chromosomal inversion karyotype and both general female willingness to mate and mate choice for large male size, however these associations were lost after several generations of laboratory culture. Here several isokaryotypic lines from wild collections of flies were derived. The willingness to mate and mate choice of females from each line were determined. Pairs of lines of opposite inversion karyotype that significantly differed in either or both willingness to mate and mate choice were crossed. The mating behaviour and inversion karyotype of the F2 progeny (all F1 progeny are heterokaryotypes) were determined. Clear differences in the general levels of female willingness to mate were found between the two inversion homokaryotypes in several families, whereas variation in the strength of female choice for large male size were not revealed. It is suggested that mate choice in this species occurs as a pleiotropic effect of selection acting on female willingness to mate.

Journal Article↗

PubMed1999

Mating stimuli influence endogenous variations in the neurosteroids 3alpha,5alpha-THP and 3alpha-Diol.

Progesterone facilitates and 5alpha-dihydrotestosterone (DHT) inhibits female sexual behaviour in rodents; their metabolites, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) and 5alpha-androstane-3alpha-17beta-Diol (3alpha-Diol), may influence the onset and termination of lordosis. Changes in these and related steroids in hormonal states associated with differences in receptivity were investigated. Rats were assigned to oestrus, metoestrus, dioestrus, pro-oestrus, mated, gestational days 5-7, 12-14, 18-20, or post-partum conditions; rats 9+ months of age were considered older. Pro-oestrus rats were exposed to the mating arena, sight and smell of a male with no tactile contact, artificial vaginocervical stimulation, standard mating, or no mating. Progesterone, 5alpha-pregnane-3,20-dione, 3alpha,5alpha-THP, oestradiol, testosterone, DHT, 3alpha-Diol, dehydroepiandrosterone, and corticosterone were measured in plasma and whole brain, midbrain, hypothalamus, cortex, amygdala, hippocampus. 3alpha,5alpha-THP and 3alpha-Diol changed with reproductive state and mating stimuli. Plasma and whole brain 3alpha,5alpha-THP and 3alpha-Diol were significantly increased in pro-oestrus versus dioestrus rats; plasma 3alpha,5alpha-THP was decreased and 3alpha-Diol increased in mated versus pro-oestrus rats. The midbrain and hypothalamus had the most evident changes in 3alpha,5alpha-THP and 3alpha-Diol between dioestrus versus pro-oestrus and pro-oestrus versus mated rats. 3alpha,5alpha-THP and 3alpha-Diol were altered differently in response to mating stimuli. 3alpha,5alpha-THP was greater in the midbrain of mated versus pro-oestrus rats; other mating-relevant stimuli decreased 3alpha,5alpha-THP. Midbrain 3alpha-Diol was increased with exposure to a male <VCS< mating. 3alpha,5alpha-THP was increased and 3alpha-Diol was decreased in the hypothalamus of mated versus pro-oestrus rats; exposure to the various mating stimuli decreased 3alpha,5alpha-THP and 3alpha-Diol. The neurosteroids, 3alpha,5alpha-THP and 3alpha-Diol, vary with mating in the hypothalamus and midbrain of rats.

Androgens↗