Promiscuous Population Research Articles

Adaptation to monogamy influences parental care but not mating behavior in the burying beetle, Nicrophorus vespilloides.

The mating system is expected to have an important influence on the evolution of mating and parenting behaviors. Although many studies have used experimental evolution to examine how mating behaviors evolve under different mating systems, this approach has seldom been used to study the evolution of parental care. We used experimental evolution to test whether adaptation to different mating systems involves changes in mating and parenting behaviors in populations of the burying beetle, Nicrophorus vespilloides. We maintained populations under monogamy or promiscuity for six generations. This manipulation had an immediate impact on reproductive performance and adult survival. Compared to monogamy, promiscuity reduced brood size and adult (particularly male) survival during breeding. After six generations of experimental evolution, there was no divergence between monogamous and promiscuous populations in mating behaviors. Parents from the promiscuous populations (especially males) displayed less care than parents from the monogamous populations. Our results are consistent with the hypothesis that male care will increase with the certainty of paternity. However, it appears that this change is not associated with a concurrent change in mating behaviors.

Variance in Female Reproductive Success Differentially Impacts Effective Population Size in the Short-Nosed Fruit Bat, Cynopterus sphinx

Effective population size (N e) quantifies the effects of micro-evolutionary processes and the rate of loss of genetic diversity in a population. Several demographic and mating parameters reduce N e. Theoretical studies elucidate the impacts of various demographic and mating system parameters on N e, while empirical studies illustrate realized N e for species with differing life histories and mating systems. However, effect of intra-specific variation in mating system on effective size remains largely unexplored. In this paper we investigated the effect of promiscuous and polygynous mating on N e in two wild populations of the short-nosed fruit bat, Cynopterus sphinx. N e/N (ratio of effective population size to census size) was lower than unity in both populations, and much lower for the polygynous population compared to promiscuous population. Elasticity analyses reveal that N e/N was sensitive to deviations in the sex ratio. Variance in female reproductive success had a higher impact on N e compared to variance in male reproductive success in the promiscuous population. However, for the polygynous population, impact of variance in male reproductive success on N e was higher than that of variance in female reproductive success. Our results suggest that depending on mating system, different populations of the same species could have alternate evolutionary trajectories. The rate of loss of genetic diversity would be lower for the promiscuous population compared to the polygynous population. Our study is the first to highlight which parameters would most significantly impact population specific N e under different mating systems.

Sexually transmitted infection and the evolution of serial monogamy.

The selective forces shaping mating systems have long been of interest to biologists. One particular selective pressure that has received comparatively little attention is sexually transmitted infections (STIs). While it has been hypothesized that STIs could drive the evolutionary emergence of monogamy, there is little theoretical support. Here we use an evolutionary invasion analysis to determine what aspects of pathogen virulence and transmission are necessary for serial monogamy to evolve in a promiscuous population. We derive a biologically intuitive invasion condition in terms of population-specific quantities. From this condition, we obtain two main results. First, when pathogen virulence causes mortality rather than sterility, monogamy is more likely to evolve. Second, we find that at intermediate pathogen transmission rates, monogamy is the most selectively advantageous, whereas at high- and low-transmission rates, monogamy is generally selected against. As a result, it is possible for a pathogen to be highly virulent, yet for promiscuity to persist.

Meningitis Criptococócica y Síndrome de Inmunodeficiencia Adquirida en el Hospital Nacional Dos de Mayo

Objetivos: Demostrar la incidencia de meningitis criptococócica (MC) en los pacientes fallecidos con infección por VIH estadio SIDA en el Hospital Nacional Dos de Mayo (HNDM). Métodos: Se realizó un estadio retrospectivo en 21 pacientes fallecidos con MC y SIDA entre enero de 1991 a diciembre de 1994 en el HNDM. Resultados: La incidencia de MC en pacientes con SIDA fue 10,2%. lodos fueron varones, siendo la mayor frecuencia entre 26 y 30 años de edad. Los factores de riesgo encontrados fueron: homosexuales 38%, bisexuales 33,3% y comportamiento heterosexual promiscuo 26,6%. Además; en 38% de los pacientes, se halló uso frecuente de alcohol, pasta de coca y marihuana. En todos los pacientes se detectó prueba de Elisa y Western Blot para VIH. El diagnóstico de MC se hizo por el hallazgo del criptococo en el LCR, examen directo 76,2%, cultivo 14,2%, y por ambos métodos en 8,5%. En 61,9% de pacientes se encontró linfopenia y en el 62,0% hipoalbuminemia. Conclusiones: La MC es una asociación frecuente en pacientes infectados con el VIH en estadio SIDA, con alta mortalidad. La población más afectada es el sexo masculino, con mayor predominancia entre los 26 a 30 años. La población heterosexual promiscua actualmente es afectada en un porcentaje importante. Los signos y síntomas mas frecuentes fueron cefalea, nauseas, vómitos y malestar general. La linfopenia y la hipoalbuminemia sérica son parámetros de mal pronóstico. El período de supervivencia fue menor de un año en el 90,5% de los pacientes.

Idiopathic AIDS Enteropathy and Treatment of Gastrointestinal Opportunistic Pathogens

Diarrhea in patients with acquired immune deficiency syndrome (AIDS) has proven to be both a diagnostic and treatment challenge since the discovery of the human immunodeficiency virus (HIV) virus more than 30 years ago. Among the main etiologies of diarrhea in this group of patients are infectious agents that span the array of viruses, bacteria, protozoa, parasites, and fungal organisms. In many instances, highly active antiretroviral therapy remains the cornerstone of therapy for both AIDS and AIDS-related diarrhea, but other targeted therapies have been developed as new pathogens are identified; however, some infections remain treatment challenges. Once identifiable infections as well as other causes of diarrhea are investigated and excluded, a unique entity known as AIDS enteropathy can be diagnosed. Known as an idiopathic, pathogen-negative diarrhea, this disease has been investigated extensively. Atypical viral pathogens, including HIV itself, as well as inflammatory and immunologic responses are potential leading causes of it. Although AIDS enteropathy can pose a diagnostic challenge so too does the treatment of it. Highly active antiretroviral therapy, nutritional supplementation, electrolyte replacements, targeted therapy for infection if indicated, and medications for symptom control all are key elements in the treatment regimen. Importantly, a multidisciplinary approach among the gastroenterologist, infectious disease physician, HIV specialists, oncology, and surgery is necessary for many patients.

Cooperative Breeding in Groups of Synchronously Mating Females and Evolution of Large Testes to Avoid Sperm Depletion in African Striped Mice1

Testis size has been related to the mating system of both vertebrates and invertebrates. These differences are regarded as adaptive responses to sperm competition in promiscuously mating species. However, not all variation in testis size can be explained by sperm competition. Here, we test the hypothesis that the evolution of large testes occurs when synchronously breeding females must be fertilized within a short period of time to avoid reproductive competition among the females. African striped mouse (Rhabdomys pumilio) males of a polygynous population with cooperative breeding and high risk of sperm depletion had testes and cauda epididymis twice as large as those of males of four different promiscuous populations with high risk of sperm competition. When paired with three females simultaneously in captivity, males of the polygynous population bred with three females within 8 days, leading to synchronous births in their harems, thereby potentially reducing the risk of infanticide. Males from the promiscuous population reproduced with only one or two females within 8 days, and births were not synchronous. We conclude that large testes are selected for in species with synchronously mating females, which is ultimately beneficial for the evolution of cooperative breeding.

Mating strategy predicts the occurrence of the Bruce effect in the vlei rat Otomys irroratus

[The Bruce effect is a phenomenon in which pregnant females terminate their pregnancies when exposed to strange males, and is hypothesised to be a female counter-strategy to infanticide risk. Since uncertain paternity decreases the incidence of infanticide, we tested the prediction that the Bruce effect would occur in mating systems where paternity is more certain (polygyny) rather than in mating systems where paternity is less certain (promiscuity). Using populations of the vlei rat Otomys irroratus that were either polygynous or promiscuous in nature, we studied the Bruce effect in captivity. Pregnancy termination almost always occurred in polygynous females but never in promiscuous females ( N = 10 per population). We expected that the signal–receptor (male–female) system of pregnancy termination is present in polygynous but not promiscuous populations and predicted an absence of the Bruce effect in encounters between individuals of different mating systems. This occurred in promiscuous females. However, 50% of polygynous females terminated their pregnancies, indicating that males of both mating strategies might carry signals to disrupt pregnancy but only polygynous females respond to these signals. The Bruce effect may be an adaptive response to infanticide risk in polygynous populations, although studies of free-living populations would be important to confirm our findings., The Bruce effect is a phenomenon in which pregnant females terminate their pregnancies when exposed to strange males, and is hypothesised to be a female counter-strategy to infanticide risk. Since uncertain paternity decreases the incidence of infanticide, we tested the prediction that the Bruce effect would occur in mating systems where paternity is more certain (polygyny) rather than in mating systems where paternity is less certain (promiscuity). Using populations of the vlei rat Otomys irroratus that were either polygynous or promiscuous in nature, we studied the Bruce effect in captivity. Pregnancy termination almost always occurred in polygynous females but never in promiscuous females ( N = 10 per population). We expected that the signal–receptor (male–female) system of pregnancy termination is present in polygynous but not promiscuous populations and predicted an absence of the Bruce effect in encounters between individuals of different mating systems. This occurred in promiscuous females. However, 50% of polygynous females terminated their pregnancies, indicating that males of both mating strategies might carry signals to disrupt pregnancy but only polygynous females respond to these signals. The Bruce effect may be an adaptive response to infanticide risk in polygynous populations, although studies of free-living populations would be important to confirm our findings.]

A measure of sexual selection in hermaphroditic animals: parentage skew and the opportunity for selection

The role of sexual selection in shaping the mating system of hermaphrodites is currently widely accepted. However, a quantification of the intensity of sexual selection in hermaphroditic animals has never been accomplished. We evaluated the opportunity for sexual selection for both the female and the male functions in the simultaneous outcrossing hermaphrodite Ophryotrocha diadema by measuring focal hermaphrodites' paternal and maternal offspring in experimental replicated monogamous and promiscuous populations, using genetic markers to estimate paternity. Opportunity for sexual selection for each of the two sexual functions was quantified by means of the Crow's index, i.e. the ratio of variance in progeny number to the squared mean number of progeny. In addition, the extent to which the reproductive success was shared among competing individuals was estimated by means of the Nonacs's B index. We documented that the strength of selection on the male and female function in hermaphrodites with external fertilization depends on the reproductive context. Under a promiscuous regime, hermaphrodites have higher opportunities for selection for both the male and the female function than under the monogamous regime. Moreover, the reproductive skew for the female function becomes greater than that for the male function, moving from monogamy to promiscuity. In our model system, allocation to one sexual function is opposed by any degree of allocation to the other, indicating that sex-specific patterns of selection operate in this model species.

Spacing pattern in a social group of stray cats: effects on male reproductive success

Reproductive consequences of male spacing patterns have received relatively little attention in nonterritorial mammals, in particular in group-living species, where most studies have focused on the relation between social rank and reproductive success. We investigated the effects of spacing pattern on male reproductive success within a social, nonterritorial, promiscuous population of stray cats, Felis catus. Male home ranges overlapped home ranges of many females, consistent with a promiscuous mating system. Furthermore, males with the largest home ranges included the most female home ranges; they successfully reproduced with these females and had the highest reproductive success. Home range size predicted male reproductive success even when controlling for the effect of social rank. However, males also reproduced with females whose home range did not overlap their home range, suggesting that males can make quick excursions outside their home range to find new mating opportunities. We conclude that, in group-living situations, a male's ability to maintain a large home range may be one of the principal causes of variation in mating success in the stray cat.

Spacing pattern in a social group of stray cats: effects on male reproductive success

Reproductive consequences of male spacing patterns have received relatively little attention in nonterritorial mammals, in particular in group-living species, where most studies have focused on the relation between social rank and reproductive success. We investigated the effects of spacing pattern on male reproductive success within a social, nonterritorial, promiscuous population of stray cats, Felis catus. Male home ranges overlapped home ranges of many females, consistent with a promiscuous mating system. Furthermore, males with the largest home ranges included the most female home ranges; they successfully reproduced with these females and had the highest reproductive success. Home range size predicted male reproductive success even when controlling for the effect of social rank. However, males also reproduced with females whose home range did not overlap their home range, suggesting that males can make quick excursions outside their home range to find new mating opportunities. We conclude that, in group-living situations, a male's ability to maintain a large home range may be one of the principal causes of variation in mating success in the stray cat.

Site Fidelity, Philopatry, and Survival of Promiscuous Saltmarsh Sharp-Tailed Sparrows in Rhode Island

AbstractWe investigated site fidelity and apparent survival in a promiscuous population of Saltmarsh Sharp-tailed Sparrows (Ammodramus caudacutus) in southern Rhode Island. Based on capture–recapture histories of 446 color-banded sparrows studied from 1993 to 1998 at our primary study site, Galilee, we observed significant variation in apparent survival rates among years, but not between sexes. Return rates of adult males (37.6%) and females (35.6%) were not significantly different during any year. Juveniles exhibited high return rates, ranging from 0 to 44%, with males (61% of returns) more likely to return than females (35%). In addition, we monitored movements of 404 color-banded sparrows at nine satellite marshes in 1997 and 1998, which supported our findings at Galilee and documented intermarsh movements by 10% of all banded birds. Lack of gender-bias in adult dispersal and strong natal philopatry of sparrows in Rhode Island occurs regularly among passerines possessing a variety of mating systems. Despite emancipation from parental and resource defense duties, adult male Saltmarsh Sharp-tailed Sparrows exhibited apparent survival rates similar to adult females. Availability of high-quality breeding habitat, which is patchy and saturated, may be the most important factor limiting dispersal for Saltmarsh Sharp-tailed Sparrows in Rhode Island.

SITE FIDELITY, PHILOPATRY, AND SURVIVAL OF PROMISCUOUS SALTMARSH SHARP-TAILED SPARROWS IN RHODE ISLAND

Abstract We investigated site fidelity and apparent survival in a promiscuous population of Saltmarsh Sharp-tailed Sparrows (Ammodramus caudacutus) in southern Rhode Island. Based on capture–recapture histories of 446 color-banded sparrows studied from 1993 to 1998 at our primary study site, Galilee, we observed significant variation in apparent survival rates among years, but not between sexes. Return rates of adult males (37.6%) and females (35.6%) were not significantly different during any year. Juveniles exhibited high return rates, ranging from 0 to 44%, with males (61% of returns) more likely to return than females (35%). In addition, we monitored movements of 404 color-banded sparrows at nine satellite marshes in 1997 and 1998, which supported our findings at Galilee and documented intermarsh movements by 10% of all banded birds. Lack of gender-bias in adult dispersal and strong natal philopatry of sparrows in Rhode Island occurs regularly among passerines possessing a variety of mating systems. D...

Importance of sexual transmission of hepatitis C virus in seropositive pregnant women: a case-control study.

The mode of hepatitis C virus (HCV) transmission in patients who deny parenteral exposure is still not understood. Seroprevalence studies of anti-HCV in sexually promiscuous populations and in spouses of infected patients have given contradictory results. We investigated the role of sexual transmission of HCV in a case-control study of risk factors for infection in a series of 43 anti-HCV positive pregnant women and 172 matched controls (4 for each case). In the univariate analysis, the following factors were associated significantly with anti-HCV seropositivity: low social class, unmarried, history of abortion, wounds which were sutured, tattooes, sharing toiletries with the partner, sexual contact outside the partnership without condom use, blood transfusion, and intravenous drug abuse, but only the last 3 factors remained significantly associated with HCV infection in multiple logistic regression analysis. The relative risk of HCV infection increased according to the increased number of sexual partners. Thus sexual transmission must be considered a possible mode of infection in HCV infected persons without parenteral exposures.

SLIM DISEASE: A NEW DISEASE IN UGANDA AND ITS ASSOCIATION WITH HTLV-III INFECTION

A new disease has recently been recognised in rural Uganda. Because the major symptoms are weight loss and diarrhoea, it is known locally as slim disease. It is strongly associated with HTLV-III infection (63 out of 71 patients) and affects females nearly as frequently as males. The clinical features are similar to those of enteropathic acquired immunodeficiency syndrome as seen in neighbouring Zaire. However, the syndrome is rarely associated with Kaposi's sarcoma (KS), although KS is endemic in this area of Uganda. Slim disease occurs predominantly in the heterosexually promiscuous population and there is no clear evidence to implicate other possible means of transmission, such as by insect vectors or re-used injection needles. The site and timing of the first reported cases suggest that the disease arose in Tanzania.

A rejoinder to Mr Hajnal's comments

Summary Mr Karmel takes up the points in Mr Hajnal's article. He analyses in detail the assumptions which are implicit in the use of female rather than male reproduction rates, and shows that female rates are appropriate either in a sexually promiscuous population, or in one where the females are ‘perfectly marriage dominant’. He goes on to examine the possibility of obtaining a ‘unique’ true rate of increase for a population and offers a theoretical solution of the problem, emphasizing the practical difficulties involved. He shows that, if such a ‘unique’ rate exists, it will in practice almost certainly lie between the ordinary male and female true rates of increase calculated from nuptially controlled net reproduction rates, and he shows how a rough estimate of such a ‘unique’ rate might be made. Whilst accepting Mr Hajnal's criticism on the subject of the measurement of the net fertility of marriage, he develops the measures involved further, and shows the relationships existing between Mr Hajnal's me...