Agricultural property,matrimonial structures,and reproductive behaviour of the Guedmiwa Berbers (Azegour Valley,Marrakech, Morocco)

This study concerns the Guedmiwa Berber population living in the Azegour Valley, at an altitude of 2000m on the northern slopes of the western range of the Haut-Atlas mountains. The reproductive behaviour of 506 Guedmiwa Berber families shows a rather elevated fertility which seems influenced at the same time by the socio-familial organisation and by the economic resources at the disposition of the family.     

Genetic differentiation, behavioural reproductive isolation and mixis cues in three sibling species of monogonont rotifers

Many aquatic species usually considered to be 'cosmopolitan' have been identified as cryptic species complexes, based on deep genetic differentiation. However, reproductive isolation among sibling cryptic species has rarely been studied, and interspecific hybridization is common in some taxa.We investigated isolation mechanisms and possible introgression among three cyclical parthenogenetic rotifer species in the Epiphanes senta complex that are found in very different freshwater habitats: temperate floodplains, subtropical desert rock pools and a tropical alpine lake. Whereas Epiphanes ukera is reproductively isolated from E. chihuahuaensis and E. hawaiiensis, the latter hybridize under laboratory conditions.While reproductive isolation is incomplete, RAPD profiles indicated unique genetic signatures and showed no evidence for introgression, indicating that these three species are diverging and have independent evolutionary trajectories.Testing cues for sexual reproduction in these cyclic parthenogens demonstrated that mixis in E. chihuahuaensis and E. ukera is influenced by population density, whereas E. hawaiiensis females rarely produce mictic offspring regardless of density. Different mixis cues are likely to separate sexual periods and effectively cause reproductive isolation between the species. Epiphanes ukera and E. chihuahuaensis males display mate guarding behaviour, and E. ukera males distinguish between conspecific and heterospecific females in mate choice experiments. Geographic isolation, along with different cues for mixis induction and mate recognition, act as reproductive barriers among these sibling species.     

Genetics of incipient speciation in Drosophila mojavensis. I. Male courtship song, mating success, and genotype x environment interactions

Few studies have examined genotype by environment (GxE) effects on premating reproductive isolation and associated behaviors, even though such effects may be common when speciation is driven by adaptation to different environments. In this study, mating success and courtship song differences among diverging populations of Drosophila mojavensis were investigated in a two-environment quantitative trait locus (QTL) analysis. Baja California and mainland Mexico populations of D. mojavensis feed and breed on different host cacti, so these host plants were used to culture F2 males to examine host-specific QTL effects and GxE interactions influencing mating success and courtship songs. Linear selection gradient analysis showed that mainland females mated with males that produced songs with significantly shorter L(long)-IPIs, burst durations, and interburst intervals. Twenty-one microsatellite loci distributed across all five major chromosomes were used to localize effects of mating success, time to copulation, and courtship song components. Male courtship success was influenced by a single detected QTL, the main effect of cactus, and four GxE interactions, whereas time to copulation was influenced by three different QTLs on the fourth chromosome. Multiple-locus restricted maximum likelihood (REML) analysis of courtship song revealed consistent effects linked with the same fourth chromosome markers that influenced time to copulation, a number of GxE interactions, and few possible cases of epistasis. GxE interactions for mate choice and song can maintain genetic variation in populations, but alter outcomes of sexual selection and isolation, so signal evolution and reproductive isolation may be slowed in diverging populations. Understanding the genetics of incipient speciation in D. mojavensis clearly depends on cactus-specific expression of traits associated with courtship behavior and sexual isolation.     

Asymmetric Assortative Mating Behaviour Reflects Incomplete Pre‐zygotic Isolation in the Nasonia Species Complex

Preference of con‐ over heterospecific mates leading to assortative mating can substantially contribute to pre‐zygotic reproductive isolation and prevent fitness losses if post‐zygotic hybridization barriers already exist. The jewel wasp genus Nasonia displays quite strong and well‐studied post‐zygotic reproductive isolation due to a ubiquitous Wolbachia infection causing cytoplasmic incompatibility between different species. Pre‐zygotic isolation, however, has received far less research attention in this model organism, especially concerning the mechanisms and criteria of mate choice. In the present study, we analysed mate rejection and mate acceptance rates in cross‐comparisons between all four Nasonia species. We put emphasis on observing which sex is more likely to interrupt interspecific matings and how discriminatory behaviour varies across the different species in all possible combinations. We found an asymmetric distribution of assortative mating among the four Nasonia species that appears to be highly influenced by the respective combinations of sex and species. Females appeared to be the main discriminators against heterospecific mating partners, but interestingly, we could also detect mate discrimination and rejection behaviour in males, a widely neglected factor in research on mating behaviour in general and on Nasonia in particular. Moreover, the asymmetry in the assortative mating behaviour was partially reflective of sym‐ or allopatric distributions of natural Nasonia populations.     

Premarital fertility in Namibia: trends, factors and consequences

Premarital fertility, defined as fertility before first marriage, was found to be highly prevalent in Namibia. According to data from the 1992 and 2000 DHS surveys, the proportion of premarital births was 43% for all births, and 60% for the first birth. This seemed to be primarily due to a late mean age at first marriage (26.4 years) and low levels of contraception before first marriage. Data were analysed using a variety of demographic methods, including multiple decrement life table and multivariate logistic models. Major variations were found by ethno-linguistic groups: Herero and Nama/Damara had the highest levels of premarital fertility (above 60%); Ovambo and Lozi had intermediate levels of premarital fertility (around 40%); Kavongo and San appeared to have kept a more traditional behaviour of early marriage and low levels of premarital fertility (around 20%). The largest ethno-linguistic group, the Ovambo, were in a special situation, with fast increasing age at marriage and average level of premarital fertility. Whites and mixed races also differed, with Afrikaans-speaking groups having a behaviour closer to the average, whereas other Europeans had less premarital fertility despite an average age at marriage. Ethnic differences remained stable after controlling for various socioeconomic factors, such as urbanization, level of education, wealth, access to mass media, and religion. Results are discussed in light of the population dynamics and political history of Namibia in the 20th century.     

Species divergence in field crickets: genetics,song, ecomorphology,and pre‐ and postzygotic isolation

Studies that simultaneously estimate levels of species divergence in genetics, reproductive and ecological traits, and pre‐ and postzygotic isolation are relatively rare. Here we compare levels of divergence in three allopatric sister species of field crickets. We compare divergence in both nuclear and mitochondrial DNA, male song, female ovipositor length, levels of pre‐ and postzygotic isolation, and male versus female contributions to prezygotic isolation. Taken together, our data show the accumulation of a multitude of potential reproductive isolating barriers if secondary contact were to become established. Furthermore, ecological and behavioural prezygotic isolation appear significantly more advanced than postzygotic isolation, with prezygotic isolation due to female behaviour exceeding that due to male behaviour.     

Fine-scale genetic structure, estuarine colonization and incipient speciation in the marine silverside fish Odontesthes argentinensis

The identification of incipient ecological species represents an opportunity to investigate current evolutionary process where adaptive divergence and reproductive isolation are associated. In this study we analysed the genetic structure of marine and estuarine populations of the silverside fish Odontesthes argentinensis using nine microsatellite loci and 396 bp of the mitochondrial DNA (mtDNA) control region. Our main objective was to investigate the relationship among estuarine colonization, divergent selection and speciation in silversides. Significant genetic structure was detected among all marine and estuarine populations. Despite the low phylogeographic structure in mtDNA haplotypes, there was clear signal of local radiations of haplotypes in more ancient populations. Divergence among marine populations was interpreted as a combined result of homing behaviour, isolation by distance and drift. On the other hand, ecological shifts due to the colonization of estuarine habitats seem to have promoted rapid adaptive divergence and reproductive isolation in estuarine populations, which were considered as incipient ecological species. This conclusion is supported by the existence of a set of environmental factors required for successful reproduction of estuarine ecotypes. The pattern of genetic structure indicates that phenotypic and reproductive divergence evolved in the face of potential gene flow between populations. We suggest that the 'divergence-with-gene-flow' model of speciation may account for the diversification of estuarine populations. The approach used can potentially identify 'incipient estuarine species', being relevant to the investigation of the evolutionary relationships of silversides in several coastal regions of the world.     

Marital mobility in populations of the High Aran Valley

The analysis of 2.623 marriage certificates in the towns in the High Aran Valley shows marriage mobility between the years 1650 and 1990 and indicates the level of population's endogamy. The results from the data collected in the town of Arties are presented as an example. The distribution of the places of origin of spouses and a factor analysis show a remarkable geographical endogamy until 1940. The results from marriage mobility are confirmed by data from blood polymorphism studies, matrimonial dispensations and surnames.     

Isolation between sympatric anadromous and resident threespine stickleback species in Mud Lake,Alaska

A sympatric pair of anadromous and resident freshwater threespine stickleback species (Gasterosteus aculeatus species complex) occurs in Mud Lake in the Matanuska-Susitna Valley, Alaska. The two forms differ in an array of morphological traits, including traits associated with predator defense (e.g., spine lengths) and trophic ecology (e.g., number of gill rakers). Mud Lake is only the third lake reported to have anadromous stickleback (which have a complete row of lateral plates) coexisting with low-plated resident stickleback in the absence of intermediate partially plated fish. Microhabitat and seasonal isolation appear to contribute to reproductive isolation between the two forms.     

Fertility and population policy in two counties in China 1980-1991

A survey of women in two highly developed rural counties of China, Sichuan and Jiangsu Provinces, was carried out in late 1991, to gain information about demographic and economic change between 1980 and 1990. Three separate surveys were conducted: the first a questionnaire administered to married women aged 30-39, eliciting information about childbearing and contraception, as well as the social and economic background of the respondents; the second, focus group interviews emphasizing the motivation for childbearing. Official information about the selected villages, townships and counties was also collected. National level data in 1987 show that individual reproductive behaviour in China failed to conform to a universal, effectively implemented, population policy. They imply either a spatial range of policies, or great diversity in the demand for children, or perhaps a combination of both. Such diversity in reproductive behaviour is also found in the study area. The purpose of the analysis was to examine the diversity in reproductive behaviour and contraceptive practice, and to discover whether differentials are influenced by area, or else exist between individuals within areas. If the former, then the explanation may be found in differences in policy formulation and implementation between areas: and if the latter, to demand for children, or else differential application of policy restrictions. The main findings were that: (1) the explanation of the pattern of fertility and contraceptive use is to be found at the individual level (within locations) rather than in policy differences between administrative units; (2) the association between income and number of children is negative, as is that between income and the propensity for uniparous women to remain unsterilized. The theory that privilege may be exercised to gain concessions from birth planning cadres is therefore not supported; (3) ideal family size differentials are largely absent, showing that social (education) and economic (income, occupation) characteristics are not responsible for differences in reproductive motivations, and implying that the nature of the demand for children is very different from that in most rural areas of the Third World; (4) data on ideal family size by sex of the existing offspring indicate only a weak preference for sons. The low demand for children, and the weak son preference, may both be explained by the social acceptability of uxorilocal marriages, and of village endogamy, together with the prohibitive costs of children, and especially of sons. This partly results from the expense of education, but most mothers emphasize marriage costs. It is speculated that the circumstances responsible for the escalating costs of children in the two countries are likely to pertain in growing areas of the country, with the privatization of education and health services, the declining support of collective institutions, and the replacement of this function by kinship networks. These on-going changes imply that any policy of reproductive restriction for the purposes of population control is likely soon to meet with diminishing resistance; and it may later be rendered unnecessary in the eyes of government officials, as fulfilled reproductive intentions lead to a fertility level below replacement level.     

Evolution of Courtship Behaviour Patterns and Reproductive Isolation in the Desmognathus ochrophaeus Complex

The extent to which differences in courtship behaviour patterns act as mechanisms of reproductive isolation is critical to understanding both speciation and the evolution of these behaviour patterns. While numerous studies have investigated intraspecific and interspecific differences in courtship, fewer interpret results in a phylogenetic framework. We describe and analyse geographic variation in the courtship behaviour patterns of the Allegheny Dusky salamander ( Desmognathus ochrophaeus ). We then examine courtship among closely related species in the D. ochrophaeus complex in a phylogenetic context. We found that populations of D. ochrophaeus separated by extensive geographic distances show little variation in courtship behaviour patterns and are sexually compatible. This contrasts with significant levels of sexual isolation between D. ochrophaeus and other species in the complex. Mapping behaviour patterns onto a phylogeny that we generated from cytochrome b sequences indicates that two behaviour patterns present in the courtship sequence of other members in the complex have either been lost in D. ochrophaeus or gained independently in other species in the complex. Loss of these behaviour patterns may result in reproductive isolation between D. ochrophaeus and its sister taxon, D. orestes .     

Contraceptive use dynamics of Asian women in Britain

In-depth interviews were conducted with married Asian women from Indian, Pakistani and Bangladeshi backgrounds, to investigate patterns of contraceptive use and influences on contraceptive decision making. The results show two distinctively different contraceptive 'lifecycles'. Non-professional women typically have little knowledge about contraception until after their marriage or first birth. Their patterns of contraceptive behaviour show low levels of contraceptive use until after their first birth, when condom use is most prevalent. Non-professional women are influenced by their extended family, religion and cultural expectations on their fertility and family planning decisions. Professional women show an entirely different pattern of contraceptive behaviour. They are more likely to have knowledge about contraception before marriage, use some method of contraception throughout their childbearing years (typically the pill) and cite personal, practical or economic considerations in their fertility decisions rather than religious, cultural or extended family influences.     

Intrinsic reproductive isolation between Trinidadian populations of the guppy, Poecilia reticulata

Although Trinidadian populations of the guppy, Poecilia reticulata, show considerable adaptive genetic differentiation, they have been assumed to show little or no reproductive isolation. We tested this assumption by crossing Caroni (Tacarigua River) and Oropuche (Oropuche R.) drainage populations from Trinidad's Northern Range, and by examining multiple aspects of reproductive compatibility in the F1, F2 and BC1 generations. In open-aquarium experiments, F1 males performed fewer numbers of mating behaviours relative to parental population controls. This is the first documentation of hybrid behavioural sterility within a species, and it suggests that such sterility may feasibly be involved in causing speciation. The crosses also uncovered hybrid breakdown for embryo viability, brood size and sperm counts. In contrast, no reductions in female fertility were detected, indicating that guppies obey Haldane's rule for sterility. Intrinsic isolation currently presents a much stronger obstacle to gene flow than behavioural isolation, and our results indicate that Trinidadian populations constitute a useful model for investigating incipient speciation.     

Seasonal migration promoting assortative mating in Littorina brevicula on a boulder shore in Japan

Littorina brevicula Philippi is one of the most common snails found in the upper intertidal zone of Japan. In Amakusa, some of the population of L. brevicula migrate to the lower zone in the winter, while the rest stay in the upper zone. Thus, during the winter, which is its reproductive season, the population of L. brevicula divides into two sub-populations. This leads to a hypothesis that the migration pattern in winter is genetically controlled and this behavioural dimorphism is maintained by reproductive isolation between the two sub-populations. In order to test this hypothesis, the following three points were investigated: (1) whether the same snails migrate in a similar way every winter, (2) whether there is a significant tidal level preference in snails, and (3) whether reproductive isolation occurs between the two sub-populations. The results showed (1) the migration behaviour of each snail was consistent over two successive winters, i.e. the same group of snails migrated downward every winter and the same group of snails stayed in the upper zone every winter, (2) transplanted snails moved toward the original zones where they were caught, suggesting that the snails actively selected their tidal zone in winter, and (3) most of the snails copulated within each sub-population. Therefore, reproductive isolation between the two sub-populations was considered to be established to some extent by the dimorphic migration behaviour. In conclusion, the migratory behaviour of L. brevicula is determined separately for each individual and might be genetically controlled, and the behavioural dimorphism may be maintained by partial reproductive isolation between the two sub-populations.     

Patterns of self compatibility, inbreeding depression, outcrossing, and sex allocation in a marine bryozoan suggest the predominating influence of sperm competition

Sex allocation by simultaneous hermaphrodites is theoretically influenced by selfing rate, which is in turn influenced by the benefits of enhanced genomic transmission and reproductive assurance relative to the cost of inbreeding depression. The experimental investigation of these influences in seed plants has a rich pedigree, yet although such an approach is equally relevant to colonial invertebrates, which globally dominate subtidal communities on firm substrata, such studies have been scarce. We reared self‐compatible genets of the marine bryozoan Celleporella hyalina s.l. in the presence and absence of allosperm, and used molecular genetic markers for paternity analysis of progeny to test theoretical predictions that: (1) genets from focal populations with high selfing rates show less inbreeding depression than from focal populations with low selfing rates; (2) genets whose selfed progeny show inbreeding depression prefer outcross sperm (allosperm); and (3) genets bias sex allocation toward female function when reared in reproductive isolation. Offspring survivorship and paternity analysis were used to estimate levels of inbreeding depression and preference for outcrossing or selfing. Sex allocation was assessed by counting male and female zooids. As predicted, inbreeding depression was severe in selfed progeny of genets derived from the populations with low self‐compatibility rates, but, with one exception, was not detected in selfed progeny of genets derived from the populations with higher self‐compatibility rates. Also, as predicted, genets whose selfed progeny showed inbreeding depression preferred outcrossing, and a genet whose selfed progeny did not show inbreeding depression preferred selfing. Contrary to prediction, sex allocation in the majority of genets was not influenced by reproductive isolation. Lack of economy of male function may reflect the over‐riding influence of allosperm‐competition in typically dense breeding populations offering good opportunity for outcrossing. We suggest that hermaphroditism may be a plesiomorphic character of the crown group Bryozoa, prevented by phylogenetic constraint from being replaced by gonochorism and therefore not necessarily adaptive in all extant clades. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 519–531.     

Life history tactics of darters (Percidae: Etheostomatiini) and their relationship with body size, reproductive behaviour, latitude and rarity

Patterns of covariation of life history traits of darters in the genus Etheostoma are reviewed. The primary pattern is associated with body size. Large darters grow faster, mature at a larger size, produce bigger clutches, and have longer reproductive and life spans, and shorter spawning seasons, than do small darters. When the effects of size are removed statistically, the dominant secondary pattern matched the r-K continuum from fast-growing, short-lived, primarily semelparous species with many small ova and a high reproductive effort (r-species) to slow-growing, long-lived, iteroparous species with few large ova and a low reproductive effort (K-species). Variation in life history traits is also influenced by reproductive behaviour, latitude, and rarity (as measured by geographic range). There are significant differences in the primary and secondary life history patterns among reproductive guilds. Latitude and rarity are not correlated with these primary and secondary patterns. Instead, they account for variation of tertiary patterns. Rare species may not match the reproductive performance of more common and widely distributed species. Future studies of life history traits in darters should focus on species whose reproductive behaviour differs from that of the species reviewed in this study, and on the demographic characteristics of rare or declining populations.     

Population structure, history and gene flow in a group of closely related land snails: genetic variation in Partula from the Society Islands of the Pacific

Previous studies of Partula land snails from the Society Islands, French Polynesia, have shown that populations within species are highly differentiated in terms of their morphology, behaviour, ecology and molecular genetic variation. Despite this level of variability, differences between species are sometimes small, possibly reflecting the fact that reproductive isolation is not always complete and there exists the opportunity for genetic exchange between taxa through hybridization. The present study uses sequence data from a mitochondrial gene to further investigate genetic variation in Society Island Partula. Most populations are found in this study to be highly differentiated, but within individual species there seems to be no simple relationship either between genetic distance and geographical proximity, or between variation in mitochondria and that in allozymes or morphological characteristics. Among species there appears to be no simple correlation between degrees of reproductive isolation and genetic relatedness according to mitochondrial DNA. The results suggest that past events as well as ongoing drift and selection may have been important in affecting patterns of variation. Similarities among species at specific localities suggest that there must have been some genetic exchange in the past, although this may not necessarily reflect ongoing rates of hybridization. The discrepancy between results for different markers probably reflects the differential effects of drift and selection on mitochondrial and nuclear genes.     

Female Choice in Humans: A Conditional Mate Selection Strategy of the Krummhörn Women (Germany, 1720–1874)

The suitors' ownership of land influenced the marriage age of the women in the Krummhörn population (Germany, 1720–1874). This led to a characteristic distribution of the categories of land ownership of husbands by the wife's age at marriage: the younger the brides, the higher was the percentage of high-status males among their bridegrooms. But the natal status of brides did not exert any significant influence on their age at marriage. Moreover, socially hypergamous women married younger than those whose marriage meant a social drop. We have interpreted these findings as the expression of a conditional female choice strategy with age-dependent decrease in demands on a marriage partner: “If you are young, be very choosy and marry only a high-quality mate; the older you become, the more you must reduce your initial standards!” On the average this strategy was adaptive, because in this population land ownership correlated with the local reproductive success of a family.     

Context-dependent aggregation in Common Frog Rana temporaria tadpoles: influence of developmental stage, predation risk and social environment

1. This study examines the aggregation behaviour and activity of larvae of the Common Frog Rana temporaria in relation to the early social environment, ontogeny and the presence of chemical cues from a predatory fish to address three main questions: (i) Does previous social interaction influence aggregation behaviour in later developmental stages? (ii) To what extent does aggregation behaviour depend upon the risk level perceived by the individual? (iii) Does aggregation behaviour change through ontogeny?
2. Tadpoles were reared from eggs either in small groups or in complete isolation. In relatively early stages of development, tadpoles showed no preference for the side of the test container containing siblings over the side containing no larvae regardless of the social context experienced (isolation or contact with siblings).
3. The presence of chemical cues from a potential predator did not trigger the aggregation behaviour of tadpoles, but it had a remarkable effect on their activity and spatial distribution. Tadpoles exposed to water preconditioned by a predator spent significantly less time swimming and avoided the central area of the test container more frequently than did controls exposed to unconditioned water.
4. Tadpoles were more active, avoided the central section and associated preferentially with conspecifics (siblings) at later stages of development regardless of the social conditioning they had previously experienced.
5. Individuals reared in groups were twice as active as individuals reared in isolation. This suggests that the early social environment experienced by larvae can influence future behaviour and thereby growth and development rates.
6. The expression of conspecific attraction is probably linked to an ontogenetic shift in larval behaviour. However, reduced activity, rather than aggregation, appears to be the basic antipredator mechanism in larval Common Frog.