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Inbreeding
Terms modified by Inbreeding Selected AbstractsTHREE-GENE IDENTITY COEFFICIENTS DEMONSTRATE THAT CLONAL REPRODUCTION PROMOTES INBREEDING AND SPATIAL RELATEDNESS IN YELLOW-CEDAR, CALLITROPSIS NOOTKATENSISEVOLUTION, Issue 10 2008Stacey Lee Thompson Asexual reproduction has the potential to promote population structuring through matings between clones as well as through limited dispersal of related progeny. Here we present an application of three-gene identity coefficients that tests whether clonal reproduction promotes inbreeding and spatial relatedness within populations. With this method, the first two genes are sampled to estimate pairwise relatedness or inbreeding, whereas the third gene is sampled from either a clone or a sexually derived individual. If three-gene coefficients are significantly greater for clones than nonclones, then clonality contributes excessively to genetic structure. First, we describe an estimator of three-gene identity and briefly evaluate its properties. We then use this estimator to test the effect of clonality on the genetic structure within populations of yellow-cedar (Callitropsis nootkatensis) using a molecular marker survey. Five microsatellite loci were genotyped for 485 trees sampled from nine populations. Our three-gene analyses show that clonal ramets promote inbreeding and spatial structure in most populations. Among-population correlations between clonal extent and genetic structure generally support these trends, yet with less statistical significance. Clones appear to contribute to genetic structure through the limited dispersal of offspring from replicated ramets of the same clonal genet, whereas this structure is likely maintained by mating among these relatives. [source] THE CHANGE IN QUANTITATIVE GENETIC VARIATION WITH INBREEDINGEVOLUTION, Issue 12 2006Josh Van Buskirk Abstract Inbreeding is known to reduce heterozygosity of neutral genetic markers, but its impact on quantitative genetic variation is debated. Theory predicts a linear decline in additive genetic variance (VA) with increasing inbreeding coefficient (F) when loci underlying the trait act additively, but a nonlinear hump-shaped relationship when dominance and epistasis are important. Predictions for heritability (h2) are similar, although the exact shape depends on the value of h2 in the absence of inbreeding. We located 22 published studies in which the level of genetic variation in [source] Stress Resistance and Environmental Dependency of Inbreeding Depression in Drosophila melanogasterCONSERVATION BIOLOGY, Issue 4 2000Jesper Dahlgaard Two important issues are whether stress and inbreeding effects are independent as opposed to synergistic, and whether inbreeding effects are general across stresses as opposed to stress-specific. We found that inbreeding reduced resistance to acetone and desiccation in adult Drosophila melanogaster, whereas resistance to knockdown heat stress was not affected. Inbred flies, however, experienced a greater proportional decrease in productivity than outbreds following heat stress. Correlations using line means indicated that all resistance traits were uncorrelated in the inbred as well as in the outbred flies. Recessive, deleterious alleles therefore did not appear to have any general deleterious effects on stress resistance. Inbreeding within a specific environment and selection for resistant genotypes may therefore purge a population of deleterious genes specific to only one environmental stress. Resumen: Tanto la endogamia como el estrés ambiental pueden tener efectos adversos sobre la adaptabilidad afectando la conservación de especies en peligro de extinción. Dos temas importantes son determinar si los efectos del estrés y la endogamia son independientes en lugar de ser sinérgicos, y determinar si los efectos de la endogamia son generales para distintos tipos de estrés o si son específicos para un tipo determinado de estrés. Encontramos que la endogamia reduce la resistencia a la acetona y la desecación en adultos de Drosophila melanogaster, mientras que la resistencia al efecto demoledor del estrés por calor no fue afectada. Sin embargo, las moscas endogámicas experimentaron una disminución proporcionalmente mayor en la productividad que aquellas moscas sin endogamia después de experimentar un estrés por calor. Las correlaciones obtenidas usando líneas medias indicaron que las características de resistencia no estuvieron correlacionadas ni en moscas con endogamia, ni en moscas sin ella. Aparentemente los alelos nocivos recesivos no tuvieron ningún efecto nocivo general en la resistencia al estrés. La endogamia dentro de un ambiente específico y la selección por genotipos resistentes podrían, por lo tanto, eliminar una población de genes nocivos específicos a un solo estrés ambiental. [source] Premating Avoidance of Inbreeding Absent in Female Guppies (Poecilia reticulata)ETHOLOGY, Issue 7 2006Åslaug Viken The recognition and avoidance of kin during mating can be an important means of reducing the potential for inbreeding depression in offspring. We report here that premating mechanisms to avoid inbreeding, either innate or learnt through juvenile experience, are at best weak in female guppies (Poecilia reticulata). Guppies are small, ovoviviparous, neo-tropical freshwater fish, with a polygamous mating system where males actively court females and females are selective of their mates. In a series of mate-choice experiments, naïve, virgin females of the Quare River population in Trinidad were given a choice between a brother and a non-sib male from the same population. Initially, females were only provided olfactory cues upon which to base their choice and then subsequently both olfactory and visual cues. Despite the females displaying mate choice, we found no evidence of them discriminating between the male types in either experiment. There was thus no indication of inbreeding avoidance, suggesting that experiences after maturation or with mature males (e.g. rare male preference), dispersal and/or post-mating mechanisms may be evolutionarily more important avoidance mechanisms. [source] THE CHANGE IN QUANTITATIVE GENETIC VARIATION WITH INBREEDINGEVOLUTION, Issue 12 2006Josh Van Buskirk Abstract Inbreeding is known to reduce heterozygosity of neutral genetic markers, but its impact on quantitative genetic variation is debated. Theory predicts a linear decline in additive genetic variance (VA) with increasing inbreeding coefficient (F) when loci underlying the trait act additively, but a nonlinear hump-shaped relationship when dominance and epistasis are important. Predictions for heritability (h2) are similar, although the exact shape depends on the value of h2 in the absence of inbreeding. We located 22 published studies in which the level of genetic variation in [source] INBREEDING IN THE SEYCHELLES WARBLER: ENVIRONMENT-DEPENDENT MATERNAL EFFECTSEVOLUTION, Issue 9 2004David S. Richardson Abstract The deleterious effects of inbreeding can be substantial in wild populations and mechanisms to avoid such matings have evolved in many organisms. In situations where social mate choice is restricted, extrapair paternity may be a strategy used by females to avoid inbreeding and increase offspring heterozygosity. In the cooperatively breeding Seychelles warbler, Acrocephalus sechellensis, neither social nor extrapair mate choice was used to avoid inbreeding facultatively, and close inbreeding occurred in approximately 5% of matings. However, a higher frequency of extra-group paternity may be selected for in female subordinates because this did reduce the frequency of mating between close relatives. Inbreeding resulted in reduced individual heterozygosity, which, against expectation, had an almost significant (P= 0.052), positive effect on survival. Conversely, low heterozygosity in the genetic mother was linked to reduced offspring survival, and the magnitude of this intergenerational inbreeding depression effect was environment-dependent. Because we controlled for genetic effects and most environmental effects (through the experimental cross-fostering of nestlings), we conclude that the reduced survival was a result of maternal effects. Our results show that inbreeding can have complicated effects even within a genetic bottlenecked population where the "purging" of recessive alleles is expected to reduce the effects of inbreeding depression. [source] Breaking taboos in the tropics: incest promotes colonization by wood-boring beetlesGLOBAL ECOLOGY, Issue 4 2001Bjarte H. Jordal Abstract 1,Inbreeding and parthenogenesis are especially frequent in colonizing species of plants and animals, and inbreeding in wood-boring species in the weevil families Scolytinae and Platypodidae is especially common on small islands. In order to study the relationship between colonization success, island attributes and mating system in these beetles, we analysed the relative proportions of inbreeders and outbreeders for 45 Pacific and Old World tropical islands plus two adjacent mainland sites, and scored islands for size, distance from nearest source population, and maximum altitude. 2,The numbers of wood-borer species decreased with decreasing island size, as expected; the degree of isolation and maximum island altitude had negligible effects on total species numbers. 3,Numbers of outbreeding species decreased more rapidly with island size than did those of inbreeders. Comparing species with similar ecology (e.g. ambrosia beetles) showed that this difference was best explained by differential success in colonization, rather than by differences in resource utilization or sampling biases. This conclusion was further supported by analyses of data from small islands, which suggested that outbreeding species have a higher degree of endemism and that inbreeding species are generally more widespread. 4,Recently established small populations necessarily go through a period of severe inbreeding, which should affect inbreeding species much less than outbreeding ones. In addition, non-genetic ecological and behavioural (,Allee') effects are also expected to reduce the success of outbreeding colonists much more than that of inbreeders: compared with inbreeders, outbreeders are expected to have slower growth rates, have greater difficulties with mate-location and be vulnerable to random extinction over a longer period. [source] Inbreeding and inbreeding depression in a threatened endemic plant, the African violet (Saintpaulia ionantha ssp. grotei), of the East Usambara Mountains, TanzaniaAFRICAN JOURNAL OF ECOLOGY, Issue 3 2010Johanna Kolehmainen Abstract Mating among closely-related individuals in small and isolated plant populations may result in reduced vigour of the inbred offspring, i.e. inbreeding depression, especially in naturally outbreeding plants. Occurrence of inbreeding and inbreeding depression was studied in Saintpaulia ionantha ssp. grotei, a threatened endemic plant species with a narrow ecological amplitude from the East Usambara Mountains. The level of inbreeding (measured as the fixation index, F) was investigated in twelve populations by analyzing variation at one microsatellite marker locus. The effect of one generation of selfing and outcrossing on the progeny fitness was studied by controlled crosses in two small patches that differ in the level isolation. The fixation index (F) across the populations was on the average 0.21 and varied among the populations from substantial inbreeding (F = 0.58) to surplus heterozygosity (F = ,0.29). High inbreeding depression (,) was observed at early and late stages of the life-cycle. The isolated patch exhibited lower inbreeding depression than did the non-isolated patch. The results of this study suggest that inbreeding and subsequent inbreeding depression are potential threats to the survival of Saintpaulia populations. Résumé L'accouplement d'individus étroitement liés, dans des petites populations végétales isolées, peut aboutir à une vigueur moindre de la progéniture de même souche, c'est-à-dire une dépression due à l'endogamie, spécialement chez des plantes qui sont naturellement exogames. L'occurrence de l'endogamie et de la dépression qui y est liée a étéétudiée chez le Saintpaulia ionantha spp. grotei, une plante endémique menacée qui n'a qu'une faible amplitude écologique dans l'est des Usambara Mountains. On a recherché le taux d'endogamie (mesuré par l'indice de fixation F) dans 12 populations en analysant la variation d'un locus microsatellite marqueur. L'effet d'une génération d'auto- et d'allofécondation sur l'aptitude (fitness) de la progéniture a étéétudié par des croisements contrôlés dans deux petites parcelles dont le degré d'isolement différait. L'indice de fixation F dans les populations était en moyenne de 0,21 et il variait d'une autofécondation substantielle (F = 0,58) à une hétérozygosité en surplus (F = ,0,29). Une forte dépression due à l'endogamie (,) a été observée aux stades précoce et tardif du cycle vital. La parcelle isolée a présenté une dépression liée à l'endogamie moins forte que celle de la parcelle non isolée. Les résultats de cette étude suggèrent que l'auto-fécondation et la dépression qui en résulte sont des menaces potentielles pour la survie des populations de Saintpaulia. [source] Inbreeding, outbreeding and environmental effects on genetic diversity in 46 walleye (Sander vitreus) populationsMOLECULAR ECOLOGY, Issue 2 2006CHRISTOPHER J. CENA Abstract Genetic diversity is recognized as an important population attribute for both conservation and evolutionary purposes; however, the functional relationships between the environment, genetic diversity, and fitness-related traits are poorly understood. We examined relationships between selected lake parameters and population genetic diversity measures in 46 walleye (Sander vitreus) populations across the province of Ontario, Canada, and then tested for relationships between six life history traits (in three categories: growth, reproductive investment, and mortality) that are closely related to fitness, and genetic diversity measures (heterozygosity, d2, and Wright's inbreeding coefficient). Positive relationships were observed between lake surface area, growing degree days, number of species, and hatchery supplementation versus genetic diversity. Walleye early growth rate was the only life history trait significantly correlated with population heterozygosity in both males and females. The relationship between FIS and male early growth rate was negative and significant (P < 0.01) and marginally nonsignificant for females (P = 0.06), consistent with inbreeding depression effects. Only one significant relationship was observed for d2: female early growth rate (P < 0.05). Stepwise regression models showed that surface area and heterozygosity had a significant effect on female early growth rate, while hatchery supplementation, surface area and heterozygosity had a significant effect on male early growth rate. The strong relationship between lake parameters, such as surface area, and hatchery supplementation, versus genetic diversity suggests inbreeding and outbreeding in some of the populations; however, the weak relationships between genetic diversity and life history traits indicate that inbreeding and outbreeding depression are not yet seriously impacting Ontario walleye populations. [source] Inbreeding and PKU allele frequency: Estimating by microsatellite approachesAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2010Luciana L. Santos Estimates of allele frequencies for recessive diseases are generally based on the frequency of affected individuals (q2). However, these estimates can be strongly biased due to inbreeding in the population. Objectives: The purpose of this study was to gain a better understanding of how inbreeding in the Minas Gerais State population affects phenylketonuria (PKU) incidence in the state and to determine the inbreeding coefficient based on microsatellites. Methods: Inbreeding coefficients of samples of 104 controls and 76 patients with PKU were estimated through a microsatellite approach. Besides, the amount and distribution of genetic variation within and among patients with PKU and control samples were characterized. Results: No genetic differentiation was observed between the samples. However, the Fis value found for samples of patients with PKU (0.042) was almost 15 times higher than that found among controls (0.003). When corrected by the inbreeding coefficient found among the controls, the PKU allele frequency decreased to 0.0057. Conclusions: The results enables us to infer that at least 35% of the PKU recessive homozygotes from the Minas Gerais population could be due to consanguineous marriages and suggest that microsatellites can be an useful approach to estimate inbreeding coefficients. Am. J. Hum. Biol. 22:716,719, 2010. © 2010 Wiley-Liss, Inc. [source] Inbreeding and demographic transition in the Orozco Valley (Basque Country, Spain)AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 6 2002J.A. Peña Inbreeding in the Orozco Valley (Basque Country, Spain) between the 18th and 20th centuries was investigated on the basis of ecclesiastical dispensations and surname lists. The variations over time are very similar to those observed elsewhere in Europe, with a major increase in the coefficient of inbreeding in the late 19th and early 20th centuries. This is due mainly to an increase in marriages between first cousins. A highly marked decrease in inbreeding is observed during the 20th century. The secular trends described by the coefficient calculated on the basis of dispensations and by that calculated on isonymy are very similar. The nonrandom component of isonymy reveals a selective search for a related spouse during the period of maximum inbreeding. These results are associated with the process of demographic transition which affected European populations as a whole in the 19th century, resulting in a greater availability of kin among potential mates and thus enabling inbreeding to increase to levels far higher than those observed for earlier centuries. Am. J. Hum. Biol. 14:713,720, 2002. © 2002 Wiley-Liss, Inc. [source] Inbreeding and density-dependent population growth in a small, isolated lion populationANIMAL CONSERVATION, Issue 4 2010M. Trinkel Abstract In South Africa, more than 30 small, enclosed game reserves have reintroduced lions over the last two decades, which now house more than 500 individuals. There is a high risk of inbreeding in these fragmented, fenced and isolated populations, which may be compounded by a lack of management guidelines. A population of 11 founder lions Panthera leo was reintroduced to Madikwe Game Reserve in 1995, and this population has in turn become a source for reestablishing other populations. Only four lineages were reintroduced, founder males were related to founder females, and since 1997, only one male lineage maintained tenure for >9 years, resulting in breeding with direct relatives. Interventionist management to limit lion population growth and inbreeding in Madikwe has taken the form of translocating, trophy hunting and culling of mainly sub adult lions. Despite this management, inbreeding started 5 years after reintroduction. Reproductive performance and thus population growth in Madikwe were dependent on the overall lion population density. When lion density was low, females first gave birth at a significantly younger age and produced larger litters, resulting in a high population growth rate, which decreased significantly when lion density in the park reached carrying capacity, that is, 61 lions. This might have profound consequences for future reestablishment of lion populations when restocking new reserves: our study illustrates the need for founder populations of reintroduced endangered predator species to be as large and genetically diverse as possible, and thereafter new genetic material should be supplemented. The development of such management guidelines is becoming very important as large predator populations become increasingly fragmented and managed as metapopulations. [source] Inbreeding and population dynamics: implications for conservation strategiesANIMAL CONSERVATION, Issue 3 2007A. McGowan No abstract is available for this article. [source] Decreased immunocompetence in a severely bottlenecked population of an endemic New Zealand birdANIMAL CONSERVATION, Issue 1 2007K. A. Hale Abstract Inbreeding resulting from severe population bottlenecks may impair an individual's immune system and render it more susceptible to disease. Although a reduced immune response could threaten the survival of highly endangered species, few studies have assessed the effect of population bottlenecks on immunocompetence. We compared the counts of leucocytes and external, blood and gastrointestinal parasite loads in two populations of the endemic New Zealand robin Petroica australis to assess the immunocompetence of birds in a severely bottlenecked population relative to its more genetically diverse source population. Despite similar parasite loads in both populations, robins in the severely bottlenecked population showed lower counts of both total leucocyte and total lymphocyte numbers. When the immune system was experimentally challenged using the phytohaemagglutinin skin test, robins in the severely bottlenecked population exhibited a significantly lower immune response than the source population, suggesting that birds passing through a severe bottleneck have a compromised immunocompetence. Our results confirm that severe bottlenecks reduce the immune response of birds and highlight the need to avoid severe bottlenecks in the recovery programmes of endangered species. [source] Inbreeding depression and founder diversity among captive and free-living populations of the endangered pink pigeon Columba mayeriANIMAL CONSERVATION, Issue 4 2004Kirsty J. Swinnerton The endemic pink pigeon has recovered from less than 20 birds in the mid-1970s to 355 free-living individuals in 2003. A major concern for the species' recovery has been the potential genetic problem of inbreeding. Captive pink pigeons bred for reintroduction were managed to maximise founder representation and minimise inbreeding. In this paper, we quantify the effect of inbreeding on survival and reproductive parameters in captive and wild populations and quantify DNA sequence variation in the mitochondrial d-loop region for pink pigeon founders. Inbreeding affected egg fertility, squab, juvenile and adult survival, but effects were strongest in highly inbred birds (F,0.25). Inbreeding depression was more apparent in free-living birds where even moderate levels of inbreeding affected survival, although highly inbred birds were equally compromised in both captive and wild populations. Mitochondrial DNA haplotypic diversity in pink pigeon founders is low, suggesting that background inbreeding is contributing to low fertility and depressed productivity in this species, as well as comparable survival of some groups of non-inbred and nominally inbred birds. Management of wild populations has boosted population growth and may be required long-term to offset the negative effects of inbreeding depression and enhance the species' survival. [source] The evolution of social inbreeding mating systems in spiders: limited male mating dispersal and lack of pre-copulatory inbreeding avoidance in a subsocial predecessorBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009JASMIN RUCH Cooperation and group living are extremely rare in spiders and only few species are known to be permanently social. Inbreeding is a key characteristic of social spiders, resulting in high degrees of within-colony relatedness that may foster kin-selected benefits of cooperation. Accordingly, philopatry and regular inbreeding are suggested to play a major role in the repeated independent origins of sociality in spiders. We conducted field observations and laboratory experiments to investigate the mating system of the subsocial spider Stegodyphus tentoriicola. The species is suggested to resemble the ,missing link' in the transition from subsociality to permanent sociality in Stegodyphus spiders because its social period is prolonged in comparison to other subsocial species. Individuals in our two study populations were spatially clustered around maternal nests, indicating that clusters consist of family groups as found in the subsocial congener Stegodyphus lineatus. Male mating dispersal was limited and we found no obvious pre-copulatory inbreeding avoidance, suggesting a high likelihood of mating with close kin. Rates of polygamy were low, a pattern ensuring high relatedness within broods. In combination with ecological constraints, such as high costs of dispersal, our findings are consistent with the hypothesis that the extended social period in S. tentoriicola is accompanied with adaptations that facilitate the transition towards permanent sociality. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 851,859. [source] Genetic Effects of Multiple Generations of Supportive BreedingCONSERVATION BIOLOGY, Issue 6 2001Jinliang Wang This procedure is intended to increase population size without introducing exogenous genes into the managed population. Previous work examining the genetic effects of a single generation of supportive breeding has shown that although a successful program increases the census population size, it may reduce the genetically effective population size and thereby induce excessive inbreeding and loss of genetic variation. We expand and generalize previous analyses of supportive breeding and consider the effects of multiple generations of supportive breeding on rates of inbreeding and genetic drift. We derived recurrence equations for the inbreeding coefficient and coancestry, and thereby equations for inbreeding and variance effective sizes, under three models for selecting captive breeders: at random, preferentially among those born in captivity, and preferentially among those born in the wild. Numerical examples indicate that supportive breeding, when carried out successfully over multiple generations, may increase not only the census but also the effective size of the supported population as a whole. If supportive breeding does not result in a substantial and continuous increase of the census size of the breeding population, however, it might be genetically harmful because of elevated rates of inbreeding and genetic drift. Resumen: La práctica de apoyar poblaciones silvestres débiles mediante la captura de una fracción de los individuos silvestres, su cautiverio para la reproducción y la liberación a su descendencia en habitas naturales para que convivan con organismos silvestres se conoce como reproducción de apoyo y se ha empleado ampliamente en la biología de la conservación y en el manejo de pesca y vida silvestre. Este procedimiento tiene la intención de incrementar el tamaño de la población sin introducir genes exógenos en la población bajo manejo. Trabajos previos sobre los efectos genéticos de una sola generación de reproducción de apoyo muestran que, aunque un programa exitoso incrementa el tamaño poblacional, puede reducir la población genéticamente efectivae inducir así un exceso de consanguinidad y pérdida de variación genética. Expandimos y generalizamos análisis previos de la reproducción de apoyo y consideramos los efectos de múltiples generaciones de reproducción de soporte en las tasas de consanguinidad y de deriva génica. Derivamos ecuaciones de recurrencia para el coeficiente de consanguinidad y de coancestría, y por tanto ecuaciones de tamaños efectivos de consanguinidad y de varianza, para tres modelos de selección de reproductores en cautiverio : aleatoria, preferentemente entre los nacidos en cautiverio y preferentemente entre los nacidos en libertad. Los ejemplos numéricos indican que la reproducción de apoyo, cuando es exitosa en múltiples generaciones, puede ser favorable para el incremento no solo del tamaño, sino del tamaño efectivo de la población soportada en su conjunto. Sin embargo, si la reproducción de soporte no resulta en un incremento sustancial y continuo del tamaño de la población, puede ser genéticamente dañina debido a las altas tasas de consanguinidad y de deriva genética. [source] Population Size, Genetic Variation, and Reproductive Success in a Rapidly Declining, Self-Incompatible Perennial (Arnica montana) in The NetherlandsCONSERVATION BIOLOGY, Issue 6 2000Sheila H. Luijten In 26 populations in The Netherlands we investigated the relationship between population size and genetic variation using allozyme markers. Genetic variation was low in A. montana ( He = 0.088). There were positive correlations between population size and the proportion of polymorphic loci, the number of effective alleles, and expected heterozygosity, but not with observed heterozygosity. There was a significantly positive correlation between population size and the inbreeding coefficient. Generally, small populations showed heterozygote excess, which decreased with increasing population size. Possibly, the heterozygous individuals in small populations are survivors from the formerly larger populations with relatively high fitness. The F statistics showed a moderately high level of differentiation among populations ( FST = 0.140 ± 0.02), implying a low level of gene flow. For three out of four allozyme loci, we found significant inbreeding ( FIS = 0.104 ± 0.03). Only 14 of 26 populations were in Hardy-Weinberg equilibrium at all four polymorphic loci. In a subset of 14 populations of various size, we investigated natural seed production and offspring fitness. Population size was positively correlated with seed set, seedling size, number of flowering stems and flowerheads, adult survival, and total relative fitness, but not with the number of florets per flowerhead, germination rate, or the proportion of germination. Offspring performance in the greenhouse was not associated with genetic diversity measured on their mothers in the field. We conclude that the fitness of small populations is significantly reduced, but that there is as yet no evidence that this was caused by inbreeding. Possibly, the self-incompatibility system of A. montana has been effective in reducing selfing rates and inbreeding depression. Resumen:Arnica montana es una especie de planta rara, en declinación rápida y autoincompatible. En 26 poblaciones de los Países Bajos investigamos la relación entre el tamaño poblacional y la variación genética mediante el uso de alozimas marcadoras. La variación genética fue baja en A. montana ( He = 0.088). Existió una correlación positiva entre el tamaño poblacional y la proporción de emplazamientos polimórficos, el número de alelos efectivos y la heterocigocidad esperada, pero no con la heterocigocidad observada. Existió una correlación positiva significativa entre el tamaño poblacional y el coeficiente de endogamia. Generalmente, las poblaciones pequeñas mostraron una heterocigocidad excesiva con disminuciones en el tamaño poblacional. Posiblemente, los individuos heterocigóticos de poblaciones pequeñas son sobrevivientes de poblaciones anteriormente grandes con una adaptabilidad relativamente alta. Las pruebas de F mostraron un nivel de diferenciación moderadamente alto entre poblaciones ( FST = 0.140 ± 0.02) lo que implica un nivel bajo de flujo de genes. Para tres de cuatro de los emplazamientos de alozimas encontramos una endogamia significativa ( FIS = 0.104 ± 0.03). Solamente 14 de las 26 poblaciones estuvieron en equilibrio Hardy-Weinberg para los cuatro emplazamientos polimórficos. En un subconjunto de 14 poblaciones de varios tamaños, investigamos la producción natural de semillas y la adaptabilidad de la descendencia. El tamaño poblacional estuvo positivamente correlacionado con el juego de semillas, el tamaño del almácigo, el número de tallos en flor y de inflorescencias, la supervivencia de adultos y la adaptabilidad total relativa, pero no con el número de flores por inflorescencia, la tasa de germinación ni la proporción de la germinación. El rendimiento de la descendencia en invernaderos no estuvo asociado con la diversidad genética medida en sus madres en el campo. Concluimos que la adaptabilidad de poblaciones pequeñas está significativamente reducida, pero no existe aún evidencia de que esto sea ocasionado por endogamia. Es posible que el sistema de autoincompatibilidad de A. montana haya sido efectivo en la reducción de tasas de autofecundación y depresión de la endogamia. [source] Stress Resistance and Environmental Dependency of Inbreeding Depression in Drosophila melanogasterCONSERVATION BIOLOGY, Issue 4 2000Jesper Dahlgaard Two important issues are whether stress and inbreeding effects are independent as opposed to synergistic, and whether inbreeding effects are general across stresses as opposed to stress-specific. We found that inbreeding reduced resistance to acetone and desiccation in adult Drosophila melanogaster, whereas resistance to knockdown heat stress was not affected. Inbred flies, however, experienced a greater proportional decrease in productivity than outbreds following heat stress. Correlations using line means indicated that all resistance traits were uncorrelated in the inbred as well as in the outbred flies. Recessive, deleterious alleles therefore did not appear to have any general deleterious effects on stress resistance. Inbreeding within a specific environment and selection for resistant genotypes may therefore purge a population of deleterious genes specific to only one environmental stress. Resumen: Tanto la endogamia como el estrés ambiental pueden tener efectos adversos sobre la adaptabilidad afectando la conservación de especies en peligro de extinción. Dos temas importantes son determinar si los efectos del estrés y la endogamia son independientes en lugar de ser sinérgicos, y determinar si los efectos de la endogamia son generales para distintos tipos de estrés o si son específicos para un tipo determinado de estrés. Encontramos que la endogamia reduce la resistencia a la acetona y la desecación en adultos de Drosophila melanogaster, mientras que la resistencia al efecto demoledor del estrés por calor no fue afectada. Sin embargo, las moscas endogámicas experimentaron una disminución proporcionalmente mayor en la productividad que aquellas moscas sin endogamia después de experimentar un estrés por calor. Las correlaciones obtenidas usando líneas medias indicaron que las características de resistencia no estuvieron correlacionadas ni en moscas con endogamia, ni en moscas sin ella. Aparentemente los alelos nocivos recesivos no tuvieron ningún efecto nocivo general en la resistencia al estrés. La endogamia dentro de un ambiente específico y la selección por genotipos resistentes podrían, por lo tanto, eliminar una población de genes nocivos específicos a un solo estrés ambiental. [source] Animal models of diabetes mellitusDIABETIC MEDICINE, Issue 4 2005D. A. Rees Abstract Animal models have been used extensively in diabetes research. Early studies used pancreatectomised dogs to confirm the central role of the pancreas in glucose homeostasis, culminating in the discovery and purification of insulin. Today, animal experimentation is contentious and subject to legal and ethical restrictions that vary throughout the world. Most experiments are carried out on rodents, although some studies are still performed on larger animals. Several toxins, including streptozotocin and alloxan, induce hyperglycaemia in rats and mice. Selective inbreeding has produced several strains of animal that are considered reasonable models of Type 1 diabetes, Type 2 diabetes and related phenotypes such as obesity and insulin resistance. Apart from their use in studying the pathogenesis of the disease and its complications, all new treatments for diabetes, including islet cell transplantation and preventative strategies, are initially investigated in animals. In recent years, molecular biological techniques have produced a large number of new animal models for the study of diabetes, including knock-in, generalized knock-out and tissue-specific knockout mice. [source] Skewed sex ratios and multiple founding in galls of the oak apple gall wasp Biorhiza pallidaECOLOGICAL ENTOMOLOGY, Issue 1 2003Rachel J. Atkinson Abstract. 1. The gall wasp Biorhiza pallida (Hymenoptera: Cynipidae) reproduces by cyclical parthenogenesis. The adults of the sexual generation develop within galls (oak apples) that contain many larval cells. 2. Folliot [(1964) Annales Des Sciences Naturelles: Zoologie, 12, 407,564] found asexual generation females to be of three reproductive types. Androphores produce only sons, gynophores produce only daughters, and gynandrophores produce both sons and daughters. In nature, most oak apples give rise to either only males or only females but a proportion produces both sexes. These mixed-sex galls could result either from eggs laid by one or more gynandrophores or from eggs laid by androphores and gynophores developing within a single gall (multiple founding). 3.,Here the frequency of mixed- and single-sex galls was quantified, and morphological and genetic analyses were carried out on the adults emerging from 10 galls to determine the frequency of multiple founding in B. pallida. 4. Seventy-five per cent of 627 galls yielded only one sex. The majority of the remaining 25% had a highly skewed sex ratio. Low genetic variation in B. pallida limited the application of allozyme-based genetic techniques, however seven of the 10 galls analysed in detail, including mixed-sex galls, appeared to have been multiply founded. Contributions by the different foundresses in multiply founded galls were highly skewed. 5. The significance of multiple founding is discussed in the light of possible adaptive scenarios (reduction of parasitoid-induced mortality, avoidance of local stochastic extinction and inbreeding) and possible competition for oviposition sites. [source] Reproductive strategies in small populations: using Atlantic salmon as a case studyECOLOGY OF FRESHWATER FISH, Issue 4 2007F. Juanes Abstract,,, Wild salmonid populations with only a few breeding adults may not exhibit a significant reduction in genetic variability compared with larger populations. Such an observation suggests that effective population sizes are larger than population size estimates based on direct adult counts and/or the mating strategy maximises outbreeding, contributing to increased heterozygosity. In the case of wild Atlantic salmon Salmo salar populations, stratification by age classes and sexes on the spawning grounds avoids inbreeding and increases genetic variability. We studied the breeding composition of four Spanish salmon populations. Over a 7-year period we concluded that the probability of within-cohort mating is very low: females generally reproduce after two sea-winters whereas males reproduce mostly as one sea-winter (grilse) and/or mature parr. Considering different levels of contribution of mature parr to spawning derived from field surveys, we developed a simple model for estimating effective population sizes and found that they doubled with 65% parr contribution expected for rivers at this latitude (43°N), and ranged from 100,800 individuals. The effect of between-cohort mating was modelled considering different ranges of differences in allele frequencies between cohorts and resulted in 28,50% increases in heterozygosity when considering a 65% parr contribution. The complex mating strategy of Atlantic salmon contributes to explain the high levels of genetic variability found for small populations of this species. This model can probably be extended to other animal species with mating strategies involving different cohorts. [source] Cryptic Kin Selection: Kin Structure in Vertebrate Populations and Opportunities for Kin-Directed CooperationETHOLOGY, Issue 3 2010Ben J. Hatchwell Animal societies of varying complexity have been the favoured testing ground for inclusive fitness theory, and there is now abundant evidence that kin selection has played a critical role in the evolution of cooperative behaviour. One of the key theoretical and empirical findings underlying this conclusion is that cooperative systems have a degree of kin structure, often the product of delayed dispersal, that facilitates interactions with relatives. However, recent population genetic studies have revealed that many non-cooperative animals also have kin-structured populations, providing more cryptic opportunities for kin selection to operate. In this article, I first review the evidence that kin structure is widespread among non-cooperative vertebrates, and then consider the various contexts in which kin selection may occur in such taxa, including: leks, brood parasitism, crèches, breeding associations, territoriality and population dynamics, foraging and predator deterrence. I describe the evidence that kin-selected benefits arise from interacting with kin in each of these contexts, notwithstanding the potential costs of kin competition and inbreeding. I conclude that as the tools required to determine population genetic structure are readily available, measurement of kin structure and the potential for kin selection on a routine basis is likely to reveal that this process has been an important driver of evolutionary adaptation in many non-cooperative as well as cooperative species. [source] Premating Avoidance of Inbreeding Absent in Female Guppies (Poecilia reticulata)ETHOLOGY, Issue 7 2006Åslaug Viken The recognition and avoidance of kin during mating can be an important means of reducing the potential for inbreeding depression in offspring. We report here that premating mechanisms to avoid inbreeding, either innate or learnt through juvenile experience, are at best weak in female guppies (Poecilia reticulata). Guppies are small, ovoviviparous, neo-tropical freshwater fish, with a polygamous mating system where males actively court females and females are selective of their mates. In a series of mate-choice experiments, naïve, virgin females of the Quare River population in Trinidad were given a choice between a brother and a non-sib male from the same population. Initially, females were only provided olfactory cues upon which to base their choice and then subsequently both olfactory and visual cues. Despite the females displaying mate choice, we found no evidence of them discriminating between the male types in either experiment. There was thus no indication of inbreeding avoidance, suggesting that experiences after maturation or with mature males (e.g. rare male preference), dispersal and/or post-mating mechanisms may be evolutionarily more important avoidance mechanisms. [source] Kin Associations during Nest Founding in an Allodapine Bee Exoneura robusta: do Females Distinguish between Relatives and Familiar Nestmates?ETHOLOGY, Issue 2 2000Nicholas J. Bull True recognition of kin can have important fitness consequences in terms of directing altruistic behaviours toward close relatives (nepotism) and avoiding inbreeding. However, recent evidence suggests that some social insect species cannot or do not distinguish their closest relatives from among nestmates in important fitness-based contexts. Such findings are relevant to kin selection theories where individuals are expected to preferentially rear close relatives in order to gain inclusive fitness benefits. Here, allozyme markers are used to examine whether female Exoneura robusta individuals preferentially nest with their closest kin when given a choice of familiar previous nestmates. The results suggest these bees do not prefer kin over non-kin nestmates. Kin associations during nest founding in this species are probably due to philopatry and/or association with previously familiar nestmates. [source] EXPERIMENTAL EVIDENCE FOR FREQUENCY DEPENDENT SELF-FERTILIZATION IN THE GYNODIOECIOUS PLANT, SILENE VULGARISEVOLUTION, Issue 6 2009Keiko Miyake After over a half century of empirical and theoretical research regarding the evolution and maintenance of gynodioecy in plants, unexplored factors influencing the relative fitnesses of females and hermaphrodites remain. Theoretical studies suggest that hermaphrodite self-fertilization (selfing) rate influences the maintenance of gynodioecy and we hypothesized that population sex ratio may influence hermaphrodite selfing rate. An experimental test for frequency-dependent self-fertilization was conducted using replicated populations constructed with different sex ratios of the gynodioecious plant Silene vulgaris. We found that hermaphrodite selfing increased with decreased hermaphrodite frequency, whereas evidence for increased inbreeding depression was equivocal. We argue that incorporation of context dependent inbreeding into future models of the evolution of gynodioecy is likely to yield novel insights into sex ratio evolution. [source] EVOLUTION OF INCOMPATIBILITY-INDUCING MICROBES IN SUBDIVIDED HOST POPULATIONSEVOLUTION, Issue 2 2009Ralph Haygood Many insects, other arthropods, and nematodes harbor maternally inherited bacteria inducing "cytoplasmic incompatibility" (CI), reduced egg hatch when infected males mate with uninfected females. Although CI drives the spread of these microbes, selection on alternative, mutually compatible strains in panmictic host populations does not act directly on CI intensity but favors higher "effective fecundity," the number of infected progeny an infected female produces. We analyze the consequences of host population subdivision using deterministic and stochastic models. In subdivided populations, effective fecundity remains the primary target of selection. For strains of equal effective fecundity, if population density is regulated locally (i.e., "soft selection"), variation among patches in infection frequencies may induce change in the relative frequencies of the strains. However, whether this change favors stronger incompatibility depends on initial frequencies. Demographic fluctuations maintain frequency variation that tends to favor stronger incompatibility. However, this effect is weak; even with small patches, minute increases in effective fecundity can offset substantial decreases in CI intensity. These results are insensitive to many details of host life cycle and migration and to systematic outbreeding or inbreeding within patches. Selection acting through transfer between host species may be required to explain the prevalence of CI. [source] THREE-GENE IDENTITY COEFFICIENTS DEMONSTRATE THAT CLONAL REPRODUCTION PROMOTES INBREEDING AND SPATIAL RELATEDNESS IN YELLOW-CEDAR, CALLITROPSIS NOOTKATENSISEVOLUTION, Issue 10 2008Stacey Lee Thompson Asexual reproduction has the potential to promote population structuring through matings between clones as well as through limited dispersal of related progeny. Here we present an application of three-gene identity coefficients that tests whether clonal reproduction promotes inbreeding and spatial relatedness within populations. With this method, the first two genes are sampled to estimate pairwise relatedness or inbreeding, whereas the third gene is sampled from either a clone or a sexually derived individual. If three-gene coefficients are significantly greater for clones than nonclones, then clonality contributes excessively to genetic structure. First, we describe an estimator of three-gene identity and briefly evaluate its properties. We then use this estimator to test the effect of clonality on the genetic structure within populations of yellow-cedar (Callitropsis nootkatensis) using a molecular marker survey. Five microsatellite loci were genotyped for 485 trees sampled from nine populations. Our three-gene analyses show that clonal ramets promote inbreeding and spatial structure in most populations. Among-population correlations between clonal extent and genetic structure generally support these trends, yet with less statistical significance. Clones appear to contribute to genetic structure through the limited dispersal of offspring from replicated ramets of the same clonal genet, whereas this structure is likely maintained by mating among these relatives. [source] INBREEDING IN THE SEYCHELLES WARBLER: ENVIRONMENT-DEPENDENT MATERNAL EFFECTSEVOLUTION, Issue 9 2004David S. Richardson Abstract The deleterious effects of inbreeding can be substantial in wild populations and mechanisms to avoid such matings have evolved in many organisms. In situations where social mate choice is restricted, extrapair paternity may be a strategy used by females to avoid inbreeding and increase offspring heterozygosity. In the cooperatively breeding Seychelles warbler, Acrocephalus sechellensis, neither social nor extrapair mate choice was used to avoid inbreeding facultatively, and close inbreeding occurred in approximately 5% of matings. However, a higher frequency of extra-group paternity may be selected for in female subordinates because this did reduce the frequency of mating between close relatives. Inbreeding resulted in reduced individual heterozygosity, which, against expectation, had an almost significant (P= 0.052), positive effect on survival. Conversely, low heterozygosity in the genetic mother was linked to reduced offspring survival, and the magnitude of this intergenerational inbreeding depression effect was environment-dependent. Because we controlled for genetic effects and most environmental effects (through the experimental cross-fostering of nestlings), we conclude that the reduced survival was a result of maternal effects. Our results show that inbreeding can have complicated effects even within a genetic bottlenecked population where the "purging" of recessive alleles is expected to reduce the effects of inbreeding depression. [source] EPISTASIS AND THE TEMPORAL CHANGE IN THE ADDITIVE VARIANCE-COVARIANCE MATRIX INDUCED BY DRIFTEVOLUTION, Issue 8 2004Carlos López-Fanjul Abstract The effect of population bottlenecks on the components of the genetic covariance generated by two neutral independent epistatic loci has been studied theoretically (additive, covA; dominance, covD; additive-by-additive, covAA; additive-by-dominance, covAD; and dominance-by-dominance, covDD). The additive-by-additive model and a more general model covering all possible types of marginal gene action at the single-locus level (additive/dominance epistatic model) were considered. The covariance components in an infinitely large panmictic population (ancestral components) were compared with their expected values at equilibrium over replicates randomly derived from the base population, after t consecutive bottlenecks of equal size N (derived components). Formulae were obtained in terms of the allele frequencies and effects at each locus, the corresponding epistatic effects and the inbreeding coefficient Ft. These expressions show that the contribution of nonadditive loci to the derived additive covariance (covAt) does not linearly decrease with inbreeding, as in the pure additive case, and may initially increase or even change sign in specific situations. Numerical examples were also analyzed, restricted for simplicity to the case of all covariance components being positive. For additive-by-additive epistasis, the condition covAt > covA only holds for high frequencies of the allele decreasing the metric traits at each locus (negative allele) if epistasis is weak, or for intermediate allele frequencies if it is strong. For the additive/dominance epistatic model, however, covAt > covA applies for low frequencies of the negative alleles at one or both loci and mild epistasis, but this result can be progressively extended to intermediate frequencies as epistasis becomes stronger. Without epistasis the same qualitative results were found, indicating that marginal dominance induced by epistasis can be considered as the primary cause of an increase of the additive covariance after bottlenecks. For all models, the magnitude of the ratio covAt/covA was inversely related to N and t. [source] | ||||||||||||||||||||||||||||||||||||||||