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At least 919 records · Page 51Linked to original sources
PubMed2001

Self-incompatibility in the genus Arabidopsis: characterization of the S locus in the outcrossing A. lyrata and its autogamous relative A. thaliana.

As a starting point for a phylogenetic study of self-incompatibility (SI) in crucifers and to elucidate the genetic basis of transitions between outcrossing and self-fertilizing mating systems in this family, we investigated the SI system of Arabidopsis lyrata. A. lyrata is an outcrossing close relative of the self-fertile A. thaliana and is thought to have diverged from A. thaliana approximately 5 million years ago and from Brassica spp 15 to 20 million years ago. Analysis of two S (sterility) locus haplotypes demonstrates that the A. lyrata S locus contains tightly linked orthologs of the S locus receptor kinase (SRK) gene and the S locus cysteine-rich protein (SCR) gene, which are the determinants of SI specificity in stigma and pollen, respectively, but lacks an S locus glycoprotein gene. As described previously in Brassica, the S haplotypes of A. lyrata differ by the rearranged order of their genes and by their variable physical sizes. Comparative mapping of the A. lyrata and Brassica S loci indicates that the S locus of crucifers is a dynamic locus that has undergone several duplication events since the Arabidopsis--Brassica split and was translocated as a unit between two distant chromosomal locations during diversification of the two taxa. Furthermore, comparative analysis of the S locus region of A. lyrata and its homeolog in self-fertile A. thaliana identified orthologs of the SRK and SCR genes and demonstrated that self-compatibility in this species is associated with inactivation of SI specificity genes.

Amino Acid Sequence↗
PubMed2001

Implications of mating patterns for conservation of the endangered plant Eriogonum ovalifolium var. vineum (Polygonaceae).

Mating patterns have direct application to conservation because of their influence on structuring genetic diversity within and among populations and on maintaining that diversity over time. We measured population and family outcrossing rates, biparental inbreeding, correlation of outcrossed paternity, and inbreeding coefficients in six populations from throughout the ecological range of the endangered plant Eriogonum ovalifolium var. vineum using naturally pollinated families. The taxon was primarily outcrossed: population outcrossing rates averaged 0.80 (SE 0.03) and family outcrossing rates averaged 0.88 (SE 0.03); neither rate varied among populations. Five population rates were significantly different from 1 while family rates differed from 1 in only one population. We found high correlated outcrossed paternity and evidence for biparental inbreeding in five populations each. As expected from the predominantly outcrossed mating system, levels of diversity were high and inbreeding coefficients among maternal individuals were low (averaging -0.05, SE 0.12). Differences between inbreeding coefficients of progeny (average 0.21, SE 0.06) and mothers indicated selection against homozygous offspring. These results indicate that it is important to maintain large populations to prevent increases in inbreeding and to maintain pollinator communities to facilitate outcrossing.

Journal Article↗
PubMed1975

Dominance and reproduction in Baboons (Papio cynocephalus).

This monograph reports on a 14 month study of yellow baboons (Papio cynocephalus) in the Masai-Amboseli Game Reserve, Kenya. The study was an attempt to determine the relationship between agonistic dominance and reproductive success in male baboons and centered around testing a priority-of-access model of mating behavior. Explicit criteria for determining dominance in baboons are presented and the consistency of dominance relationships through time is analyzed for all classes of individuals. Related data on reproductive cycle length, perineal and behavioral indications of the optimal day for mating, changes in female behavior during estrus, and effects of the presence of estrous females on group organization are also included. This work constitutes the first comprehensive field study of baboon mating systems and social organization and emphasizes the use of systematic behavior sampling techniques in the field and quantitative models in the study of primate social behavior.

Aggression↗
PubMedDate not supplied

[Frequency-dependent sexual selection in a natural population of oak leaf-roller moth (Tortrix viridana L.)].

A mating system on the esterase locus Est-4 was studied in a natural population of oak leaf-roller moth Tortrix viridana L. Frequency-dependent sexual selection was revealed, which manifested itself in a "rare-type advantage". On the basis of obtained data, a new hypothesis for explanation of the "rare-type advantage" phenomenon is proposed. The hypothesis proceeds from the genetically determined choice of sexual partner, depending on the degree of phenotypic likeness.

Alleles↗
PubMed2002

[Genetic composition of the Chilean population. Analysis of mitochondrial DNA polymorphism].

BACKGROUND: The analysis of mitochondrial DNA restriction site polymorphisms assigns most Latin American aborgines to four haplogroups. These are characterized by determined polymorphic restriction sites and a deletion of 9 base pairs in the intergenic region V. AIM: To study the distribution of mitochondrial DNA haplogroups in Chilean aboriginal groups, as well as in the mixed population of Santiago. MATERIAL AND METHODS: One hundred twenty Aymara subjects and 23 Atacameño subjects from the Northern part of Chile and 162 randomly chosen subjects residing in Santiago were studied. DNA was extracted from peripheral lymphocytes. Mitochondrial DNA was amplified by means of polymerase chain reaction. RESULTS: The frequency of haplogroup B decreases from north to south. Aymaras in the north have the highest frequency (64%) and it is absent among the Yamanas (previously studied) in the extreme South. Haplogroups C and D show an inverse tendency. It is noteworthy that 84% of mitochondrial haplogroups of the mixed population of Santiago are of Amerindian origin whereas the Y-chromosomes are mainly European. CONCLUSIONS: The peculiar distribution of haplotypes indicate that the population of Santiago is the result of an asymmetric mating system in which the females ancestors were mainly Amerindian and the male ancestors mainly European.

Chile↗
PubMed2001

Generating data in models including direct and maternal dominance effects.

Algorithms are presented to simulate multiple generations of animal data by a model including direct additive genetic, maternal additive genetic, direct dominance, maternal dominance and permanent environmental effects. Dominance effects were computed as parental subclasses. Testing involved five single trait models that included direct contemporary group and direct additive effects, and different combinations of maternal, permanent environmental, and dominance effects. Simulated populations included 5 generations of animals and 20 contemporary groups per generation. The base population contained 200 sires and 600 dams. Variance components were estimated by Average-Information Restricted Maximum Likelihood (AIREML). No significant bias was observed. The simulation algorithms can be used in research involving dominance models, such as evaluation of mating systems exploiting special combining abilities of prospective parents.

Journal Article↗
PubMed2003

Evolutionary implications of a high selfing rate in the freshwater snail Lymnaea truncatula.

Self-compatible hermaphroditic organisms that mix self-fertilization and outcrossing are of great interest for investigating the evolution of mating systems. We investigate the evolution of selfing in Lymnaea truncatula, a self-compatible hermaphroditic freshwater snail. We first analyze the consequences of selfing in terms of genetic variability within and among populations and then investigate how these consequences along with the species ecology (harshness of the habitat and parasitism) might govern the evolution of selfing. Snails from 13 localities (classified as temporary or permanent depending on their water availability) were sampled in western Switzerland and genotyped for seven microsatellite loci. F(IS) (estimated on adults) and progeny array analyses (on hatchlings) provided similar selfing rate estimates of 80%. Populations presented a low polymorphism and were highly differentiated (F(ST) = 0.58). Although the reproductive assurance hypothesis would predict higher selfing rate in temporary populations, no difference in selfing level was observed between temporary and permanent populations. However, allelic richness and gene diversity declined in temporary habitats, presumably reflecting drift. Infection levels varied but were not simply related to either estimated population selfing rate or to differences in heterozygosity. These findings and the similar selfing rates estimated for hatchlings and adults suggest that within-population inbreeding depression is low in L. truncatula.

Alleles↗
PubMed2002

Female remating, sperm competition and sexual selection in Drosophila.

Female remating is fundamental to evolutionary biology as it determines the pattern of sexual selection and sexual conflict. Remating in females is an important component of Drosophila mating systems because it affects sperm usage patterns and sexual selection. Remating is common in females of many species of Drosophila in both natural and laboratory populations. It has been reported in many insect species and also in vertebrates. Female remating is a prerequisite for sperm competition between males, and the consequences of this competition, such as sperm precedence or sperm displacement, have been reported for many species of Drosophila. Female remating is dependent on the amount of sperm stored, the male seminal fluid components, nutrition, the quantity of eggs laid, experimental design and density of flies in laboratory. Remating by a female is an insurance against male sterility and sub-fertility and increases genetic heterogeneity of female offspring. Remating gives greater female productivity in many species of Drosophila. We examined female remating with respect to sperm competition and sexual selection in Drosophila and addressed the possible benefits for females. We also reviewed the role of accessory gland fluid in remating, costs associated with remating, the genetic basis of female remating and some possible mechanisms of sperm competition in the light of last male sperm priority and paternity assurance in Drosophila and other insects. We also suggest future areas of research.

Animals↗
PubMed2003

[Demography and nesting ecology of green iguana, Iguana iguana (Squamata: Iguanidae), in 2 exploited populations in Depresión Momposina, Colombia].

We studied the demography and nesting ecology of two populations of Iguana iguana that face heavy exploitation and habitat modification in the Momposina Depression, Colombia. Lineal transect data was analyzed using the Fourier model to provide estimates of social group densities, which was found to differ both within and among populations (1.05-6.0 groups/ha). Mean group size and overall iguana density estimates varied between populations as well (1.5-13.7 iguanas/ha). The density estimates were far lower than those reported from more protected areas in Panama and Venezuela. Iguana densities were consistently higher in sites located along rivers (2.5 iguanas/group) than in sites along the margin of marshes, probably due to vegetational differences (1.5 iguanas/group). There was no correlation between density estimates and estimates of relative abundance (number of iguanas seen/hour/person) due to differing detectabilities of iguana groups among sites. The adult sex ratio (1:2.5 males:females) agreed well with other reports in the literature based upon observation of adult social groups, and probably results from the polygynous mating system in this species rather than a real demographic skew. Nesting in this population occurs from the end of January through March and hatching occurs between April and May. We monitored 34 nests, which suffered little vertebrate predation, perhaps due to the lack of a complete vertebrate fauna in this densely inhabited area, but nests suffered from inundation, cattle trampling, and infestation by phorid fly larvae. Clutch sizes in these populations were lower than all other published reports except for the iguana population on the highly xeric island of Curaçao, implying that adult females in our area are unusually small. We argue that this is more likely the result of the exploitation of these populations rather than an adaptive response to environmentally extreme conditions.

Animals↗
PubMed2003

[Review on genetic diversity in Pinus].

The ways of probing genetic diversity of pines involve many aspects, such as morphology, chromosome, isozyme, DNA, etc. The phenotypic characteristics in pines vary widely and the differences of inheritability(h2) are obvious among characteristics and among species. Up to now,isozyme is still the most common means to measure genetic diversity of pines. Generally,there are high allozyme diversity within populations and low differentiation coefficient among populations, but differences exist between species in Pinus. The variations of chromosome among pines are very low and the karyotypes of pines are consentaneous,but the genomes of pines in cell nucleus are much larger than that of broadleaves. Diversity of pines are abundant at nucleus DNA level but are poor at plastid DNA level, such as ctDNA. There are many factors that will affect genetic diversity of pines, in which mating system and environment are two main factors. Finally,we reviewed the research on origin of Pinus and conservation strategy of genetic diversity,etc.

English Abstract↗
PubMed2005

Diallel analysis of superior fiber quality properties in selected upland cottons.

Twenty cross combinations were produced using a complete diallel-mating system with five varieties or lines that differed in fiber properties in Upland cotton to determine the inheritance and breeding merits of superior fiber properties. Evaluations of parents and F1 ' s were conducted in two years. The results showed that fiber length uniformity was greatly affected by environmental factors, whereas the other fiber properties were mainly controlled by genetic factors. There were no significant interaction effect of environment with genotype for fiber strength or length, but there were significant environment interactions with additive and maternal affects for Micronaire, and with the dominance effects for elongation. There were no maternal effect, and additive effects predominated for the all fiber properties. Additive heritability was high for fiber strength and length, 77.6% and 73.2% respectively; for Micronaire, it was 45.2%, while the dominance effect was 11.5%, which was the highest among fiber properties. Micronaire had significant heterosis over mid-parent based on population mean (3.2%), while the other fiber properties showed no heterosis. Therefore, the performance of fiber properties in F1 ' s can be predicted from the average value of both parents. Since the additive heritability of strength, length, and fineness of fiber were high, these traits can be selected in early generations in breeding for high quality fiber properties.

Breeding↗
PubMed2005

Self-fertilization and the escape from pollen limitation in variable pollination environments.

Seed production in many plants is pollen limited, likely because of unpredictable variation in the pollinator environment. One way for plants to escape the consequences of pollinator variability is to evolve mating systems, such as autonomous selfing, that assure reproduction without relying on pollinators. We explore this hypothesis through the construction and analysis of heuristic models of plant population dynamics in seed- or site-limited populations. Our analysis suggests several important points: the familiar rule that inbreeding depression greater than 0.5 maintains outcrossing significantly underestimates the threshold required under pollen limited conditions with prior selfing; variability in the pollination environment erodes the ability of inbreeding depression to maintain outcrossing; and variable pollination environments can result in stable intermediate rates of prior selfing. The results reflect the importance of geometric mean fitness (which in a variable environment is less than the arithmetic mean) in the face of temporal variation.

Genetics, Population↗
PubMed2005

The effect of self-fertilization, inbreeding depression, and population size on autopolyploid establishment.

The minority cytotype exclusion principle describes how random mating between diploid and autotetraploid cytotypes hinders establishment of the rare cytotype. We present deterministic and stochastic models to ascertain how selfing, inbreeding depression, unreduced gamete production, and finite population size affect minority cytotype exclusion and the establishment of autotetraploids. Results demonstrate that higher selfing rates and lower inbreeding depression in autotetraploids facilitate establishment of autotetraploid populations. Stochastic effects due to finite population size increase the probability of polyploid establishment and decrease the mean time to tetraploid fixation. Our results extend the minority cytotype exclusion principle to include important features of plant reproduction and demonstrate that variation in mating system parameters significantly influences the conditions necessary for polyploid establishment.

Computer Simulation↗
PubMed2005

Does large body size in males evolve to facilitate forcible insemination? A study on garter snakes.

A trend for larger males to obtain a disproportionately high number of matings, as occurs in many animal populations, typically is attributed either to female choice or success in male-male rivalry; an alternative mechanism, that larger males are better able to coercively inseminate females, has received much less attention. For example, previous studies on garter snakes (Thamnophis sirtalis parietalis) at communal dens in Manitoba have shown that the mating benefit to larger body size in males is due to size-dependent advantages in male-male rivalry. However, this previous work ignored the possibility that larger males may obtain more matings because of male-female interactions. In staged trials within outdoor arenas, larger body size enhanced male mating success regardless of whether a rival male was present. The mechanism involved was coercion rather than female choice, because mating occurred most often (and soonest) in females that were least able to resist courtship-induced hypoxic stress. Males do physically displace rivals from optimal positions in the mating ball, and larger males are better able to resist such displacement. Nonetheless, larger body size enhances male mating success even in the absence of such male-male interactions. Thus, even in mating systems where males compete physically and where larger body size confers a significant advantage in male-male competition, the actual selective force for larger body size in males may relate to forcible insemination of unreceptive females. Experimental studies are needed to determine whether the same situation occurs in other organisms in which body-size advantages have been attributed to male-male rather than male-female interactions.

Aggression↗
PubMed2006

Impact of insect pollinator group and floral display size on outcrossing rate.

Despite the strong influence of pollination ecology on the evolution of selfing, we have little information on how distinct groups of insect pollinators influence outcrossing rate. However, differences in behavior between pollinator groups could easily influence how each group affects outcrossing rate. We examined the influence of distinct insect pollinator groups on outcrossing rate in the rocky mountain columbine, Aquilegia coerulea. The impact of population size, plant density, size of floral display, and herkogamy (spatial separation between anthers and stigmas) on outcrossing rate was also considered as these variables were previously found to affect outcrossing rate in some plant species. We quantified correlations between all independent variables and used simple and two-factor regressions to determine direct and indirect impact of each independent variable on outcrossing rate. Outcrossing rate increased significantly with hawkmoth abundance but not with the abundance of any of the other groups of floral visitors, which included bumblebees, solitary bees, syrphid flies, and muscidae. Outcrossing rate was also significantly affected by floral display size and together, hawkmoth abundance and floral display size explained 87% of the variation in outcrossing rate. None of the other independent variables directly affected the outcrossing rate. This is the first report of a significant impact of pollinator type on outcrossing rate. Hawkmoths did not visit fewer flowers per plant relative to other pollinator groups but preferred visiting female-phase flowers first on a plant. Both the behavior of pollinators and floral display size affected outcrossing rate via their impact on the level of geitonogamous (among flower) selfing. Given that geitonogamous selfing is never advantageous, the variation in outcrossing rate and maintenance of mixed mating systems in populations of A. coerulea may not require an adaptive explanation.

Animals↗
PubMed2006

Cyto-nuclear epistasis: two-locus random genetic drift in hermaphroditic and dioecious species.

We report the findings of our theoretical investigation of the effect of random genetic drift on the covariance of identity-by-descent (ibd) of nuclear and cytoplasmic genes. The covariance in ibd measures of the degree to which cyto-nuclear gene combinations are heritable, that is, transmitted together from parents to offspring. We show how the mating system affects the covariance of ibd, a potentially important aspect of host-pathogen or host-symbiont coevolution. The magnitude of this covariance influences the degree to which the evolution of apparently neutral cytoplasmic genes, often used in molecular phylogenetics, might be influenced by selection acting on unlinked nuclear genes. To the extent that cyto-nuclear gene combinations are inherited together, genomic conflict is mitigated and intergenomic transfer it facilitated, because genes in both organelle and nuclear genomes share the same evolutionary fate. The covariance of ibd also affects the rate at which cyto-nuclear epistatic variance is converted to additive variance necessary for a response to selection. We find that conversion is biased in species with separate sexes, so that the increment of additive variance added to the nuclear genome exceeds that added to the cytoplasmic genome. As a result, the host might have an adaptive advantage in a coevolutionary arms race with vertically (maternally) transmitted pathogens. Similarly, the nuclear genome could be a source of compensatory mutations for its organellar genomes, as occurs in cytoplasmic male sterility in some plant species. We also discuss the possibility that adaptive cytoplasmic elements, such as favorable mitochondrial mutations or endosymbionts (e.g., Wolbachia), have the potential to release heritable nuclear variation as they sweep through a host population, supporting the view that cytoplasmic introgression plays an important role in adaptation and speciation.

Alleles↗
PubMed2005

Sexual selection and the evolution of visually conspicuous sexually dimorphic traits in male monkeys, apes, and human beings.

Striking secondary sexual traits, such as brightly colored "sexual skin," capes of hair, beards, and other facial adornments occur in adult males of many anthropoid primate species. This review focuses upon the role of sexual selection in the evolution of these traits. A quantitative approach is used to measure sexually dimorphic characters and to compare their development in the monogamous, polygynous, and multimale-multifemale mating systems of monkeys, apes, and human beings.

Animals↗
PubMed2006

Ovule discounting in an outcrossing, cryptically dioecious tree.

Ovule discounting denotes the reduction in the number of ovules available for cross-fertilization due to the interference of inferior pollen. Traditionally, ovule discounting has been discussed solely from the perspective of compromised outcrossing opportunities as a result of selfing, but the principle is more general. Here, we extend its applicability beyond the simple contrast between selfing and outcrossing by showing that, in the cryptically dioecious tree species Fraxinus ornus, ovule discounting through frequent outcrossing with inferior fathers also constitutes a substantial cost of mating. In F. ornus, hermaphrodites produce pollen capable of siring offspring, but these offspring are less viable than those sired by males and are inferred to produce few, if any, surviving progeny. In this paper, we used microsatellite markers to analyze the mating system and paternity in a wild population of F. ornus. We found that the effective number of sires per mother was low (N(ep) = 2.93 to 4.95), and that paternity was correlated among progeny sampled from the same mother, but not among progeny sampled from neighboring mothers. Despite the existence of a local spatial genetic structure (up to 30 m), we found no evidence of biparental inbreeding. There was negligible selfing by hermaphrodites, but they sired approximately one fourth of the seeds produced by other hermaphrodites. Given that these progeny are not inferred to reach reproductive maturity, this constitutes a substantial cost of ovule discounting in the broad sense. We discuss the possible reasons for why hermaphrodites invest resources into inferior pollen.

Flowers↗