Occurrence Of Selfing Research Articles

Population size as a major determinant of mating system and population genetic differentiation in a narrow endemic chasmophyte

BackgroundMating system is one of the major determinants of intra- and interspecific genetic structure, but may vary within and between plant populations. Our study model included all known populations of Moehringia tommasinii (Caryophyllaceae), a narrow endemic plant inhabiting rock crevices in the northwestern Adriatic, and some populations of co-occurring and widespread M. muscosa, an ecologically divergent relative with an overlapping flowering period. We performed reciprocal crosses within and between taxa and used molecular markers to assess the extent of gene flow within and between populations and taxa. Using coefficient of inbreeding, population size, seed weight, pollen-to-ovule ratio, and flower display size, we also looked for evidence of a selfing syndrome.ResultsA surprisingly high variation in mating systems was observed among populations of M. tommasinii. These populations exhibited genetic structuring, with their size positively correlated with both seed weight and pollen production. Although a selfing syndrome could not be confirmed as the majority of selfing resulted from allogamous treatments, the occurrence of selfing was notable. In the presence of M. muscosa, at a site where both species coexist closely, a distinct pattern of fruit production was observed in M. tommasinii following various pollination treatments. Molecular and morphometric data provided evidence of hybridization followed by local extinction at this site.ConclusionsPopulation size proved to be the most important factor affecting the mating system in genetically structured populations of M. tommasinii. Lighter seeds and lower pollen production observed in populations with pronounced selfing do not provide enough evidence for the selfing syndrome. Detected gene flow between M. tommasinii and the sympatric M. muscosa suggested weak reproductive barriers between the taxa, which could pose a conservation problems for the former species. Hybridization leading to local extinction may also resulted in floral polymorphism and disruption of mating patterns of M. tommasinii.

In vivo maternal haploid induction based on genome editing of DMP in Brassica oleracea.

In vivo maternal haploid induction based on genome editing of DMP in Brassica oleracea.

Opening the black box: microspatial patterns of zoospore dispersal, parentage, and selfing in the kelp Ecklonia cava as revealed by microsatellite markers

We examined the early life stage process of the kelp Ecklonia cava from zoospore settlement to juvenile sporophyte in the field. The microspatial genetic structure of an E. cava population in a 4 m × 4 m area was analyzed using microsatellite markers to evaluate the spatial distribution of individuals. Within this area, 169 adults and 87 juveniles were analyzed, and the distributional pattern was aggregated for juveniles, uniform for adults, and random for all individuals. The kinship coefficient decreased with increasing distance and reached zero at approximately 2 m. Using a parentage analysis, the parents of 8 and 46 juveniles in the study area were identified at the 95% and 80% confidence levels, respectively. Among the juveniles, selfing was confirmed in 3 and 7 individuals at the 95% and 80% confidence levels, respectively. Although the selfing juveniles that survived appeared to grow normally, the frequent occurrence of selfing may drive the distributional change between juveniles and adults. Most of the parents had two or fewer juvenile offspring within 2.5 m in the study area. Although the stipe length of the parents did not affect the dispersal distance of the zoospores, each parent appeared to release zoospores in a specific direction. In E. cava, the local population may be maintained by the short dispersal distance of most spores and the occurrence of selfing, and the rare zoospore settlement in distant areas may allow low levels of gene flow among local populations.

Epidemiology of Self - Burning in Iranian Townships Covered by Shiraz University of Medical Sciences

Background:: Self - burning is known as an extremely violent means of suicide. Objectives:: This study aimed to investigate the epidemiology of self - burning in Iranian townships covered by Shiraz University of Medical Sciences during years 2009 to 2012. Patients and Methods: This cross - sectional research was performed on 250 self - burning cases and 181 self - burning attempts. Data was collected from the Comprehensive Suicide Prevention Program Checklist. To analyze the data, the chi - square test and logistic regression model were utilized. Results: Most self - burning cases were observed in females (70.4%), married individuals (60.4%), an age group of 15 to 24 years (38%), and rural residents (60.8%). Moreover, the highest and lowest self - burning cases had occurred during spring (31.2%) and fall (17.6%) (P = 0.736). Conclusions: The findings are indicative of a high occurrence of self - burning among young married females. Therefore, it is vital to provide this at risk group with the necessary prevention programs.

Exploring college English language learners’ self and social regulation of learning during wiki-supported collaborative reading activities

Students’ regulation has been conceptualized as an important impetus for effective and efficient collaborative learning. However, little empirical evidence has been reported about language learners’ regulatory behaviors in computer-supported collaborative learning (CSCL). The purpose of this study is to investigate the occurrence of self and social aspects of regulation during wiki-supported collaborative reading activities in the context of learning English as a foreign language (EFL). Sixty Chinese college students organized in twelve groups participated in this study over a sixteen-week semester. Using an integrated method of content analysis and sequential analysis, students’ chat logs were coded and analyzed to explore the characteristics of students’ self and social regulatory behaviors in terms of regulation type, regulation process, and regulation focus. Results indicate that all groups demonstrated active social regulation in the collaborative activities. Compared with low-performing groups, high-performing groups displayed distinctively different patterns of regulatory behaviors in “social regulation,” “evaluating,” “content monitoring,” and “social emotional regulation.” Moreover, the analysis further reveals a more continuous and smooth regulation in the high-performing groups, while low-performing groups tended to be lost in a single repeated regulatory behavior pattern such as “self-regulation” or “organizing”. This study not only fills a gap in the current collaborative English learning literature, but also contributes to our knowledge of social regulation in CSCL. Pedagogical implications and future research are also addressed.

Changes in primary school students’ use of self and social forms of regulation of learning across collaborative inquiry activities

This study investigated how the occurrence of self and social forms of regulation of learning processes changes over time across the sequence of collaborative inquiry tasks. Two groups of three primary school students (7th grade) were videotaped while working in collaborative inquiry activities in a regular science classroom during a 7-week period, and participated in stimulated-recall and semi-structured interviews. The results show evidence that the groups engaged increasingly in more socially shared regulation along the sequence of collaborative inquiry tasks, whereas no meaningful change was observed in the occurrence of co-regulation processes over time. Moreover, different patterns of temporal change were identified for each group and for each individual group member, and appeared to be associated with the individual and group level characteristics.

Pollination biology of the hexaploid self-compatible species Turnera velutina (Passifloraceae).

The evolution of monomorphisms from heterostylous ancestors has been related to the presence of homostyly and the loss of self-incompatibility, allowing the occurrence of selfing, which could be advantageous under pollinator limitation. However, flowers of some monomorphic species show herkogamy, attraction and rewarding traits that presumably favour cross-pollination and/or a mixed mating system. This study evaluated the contributions of pollinators, breeding system and floral traits to the reproduction of Turnera velutina, a herkogamous monomorphic species. Floral visitors and frequency of visits were recorded, controlled hand cross-pollinations were conducted under greenhouse and natural conditions, and individual variation in floral traits was characterised to determine their contribution to seed production. Apis mellifera was the most frequent floral visitor. Flowers presented approach herkogamy, high variation in nectar features, and a positive correlation of floral length with nectar volume and sugar concentration. Seed production did not differ between manual self- and cross-pollinations, controls or open cross-pollinations, but autonomous self-pollination produced, on average, 82.74% fewer seeds than the other forms, irrespective of the level of herkogamy. Differences in seed production among autonomous self-pollination and other treatments showed that T.velutina flowers depend on insect pollination for reproduction, and that approach herkogamy drastically reduced seed production in the absence of pollen vectors. The lack of differences in seed production from manual cross- and self-pollinations suggests the possible presence of a mixed mating system in the studied population. Overall, this species was possibly derived from a distylous ancestor but appears fully capable of outcrossing despite being monomorphic.

Genetic consequences of fragmentation in “arbor vitae,” eastern white cedar (Thuja occidentalisL.), toward the northern limit of its distribution range

We tested the hypothesis that marginal fragmented populations of eastern white cedar (EWC) are genetically isolated due to reduced pollen and gene flow. In accordance with the central-marginal model, we predicted a decrease in population genetic diversity and an increase in differentiation along the latitudinal gradient from the boreal mixed-wood to northern coniferous forest. A total of 24 eastern white cedar populations were sampled along the north-south latitudinal gradient for microsatellite genotyping analysis. Positive Fis values and heterozygote deficiency were observed in populations from the marginal (Fis = 0.244; PHW = 0.0042) and discontinuous zones (Fis = 0.166; PHW = 0.0042). However, populations from the continuous zone were in HW equilibrium (Fis = −0.007; PHW = 0.3625). There were no significant latitudinal effects on gene diversity (Hs), allelic richness (AR), or population differentiation (Fst). Bayesian and NJT (neighbor-joining tree) analyses demonstrated the presence of a population structure that was partly consistent with the geographic origins of the populations. The impact of population fragmentation on the genetic structure of EWC is to create a positive inbreeding coefficient, which was two to three times higher on average than that of a population from the continuous zone. This result indicated a higher occurrence of selfing within fragmented EWC populations coupled with a higher degree of gene exchange among near-neighbor relatives, thereby leading to significant inbreeding. Increased population isolation was apparently not correlated with a detectable effect on genetic diversity. Overall, the fragmented populations of EWC appear well-buffered against effects of inbreeding on genetic erosion.

Self and social regulation of learning during collaborative activities in the classroom: The interplay of individual and group cognition

The purpose of the present research was to advance the development of knowledge regarding social aspects of self-regulated learning (SRL). The study had the objective of exploring the occurrence of self and social aspects of regulation during collaborative activities within regular primary science classes. Through a multiple case study approach, 8 children organised in two work groups were videotaped working in collaborative activities during one academic semester. The findings show a general increase of SRL activity within the groups during the semester, and positive relationships between focus of the activity and type of social regulation. The study sheds light on the advantages of combining analytical and holistic analysis when researching collaborative activities in the classroom. Implications for practice and future research are discussed.

Ecologia da polinização da amoreira-preta (Rubus sp) (Rosaceae) em Timbó-SC, Brasil

O presente trabalho verificou experimentalmente a ecologia da polinização da amoreira-preta (Rubus sp.). Objetivou-se confirmar a síndrome de polinização de Rubus sp., por meio de análise de seu sistema reprodutivo, quantificação da produção diária de néctar, levantamento da entomofauna que visita as flores da amoreira na área de estudo e análise do seu comportamento polinizador. Os experimentos foram realizados em uma área de cultivo de amoreira-preta, no mês de dezembro de 2005, município de Timbó (SC). Constatou-se que a maior taxa de frutificação (48,3 % ± 3,2) ocorreu via polinização livre, onde os insetos não foram excluídos. Foi verificada a ocorrência de autopolinização, porém com taxa inferior de frutificação (12,2% ± 4,9). A anemofilia não foi constatada na espécie. A avaliação da produção de néctar em Rubus sp. resultou em valores compatíveis com a síndrome de melitofilia. Os visitantes florais coletados e observados sobre as flores de Rubus sp. foram predominantemente abelhas da ordem Hymenoptera (97%), que iniciam, em menor número, a atividade de forrageamento às 8h, com pico de atividade às 12h e declinando até às 16h. As coletas resultaram numa amostragem de 1.360 abelhas, divididas em quatro famílias e 13 espécies. A família com maior riqueza de espécies (N = 7) foi Halictidae e a mais abundante foi Apidae, com 1.288 indivíduos. Em Apidae, houve o predomínio da espécie exótica Apis mellifera, cuja representação na amostra foi de 1.246 indivíduos. Os dados da abundância e as observações naturalísticas do seu comportamento da flor apontaram A. mellifera como o principal polinizador de Rubus sp., mas confirmam que as demais espécies de abelhas também participam na polinização de Rubus sp.

Polyploidy influences sexual system and mating patterns in the moss Atrichum undulatum sensu lato

Evolutionary transitions between separate and combined sexes have frequently occurred across various plant lineages. In mosses, which are haploid-dominant, evolutionary transitions from separate to combined sexes are often associated with genome doubling. Polyploidy and hermaphroditism have strong effects on the inbreeding depression of a population, and are subsequently predicted to affect the mating system. We tested the association between ploidy (haploid, diploid or triploid gametophytes) and mating system in 21 populations of Atrichum undulatum sensu lato, where sex ratios vary widely. For each population, we measured the sex ratio, estimated selfing rates using allozyme markers and determined the level of ploidy through flow cytometry. Hermaphrodites in A. undulatum were either diploid or triploid. However, many diploid populations were strictly separate-sexed, suggesting that hermaphroditism is not a necessary result of genome doubling. Levels of selfing were strongly supported as being greater than zero in one population with strictly separate-sexed individuals, and one-third of populations with hermaphrodites. Although hermaphrodites are associated with triploidy, hermaphroditism is not a necessary outcome of genome duplication. Hermaphroditism, but not genome duplication alone, increased estimated selfing rates, probably due to the occurrence of selfing within a gametophyte. Thus, genome duplication can influence the mating system and the associated evolution and maintenance of reproductive traits.

Fine-scale analysis of genetic structure in the brooding coral Seriatopora hystrix from the Red Sea

The dispersal of gametes and larvae plays a key role in the population dynamics of sessile marine invertebrates. Species with internal fertilisation are often associated with very localised larval dispersal, which may cause small-scale patterns of neutral genetic variation. This study on the brooding coral Seriatopora hystrix from the Red Sea focused on the smallest possible scale: Two S. hystrix stands (~100 colonies each) near Dahab were completely sampled, mapped and analysed at five microsatellite markers. The sexual mode of reproduction, the likely occurrence of selfing and the level of immigration were in agreement with previous studies on this species. Contrary to previous findings, both stands were in Hardy–Weinberg proportions. Also, no evidence for spatially restricted larval dispersal within the sampled areas was found. Differences between this and previous studies on S. hystrix could reflect variation in life history or varying environmental conditions, which opens intriguing questions for future research.

Self-fertilization as an alternative mode of reproduction in the solitary tunicate Pyura chilensis

The hermaphroditic broadcasting tunicate Pyura chilensis Molina, 1782 is a sessile filter-feeder organism that occurs in intertidal and subtidal habitats along the Chilean and Peruvian coast. In natural populations, P. chilensis form dense aggregations, small patches or occur as isolated individuals. This suggests that self-fertilization could be a potential insurance against adverse conditions for cross-fertilization. In this study, P. chilensis were reared in the laboratory as isolated and paired individuals, to assess occurrence and success of fertilization, settlement and metamorphosis. Occurrence of self-fertilization was also compared between specimens forced to cross-fertilize and specimens maintained in reproductive isolation for different periods. We also manipulated cross- and self-fertilization using strip-spawned gametes. Our study shows that P. chilensis is a hermaphroditic species with adolescent gonochorism; that is, individuals first developed male function and then later male and female functions simultaneously as specimens increased in size (protandrous hermaphroditism). The results also show more frequent fertilization in paired specimens and in manipulated fertilization involving cross sperm. Moreover, no perceptible differences in fertilization, settlement, and metamorphosis success among self and outcross progeny were found. Prolonged periods of reproductive isolation resulted in more frequent self-fertilization. Occurrence of selfing and highly successful settlement and metamorphosis of progeny originating from reproductively-isolated specimens suggest that even though outcrossing predominates, selfing is an advantageous alternative when sources of allosperm are scarce.

Occurrence of self reported hand eczema in Swedish bakers.

OBJECTIVES: To estimate the risk of bakers developing hand eczema. The importance of atopy was studied as well as change of job due to hand eczema. METHODS: A retrospective cohort...

MECHANISMS OF ALLO-RECOGNITION

There is evidence of two pathways of allorecognition, the direct pathway where T cells recognize intact allo-MHC molecules on the surface of target cells, and the indirect pathway where T cells recognize processed allo-MHC presented by self antigen-presenting cells. We used synthetic class II MHC allopeptides to study the cellular mechanisms of the indirect allorecognition pathway and its potential role in vascularized allograft rejection. LEW (RT1l) rat T cells--which are primed by immunization with a mixture of four 25 mer class II MHC allopeptides, representing the full length sequence of the beta chain of the hypervariable domain of the RT1.Du (WF), or by primary WF (RT1u) vascularized cardiac allografts--were capable of recognizing and proliferating to specific polymorphic class II MHC sequences when presented as peptides by responder APCs. T cells from naive LEW animals, WF animals immunized with syngeneic RT1.Du beta peptides, or LEW recipients of third-party BN (RT1n) vascularized cardiac allografts did not proliferate to the RT1.Du beta peptides, indicating the specificity of allopeptide recognition. In the strain combination used, immunogenicity of class II MHC allopeptides is determined by factors other than polymorphisms alone, since epitopic differences in 2 of the 4 RT1.Du beta allopeptides were not immunogenic. Responder T cells were CD4+, and were inhibited by monomorphic anticlass II monoclonal antibodies, and by specific anticlass II alloantibodies. These observations confirm the occurrence of self MHC-restricted recognition of processed allo-MHC in primary vascularized allograft rejection, and provide the rationale to develop novel and specific immunotherapies in organ transplantation.

The Evolution of the Selfing Rate in Functionally Hermaphrodite Plants and Animals

Selfing, the fusion of male and female gametes from a single genetic individual or colony, is possible in many plants and also in hermaphrodite animals. We review the occurrence of selfing and mechanisms for its avoidance, in functionally hermaphrodite animal and plants. We discuss means by which selfing can be detected and briefly review techniques for estimation of selfing frequencies in natural populations. Although many functionally hcmaphrodite species are probably almost complete outcrossers or inbreeders, mixed mating systems are also found in both plant and animal populations. We review theories for the advantages and disadvantages of selfing, and for the maintenance of mixed mating systems, together

Self-directed behaviour and hippocampal electrical activity in rabbits living in a semi-natural environment

Rabbits living in a semi-natural environment show a variety of behavioural elements related to voluntary or automatic movements. The aim of the present experiment was to study the hippocampal electrical correlates of self-directed activities occurring during spontaneous behaviour and emotional responses (the presence of a second rabbit of the same sex: intruder). Behaviour was divided into two broad categories. One included autocleaning elements such as scratching, shaking, washing and self-grooming. The other was characterized by consummatory activities: eating and drinking. Hippocampal activity was recorded by telemetry and the EEG periods related to specific behavioural elements were selected and analyzed. The electrical parameters were different for the various behavioural elements, for example rhythmic and irregular EEG patterns were recorded in different percentages during autocleaning and consummatory activities. Differences were also observed in the frequency peak distributions of power spectra. Confrontations influenced the occurrence of self directed behavioural elements and modified the pattern and frequency of hippocampal EEG during autocleaning activities. Results show that environmental variations can affect automatic behaviours and influence the mechanisms of hippocampal function.

TEMPORAL PATTERNS IN THE APPEARANCE OF MATING TYPE INSTABILITY IN <i>PARAMECIUM CAUDATUM</i>

By daily isolation line culture and tube transfer culture, we observed the time of initial occurrence of selfing conjugation in the clones of mating type VI of Paramecium caudatum, syngen 3. In most clones, selfing began to occur from 80 to 120 fissions after conjugation. No great difference in the time of occurrence of selfing was observed between progenies of different crosses.

CYTOGENETICS OF <i>SCILLA SCILLOIDES</i> COMPLEX

1. Several types of hypo- and hyper-ploids were found along with euploids BB, BBB, ABB, AABB, and ABBB among plants from a natural population of Scilla scilloides Druce at Nakabaru. Here A (x=8) indicates one of two genomes which compose the S. scilloides complex, and B (x=9) another one. Lacking or additional chromosomes in hypo- and hyper-ploids, ABB-1, -2, ABB+1, +2, +3, +5, AABB-1, -2, -3, were confirmed to be members of the genome A.2. The majority of progenies from seeds collected from ABB open-pollinated in the natural population was hypo- and hyper-ploid. Hypo- and hyper-ploids were also found in the progenies from the seeds from the mother plants BB and AABB. These facts indicate frequent occurrence of selfing of, and/or crossing between ABB, as well as crossing of ABB with BB and/or AABB. Therefore, ABB is primarily responsible for the origin of hypo- and hyper-ploids in the natural population.

Analyses of the Change of Mating Type During Vegetative Reproduction in <i>Paramecium caudatum</i>

1. Some peculiar unstable caryonides, all individuals of which change their mating type during vegetative reproduction, were isolated from crosses of types XXIV and XXIII and from selfings of type XXIV in syngen 12 of Paramecium caudatum.2. The change of mating type was reversible and affected by fission rate. The low fission rate favors the change to and the maintenance of type XXIII whereas the high fission rate favors the expression of type XXIV.3. In ordinary selfing caryonides, the occurrence of selfing is due to the change of mating type during vegetative reproduction, which is also affected by fission rate. But in this case the change occurs only in a part of members of a caryonide.4. The difference in the ratios of the changing individuals was clonal, though some slight differences were also observed in sister caryonides.5. As to the patterns of inactivation of mating type substance by formalin, the unstable caryonide mentioned above was intermediate between types XXIV and XXIII.6. In the light of these results, some considerations on the differentiation of mating types were presented.