Autotransplantation after primary bone repair of a recipient site with a large periradicular lesion: a case report.

AIM: To describe a case of autotransplantation nine weeks after the extraction of a hopeless tooth with a large periradicular lesion, which enabled the healing of the recipient site. SUMMARY: A 19-year-old male in generally good health was referred for evaluation of tooth 46. Clinically, there were class III mobility and sensitivity to percussion and palpation. There was a mesio-lingual swelling and a single narrow deep pocket of 15 mm at the disto-lingual aspect. CBCT imaging revealed a radiolucent area over 15 mm in diameter that extended from the mesial aspect of the mesial root of tooth 47 to the distal aspect of tooth 45. The radiolucent area was in proximity to the inferior alveolar canal and penetrated the buccal and the lingual cortical plates. The tooth was diagnosed with previously treated tooth, acute apical abscess and vertical root fracture. Tooth 46 was extracted, and a delicate curettage and drainage were performed. Nine weeks afterwards, a second surgery was performed: extraction of the impacted immature third molar (tooth 48). Immediately after the extraction, the tooth was replanted in the healing socket of tooth 46, and sufficient initial stability achieved. At a 1-year follow-up, the tooth had normal mobility, no sensitivity to palpation and percussion, and responded to thermal pulp testing. The soft tissue was normal, probing depths up to 3-mm, without swelling or sinus tract. Radiographically, periapical healing at the recipient site was observed. Compared to the post-operative periapical radiography immediately after the procedure, there was no change in the distal root dimensions. In the mesial root, development of the root length and a closed apex was demonstrated.

[Necrotizing ulcerative diseases in military population].

Necrotizing ulcerative diseases were prevalent in military personnel throughout history. Nowadays, its prevalence declined substantially in industrialized countries. Studies among immunocompromised patients suggest it is still a reason for concern among this population. We present two cases diagnosed and treated at our department. It seems that necrotizing ulcerative diseases are still a relevant entity in the Israeli Defense forces therefore it is of great importance to conduct proper diagnosis, treatment and follow up of the patients.

Quantitative genetics of feeding behavior in two ecological races of the pea aphid, Acyrthosiphon pisum.

Much of the diversity of herbivorous insects stems from the adaptive divergence of populations onto different host plants. This often involves the evolution of specialized patterns of host acceptance that in turn lead to assortative mating for insects that mate exclusively on their hosts. Here, we explore the genetic architecture of feeding behavior in a herbivorous insect that has become a model for the study of incipient speciation, the pea aphid (Acyrthosiphon pisum). We use crosses between individuals specialized to either alfalfa or red clover in order to perform both a biometrical analysis and a quantitative trait locus (QTL) analysis of key feeding behaviors. For each character in each environment, Castle-Wright's estimator for the number of effective factors segregating ranged from 0.11 to 2.54. Similarly, between 0 and 3 QTLs were detected. In one case, a single QTL explained over 50% of the variance in the F2, suggesting that at least one gene (or a complex of tightly linked genes) has a major effect on feeding behavior in the pea aphid. However, the identified QTL explain only 23-73% of the genetic variance for these characters thus additional genes of minor effect are also involved. We found a variety of modes of gene action, including several cases of non-additive gene action. Our results suggest that feeding behavior in pea aphids is neither simple nor highly polygenic. The oligogenetic basis of variation in feeding behavior may facilitate host shifts, providing one explanation for the frequent divergence and speciation of herbivorous insects.

Genetic linkage of ecological specialization and reproductive isolation in pea aphids.

The evolution of ecological specialization generates biological diversity and may lead to speciation. Genetic architecture can either speed or retard this process. If resource use and mate choice have a common genetic basis through pleiotropy or close linkage, the resulting genetic correlations can promote the joint evolution of specialization and reproductive isolation, facilitating speciation. Here we present a model of the role of genetic correlations in specialization and speciation, and test it by analysing the genetic architecture of key traits in two highly specialized host races of the pea aphid (Acyrthosiphon pisum pisum; Hemiptera : Aphididae). We found several complexes of pleiotropic or closely linked quantitative trait loci (QTL) that affect key traits in ways that would promote speciation: QTL with antagonistic effects on performance on the two hosts are linked to QTL that produce asortative mating (through habitat choice). This type of genetic architecture may be common in taxa that have speciated under divergent natural selection.

Sympatric speciation in animals: the ugly duckling grows up.

Sympatric speciation has become increasingly accepted in the past decade, as a result of new models substantiating its plausibility and new evidence that the conditions specified by the models are met in many natural populations. Retrospective phylogenetic and population genetic signatures of sympatric speciation have also been derived, and these are beginning to be tested. This new work has helped increase the acceptance of sympatric speciation as a plausible process, although it remains difficult to show conclusively that specific pairs of taxa have speciated through sympatric processes alone. It might be time for a re-evaluation of the geographical classification of speciation modes in favor of one based primarily on evolutionary mechanisms

Are we alone? Lessons from the evolution of life on earth.

The understanding of life on Earth that we have obtained from the science of evolutionary biology offers clues to the qustion of what life might be like if found elsewhere. After presenting the basics of the evolutionary process, I discuss the factors that determine the outcome of evolution, the role of key innovations and extinction in evolution, and whether the evolution of human life is inevitable.

Reproductive isolation between divergent races of pea aphids on two hosts. II. Selection against migrants and hybrids in the parental environments.

Sympatric races of pea aphids on alfalfa and red clover are highly ecologically specialized and significantly reproductively isolated. Much of the restriction of gene flow between the specialized populations is due to habitat choice behavior of the winged colonizers (Via 1999). Here, we document additional pre- and postmating reproductive isolation through selection against migrants and hybrids in the parental environments. First, a group of randomly chosen genotypes from each race that were experimentally migrated between hosts had very low survival and reproduction on the alternate host relative to genotypes originating from that host (natives). Such selection against cross-host migrants forms a premating barrier to gene flow because it is likely to reduce migrant frequencies before the sexual forms are induced in the fall. Our reciprocal transplant experiment also shows that natural selection acts directly on individual migrants between the crops to favor host choice behavior: genotypes from each host suffered large losses of fitness when forced to migrate to the alternate host plant relative to the fitness they would have enjoyed had they been able to choose their native host. In a companion field study, sequential sampling throughout the summer in newly colonized fields of both alfalfa and clover revealed a decrease in the frequency of host-specific marker alleles characteristic of the alternate crop. These field data further support the hypothesis that selection disfavors migrants that cross between crops. Second, when two sets of F1 hybrids between the races were reciprocally tested on alfalfa and clover, both sets had significantly lower average fitness than the specialized parent in each of the two environments. This demographic selection against hybrids in the parental environments is a source of postmating reproductive isolation between the specialized races. Finally, significant genetic variation in fitness traits was seen among F1 hybrid genotypes from both crosses between alfalfa and clover specialists. Although this variation suggests that a generalized pea aphid could evolve, such generalists are not seen in field collections of these populations.

Natural selection and genetic differentiation of behaviour between parasitoids from wild and cultivated habitats

Differences in behaviour between individuals in populations living in different environments may result from evolution proceeding differently in each population. The parasitoid wasp Cotesia glomerata (L.) (Hymenoptera: Braconidae) parasitizes early instar larvae of butterflies in the family Pieridae. In the study area the only host of C. glomerata is the Small Cabbage White Butterfly [Pieris rapae (L.) (Lepidoptera: Pieridae)], which feeds on cruciferous host plants in a variety of habitats. The behaviour of this parasitoid wasp collected from two habitat types (wild and agricultural) was observed in a reciprocal transplant-style experiment in a greenhouse. Differences in behaviour between wasp sources and test habitat type were analysed using canonical analysis in multivariate analysis of variance. Directional selection on parasitoid behaviour in each test habitat type was estimated by regressing the relative rate of parasitism (a measure of relative fitness) on the behavioural character state. We found that there is genetic differentiation of behaviour between wasps from wild and cultivated habitats and that a different set of behaviours is associated with short-term fitness within models of each source habitat. There was no evidence of local adaptation of wasps to either habitat.

Cannibalism facilitates the use of a novel environment in the flour beetle, Tribolium castaneum.

Cannibalism is well known to affect both the population dynamics and the competitive relationships of organisms. Cannibalistic behaviour commonly increases in stressful conditions, such as when density is high or food is scarce, and cannibals often obtain a nutritional benefit. Might cannibalism also increase in a novel environment to which a population is poorly adapted physiologically? Moreover, might cannibalistic behaviour provide enough of a nutritional advantage in a nutritionally stressful environment to rescue individuals from its adverse effects and thus permit colonization and range expansion? Previous work has shown that oat flour is a particularly stressful environment for Tribolium castaneum. In the study reported here, egg cannibalism by two strains of T. castaneum was significantly enhanced in oat flour, and egg eating rescued larvae from the adverse demographic effects of this poor environment. Development time of the cannibals was accelerated almost to the level seen for individuals reared in the nutritionally superior environment (wheat plus brewer's yeast). Their survival and fecundity also increased relative to individuals reared in oat flour without the opportunity to cannibalize. A sib analysis revealed that for larvae reared in the presence of victim eggs, the extent of cannibalism was genetically variable, so that this trait could evolve, given a selective benefit exceeding its cost. These results suggest that colonization of a marginal new environment could be facilitated by enhanced rates of cannibalism. The possible interplay between cannibalism and physiological adaptation to a new environment is discussed.

Evolution in heterogeneous environments: genetic variability within and across different grains in Tribolium castaneum.

The course of adaptation to heterogeneous environments is influenced by the magnitude of genetic variation for ecologically important characters within each environment and the extent of genotype x environment interaction. Using the genetic correlation between the expression of characters in different environments as a measure of genotype x environment interaction is particularly useful for evolutionary interpretation. In this study, we estimated patterns of genetic variability and cross-environment genetic correlations for pupal weight and development time in two strains of the flour beetle Tribolium castaneum in five flours (wheat with brewer's yeast, wheat, rice, corn and oat). Wheat plus yeast is the standard medium in which the strains have been reared for hundreds of generations; other flours are novel environments. The results indicated moderate levels of genetic variation within the various flours for pupal weight but not for development time. Performance varied considerably across flours, with the highest performance for both strains found in the standard medium and the poorest in oat flour. The genetic correlations of pupal weight across flours in both strains were generally not significantly different from + 1. This suggests that evolution of body size in different flours cannot proceed independently, and that improved performance in the novel flours may produce declines in fitness in the standard environment.

Adaptive phenotypic plasticity: consensus and controversy.

Phenotypic plasticity is an environmentally based change in the phenotype. Understanding the evolution of adaptive phenotypic plasticity has been hampered by dissenting opinions on the merits of different methods of description, on the underlying genetic mechanisms, and on the way that plasticity is affected by natural selection in a heterogeneous environment. During much of this debate, the authors of this article have held opposing views. Here, we attempt to lay out current issues and summarize the areas of consensus and controversy surrounding the evolution of plasticity and the reaction norm (the set of phenotypes produced by a genotype over a range of environments).

Mitochondrial DNA diversity in the pea aphid Acyrthosiphon pisum.

The pea aphid Acyrthosiphon pisum has been established in North America for at least a century and occurs on a broad range of host plants. Despite its importance as a crop pest, there is little understanding of the genetic structure of its populations or the extent of genetic divergence associated with different host plant utilization. This study examined the extent of mitochondrial DNA (mtDNA) diversity among 35 clones of pea aphids from alfalfa. Polymorphisms were detected at only 2 of 126 restriction sites, suggesting the same impoverished level of genetic diversity found in prior allozyme studies. However, length variation was common and apparently arose as a result of tandem repeats in two regions of the mtDNA molecule. Region 1 occurred in proximity to the control region of the molecule, while region 2 was close to a cluster of tRNA genes flanking the NAD-dehydrogenase subunit 3 gene on the opposite side of the mtDNA molecule. Each of the aphid clones was homoplasmic for a single length variant in region 1, which varied with respect to the number of copies of a 120-bp repeat. By contrast, one-third of the clones were heteroplasmic at region 2, where they possessed a variable number of copies of a 210-bp repeat. Reanalysis of clones after 30 generations of parthenogenetic reproduction established the stability of length variants over this interval, suggesting their value in studies of the genetic structure of aphid populations.

Natural selection on body size in Tribolium: possible genetic constraints on adaptive evolution.

To determine whether genetic constraints on adaptive evolution were operating in a laboratory population of a flour beetle, Tribolium castaneum, we first estimated the direct selection acting on each of several body size traits. Strong selection in males for an increase in pupal weight and a decrease in the ratio of adult to pupal weight occurred. In addition, a non-significant trend for a decrease in adult width was found. No significant selection on females was detected, although there were trends toward an increase in pupal weight and a decrease in adult width. These estimates were then combined with estimates of the genetic variances and covariances of the traits to predict the multivariate response to selection, that is, the evolutionary change in the traits across one generation. These projections showed only a small predicted change in male pupal weight in spite of the strong selection on pupal weight, and a relatively large predicted increase in width in spite of the possible negative direct selection on this trait. Both of these results were due in part to the positive genetic covariance between pupal weight and width, and they therefore suggest the possibility of genetic constraints on adaptive evolution of these traits.