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PubMed1995

Cytogenetic evolution patterns in non-Hodgkin's lymphoma.

Secondary chromosomal aberrations were surveyed in non-Hodgkin's lymphomas (NHL) reported in the literature with one of the following, presently recognized, primary abnormalities: t(2;5), +3, t(3;14), del(6q), +X, and -Y. Of 2,175 NHLs with clonal karyotypic changes, 908 (42%) had one of the 13 selected primary chromosome rearrangements, and 670 (74%) of these lymphomas displayed additional abnormalities. The type and frequency of the secondary aberrations were ascertained and then correlated with both the type of primary abnormality and morphologic subtype; low-, intermediate, and high-grade according to the Working Formulation. The incidence of secondary aberrations differed not only among the primary abnormality subgroups, from 0% in del(11q) NHLs to 93% in t(3;14) lymphomas (P < .001) but also between B- and T-cell NHLs (78% versus 55%, P< .001) and among the different histologic subgroups: 66% in low-, 85% in intermediate-, and 71% in high-grade lymphomas (P < .001). The mean number of secondary changes per case also varied among the primary abnormalities, from none in del(11q) NHLs to 12.0 in inv(14) lymphomas (P < .001), and among the morphologic subtypes: 4.6 in low-, 6.7 in intermediate-, and 3.6 in high-grade NHL (P < .001). Recurrent secondary aberrations were found in 6 of the 13 primary abnormality subgroups: t(2;5), t(3;14), t(8;14), t(11;14), inv(14), and t(14;18). The most frequent secondary aberrations were +X, -Y, dup(1q), del(6q) varied both within and among the primary abnormalities; the most frequent imbalances were a gain of 1q23-31 and losses of 6q21, 6q23, and 6q25. Other common imbalances were deletions of 1p31-36, 1q31-44, 2q34-37, 7q35-36, 9p22-24, 11q23-25, 13q13-21, and duplication of 12q13-22. The distribution of the secondary changes was clearly nonrandom with the most common anomalies being -Y and +7 in t(2;5); +X, del(6q), and +7 in t(3;14); dup(1q) and +7 in t(8;14); -Y, del(6q), and -13 in t(11;14); del(6q), -17, and -18 in inv(14); and del(6q), +7, and +12 in t(14;18) NHLs. In general, the secondary aberrations were similar in lymphomas of different histologic subtypes but with the same primary abnormality, although some significant differences were discerned: +3, del(6q), +7, and +18 wee more common (P < .01) in intermediate-grade than in high-grade t(8;14) NHLs; monosomy 13 occurred only in intermediate-grade t(11;14) NHLs (P < .05); and +7 and t(8;14)/t(8;22) were more frequent (P < .01 and P< .001, respectively) in high-grade than in low- and intermediate-grade t(14;18) NHLs.(ABSTRACT TRUNCATED AT 400 WORDS)

Chromosome Aberrations↗
PubMedDate not supplied

Management of bladder cancer.

Bladder cancer is a paradigm of malignancy, representing the spectrum from localized to metastatic disease, and manifesting varied histologic types, including transitional cell carcinoma, squamous cell carcinoma, and adenocarcinoma. Preclinical and clinical data suggest that a common stem cell of origin gives rise to the different histologic types and that these patterns are of clonal origin. Localized bladder cancer is managed optimally by transurethral resection, with or without adjuvant intravesical chemotherapy. Invasive cancer or relapsed superficial disease may require more radical surgery or radical radiotherapy. In recent years, the evolution of techniques of continent urinary diversion or of bladder replacement has revolutionized the management of invasive disease. However, the 5-year survival for invasive bladder cancer is still approximately 50%, and innovative strategies have been developed, combining definitive local treatment and systemic chemotherapy, in an attempt to improve survival. For patients with metastatic disease, the combination of methotrexate, vinblastine, doxorubicin, and cisplatin (the MVAC regimen) has achieved response rates as high as 70% but with a median survival of only 12 months. Until cure rates are improved, one of the hallmarks of effective management of metastatic disease will remain the provision of thorough and well-structured palliative treatment programs. Recently, the introduction of new agents (such as paclitaxel, gallium, ifosfamide, and gemcitabine) has led to promising response rates, and further clinical trials of these agents alone and in combination are in progress. In addition, an improved understanding of the mechanisms of resistance to treatment, including the implications of the expression of p-glycoprotein, p53 proteins, and other biochemical predictors of outcome, and of strategies to overcome such resistance, may lead to more effective management of advanced disease. Furthermore, real progress will be made only through the application of well-designed clinical trials to test the efficacy and toxicity of the new strategies of treatment.

Administration, Intravesical↗
PubMed1996

Immunodominance, competition and evolution in immunological responses to helminth parasite antigens.

The paper describes the development and analysis of a mathematical framework for the study of the within-host population dynamics of the interaction between macroparasites and the human immune system. Simple models of this interaction based on the proliferation of T cell clones specific to parasite antigen, and the impact of clonal expansion on parasite survival, capture the basic features of age-related changes in worm loads within human communities. The model is generalized to multiple epitopes on a single antigen, and reveals competitive exclusion amongst T cells, with a single clone becoming immunodominant in the absence of cross-reactive responses and genetic variation. The introduction of genetic heterogeneity and concomitant variability in the immunogenicity of specific epitopes induces additional complexity into the dynamical interaction. Most importantly, multiple epitope models with antigenic variation suggest that the immunodominant response may not necessarily be targeted at the epitope at which some strains show the greatest immunogenicity. High immunogenicity at a particular epitope can be masked by genetic variability even though many of the variants are more immunogenic at this epitope by comparison with the epitope to which the immunodominant immunological response is directed.

Animals↗
PubMed1991

Evolution of discriminatory aggression in marine invertebrates.

Many species of sessile marine organisms show allotype-conditional aggression towards conspecifics. However, a recent theoretical analysis (Grosberg & Quinn, 1989, Evolution 43, 504-515.) was unable to find conditions permitting a discriminatory ESS against unconditionally aggressive or non-aggressive strategies. This study shows that discrimination can be an ESS if animals interact with clonemates more frequently than randomly as occurs when animals reproduce by budding of fission. This agrees well with the observation that clonal sea anemones are usually discriminators and solitary species usually non-aggressive to conspecifics (Francis, 1988, Biol. Bull. 174, 241-253.) In addition, discrimination can be an ESS if discriminators retaliate against unconditionally aggressive conspecifics of the same allotype, or if the payoff to two sharers of a resource is greater than the payoff to both when sharing does not occur.

Aggression↗
PubMed1991

Evolutionary lines among Salmonella enteritidis phage types are identified by insertion sequence IS200 distribution.

A survey was made of the presence, copy number and location of the Salmonella-specific DNA insertion element IS200, within the genomes of the 27 phage type strains of Salmonella enteritidis. All the phage type strains contained copies of IS200 revealed by genomic Southern blot hybridizations with a 300-bp DNA probe internal to the element. Restriction site variation around IS200 insertion sites was examined. Three fundamental patterns of hybridization corresponding to chromosomal IS200 loci were found. In terms of population genetics, these 'IS200 profiles' correspond to clonal lineages of recent evolutionary origin, and underline the phage-typing scheme for epidemiological subdivision of S. enteritidis. The molecular analysis is consistent with genetic selection pressures which are apparent in the observed epidemiological distribution of S. enteritidis, since each clonal lineage contained one of the phage types of major clinical importance in the U.K.

Biological Evolution↗
PubMed1997

Microevolution and epidemic spread of serogroup A Neisseria meningitidis--a review.

An extensive and representative strain collection of serogroup A Neisseria meningitidis was established. These bacteria were obtained from different endemic and epidemic/pandemic sources and include strains from diseased patients and healthy carriers. The genetic relationships of the bacteria were defined by multi-locus enzyme electrophoresis and sequence polymorphisms of genetically variable antigens have been analyzed in closely-related groupings. The results are interpreted as reflecting a balance of recombination events, which disrupt clonal relationships, and sequential bottlenecks, which purify the bacterial population of genetic variants during epidemic spread.

Alleles↗
PubMed2003

Parasite-mediated selection in experimental Daphnia magna populations.

It has been suggested that parasites are a strong selecting force for their hosts and therefore may alter the outcome of competition among host genotypes. We tested the extent to which parasite-mediated selection by different parasite species influenced competition among clones of the cyclic parthenogen Daphnia magna. We monitored clone frequency changes in laboratory microcosm populations consisting of 21 D. magna clones. Parasite treatments (two microsporidians, Glugoides intestinalis and Ordospora colligata) and a parasite-free control treatment were followed over a nine-month period. A further treatment with the bacterium Pasteuria ramosa failed. We found significant differences in clonal success among the treatments: the two parasite treatments differed from the control treatment and from each other. Additionally, we measured the clone-specific population carrying capacity, competitive ability against tester clones, and reproductive success of infected and uninfected females to test whether they correlate with clonal success in the microcosms. The clone-specific competitive ability was a good predictor of clonal success in the microcosms, but clonal carrying capacity and host reproductive success were not. Our study shows that parasite-mediated selection can strongly alter the outcome of clonal competition. The results suggest that parasites may influence microevolution in Daphnia populations during periods of asexual reproduction.

Animals↗
PubMed2006

Temporal and dose-dependent relationships between in vivo B cell receptor-targeted proliferation and deletion-induced by a microbial B cell toxin.

The effective functioning of the adaptive immune system requires careful clonal regulation within the B cell compartment. Some microbial pathogens produce virulence factors, like staphylococcal protein A, which interact at high frequencies with B lymphocyte through unconventional binding sites in BCR variable region frameworks conserved during evolution. We have characterized the in vivo effect of staphylococcal protein A treatment on peripheral B cells bearing susceptible BCR, and found a dose-dependent direct relationship over the range of 2 mg to <0.2 microg in the magnitude of induced BCR-targeted supraclonal cell death. Significantly, some level of targeted B cell proliferation was always detectable, with greatest interim supraclonal expansion demonstrated at 2 days after 20-microg treatment. Subsequently, this transient expansion always collapsed. In direct comparisons, i.p. treatment was more efficacious than i.v. treatment, although at higher doses this finding was less marked. These studies elucidate a general paradigm in which in vivo encounters with a B cell superantigen are uniformly associated with proliferative expansion followed by deletion that is more rapid and complete with higher doses, whereas lower doses lead to greater transient in vivo expansion with delayed deletion to levels at later times that are still quantitatively proportional to the dose. Our results document the potent in vivo B cell-targeted properties of a microbial B cell superantigen, even at submicrogram doses associated with great molar excess of circulating Ig, and clearly illustrate the intertwined relationships between targeted proliferative cycling and apoptotic death that is induced by a microbial B cell superantigen.

Animals↗
PubMed2003

Polyembryony in parasitic wasps: evolution of a novel mode of development.

Major developmental innovations have been associated with adaptive radiations that have allowed particular groups of organisms to occupy empty ecospace. Well-known developmental novelties associated with the conquest of new habitats include the evolution of the tetrapode limb, allowing the radiation of vertebrates into a terrestrial habitat, and formation of insect wings that permitted their dispersal into the air. However, an understanding of the evolutionary forces and molecular mechanisms behind developmental novelties still remains tenuous. A little-studied adaptive radiation in insects from the developmental perspective is the evolution of parasitism. The parasitic lifestyle has allowed parasitic insects to occupy a novel ecological niche where they have evolved a plethora of life history strategies and modes of embryogenesis, developing on or within the body of the host. One of the most striking adaptations to development within the body of the host includes polyembryonic development, where certain wasps form clonally up to 2000 embryos from a single egg. Taking advantage of well-established insect phylogeny, techniques developed in a model insect, the fruit fly, and a wealth of knowledge in comparative insect embryology, we are starting to tease apart the evolutionary events that have led to this novel mode of development in insects.

Animals↗
PubMed1995

Study of the immunohistochemistry and T cell clonality of enteropathy-associated T cell lymphoma.

Specimens from 23 patients with enteropathy-associated T cell lymphoma were studied by immunohistochemistry after antigen retrieval. Specimens from 14 of these patients were investigated for the presence of clonal T cell gene rearrangements in both the tumor and the adjacent enteropathic intestine by the polymerase chain reaction. Primers for T cell receptor beta and gamma genes were used in a combination that permits the identification of approximately 90% of T cell receptor rearrangements. Clonal rearrangements of the T cell receptor were found in 13 of the 14 tumors studied. Specimens of enteropathic bowel resected with the tumor, but showing no morphological or immunohistochemical evidence of tumor involvement, showed clonal T cell receptor gene rearrangements in 11 cases. In 10 of these, the amplified DNA was of the same molecular weight in the enteropathic bowel as in the corresponding tumor. In 2 cases, sequencing the polymerase chain reaction product showed identical T cell receptor gene rearrangements in the tumor and in the adjacent intestine. Uniform staining for p53 was seen in 22 of the 23 tumors. In 9 of 19 cases studied, collections of small lymphocytes in the enteropathic bowel expressed p53. In all but one of these specimens, a clonal rearrangement of the T cell receptor genes was identified. We interpret these findings as support for the concept that enteropathy-associated T cell lymphoma arises on a background of gluten-sensitive enteropathy with evolution of neoplastic T cell clones from the reactive T cell population present in the enteropathic bowel.

Adult↗
PubMed1999

Selective pressure as an essential force in molecular evolution of myeloid leukemic clones: a view from the window of Fanconi anemia.

Specific chromosomal deletions are commonly found in bone marrow cells of children with Fanconi anemia (FA) whose disease has evolved to myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). Identical deletions are found in adults with MDS/AML with a history of exposure to alkylating agents (secondary MDS/AML). While deleted chromosomal regions likely harbor genes encoding proteins with tumor suppressor (TS) function, such genes have not been identified and the environmental forces by which these mutant clones are selected remain unclear. A consistent signaling abnormality in cells bearing mutations of the Fanconi anemia complementation group C (FA-C) gene (FANCC) has revealed a potential selective force. Hematopoietic progenitor cells from patients and mice with FANCC mutations are hypersensitive to the inhibitory effects of IFNgamma and TNFalpha. Consequently, clonal outgrowths in FA likely result from strong selective pressure for stem and/or progenitor cells resistant to these inhibitory cytokines. Additional mutations that inactivate signaling pathways for these inhibitors would create a cell with a profound proliferative advantage over its apoptosis-prone counterparts. Here, we present preliminary evidence supporting a selection-based model of leukemic evolution and argue that MDS in FA patients is a de facto model of secondary MDS in non-FA adults.

Acute Disease↗
PubMed1989

The NK model of rugged fitness landscapes and its application to maturation of the immune response.

Adaptive evolution is, to a large extent, a complex combinatorial optimization process. Such processes can be characterized as "uphill walks on rugged fitness landscapes". Concrete examples of fitness landscapes include the distribution of any specific functional property such as the capacity to catalyze a specific reaction, or bind a specific ligand, in "protein space". In particular, the property might be the affinity of all possible antibody molecules for a specific antigenic determinant. That affinity landscape presumably plays a critical role in maturation of the immune response. In this process, hypermutation and clonal selection act to select antibody V region mutant variants with successively higher affinity for the immunizing antigen. The actual statistical structure of affinity landscapes, although knowable, is currently unknown. Here, we analyze a class of mathematical models we call NK models. We show that these models capture significant features of the maturation of the immune response, which is currently thought to share features with general protein evolution. The NK models have the important property that, as the parameter K increases, the "ruggedness" of the NK landscape varies from a single peaked "Fujiyama" landscape to a multi-peaked "badlands" landscape. Walks to local optima on such landscapes become shorter as K increases. This fact allows us to choose a value of K that corresponds to the experimentally observed number of mutational "steps", 6-8, taken as an antibody sequence matures. If the mature antibody is taken to correspond to a local optimum in the model, tuning the model requires that K be about 40, implying that the functional contribution of each amino acid in the V region is affected by about 40 others. Given this value of K, the model then predicts several features of "antibody space" that are in qualitative agreement with experiment: (1) The fraction of fitter variants of an initial "roughed in" germ line antibody amplified by clonal selection is about 1-2%. (2) Mutations at some sites of the mature antibody hardly affect antibody function at all, but mutations at other sites dramatically decrease function. (3) The same "roughed in" antibody sequence can "walk" to many mature antibody sequences. (4) Many adaptive walks can end on the same local optimum. (5) Comparison of different mature sequences derived from the same initial V region shows evolutionary hot spots and parallel mutations. All these predictions are open to detailed testing by obtaining monoclonal antibodies early in the immune response and carrying out in vitro mutagenesis and adaptive hill climbing with respect to affinity for the immunizing antigen.

Amino Acid Sequence↗
PubMed2004

Distribution and characterization of staphylococcal interspersed repeat units (SIRUs) and potential use for strain differentiation.

Variable-number tandem repeats (VNTRs) have been shown to be a powerful tool in the determination of evolutionary relationships and population genetics of bacteria. The sequencing of a number of Staphylococcus aureus genomes has allowed the identification of novel VNTR sequences in S. aureus, which are similar to those used in the study of the evolution of Mycobacterium tuberculosis clades. Seven VNTRs, termed staphylococcal interspersed repeat units (SIRUs), distributed around the genome are described, occurring in both unique and multiple sites, and varying in length from 48 to 159 bp. Variations in copy numbers were observed in all loci, within both the sequenced genomes and the UK epidemic methicillin-resistant S. aureus (EMRSA) isolates. Clonally related UK EMRSA isolates were clustered using SIRUs, which provided a greater degree of discrimination than multi-locus sequence typing, indicating that VNTRs may be a more appropriate evolutionary marker for studying transmission events and the geographical spread of S. aureus clades.

Bacterial Typing Techniques↗
PubMedDate not supplied

Chromosome studies of enriched blast cell fractions in myelodysplastic syndromes terminating in acute myeloid leukemia.

For a better understanding of the karyotype evolution of different marrow cell populations in the course of MDS, 6 patients who eventually developed overt leukemia, belonging to a series of 46 MDS referred to our Institution, were studied ad diagnosis and at leukemic progression. In each case the blast cells were separated from the maturing precursors of the erythroid and granulocytic lineage by centrifugation on a Percoll density gradient. Parallel chromosome investigations were performed in each cell fraction. Cytogenetic analysis performed at presentation did not reveal distinctive karyotype features in metaphases arising in the blast enriched cell fraction, as compared with those obtained from the fraction containing erythroblasts and promyelocytes--myelocytes. These findings suggest that in the initial phase of MDS blast cells may lack distinctive cytogenetic features and may thus represent part of a clonal preleukemic proliferation. At the time of leukemia onset, clonal aberrations [trisomy 21 and del(11)(q23)] showing a restricted pattern of distribution within the blast cell enriched fractions were detected in two patients, whereas one patient showed an increase in size of the abnormal clone carrying monosomy 7, an aberration detected in metaphases obtained from both cell fractions. Thus, some evolutive steps in the natural history of these disorders can be heralded by the acquisition of chromosome aberrations more readily detectable in blast enriched cell fractions. In some cases, partial loss of differentiative capability by the abnormal clone may account for the detection, at leukemia onset, of chromosome aberrations involving both the blast cell fraction and the erythroblast-promyelocyte enriched cell fraction.

Blast Crisis↗
PubMed1986

Effects of antigen and internal environment on anti-phosphorylcholine immune responses of autoimmune aged NZB/W F1 mice.

The idiotypic profile of anti-phosphorylcholine plaque-forming cell responses and their evolution with ageing were studied in (NZB X NZW) F1 mice. Our results showed that the anti-phosphorylcholine plaque-forming cell response induced by phosphorylcholine coupled to keyhole limpet haemocyanin and, paralleling, the T15 idiotype clonal dominance declined with ageing. This loss of immune competence was also observed with another thymus-dependent (phosphorylcholine coupled to egg globulin) as well as thymus-independent (capsular polysaccharide of Streptococcus pneumoniae strain R36a) antigens. In contrast, old mice challenged with an antigenic preparation of Neisseria meningitidis showed an immune response not significantly different from that elicited by the same antigen in young mice. The hapten-augmentable plaque-forming cells were assayed to determine whether a putative auto-antiidiotypic regulation underlies this loss of immune competence. Only minimal numbers and non-significant differences between young and old mice immunized with any antigen could be detected. Further studies using an adoptive transfer system demonstrated that cells from aged mice were able to support a normal anti-phosphorylcholine response when transferred into lethally irradiated young recipients. Our results suggest that no permanent cellular defects, but rather internal environment or/and radioresistant suppressor cells, are involved in this loss of immune competence. The role played by these factors and their effect on distinct subpopulations of B cells are discussed.

Aging↗
PubMed1983

The Ernst W. Bertner Memorial Award lecture: the evolution of biological heterogeneity in metastatic neoplasms.

The complexity of the processes of tumor progression and metastasis makes it difficult to provide generalized rules. Results and hypotheses that are based upon a single tumor system or a simple experimental technique are likely to be revised as more data become available. However, bearing these limitations in mind and ignoring the above warnings, I wish to conclude the following: By the time of diagnosis, many malignant neoplasms are heterogeneous, i.e., they contain subpopulations of cells with different biological characteristics. The process of metastasis involves a sequence of complex events whose outcome depends on tumor cell properties and host factors. The metastatic process selects variants from a heterogeneous starting population. The diversity for the metastatic phenotype may be a consequence of the multicellular origin of a neoplasm or it may be the result of continuous evolution and progression in tumors of unicellular origin. Metastatic clones appear, in general, to be less stable than nonmetastatic clones. Metastatic clones exhibit an increased rate of spontaneous mutation compared with nonmetastatic clones. Some metastases may be clonal in their origin, and multiple metastases can originate from different progenitor cells. Biological diversity can rapidly develop within individual metastases. The acquisition of phenotypic heterogeneity by populations of tumor cells imposes a degree of stability on the tumor as a whole. The generation of biological diversity in malignant neoplasms and within and among metastases has profound implications both for studies on the pathogenesis of cancer metastasis and for the design of any successful approach to the treatment of this disease.

Animals↗
PubMed1997

Potential biomarkers in predicting progression of epithelial hyperplastic lesions of the larynx.

Factors contributing to malignant transformation of laryngeal pre-neoplastic lesions remain largely unknown. Potential etiologic factors may be related to a genetically controlled sensitivity to environmental carcinogens. In this study, we investigated bleomycin-induced chromosome fragility in 15 patients with laryngeal keratoses who experienced a malignant transformation of pre-neoplastic lesions during follow-up, as compared with chromosome fragility in 15 historical controls with no progression of laryngeal keratoses during a 10-year follow-up, in a match-paired analysis. Chromosomal analysis demonstrated a higher sensitivity to clastogens in patients with malignant progression of laryngeal pre-neoplastic lesions than that of control patients with no evolution of their original laryngeal keratoses (p < 0.01). Furthermore, in the attempt to identify possible prognostic markers we studied proliferative activity (MIB-1 expression) and p53 gene aberration in biopsy samples from non-invasive and invasive laryngeal lesions in both groups. p53 immunostaining was observed in 10/15 (66.7%) of pre-neoplastic lesions and in 11/15 (73.3%) of metachronous laryngeal cancers. No differences in terms of p53 expression were noted between transformed and not-transformed lesions. Mutations at p53 gene were observed in 3/15 (20%) of pre-invasive biopsies and in 4/5 (80%) of the laryngeal cancers analyzed. Our data suggest that p53 alteration is an early event in the genesis of a subset of laryngeal carcinomas and that there is no conclusive data about the possible clonal development of metachronous laryngeal carcinoma from a p53 mutated pre-invasive disease in the same patient. MIB-1 expression was found to progressively increase with degree of epithelial hyperplasia and dysplasia in both transformed (p = 0.007) and not-transformed (p < 0.1) lesions. Surprisingly, pre-invasive lesions with tumor evolution showed a lower proliferative activity when compared with laryngeal lesions without malignant transformation (p = 0.013). These data suggests that subjects with pre-neoplastic laryngeal lesion showing an increased susceptibility to carcinogens and with less proliferative disease could be at a higher risk for development of laryngeal carcinoma.

Antigens, Nuclear↗
PubMed2006

Rare sexual reproduction events in the clonal reproduction system of introduced populations of the little fire ant.

A unique reproductive system has previously been described in Wasmannia auropunctata, a widespread invasive ant species, where males are produced clonally, female queens are parthenogens, and female workers are produced sexually. However, these findings were mostly based on samples originating from only a limited part of the native range of the species in South America. We used microsatellite markers to uncover the reproductive modes displayed by a large number of nests collected in various invasive W. auropunctata populations introduced 40 years ago into New Caledonia, where the species now forms a single 450-km-long supercolony. Although the main reproduction system in New Caledonia remained clonality for both male and female reproductives, we found evidence of rare sexual reproduction events that led to the production of both new queen and male clonal lineages. All clonal lineages observed in New Caledonia potentially derived from sexual reproduction, recombination, and mutation events from a single female and a single male genotype. Hence, the male and female gene pools are not strictly separated in New Caledonia and the two sexes do not follow independent evolutionary trajectories. Our results also suggest genetic determination for both parthenogenesis and caste. We discuss the evolutionary implications of the emergence of sex in the clonal reproduction system of introduced populations of W. auropunctata.

Animals↗