Parthenogenesis Research Papers - Academia.edu (original) (raw)

Patterns of variation in chromosomes, mitochondrial DNA and allozymes were assessed for two parthenogenetic (Lepidodactylus lugubris and Hemidactylus garnotii) and one sexual (H. frenatus) species of house gecko that have colonized remote... more

Patterns of variation in chromosomes, mitochondrial DNA and allozymes were assessed for two parthenogenetic (Lepidodactylus lugubris and Hemidactylus garnotii) and one sexual (H. frenatus) species of house gecko that have colonized remote Pacific Ocean islands. The aims were to test the assumed recency of colonization and to provide information on the amount and distribution of genetic variation. Lepidodactylus lugubris was found to have diploid and triploid clones, high heterozygosity and moderate diversity for allozymes, and only two common types of mtDNA. The common clones distinguished by genetic analysis were geographically widespread. Together the genetic data suggest multiple origins of L. lugubris, with multiple recent invasions of the Pacific Ocean islands. Hemidactylus garnotii had low genetic diversity for chromosomes, mtDNA and allozymes. In contrast, its sexual congener, H. frenalus, had unusually high levels of mtDNA diversity, with some widespread variants. The low level of mtDNA diversity in the parthogenetic species provides strong support for the assumption that these are recent colonists of Pacific Islands.

The genus Brevipalpus includes most of the economically important species of Tenuipalpidae. Many Brevipalpus species reproduce by theletokous parthenogenesis while other species reproduce by male fertilization of female eggs. Previous... more

The genus Brevipalpus includes most of the economically important species of Tenuipalpidae. Many Brevipalpus species reproduce by theletokous parthenogenesis while other species reproduce by male fertilization of female eggs. Previous researchers have determined that Brevipalpus californicus (Banks), B. obovatus Donnadieu, and B. phoenicis (Geijskes) females were haploid with two chromosomes. The life cycle and developmental times for these three species are reviewed. Longevity of each Brevipalpus species is two to three times greater than corresponding longevities of various tetranychid mites. Brevipalpus mites inject toxic saliva into fruits, leaves, stems, twigs, and bud tissues of numerous plants including citrus. Feeding injury symptoms on selected plants include: chlorosis, blistering, bronzing, or necrotic areas on leaves by one or more Brevipalpus mites. Premature leaf drop occurred on ‘Robinson’ tangerine leaves in Florida (USA). Leaf drop was observed in several sweet orange and grapefruit orchards in Texas (USA) that were heavily infested with Brevipalpus mites feeding on the twigs, leaves, and fruit. Initial circular chlorotic areas appear on both sweet orange and grapefruit varieties in association with developing populations of Brevipalpus mites in Texas. These feeding sites become progressively necrotic, darker in color, and eventually develop into irregular scab-like lesions on affected fruit. Russeting and cracking of the fruits of other plant hosts are reported. Stunting of leaves and the development of Brevipalpus galls on terminal buds were recorded on sour orange, Citrus aurantium L., seedlings heavily infested with B. californicus in an insectary. The most significant threat posed by these mites is as vectors of a potentially invasive viral disease called citrus leprosis.

Aphids exhibit divergent modes of embryogenesis during the sexual and asexual phases of the life cycle. To explore how a single genome can give rise to these alternative developmental modes, we have initiated embryological studies of the... more

Aphids exhibit divergent modes of embryogenesis during the sexual and asexual phases of the life cycle. To explore how a single genome can give rise to these alternative developmental modes, we have initiated embryological studies of the pea aphid, Acyrthosiphon pisum. Here we present a detailed description of parthenogenetic, viviparous embryonic development in the pea aphid. We compare and contrast development of the parthenogenetic embryo with that of the embryo resulting from sexual reproduction. The primary difference between the embryos is the scale on which development occurs: early parthenogenetic development occurs in a volume approximately three orders of magnitude smaller than the sexual egg, largely because of the apparent absence of yolk in the parthenogenetic egg. This results in a drastically different duration of syncytial energid cleavage and, presumably, patterning processes in the two embryos must act at scales that differ by orders of magnitude. The eggs also dev...

Hera was indigenous and represents a matrilinear system; she reigned alone at Argos, at Samos, her temple at Olympia is distinct from and far earlier than that of Zeus. Her first husband, or rather consort, was Herakles [Heracles]. The... more

some reflections on science, myth and the female body

In many parts of the world, the tobacco specialist Myzus persicae nicotianae is isolated from the generalist Myzus persicae s.s. because either or both taxa reproduce parthenogenetically. Here we investigated how the genomic integrity of... more

In many parts of the world, the tobacco specialist Myzus persicae nicotianae is isolated from the generalist Myzus persicae s.s. because either or both taxa reproduce parthenogenetically. Here we investigated how the genomic integrity of the tobacco specialist is maintained in Greece, where both taxa have a bisexual generation on peach. Microsatellite DNA analysis revealed greatest genetic divergence between populations in tobacco-growing regions and those in a region where tobacco is not cultivated. This was irrespective of reproductive mode, which has an important effect on population structure. Bayesian clustering and admixture analyses split the aphid genotypes into three groups, corresponding with persicae, bisexual nicotianae and unisexual nicotianae, respectively. Genetic distance parameters showed strong regional differentiation but marked year-on-year stability, indicating low interpopulation migration. Assortative mating between taxa is promoted by differences in the daily rhythm of female signalling behaviour, with peak activity coinciding with periods of consubspecific male searching activity. Males showed greater attraction to the sex pheromone of their own subspecies. Thus, despite relatively low overall genetic differentiation, processes are in place facilitating further genomic divergence and eventual speciation. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 687–702.

Virgin birth is a common theme in religious myths, science fiction, lesbian and feminist imaginaries, and sensational news stories. Virgin birth enters a laboratory setting through biologists' use of the term parthenogenesis (Greek for... more

Virgin birth is a common theme in religious myths, science fiction, lesbian and feminist imaginaries, and sensational news stories. Virgin birth enters a laboratory setting through biologists' use of the term parthenogenesis (Greek for virgin birth) to describe various forms of development without sperm. Scientific consensus holds that viable mammalian parthenogenesis is impossible; that is, mammalian embryos require both a maternal and a paternal contribution to develop completely. This essay investigates the historical development of that consensus and the evolving scientific language of parthenogenesis after the birth of Kaguya, a mouse with two mothers and no father. I qualitatively analyze 202 peer-reviewed scientific publications that cite the Kaguya experiment, and find unconventional interpretations of sex and parenthood, even in publications that maintain the impossibility of mammalian parthenogenesis. Though many scientists insist that males are necessary, they also describe eggs as paternal, embryos as sperm-free, and bimaternal sexual reproduction as something distinct from parthenogenesis. I argue that the scientific language used to explain the Kaguya experiment both supports a heteronormative reproductive status quo and simultaneously challenges it, offering bimaternal sexual reproduction as a feasible alternative.

Abstract Thelytokous parthenogenesis, the production of female-only offspring from unfertilized eggs, has been described in all the insect orders, but is a rare phenomenon in the Odonata (dragonflies and damselflies). The only-known case... more

Abstract Thelytokous parthenogenesis, the production of female-only offspring from unfertilized eggs, has been described in all the insect orders, but is a rare phenomenon in the Odonata (dragonflies and damselflies). The only-known case of parthenogenesis in this group is the North American damselfly species Ischnura hastata, which has parthenogenetic populations in the Azores Islands. Here, we present for the first time the results of laboratory rearing, which showed parthenogenetic reproduction in the Azorean I.

Polyploid genomes evolve and follow a series of dynamic transfigurations along with adaptation and speciation. The initial formation of a new polyploid individual within a diploid population usually involves a triploid bridge, a two-step... more

Polyploid genomes evolve and follow a series of dynamic transfigurations along with adaptation and speciation. The initial formation of a new polyploid individual within a diploid population usually involves a triploid bridge, a two-step mechanism of cell fusions between ubiquitous (reduced) and rare (unreduced) gametes. The primary fusion event creates an intermediate triploid individual with unbalanced genome sets, a situation of genomic-shock characterized by gene expression dysregulation, high dosage sensitivity, disturbed cell divisions, and physiological and reproductive attributes drastically altered. This near-sterile neotriploid must produce (even) eupolyploids through secondary fusion events to restore genome steadiness, meiotic balance, and fertility required for the demographic establishment of a nascent lineage. Natural conditions locate several difficulties to polyploid establishment, including the production of highly unbalanced and rarely unreduced (euploid) gametes, frequency-dependent disadvantages (minority cytotype exclusion), severe fitness loss, and ecological competition with diploid parents. Persistence and adaptation of neopolyploids depend upon genetic and phenotypic novelty coupled to joint selective forces that preserve shock-induced genomic changes (subgenome homeolog partitioning) and drive meiotic (reproductive) stabilization and ecological diversification. Thus, polyploid establishment through the triploid bridge is a feasible but not ubiquitous process that requires a number of low-probability events and singular circumstances. Yet, frequencies of polyploids suggest that polyploid establishment is a pervasive process. To explain this disparity, and supported in experimental evidence, I propose that situations like hybridization and ploidy-state transitions associated to genomic shock and substantial developmental alterations can transiently activate apomixis as a mechanism to halt genomic instability and cancel factors restraining neopolyploid's sexual fertility, particularly in triploids. Apomixis –as a temporal alternative to sex– skip meiosis and syngamy, and thus can freeze genomic attributes, avoid unbalanced chromosomal segregation and increase the formation of unreduced euploid gametes, elude frequency-dependent reproductive disadvantages by parthenogenetic development of the embryo and permissive development of endosperm during seed formation, and increase the effective population size of the neopolyploid lineage favoring the formation rate of eupolyploids compared to aneuploids. The subsequent action of genome resilience mechanisms that alleviate transcriptomic shock and selection upon gene interactions might restore a stable
meiosis and sexual fertility within few generations, as observed in synthetic polyploids. Alternatively, provided that resilience mechanisms fail, the neopolyploid might retain apomixis and hold genomically and transcriptionally altered states for many generations.

According to a dominant view in the scholarly literature, Musschenbroek is to be considered a follower of Newton’s methodology, i.e. as a natural philosopher who, although he occasionally departed from Newton’s doctrines, aligned himself... more

According to a dominant view in the scholarly literature, Musschenbroek is to be considered a follower of Newton’s methodology, i.e. as a natural philosopher who, although he occasionally departed from Newton’s doctrines, aligned himself to Newton’s methodological views. Few scholars have, however, explained in full detail what it means to claim that Musschenbroek followed Newton’s method. The purpose of this essay is to get more grip on this matter.

Los defensores del método partenogénico afirman evitar el problema ético que supone la clonación para la obtención de embriones de los que se puedan derivar líneas celulares útiles en terapia regenerativa. En el caso de la clonación, así... more

Los defensores del método partenogénico afirman evitar el problema ético que supone la clonación para la obtención de embriones de los que se puedan derivar líneas celulares útiles en terapia regenerativa. En el caso de la clonación, así como en la
4
utilización de embriones obtenidos por fecundación in vitro, estos deben ser destruidos para la obtención de las células troncales, lo que implica la destrucción de seres humanos.
No sería este el caso, según afirman los partidarios de la partenogénesis, de esta técnica, en la que el partenote no sería considerado como ser humano

Apomixis, the asexual reproduction via seed, often occurs in huge plant polyploid complexes with large geographical distributions. However, the long-term evolutionary fate of asexuals traditionally was regarded as doomed by extinction. A... more

Apomixis, the asexual reproduction via seed, often occurs in huge plant polyploid complexes with large geographical distributions. However, the long-term evolutionary fate of asexuals traditionally was regarded as doomed by extinction. A seven-step evolutionary model is presented to explain the role of sex → apomixis shifts on geographical cytotype distributions, and the potential consequences of reversals apomixis → sex on plant diversity. Accordingly, apomictic polyploid genotypes act as facilitators for range expansions of asexual taxa in agamic complexes by functioning as pioneer explorers of new niches. High intragenomic (allelic) diversity and epigenetic variability may help for rapid adaptation. Therefore, they could rapidly expand the distribution areas of their progenitor sexual populations by occupying new ecological niches and geographical areas. Hence, apomixis would result in divergent patterns of geographic distribution between sexual and asexuals, a pattern described as “geographical parthenogenesis,” in which apomicts occupy extensive geographical areas and higher latitudinal zones while sexual relatives are restricted to small refugees. Later on, reversals to complete sexuality would allow for the establishment of new sexual populations in different habitats without the long-term disadvantages of asexuality. The new sexual recombinants will be genetically isolated from the original sexual populations and consequently predisposed to a divergent evolution, and potentially enabled to evolve into new sexual species. The present model stresses a previously unidentified evolutionary significance of the geographical parthenogenesis as a motor for plant diversification.

Orconectes limosus, a North American crayfish species, is one of the most important aquatic invaders in European inland waters. Despite more than 120 years occurrence in Europe and intense research, there are still gaps in knowledge of... more

Orconectes limosus, a North American crayfish species, is one of the most important aquatic invaders in European inland waters. Despite more than 120 years occurrence in Europe and intense research, there are still gaps in knowledge of its life history and ecology. Investigation into O. limosus invasive success requires identifying the mechanisms that enabled them to establish dense and widespread populations from small initial numbers without observable limitation by an introduction bottleneck. In part, O. limosus success may lie in its ability to reproduce by facultative parthenogenesis. Moreover, there are possible other mating scenarios, because of two mating seasons (autumn and spring) in O. limosus. This work investigated the effect of four reproductive scenarios (autumn mating only, spring mating only, autumn and spring mating, and without mating) on the reproductive success of O. limosus. Females successfully reproduced in all tested mating regimes using parthenogenesis as w...