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Leo W Beukeboom - One of the best experts on this subject based on the ideXlab platform.
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diploid males support a two step mechanism of endosymbiont induced thelytoky in a parasitoid wasp
BMC Evolutionary Biology, 2015Co-Authors: Bart A Pannebakker, Bregje Wertheim, Louis Van De Zande, Tanja Schwander, Leo W BeukeboomAbstract:Background Haplodiploidy, where females develop from diploid, fertilized eggs and males from haploid, unfertilized eggs, is abundant in some insect lineages. Some species in these lineages reproduce by thelytoky that is caused by infection with endosymbionts: infected females lay haploid eggs that undergo diploidization and develop into females, while males are very rare or absent. It is generally assumed that in thelytokous wasps, endosymbionts merely diploidize the unfertilized eggs, which would then trigger female development.
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Thelytoky in Hymenoptera with Venturia canescens and Leptopilina clavipes as Case
2014Co-Authors: Irene Mateo Leach, Bart A Pannebakker, Maria Victoria Schneider, Gerard Driessen, Leo W Beukeboom, Louis Van De Z, Mateo I. LeachAbstract:Abstract The insect order of Hymenoptera comprises around 200.000 described species of ants, bees, wasps and sawflies, many of which serve important ecological and economic functions. All Hymenoptera have a haplodiploid mode of reproduc-tion. Males always develop from unfertilized eggs and are haploid. Females are always diploid and can develop from both fertilized and unfertilized eggs. Within Haplodiploidy, arrhenotoky is the most common mode of reproduction: unfertil-ized eggs develop into males that are haploid and 100 % related to their mother, whereas fertilized eggs yield diploid females with a haploid complement of both parents. Thelytoky is a less common mode of reproduction. Thelytokous females develop parthenogenetically from unfertilized eggs after restoration of diploidy and are 100 % related to their mother. Two distinctive classes of thelytoky can be dis-tinguished based upon the causal mechanism: thelytoky can be induced by nuclear genes or be based on cytoplasmic genes including microorganisms. Most thelytok-ous hymenopterans reproduce by some form of automixis: both terminal fusion and central fusion have been found, while most cases of microbe-induced thelytoky are a form of gamete duplication. These different mechanisms can have a number of important implications for the genetic make-up of individuals and the amount and structure of genetic variation in populations. We discuss these implications and their evolutionary consequences, with a special focus on the ichneumonid parasitoid wasp Venturia canescens, in which thelytoky has a genetic basis, and the figitid parasitoid wasp Leptopilina clavipes, which has Wolbachia-induced thelytoky. 17.1 Thelytoky in Hymenoptera 17.1.
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Manipulation of arthropod sex determination by endosymbionts: diversity and molecular mechanisms
Sexual Development, 2014Co-Authors: Fabrice Vavre, Leo W BeukeboomAbstract:Arthropods exhibit a large variety of sex-determination systems both at the chromosomal andmolecular level. Male heterogamety, female heterogamety, and Haplodiploidy occurfrequently, but partially different genes are involved. Endosymbionts, such as Wolbachia,Cardinium, Rickettsia and Spiroplasma, can manipulate host reproduction and sexdetermination. Four major reproductive manipulation types are distinguished: cytoplasmicincompatibility, thelytokous parthenogenesis, male killing and feminization. In this review, wesummarize the effects of these manipulation types, and how they interfere with arthropod sexdetermination in terms of host developmental timing, alteration of sex determination andmodification of sexual differentiation pathways. Transitions between different manipulationtypes occur frequently, which suggests that they are based on similar molecular processes. Wediscuss how mechanisms of reproductive manipulation and host sex determination can beinformative on each other, with a special focus on Haplodiploidy. We end with futuredirections on how study of endosymbiont manipulation of host reproduction can be key tofurther study of arthropod sex determination.
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hybrid incompatibilities in the parasitic wasp genus nasonia negative effects of hemizygosity and the identification of transmission ratio distortion loci
Heredity, 2012Co-Authors: T. Koevoets, Louis Van De Zande, Oliver Niehuis, Leo W BeukeboomAbstract:The occurrence of hybrid incompatibilities forms an important stage during the evolution of reproductive isolation. In early stages of speciation, males and females often respond differently to hybridization. Haldane's rule states that the heterogametic sex suffers more from hybridization than the homogametic sex. Although haplodiploid reproduction (haploid males, diploid females) does not involve sex chromosomes, sex-specific incompatibilities are predicted to be prevalent in haplodiploid species. Here, we evaluate the effect of sex/ploidy level on hybrid incompatibilities and locate genomic regions that cause increased mortality rates in hybrid males of the haplodiploid wasps Nasonia vitripennis and Nasonia longicornis. Our data show that diploid F1 hybrid females suffer less from hybridization than haploid F2 hybrid males. The latter not only suffer from an increased mortality rate, but also from behavioural and spermatogenic sterility. Genetic mapping in recombinant F2 male hybrids revealed that the observed hybrid mortality is most likely due to a disruption of cytonuclear interactions. As these sex-specific hybrid incompatibilities follow predictions based on Haldane's rule, our data accentuate the need to broaden the view of Haldane's rule to include species with haplodiploid sex determination, consistent with Haldane's original definition.
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Genetics of sex determination in the haplodiploid wasp Nasonia vitripennis (Hymenoptera: Chalcidoidea).
Journal of genetics, 2010Co-Authors: Leo W Beukeboom, Louis Van De ZandeAbstract:The parasitoid wasp Nasonia vitripennis reproduces by Haplodiploidy; males are haploid and females are diploid. Sex determination in Nasonia is not governed by complementary alleles at one or more sex loci. As in most other insects, the sex-determining pathway consists of the basal switch doublesex that is sex-specifically regulated by transformer. Analysis of a polyploid and a mutant gynandromorphic strain, suggested a parent-specific effect (imprinting) on sex determination in Nasonia. Zygotic activity of transformer is autoregulated and depends on a combination of maternal provision of tra mRNA and a paternal genome set. This constitutes a novel way of transformer control in insect sex determination implying maternal imprinting. The nature of the maternal imprint is not yet known and it remains to be determined how broadly the Nasonia sex-determining mechanism applies to other haplodiploids.
Stuart A West - One of the best experts on this subject based on the ideXlab platform.
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Haplodiploidy and the evolution of eusociality worker reproduction
The American Naturalist, 2013Co-Authors: Joao Alpedrinha, Andy Gardner, Stuart A WestAbstract:AbstractHamilton suggested that inflated relatedness between sisters promotes the evolution of eusociality in haplodiploid populations. Trivers and Hare observed that for this to occur, workers have to direct helping preferentially toward the production of sisters. Building on this, they proposed two biological scenarios whereby Haplodiploidy could act to promote the evolution of eusociality: (a) workers biasing the sex allocation of the queen’s brood toward females and (b) workers replacing the queen’s sons with their own sons. This “worker revolution,” whereby the worker class seizes control of sex allocation and reproduction, is expected to lead to helping being promoted in worker-controlled colonies. Here, we use a kin-selection approach to model the two scenarios suggested by Trivers and Hare. We show that (1) worker control of sex allocation may promote helping, but this effect is likely to be weak and short lived; and (2) worker reproduction tends to inhibit rather than promote helping. Furthermore...
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Haplodiploidy and the evolution of eusociality split sex ratios
The American Naturalist, 2012Co-Authors: Andy Gardner, Joao Alpedrinha, Stuart A WestAbstract:It is generally accepted that from a theoretical perspec- tive, Haplodiploidy should facilitate the evolution of eusociality. How- ever, the "Haplodiploidy hypothesis" rests on theoretical arguments that were made before recent advances in our empirical understand- ing of sex allocation and the route by which eusociality evolved. Here we show that several possible promoters of the Haplodiploidy effect would have been unimportant on the route to eusociality, because they involve traits that evolved only after eusociality had become established. We then focus on two biological mechanisms that could have played a role: split sex ratios as a result of either queen virginity or queen replacement. We find that these mechanisms can lead hap- lodiploidy to facilitating the evolution of helping but that their im- portance varies from appreciable to negligible, depending on the assumptions. Furthermore, under certain conditions, Haplodiploidy can even inhibit the evolution of helping. In contrast, we find that the level of promiscuity has a strong and consistently negative in- fluence on selection for helping. Consequently, from a relatedness perspective, monogamy is likely to have been a more important driver of eusociality than the Haplodiploidy effect.
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Kin discrimination and sex ratios in a parasitoid wasp
Journal of evolutionary biology, 2003Co-Authors: Sarah E. Reece, David M. Shuker, Ido Pen, Alison B. Duncan, A Choudhary, C M Batchelor, Stuart A WestAbstract:Sex ratio theory provides a clear and simple way to test if nonsocial haplodiploid wasps can discriminate between kin and nonkin. Specifically, if females can discriminate siblings from nonrelatives, then they are expected to produce a higher proportion of daughters if they mate with a sibling. This prediction arises because in haplodiploids, inbreeding (sib-mating) causes a mother to be relatively more related to her daughters than her sons. Here we formally model this prediction for when multiple females lay eggs in a patch, and test it with the parasitoid wasp Nasonia vitripennis. Our results show that females do not adjust their sex ratio behaviour dependent upon whether they mate with a sibling or nonrelative, in response to either direct genetic or a range of indirect environmental cues. This suggests that females of N. vitripennis cannot discriminate between kin and nonkin. The implications of our results for the understanding of sex ratio and social evolution are discussed.
Laura Ross - One of the best experts on this subject based on the ideXlab platform.
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How to make a haploid male
Wiley, 2019Co-Authors: Laura Ross, Nicholas G. Davies, Andy GardnerAbstract:Abstract Haplodiploidy has evolved repeatedly among invertebrates, and appears to be associated with inbreeding. Evolutionary biologists have long debated the possible benefits for females in diplodiploid species to produce haploid sons–beginning their population's transition to Haplodiploidy–and whether inbreeding promotes or inhibits this transition. However, little attention has been given to what makes a haploid individual male rather than female, and whether the mechanism of sex determination may modulate the costs and benefits of male haploidy. We remedy this by performing a theoretical analysis of the origin and invasion of male haploidy across the full range of sex‐determination mechanisms and sib‐mating rates. We find that male haploidy is facilitated by three different mechanisms of sex determination–all involving male heterogamety–and impeded by the others. We also find that inbreeding does not pose an obvious evolutionary barrier, on account of a previously neglected sex‐ratio effect whereby the production of haploid sons leads to an abundance of granddaughters that is advantageous in the context of inbreeding. We find empirical support for these predictions in a survey of sex determination and inbreeding across haplodiploids and their sister taxa
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sex determination sex chromosomes and karyotype evolution in insects
Journal of Heredity, 2017Co-Authors: Heath Blackmon, Laura Ross, Doris BachtrogAbstract:: Insects harbor a tremendous diversity of sex determining mechanisms both within and between groups. For example, in some orders such as Hymenoptera, all members are haplodiploid, whereas Diptera contain species with homomorphic as well as male and female heterogametic sex chromosome systems or paternal genome elimination. We have established a large database on karyotypes and sex chromosomes in insects, containing information on over 13000 species covering 29 orders of insects. This database constitutes a unique starting point to report phylogenetic patterns on the distribution of sex determination mechanisms, sex chromosomes, and karyotypes among insects and allows us to test general theories on the evolutionary dynamics of karyotypes, sex chromosomes, and sex determination systems in a comparative framework. Phylogenetic analysis reveals that male heterogamety is the ancestral mode of sex determination in insects, and transitions to female heterogamety are extremely rare. Many insect orders harbor species with complex sex chromosomes, and gains and losses of the sex-limited chromosome are frequent in some groups. Haplodiploidy originated several times within insects, and parthenogenesis is rare but evolves frequently. Providing a single source to electronically access data previously distributed among more than 500 articles and books will not only accelerate analyses of the assembled data, but also provide a unique resource to guide research on which taxa are likely to be informative to address specific questions, for example, for genome sequencing projects or large-scale comparative studies.
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the evolutionary dynamics of Haplodiploidy genome architecture and haploid viability
Evolution, 2015Co-Authors: Heath Blackmon, Nate B Hardy, Laura RossAbstract:Haplodiploid reproduction, in which males are haploid and females are diploid, is widespread among animals, yet we understand little about the forces responsible for its evolution. The current theory is that Haplodiploidy has evolved through genetic conflicts, as it provides a transmission advantage to mothers. Male viability is thought to be a major limiting factor; diploid individuals tend to harbor many recessive lethal mutations. This theory predicts that the evolution of Haplodiploidy is more likely in male heterogametic lineages with few chromosomes, as genes on the X chromosome are often expressed in a haploid environment, and the fewer the chromosome number, the greater the proportion of the total genome that is X-linked. We test this prediction with comparative phylogenetic analyses of mites, among which Haplodiploidy has evolved repeatedly. We recover a negative correlation between chromosome number and Haplodiploidy, find evidence that low chromosome number evolved prior to Haplodiploidy, and that it is unlikely that diplodiploidy has reevolved from haplodiploid lineages of mites. These results are consistent with the predicted importance of haploid male viability.
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Haplodiploidy and the reproductive ecology of arthropods
Current opinion in insect science, 2015Co-Authors: Andres G De La Filia, Stevie A Bain, Laura RossAbstract:Approximately 15% of all arthropods reproduce through Haplodiploidy. Yet it is unclear how this mode of reproduction affects other aspects of reproductive ecology. In this review we outline predictions on how Haplodiploidy might affect mating system evolution, the evolution of traits under sexual or sexual antagonistic selection, sex allocation decisions and the evolution of parental care. We also give an overview of the phylogenetic distribution of Haplodiploidy. Finally, we discuss how comparisons between different types of Haplodiploidy (arrhenotoky, PGE with haploid vs somatically diploid males) might help to discriminate between the effects of virgin birth, haploid gene expression and those of haploid gene transmission.
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Haplodiploidy sex ratio adjustment and eusociality
The American Naturalist, 2013Co-Authors: Andy Gardner, Laura RossAbstract:Hamilton's "Haplodiploidy hypothesis" holds that inflated sororal relatedness has promoted altruistic sib rearing in haplodiploids, potentially explaining their apparent predisposition to eusociality. Here, we suggest that Haplodiploidy may instead promote eusociality simply by facilitating sex-ratio adjustment. Specifically, Haplodiploidy may enable sex-ratio bias toward the more helpful sex, owing to "local resource enhancement," and such sex-ratio bias may promote the evolution of helping by individuals of that sex, owing to the "rarer-sex effect." This could explain why Haplodiploidy appears to have been important for eusociality in taxa with only female helpers, such as ants, wasps, and bees, but not in taxa with both male and female helpers, such as termites.
Ido Pen - One of the best experts on this subject based on the ideXlab platform.
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queen worker conflict can drive the evolution of social polymorphism and split sex ratios in facultatively eusocial life cycles
Evolution, 2020Co-Authors: Andres E Quinones, Gil J B Henriques, Ido PenAbstract:Hamilton's idea that Haplodiploidy favors the evolution of altruism-the Haplodiploidy hypothesis-relies on the relatedness asymmetry between the sexes caused by the sex-specific ploidies. Theoretical work on the consequences of relatedness asymmetries has significantly improved our understanding of sex allocation and intracolony conflicts, but the importance of Haplodiploidy for the evolution of altruism came to be seen as minor. However, recently it was shown that Haplodiploidy can strongly favor the evolution of eusociality, provided additional "preadaptations" are also present, such as the production of multiple broods per season and maternal ability to bias offspring sex ratios. These results were obtained assuming no influence of workers on the sex ratio, even though worker control of the sex ratio is known to occur. Here, we model the evolution of sex-specific fratricide as a mechanism of worker control over the sex ratio. We show that fratricide can facilitate the initial evolution of helping. However, fratricide can also hamper the evolution of unconditional help. Instead, social polymorphism evolves a mixture of helping and dispersing offspring. Finally, we show that the co-evolution of sex-allocation strategies of workers (fratricide) and queens leads to a split production of the sexes, with some colonies specializing in males and others in females. Thus, the model predicts that fratricide spawns a diversity of co-existing life cycles that strongly vary in degree of sociality and sex ratios.
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a unified model of hymenopteran preadaptations that trigger the evolutionary transition to eusociality
Nature Communications, 2017Co-Authors: Andres E Quinones, Ido PenAbstract:Explaining the origin of eusociality, with strict division of labour between workers and reproductives, remains one of evolutionary biology's greatest challenges. Specific combinations of genetic, behavioural and demographic traits in Hymenoptera are thought to explain their relatively high frequency of eusociality, but quantitative models integrating such preadaptations are lacking. Here we use mathematical models to show that the joint evolution of helping behaviour and maternal sex ratio adjustment can synergistically trigger both a behavioural change from solitary to eusocial breeding, and a demographic change from a life cycle with two reproductive broods to a life cycle in which an unmated cohort of female workers precedes a final generation of dispersing reproductives. Specific suits of preadaptations are particularly favourable to the evolution of eusociality: lifetime monogamy, bivoltinism with male generation overlap, hibernation of mated females and Haplodiploidy with maternal sex ratio adjustment. The joint effects of these preadaptations may explain the abundance of eusociality in the Hymenoptera and its virtual absence in other haplodiploid lineages.
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The evolution of Haplodiploidy by male-killing endosymbionts: importance of population structure and endosymbiont mutualisms.
Journal of evolutionary biology, 2009Co-Authors: Bram Kuijper, Ido PenAbstract:Haplodiploid inheritance systems, characterized by male transmission of only their maternally inherited genomic elements, have evolved more than 20 times within the animal kingdom. A number of theoretical studies have argued that infection with certain male-killing endosymbionts can potentially lead to the evolution of Haplodiploidy. By explicitly investigating the coevolutionary dynamics between host and endosymbiont, we show that the assumptions of current models cannot explain the evolution of Haplodiploidy very well, as the endosymbiont will often go extinct in the long term. Here, we provide two additional mechanisms that can explain the stable evolution of Haplodiploidy by male-killing endosymbionts. First of all, a spatially structured population can facilitate the long-term persistence of Haplodiploidy, but this applies only when levels of inbreeding are very high. By contrast, endosymbionts that are mutualistic with their hosts provide a much more general and promising route to the stable evolution of Haplodiploidy. This model is the first to provide a formal explanation of the supposed association between the evolution of Haplodiploidy and the highly inbred lifestyles of some ancestors, while it also provides a hypothesis for the evolution of Haplodiploidy in more outbred ancestors.
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Kin discrimination and sex ratios in a parasitoid wasp
Journal of evolutionary biology, 2003Co-Authors: Sarah E. Reece, David M. Shuker, Ido Pen, Alison B. Duncan, A Choudhary, C M Batchelor, Stuart A WestAbstract:Sex ratio theory provides a clear and simple way to test if nonsocial haplodiploid wasps can discriminate between kin and nonkin. Specifically, if females can discriminate siblings from nonrelatives, then they are expected to produce a higher proportion of daughters if they mate with a sibling. This prediction arises because in haplodiploids, inbreeding (sib-mating) causes a mother to be relatively more related to her daughters than her sons. Here we formally model this prediction for when multiple females lay eggs in a patch, and test it with the parasitoid wasp Nasonia vitripennis. Our results show that females do not adjust their sex ratio behaviour dependent upon whether they mate with a sibling or nonrelative, in response to either direct genetic or a range of indirect environmental cues. This suggests that females of N. vitripennis cannot discriminate between kin and nonkin. The implications of our results for the understanding of sex ratio and social evolution are discussed.
Benjamin B. Normark - One of the best experts on this subject based on the ideXlab platform.
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Perspective: maternal kin groups and the origins of asymmetric genetic systems-genomic imprinting, Haplodiploidy, and parthenogenesis.
Evolution, 2006Co-Authors: Benjamin B. NormarkAbstract:The genetic systems of animals and plants are typically eumendelian. That is, an equal complement of autosomes is inherited from each of two parents, and at each locus, each parent's allele is equally likely to be expressed and equally likely to be transmitted. Genetic systems that violate any of these eumendelian symmetries are termed asymmetric and include parent-specific gene expression (PSGE), Haplodiploidy, thelytoky, and related systems. Asymmetric genetic systems typically arise in lineages with close associations between kin (gregarious siblings, brooding, or viviparity). To date, different explanatory frameworks have been proposed to account for each of the different asymmetric genetic systems. Haig's kinship theory of genomic imprinting argues that PSGE arises when kinship asymmetries between interacting kin create conflicts between maternally and paternally derived alleles. Greater maternal than paternal relatedness within groups selects for more “abstemious” expression of maternally derived alleles and more “greedy” expression of paternally derived alleles. Here, I argue that this process may also underlie origins of Haplodiploidy and many origins of thelytoky. The tendency for paternal alleles to be more “greedy” in maternal kin groups means that maternal-paternal conflict is not a zero-sum game: the maternal optimum will more closely correspond to the optimum for family groups and demes and for associated entities such as symbionts. Often in these circumstances, partial or complete suppression of paternal gene expression will evolve (Haplodiploidy, thelytoky), or other features of the life cycle will evolve to minimize the conflict (monogamy, inbreeding). Maternally transmitted cytoplasmic elements and maternally imprinted nuclear alleles have a shared interest in minimizing agonistic interactions between female siblings and may cooperate to exclude the paternal genome. Eusociality is the most dramatic expression of the conflict-reducing effects of Haplodiploidy, but its original and more widespread function may be suppression of intrafamilial cannibalism. In rare circumstances in which paternal gene products gain access to maternal physiology via a placenta, PSGE with greedy paternal gene expression can persist (e.g., in mammals).
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Haplodiploidy as an outcome of coevolution between male killing cytoplasmic elements and their hosts
Evolution, 2004Co-Authors: Benjamin B. NormarkAbstract:Haplodiploidy (encompassing both arrhenotoky and paternal genome elimination) could have originated from coevolution between male-killing endosymbiotic bacteria and their hosts. In insects, Haplodiploidy tends to arise in lineages that rely on maternally transmitted bacteria for nutrition and that have gregarious broods in which competition between siblings may occur. When siblings compete, there is strong selection on maternally transmitted elements to kill males. I consider a hypothetical bacterial phenotype that renders male zygotes effectively haploid by preventing chromosome decondensation in male-determining sperm nuclei. By causing high male mortality, such a phenotype can be advantageous to the bacterial lineage. By eliminating paternal genes, it can also be advantageous to the host female. A simple model shows that the host female will benefit under a wide range of values for the efficiency of resource re-allocation, the efficiency of transmission, and the viability of haploid males. This hypothesis helps to explain the ecological correlates of the origins of Haplodiploidy, as well as such otherwise puzzling phenomena as obligate cannibalism by male Micromalthus beetles, reversion to diploidy by aposymbiotic male stictococcid scale insects, and the bizarre genomic constitution of scale insect bacteriomes.
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THE EVOLUTION OF ALTERNATIVE GENETIC SYSTEMS IN INSECTS
Annual Review of Entomology, 2002Co-Authors: Benjamin B. NormarkAbstract:▪ Abstract There are three major classes of insect genetic systems: those with diploid males (diplodiploidy), those with effectively haploid males (Haplodiploidy), and those without males (thelytoky). Mixed systems, involving cyclic or facultative switching between thelytoky and either of the other systems, also occur. I present a classification of the genetic systems of insects and estimate the number of evolutionary transitions between them that have occurred. Obligate thelytoky has arisen from each of the other systems, and there is evidence that over 900 such origins have occurred. The number of origins of facultative thelytoky and the number of reversions from obligate thelytoky to facultative and cyclic thelytoky are difficult to estimate. The other transitions are few in number: five origins of cyclic thelytoky, eight origins of obligate Haplodiploidy (including paternal genome elimination), the strange case of Micromalthus, and the two reversions from Haplodiploidy to diplodiploidy in scale insect...
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Evolutionary radiation of an inbreeding haplodiploid beetle lineage (Curculionidae, Scolytinae)
Biological Journal of The Linnean Society, 2000Co-Authors: Bjarte H. Jordal, Benjamin B. Normark, Brian D. FarrellAbstract:Haplodiploidy is a highly unusual genetic system that has arisen at least 17 times in animals of varying lifestyles, but most of these haplodiploid lineages remain relatively poorly known. In particular, the ecological and genetic circumstances under which Haplodiploidy originates have been difficult to resolve. A recent molecular-phylogenetic study has resolved the phylogenetic position of the haplodiploid clade of scolytine beetles as the sister group of the genus Dryocoetes. Haplodiploid bark beetles are remarkable in that the entire clade of over 1300 species are apparently extreme (sib-mating) inbreeders, most of which cultivate fungi for food while some attack phloem, twigs or seeds. Here we present a much more detailed molecular-phylogenetic study of this clade. Using partial sequences of elongation factor 1-alpha and the mitochondrial small ribosomal subunit (12S), we reconstructed the phylogeny for 48 taxa within the haplodiploid clade, as well as two species of the diplodiploid sister genus Dryocoetes. Results indicate that the genus Ozopemon is the basal lineage of the haplodiploid clade. Since Ozopemon, Dryocoetes, and other outgroups are phloem-feeding, this strongly suggest that Haplodiploidy and inbreeding evolved in a phloem feeding ancestor. Following the divergence of Ozopemon there is a series of extremely short internodes near the base of the clade, suggesting a very rapid rate of diversification in early Miocene (based on fossil evidence and sequence divergence). Among the many substrates for breeding and food resources utilized within this species-rich clade, the cultivation of yeast-like ambrosia fungi in tunnels deep into the wood predominates (nearly 90% of the species). The number of transitions to feeding on such fungi was few, possibly only one, and is perhaps an irreversible transition. The habit of feeding on fungi cultured in xylem makes it possible for the beetles to use a great variety of plant taxa. This extreme resource generalism, in conjunction with the colonization advantage conferred by Haplodiploidy and inbreeding, may have promoted the rapid diversification of this clade.
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Regular ArticleEvolutionary radiation of an inbreeding haplodiploid beetle lineage (Curculionidae, Scolytinae)
Biological Journal of The Linnean Society, 2000Co-Authors: Bjarte H. Jordal, Benjamin B. Normark, Brian D. FarrellAbstract:Haplodiploidy is a highly unusual genetic system that has arisen at least 17 times in animals of varying lifestyles, but most of these haplodiploid lineages remain relatively poorly known. In particular, the ecological and genetic circumstances under which Haplodiploidy originates have been difficult to resolve. A recent molecular-phylogenetic study has resolved the phylogenetic position of the haplodiploid clade of scolytine beetles as the sister group of the genusDryocoetes . Haplodiploid bark beetles are remarkable in that the entire clade of over 1300 species are apparently extreme (sib-mating) inbreeders, most of which cultivate fungi for food while some attack phloem, twigs or seeds. Here we present a much more detailed molecular-phylogenetic study of this clade. Using partial sequences of elongation factor 1-alpha and the mitochondrial small ribosomal subunit (12S), we reconstructed the phylogeny for 48 taxa within the haplodiploid clade, as well as two species of the diplodiploid sister genus Dryocoetes. Results indicate that the genus Ozopemon is the basal lineage of the haplodiploid clade. Since Ozopemon, Dryocoetes, and other outgroups are phloem-feeding, this strongly suggest that Haplodiploidy and inbreeding evolved in a phloem feeding ancestor. Following the divergence ofOzopemon there is a series of extremely short internodes near the base of the clade, suggesting a very rapid rate of diversification in early Miocene (based on fossil evidence and sequence divergence). Among the many substrates for breeding and food resources utilized within this species-rich clade, the cultivation of yeast-like ambrosia fungi in tunnels deep into the wood predominates (nearly 90% of the species). The number of transitions to feeding on such fungi was few, possibly only one, and is perhaps an irreversible transition. The habit of feeding on fungi cultured in xylem makes it possible for the beetles to use a great variety of plant taxa. This extreme resource generalism, in conjunction with the colonization advantage conferred by Haplodiploidy and inbreeding, may have promoted the rapid diversification of this clade.
