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1.
Shan-Liang Xu Wei Zhou Ping Chen Jian-Kai Zhou Xiu Zou Chun-Lin Wang Dan-Li Wang Yun-Long Zhao 《Development genes and evolution》2014,224(3):147-157
The gene doublesex (dsx) has shown deep conservation in the sex determination in many organisms. Environmental stimuli initiate a switch in the reproductive strategy of Daphnia pulex from asexual to sexual reproduction; however, occasionally, changes in environmental conditions will not lead to this transition. So study genetic responses to environmental stimuli and the molecular basis for the switch of reproductive stages are urgently needed. Therefore, we isolated and sequenced a D. pulex doublesex1 gene (Dpdsx1) and analyzed its expression and location by quantitative polymerase chain reaction (qPCR) and whole-mount in situ hybridization in D. pulex during different stages of reproduction. The predicted amino acid sequence has 335 amino acids that contained one DM domain and one dimerization domain, which is characteristic of insect orthologs of Dsx. Real-time PCR showed that Dpdsx1 expression decreased significantly (P?<?0.05) in different reproductive stages in the following order: male, parthenogenetic female, ephippial female, resting egg, and juvenile female. Whole-mount in situ hybridization revealed that Dpdsx1 is expressed in the first antennae, first thoracic limb and compound eye in males, whereas expression levels in the corresponding sites of parthenogenetic and ephippial females were relatively weak. Dpdsx1 could not be detected in the gonads of males or ephippial and parthenogenetic females. Taken together, these different reproductive stages’ and sex specific expression patterns are regulated temporally and spatially. We speculate that Dpdsx1 may involve in switching different stages of reproduction and in sexual differentiation in D. pulex. 相似文献
2.
Cyclic parthenogenesis (heterogony) is a widespread reproductive mode found in diverse taxa such as digenean trematodes, gall
wasps, gall midges, aphids, cladocerans and rotifers. It is of particular interest as it combines the advantages of asexual
reproduction (rapid population growth) and sexual reproduction (recombination). Usually sexual reproduction is initiated when,
or slightly before, environmental conditions deteriorate, and often results in the production of resting stages. The optimal
timing of diapause induction must thus be under strong natural selection. Using the cladoceran Daphnia as a model system, we show here for the first time that the switch from parthenogenetic to sexual reproduction in a cyclical
parthenogenetic organism can be influenced by the chemical composition of food. Under crowding conditions Daphnia reproduced parthenogenetically with subitaneous eggs when fed the algal species Cryptomonas sp., but started the production of resting eggs when fed with the green algal species Scenedesmus obliquus. Supplementation experiments with lipids and especially proteins showed that the induction of resting egg production in two
clones of different Daphnia species was due to a dietary deficiency in the green alga. Hence, the low food quality induced a switch in the reproductive
mode that may contribute to optimal timing of the sexual reproduction of Daphnia in nature. Furthermore, our results have two other major implications: first, they suggest that protein compounds should
be added to the list of diet constituents potentially limiting or influencing Daphnia reproduction. Second, we show that the role of food quality goes far beyond the up to now documented effects of food quality
on somatic growth and trophic transfer efficiency of herbivores: due to its effects on sexual reproduction and the production
of resting eggs, food quality might influence genetic diversity and long-term persistence of Daphnia in lakes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Genotypic characteristics of the Cladocera 总被引:11,自引:10,他引:1
Paul D. N. Hebert 《Hydrobiologia》1987,145(1):183-193
Work on the genetics of cladocerans reproducing by cyclic parthenogenesis has indicated that populations usually include a
large number of genotypes, whose frequencies are in close approximation to Hardy-Weinberg equilibrium. Less diverse genotypic
arrays and pronounced instability in genotype frequencies occur only in permanent populations exposed to limited ephippial
recruitment. Genetic diversification among local cladoceran populations is greater than in most other organisms as a consequence
of the inefficiency of passive dispersal. Genotypic characteristics of cladocerans reproducing by obligate parthenogenesis
are markedly different from those of cyclic parthenogens. Local populations include few clones, but genetic distances between
them are often large and accompanied by significant ecological and morphological divergence. When considered over their entire
range, cladoceran taxa reproducing by obligate asexuality are the most genotypically diverse asexual organisms known. This
diversity has originated from the spread of a sex-limited meiosis suppressor through species that originally reproduced by
cyclic parthenogenesis. The confused state of cladoceran taxonomy is partially a consequence of the presence of such obligately
asexual groups, but also results from the occurrence of hybridization and sibling species. The genome size of cladocerans
is exceptionally small and is associated with a large amount of endopolyploidy. Somatic tissues in adult cladocerans show
a range in nuclear DNA content from 2–2048 c. DNA quantification studies have additionally revealed the frequent occurrence
of polyploid clones in obligately asexual taxa. 相似文献
4.
Life-history changes that accompany the transition from sexual to parthenogenetic reproduction in Drosophila mercatorum 总被引:1,自引:0,他引:1
In spite of the predicted genetic and ecological costs of sex, most natural populations maintain sexual reproduction, even those capable of facultative parthenogenesis. Unfertilized eggs from natural populations of Drosophila mercatorum occasionally develop into viable adults, but obligately parthenogenetic populations are unknown in this species. To evaluate the microevolutionary forces that both favor and constrain the evolution of parthenogenesis in D. mercatorum, we have measured parthenogenetic rates across a natural, sexually reproducing population and characterized the life-history changes that accompany the transition from sexual to parthenogenetic reproduction in laboratory strains. A highly significant difference in parthenogenetic rate was found between two populations in close geographic proximity, with increased rate found with lower population density. Laboratory strains of parthenogenetic females suffered increased mortality and reduced egg viability relative to their virgin counterparts from a sexual strain. Lifetime egg production was similar across all strains, but a shift in peak egg production to an earlier age also occurred. The combination of these life-history traits resulted in a higher net reproductive value for sexual females, but because they also had a longer generation time, intrinsic rate of increase was not as dramatically different from parthenogenetic females. In environments with high early mortality, there may be no fitness disadvantage to parthenogenesis, but the predicted ecological advantage of a twofold increase in intrinsic rate of increase was not realized. These results support the theory of Stalker (1956) that parthenogenesis is favored in environments in which sexual reproduction is difficult or impossible. 相似文献
5.
The influence of changing temperature on the life history of Daphniopsis ephemeralis 总被引:1,自引:0,他引:1
We present evidence which suggests that for Daphniopsis ephemeralischanges in water temperature may directly cue changes in sexratio, ephippial and parthenogenetic egg production and indirectlydetermine female body size. Field data suggested that over anannual cycle, a population of D. ephemeralis comprised animalswith three distinct life history phases. The first was madeup of exephippial females which hatched in the fall. They produceda second group made up of large parthenogenetic females whichcould produce more than one overwintering generation. In thespring these parthenogenetic females gave rise to a third lifehistory phase which comprised males and small ephippial females.Field enclosure experiments suggested that the small size ofspring females was not related to predation. Laboratory experimentssuggested that ephippial egg production at small body sizeswas associated with increasing temperature. Theseexperiments also suggested that the fall reproductive pattern(parthenogenetic eggs and large body sizes) was associated withdecreasing temperatures. We conclude that directionalityof seasonal temperature change may be the prime factor responsiblefor D. ephemeralis life history changes observed in the field. 相似文献
6.
Curtis M. Lively 《Evolution; international journal of organic evolution》1992,46(4):907-913
Two alternative (but not mutually exclusive) hypotheses were contrasted for their abilities to explain the distribution of parthenogenesis in the freshwater snail Potamopyrgus antipodarum: the reproductive assurance hypothesis, which predicts that parthenogenesis will be favored in sparse populations where mates are difficult to find, and the Red Queen hypothesis, which predicts that parthenogenesis will be favored in populations that have a low risk of parasitism. The results were inconsistent with the prediction of the reproductive assurance hypothesis; male frequency was not significantly or positively correlated with snail density. Thus, there was no support for any of the hypotheses for the maintenance of sex that rely on selection for reproductive assurance to explain the distribution of parthenogenesis (e.g., recombinational repair). The results, however, were consistent with the Red Queen hypothesis; male frequency was positively and significantly correlated with the frequency of individuals infected by trematodes. This correlation suggests that parthenogenetic females have replaced sexual females in populations where parasites are rare, and that sexual females have persisted in populations where parasites are common. 相似文献
7.
John J. Gilbert 《Freshwater Biology》2004,49(11):1505-1515
1. In the heterogonic life cycle of monogonont rotifers, amictic (female‐producing) females develop from two types of eggs: fertilised resting (diapausing) eggs and parthenogenetic subitaneous eggs. Females hatched from resting eggs initiate clonal populations by female parthenogenesis and are called stem females. This study compares females from resting and parthenogenetic eggs that were produced under identical culture conditions and were of similar birth order. 2. Newborn stem females had many more lipid droplets in their tissues than similar‐sized, newborn females from parthenogenetic eggs. When neonates were stained with Nile Red and viewed under epifluorescent illumination, these droplets were shown to be sites of neutral‐lipid storage products. 3. Stem females had no posterolateral spines and short anterior spines, while their mothers and offspring in subsequent, parthenogenetic generations typically had long posterolateral spines and elongated anterior spines. 4. Newborn stem females survived starvation significantly longer than newborn females from parthenogenetic eggs. 5. When females from resting and parthenogenetic eggs were cultured from birth to death at a high food concentration, the reproductive potential (r day?1) of the stem females was significantly higher (0.82–0.88 versus 0.70), primarily because of egg production at an earlier age. The mean lifetime fecundity (Ro) of stem females was significantly greater than that of females from parthenogenetic eggs. 6. Extensive lipid reserves should increase the ability of stem females to colonise new habitats. Firstly, compared with females from parthenogenetic eggs, stem females are more likely to experience starvation or food limitation. Resting eggs hatch in response to physical and chemical factors that are not directly related to food availability, and from sediments that may be far from food‐rich surface waters. Secondly, when food is abundant, stem females have a greater reproductive potential. 相似文献
8.
Worldwide, parthenogenetic reproduction has evolved many times in the stick insects (Phasmatidae). Many parthenogenetic stick insects show the distribution pattern known as geographic parthenogenesis, in that they occupy habitats that are at higher altitude or latitude compared with their sexual relatives. Although it is often assumed that, in the short term, parthenogenetic populations will have a reproductive advantage over sexual populations; this is not necessarily the case. We present data on the distribution and evolutionary relationships of sexual and asexual populations of the New Zealand stick insect, Clitarchus hookeri. Males are common in the northern half of the species’ range but rare or absent elsewhere, and we found that most C. hookeri from putative‐parthenogenetic populations share a common ancestor. Female stick insects from bisexual populations of Clitarchus hookeri are capable of parthenogenetic reproduction, but those insects from putative‐parthenogenetic populations produced few offspring via sexual reproduction when males were available. We found similar fertility (hatching success) in mated and virgin females. Mated females produce equal numbers of male and female offspring, with most hatching about 9–16 weeks after laying. In contrast, most eggs from unmated females took longer to hatch (21–23 weeks), and most offspring were female. It appears that all C. hookeri females are capable of parthenogenetic reproduction, and thus could benefit from the numerical advantage this yields. Nevertheless, our phylogeographic evidence shows that the majority of all‐female populations over a wide geographic area originate from a single loss of sexual reproduction. 相似文献
9.
We calibrated four stages of hypodermal retraction and cuticle regeneration with five stages of parthenogenetic egg development in Daphnia. Using the hypodermal retraction stages, we found that epibiotic burden increased with elapsed intermolt time for juvenile, male, and female Daphnia bearing parthenogenetic or ephippial eggs. The rate of increase of burden was similar for adult females of two Daphnia species and for males and females of D. pulex. Rate of increase of burden was similar between juvenile and adult females of D. galeata mendotae and D. pulex. 相似文献
10.
C. Pérez-Martínez J. Barea-Arco J. M. Conde-Porcuna R. Morales-Baquero 《Hydrobiologia》2007,594(1):75-82
For three consecutive years, a population study of Daphnia pulicaria was undertaken in Río Seco Lake, a small high-mountain lake, in order to elucidate the reproductive strategies adopted by
Daphnia in this system. Daphnia appears to colonize this lake every spring by hatching from ephippia and reproduce by means of subitaneous (non-diapausing)
and ephippial (diapausing) eggs. D. pulicaria in this lake is an obligate parthenogenetic population. There is a short time period for subitaneous egg production and a
much longer period for ephippial egg production. The contribution of subitaneous eggs to Daphnia population density and structure appears to be low. Diapause onset showed a high temporal synchronization in the three studied
years in Río Seco Lake, and day-length emerged as the main cue triggering diapause onset and the main explanatory factor for
the proportion of ephippial females observed. The development and reproduction of D. pulicaria in Río Seco Lake involves taking a gamble on resting forms to guarantee inter-annual Daphnia persistence in the lake, giving priority to investment in future generations.
Guest editor: Piet Spaak
Cladocera: Proceedings of the 7th International Symposium on Cladocera 相似文献
11.
Maternal effects can significantly impact offspring performance. Provisioning of offspring with energy stores can quantitatively alter their growth rates, survivorship, and future fecundity, and influence population regulatory mechanisms. In this paper, we show that maternal effects can also qualitatively affect offspring reproduction (i.e. their mode of reproduction). The freshwater herbivore Daphnia pulex can change the amount of energy allocated between asexual and ephippial egg production. Our experiments on individuals, experiencing “step‐up” or “step‐down” food manipulations, reveal that offspring qualitatively shift their energy allocation away from asexual reproduction to ephippial egg production when there is a simple mismatch between maternal and offspring food environments. We show that the response is asymmetric with respect to changes in food level, ephippial egg production is higher with a greater mismatch between environments, and that the effect can be observed in dynamic experimental populations. These results point to a “generational memory” that could challenge our interpretation of field patterns and mechanisms influencing population dynamics in Daphnia–algal systems. 相似文献
12.
Paul D. N. Hebert Margaret J. Beaton Steven S. Schwartz David J. Stanton 《Evolution; international journal of organic evolution》1989,43(5):1004-1015
There is growing evidence that transitions from sexual to asexual reproduction are often provoked by internal genetic factors rather than extrinsic selection pressures. In the cladoceran crustacean Daphnia pulex, the shift to asexuality has been linked to sex-limited meiosis suppression. Most populations of this species reproduce by obligate parthenogenesis, but cyclically parthenogenetic populations persist in the southern portion of its range. The meiosis-suppressor model predicts that asexuality in D. pulex has polyphyletic origins and that the coexistence of cyclically parthenogenetic lines with male-producing obligately asexual clones should be unstable. For the present study, we examined the genotypic structure of D. pulex populations from a region in which there is an abrupt microgeographical shift in breeding system. Populations in Michigan largely reproduce by cyclic parthenogenesis, while those in Ontario are obligately asexual. Allozyme studies on 77 populations from this area revealed 50 obligately asexual clones, divisible into two groups: one derived from a single parent species and the other derived via interspecific hybridization. Although nearly 50% of the clones retained male production, there was, as predicted, no evidence of coexistence between cyclically parthenogenetic populations and male-producing obligately asexual clones. The survey did, however, reveal a low incidence of cyclically parthenogenetic populations in Ontario. The high genotypic diversity of these populations suggests that they are not only resistant to meiosis suppression, but able to rework genetic variation gained from asexual clones into a sexual breeding system. 相似文献
13.
Asexual reproduction could offer up to a two‐fold fitness advantage over sexual reproduction, yet higher organisms usually reproduce sexually. Even in facultatively parthenogenetic species, where both sexual and asexual reproduction is sometimes possible, asexual reproduction is rare. Thus, the debate over the evolution of sex has focused on ecological and mutation‐elimination advantages of sex. An alternative explanation for the predominance of sex is that it is difficult for an organism to accomplish asexual reproduction once sexual reproduction has evolved. Difficulty in returning to asexuality could reflect developmental or genetic constraints. Here, we investigate the role of genetic factors in limiting asexual reproduction in Nauphoeta cinerea, an African cockroach with facultative parthenogenesis that nearly always reproduces sexually. We show that when N. cinerea females do reproduce asexually, offspring are genetically identical to their mothers. However, asexual reproduction is limited to a nonrandom subset of the genotypes in the population. Only females that have a high level of heterozygosity are capable of parthenogenetic reproduction and there is a strong familial influence on the ability to reproduce parthenogenetically. Although the mechanism by which genetic variation facilitates asexual reproduction is unknown, we suggest that heterosis may facilitate the switch from producing haploid meiotic eggs to diploid, essentially mitotic, eggs. 相似文献
14.
Parthenogenesis has evolved independently in more than 10 Drosophila species. Most cases are tychoparthenogenesis, which is occasional or accidental parthenogenesis in normally bisexual species with a low hatching rate of eggs produced by virgin females; this form is presumed to be an early stage of parthenogenesis. To address how parthenogenesis and sexual reproduction coexist in Drosophila populations, we investigated several reproductive traits, including the fertility, parthenogenetic capability, diploidization mechanisms, and mating propensity of parthenogenetic D. albomicans. The fertility of mated parthenogenetic females was significantly higher than that of virgin females. The mated females could still produce parthenogenetic offspring but predominantly produced offspring by sexual reproduction. Both mated parthenogenetic females and their parthenogenetic-sexual descendants were capable of parthenogenesis. The alleles responsible for parthenogenesis can be propagated through both parthenogenesis and sexual reproduction. As diploidy is restored predominantly by gamete duplication, heterozygosity would be very low in parthenogenetic individuals. Hence, genetic variation in parthenogenetic genomes would result from sexual reproduction. The mating propensity of females after more than 20 years of isolation from males was decreased. If mutations reducing mating propensities could occur under male-limited conditions in natural populations, decreased mating propensity might accelerate tychoparthenogenesis through a positive feedback mechanism. This process provides an opportunity for the evolution of obligate parthenogenesis. Therefore, the persistence of facultative parthenogenesis may be an adaptive reproductive strategy in Drosophila when a few founders colonize a new niche or when small populations are distributed at the edge of a species'' range, consistent with models of geographical parthenogenesis. 相似文献
15.
Microbe-associated parthenogenesis (thelytoky) has been discovered in nineTrichogramma species, parasitoids of mainly lepidopteran eggs. Parthenogenetic and bisexual conspecifics co-occur in many field populations.
As an initial step to understand the dynamics of these two reproductive strategies we studied the effect of microbe-associated
parthenogenesis on fecundity. The fecundity of two parthenogenetic isofemale lines ofT. pretiosum and one ofT. deion was compared with bisexual lines derived from them by antibiotic treatment. In all three cases parthenogenetic females were
less fecund over their lifetime than bisexual females. Also, parthenogenetic females produced fewer daughters in two cases
and in one case a similar number of daughters as their respective bisexual counterparts. The lack of mating and insemination
was excluded as an explanation for the reduced fecundity of parthenogenetic females, because mated and virgin parthenogenetic
females produce the same number of offspring. Antibiotic treatment can also be excluded because females of field-collected
bisexual line treated with antibiotics produced the same number of offspring as untreated females. The reduced fecundity of
parthenogenetic females was caused by a lower number of eggs being laid rather than by a greater developmental mortality.
Parthenogenetic females produced less daughters than bisexual females when host availability was not limiting, but when host
availability was severely limited, parthenogenetic females produced more daughters than the bisexual females. 相似文献
16.
Crowding is known to have a major influence on reproduction in the freshwater microcrustacean Daphnia pulex. We analyzed reproductive output of six different D. pulex genotypes under two different density regimes in the laboratory. Four of these genotypes reproduce via obligate parthenogenesis,
allowing thorough analysis of the life history strategies of some asexual lines. Among 30,109 neonate offspring and 1041 resting
egg ephippia collected, several trends were evident. Crowding induced increased resting egg production and reduced neonate
offspring production among all genotypes. Offspring sex ratios grew more male-biased with maternal age. The extent, but not
direction, of each of these trends varied among genotypes. Offspring sex ratios, and the very direction in which they changed
in response to crowding, differed significantly among genotypes with some genotypes producing more and others fewer males
in response to crowding. Obligately parthenogenetic genotypes seemed to respond to the crowding stimulus in similar ways as
the facultatively parthenogenetic genotypes, as expected from the sexual origins of their genomes. The inter-genotype variation
in life-history traits observed in this and other investigations calls into question the common practice of extrapolating
results from a single Daphnia genotype to an entire species. Our findings are considered in the context of other research in the field of environmental
influences on Daphnia reproduction with a review of representative literature. 相似文献
17.
The problem of the maintenance of anisogamous sex is addressed by considering the effect of fertilization on the fitness of parthenogenetic females when such fertilization yields inviable triploid progeny. We consider four types of parthenogenesis: (i) apomixis, (ii) homogametic amphimixis, (iii) heterogametic amphimixis, and (iv) homogametic automixis. Homozygous sexual populations are genetically stable if males or selection eliminate the excess females produced by heterozygous parthenogenetic genotypes. Homozygous parthenogenetic populations are stable if the parthenogenetic output of homozygotes exceeds that of heterozygotes. In turn, sex can only invade heterozygous parthenogenetic populations when sexual output of parthenogens is larger than their parthenogenetic output. The existence of interior stable equilibria generally requires the instability of at least one boundary and some degree of heterosis. In a two-locus model, we study the evolution of mechanisms protecting either sex or parthenogenesis in reproductively polymorphic populations. We find that males do not respond to the presence of parthenogenesis in such a way as to eliminate it, but parthenogenesis is subject to selective pressures increasing reproductive isolation, and thus the success of parthenogenesis. The results suggest that reproductively polymorphic populations are ephemeral. 相似文献
18.
Populations of the vernal cladoceranDaphniopsis ephemeralis are found in woodland ponds throughout southern Ontario. The species reproduces by cyclic parthenogenesis, and genotype frequencies
at allozyme loci are ordinarily in good agreement with Hardy-Weinberg expectations. Occasional heterozygote deficiencies are
apparently the consequence of admixture of ephippial hatchlings produced in temporally separated bouts of sexual reproduction.
Considerable heterogeneity in genotypic frequencies exists among local populations in southwestern Ontario, indicating that
gene flow among populations is restricted. Inbreeding coefficients suggest that populations receive an average of 0.3 migrants
per generation. The completion of a sexual life cycle is made possible despite the brief persistence of populations by the
emergence of males from ephippial eggs and by the production of equal numbers of male and female progeny in the first parthenogenetic
brood. 相似文献
19.
Cyclical parthenogenesis presents an interesting challenge for the study of sex allocation, as individuals’ allocation decisions involve both the choice between sexual and asexual reproduction, and the choice between sons and daughters. Male production is therefore expected to depend on ecological and evolutionary drivers of overall investment in sex, and those influencing male reproductive value during sexual periods. We manipulated experimental populations, and made repeated observations of natural populations over their growing season, to disentangle effects of population density and the timing of sex from effects of adult sex ratio on sex allocation in cyclically parthenogenetic Daphnia magna. Male production increased with population density, the major ecological driver of sexual reproduction; however, this response was dampened when the population sex ratio was more male‐biased. Thus, in line with sex ratio theory, we show that D. magna adjust offspring sex allocation in response to the current population sex ratio. 相似文献
20.
The thelytokous parasitoid, Eretmocerus mundus (Australian parthenogenetic form) was infected with a species of Group B Wolbachia. Antibiotic treatment of the parasitoid cured parthenogenesis and lead to male production and reduced egg hatching by virgin females. For each generation infected females produced more progeny than cured females. The descendants of individuals treated with antibiotic were in most cases free of a detectable infection. Both treated females and descendant females mated and received sperm, but these were not used as mated and unmated cured females produced offspring with a similar sex ratio. Males produced as a result of the antibiotic treatment were at least partially functional as they produced sperm and copulated with and inseminated females. However, no sexual line could be established. 相似文献