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1.
In colonies of the queen‐polymorphic ant Vollenhovia emeryi, some colonies produce only long‐winged (L) queens, while others produce only short‐winged (S) queens. At four nuclear microsatellite loci, males in the S colony had alleles that were different from those of their queen. This suggests that the nuclear genome of males is not inherited from their colony queen, as has also been described for Wasmannia auropunctata (Roger). In V. emeryi the possibility of male transfer from other colonies has not been ruled out because previous studies of this species have obtained only nuclear gene information. We analyzed both mitochondrial and nuclear genes for S queens, S males and L queens to clarify the origins of males. Sequence analyses showed that although S queens and S males shared the same mtDNA haplotype, they had a different genotype at a nuclear gene (long‐wavelength opsin) locus. Neighbor‐joining analysis based on the four microsatellite loci also suggested gene pool separation between S queens and S males. These results are consistent with predictions of clonal reproduction by males. While L queens share opsin genotypes with S males, they have very different mtDNA sequences. Hybridization in the near past between S queens and L males or gene transmission from S males to L queen populations in the present would explain these differences. 相似文献
2.
Angelica Ardehed Daniel Johansson Ellen Schagerström Lena Kautsky Kerstin Johannesson Ricardo T. Pereyra 《Ecology and evolution》2015,5(19):4233-4245
In dioecious species with both sexual and asexual reproduction, the spatial distribution of individual clones affects the potential for sexual reproduction and local adaptation. The seaweed Fucus radicans, endemic to the Baltic Sea, has separate sexes, but new attached thalli may also form asexually. We mapped the spatial distribution of clones (multilocus genotypes, MLGs) over macrogeographic (>500 km) and microgeographic (<100 m) scales in the Baltic Sea to assess the relationship between clonal spatial structure, sexual recruitment, and the potential for natural selection. Sexual recruitment was predominant in some areas, while in others asexual recruitment dominated. Where clones of both sexes were locally intermingled, sexual recruitment was nevertheless low. In some highly clonal populations, the sex ratio was strongly skewed due to dominance of one or a few clones of the same sex. The two largest clones (one female and one male) were distributed over 100–550 km of coast and accompanied by small and local MLGs formed by somatic mutations and differing by 1–2 mutations from the large clones. Rare sexual events, occasional long‐distance migration, and somatic mutations contribute new genotypic variation potentially available to natural selection. However, dominance of a few very large (and presumably old) clones over extensive spatial and temporal scales suggested that either these have superior traits or natural selection has only been marginally involved in the structuring of genotypes. 相似文献
3.
K. L. Haag E. Sheikh‐Jabbari F. Ben‐Ami D. Ebert 《Journal of evolutionary biology》2013,26(5):1117-1128
Assessing the mode of reproduction of microparasites remains a difficult task because direct evidence for sexual processes is often absent and the biological covariates of sex and asex are poorly known. Species with geographically divergent modes of reproduction offer the possibility to explore some of these covariates, for example, the influence of life‐history traits, mode of transmission and life‐cycle complexity. Here, we present a phylogeographical study of a microsporidian parasite, which allows us to relate population genetic structure and mode of reproduction to its geographically diverged life histories. We show that in microsporidians from the genus Hamiltosporidium, that use the cladoceran Daphnia as host, an epidemic population structure has evolved, most probably since the last Ice Age. We partially sequenced three housekeeping genes (alpha tubulin, beta tubulin and hsp70) and genotyped seven microsatellite loci in 51 Hamiltosporidium isolates sampled within Europe and the Middle East. We found two phylogenetically related asexual parasite lines, one each from Fennoscandia and Israel, which share the unique ability of being transmitted both vertically and horizontally from Daphnia to Daphnia. The sexual forms cannot transmit horizontally among Daphnia, but presumably have a complex life cycle with a second host species. In spite of the similarities between the two asexual lineages, a clustering analysis based on microsatellite polymorphisms shows that asexual Fennoscandian parasites do not share ancestry with any other Hamiltosporidium that we have sampled. Moreover, allele sequence divergence at the hsp70 locus is twice as large in Fennoscandian than in Israeli parasites. Our results indicate that asexual reproduction evolved twice independently, first in Fennoscandian and more recently in the Israeli parasites. We conclude that the independent origin of asexuality in these two populations is associated with the altered parasite mode of transmission and the underlying dynamics of host populations. 相似文献
4.
Diana Kim John Waller Andrea S. Aspbury Caitlin R. Gabor 《Ethology : formerly Zeitschrift fur Tierpsychologie》2014,120(11):1053-1061
Gynogenetic species rely on sperm from heterospecifics for reproduction but do not receive genetic benefits from mating because none of the paternal genome is incorporated into offspring. The gynogenetic Amazon molly (Poecilia formosa) is a species of hybrid origins that are sympatric with one of the two parent species that provide sperm for reproduction, P. latipinna or P. mexicana. Amazons should not prefer to mate with one species over the other because sperm from both species will trigger embryogenesis, but mating preferences may be present in Amazons through other mechanisms. Amazons may prefer the more familiar species (males found in sympatry), or Amazons may prefer males with the greatest lateral projection area (LPA), a preference that is present in the parent species and may be retained within the Amazon hybrid genome. We tested association preferences of two populations of Amazons sympatric with either P. mexicana or P. latipinna. We first performed live trials to test whether Amazons preferred one host species over the other and found that neither population of Amazons showed a preference. We then tested whether Amazons preferred sympatric male (familiar) host or the male with the greatest lateral projection area (LPA) using four animated male models that varied in host species and manipulation of LPA. We found Amazons from a population sympatric with P. latipinna showed no variation in their association preference across the different models. In contrast, Amazons from a population sympatric with P. mexicana (naturally small LPA) spent more time associating with the male models that had smaller LPA, which is more familiar to this population of Amazons. We suggest that Amazons may have population differences in mating preferences, where Amazons sympatric with P. latipinna may not show mating preference for host species, but Amazons sympatric with P. mexicana may show preferences for more familiar‐shaped males. 相似文献
5.
半夏的繁殖生物学研究 总被引：26，自引：0，他引：26
对“泰半夏”（Ｐｉｎｅｌｌｉａｔｅｒｎａｔａ（Ｔｈｕｎｂ．）Ｂｒｅｉｔ．）的块茎和珠芽栽培观察结果表明：（１）不同繁殖体的叶形和珠芽所发生的变化与实验用的播种材料有关,珠芽发生频率与叶形变化呈正相关;（２）半夏倒苗既是对不利环境条件的一种适应,也是一种有效的无性繁殖方式;（３）半夏有性繁殖是属于同株异花传粉类型,但与无性繁殖相比,有性繁殖在种质繁衍上仅起着次要作用。 相似文献
6.
Y. Kohli L. J. Brunner H. YOELL M. G. Milgroom† J. B. Anderson R. A. A. Morrall‡ L. M. Kohn 《Molecular ecology》1995,4(1):69-77
Two thousand seven hundred and forty-seven isolates of Sclerotinia sclerotiorum were sampled from four field populations of canola in western Canada. Each field was sampled in a grid of 128 50-m 50-m quadrats plus four intensive quadrats each sampled in a diagonal transect. Sampling was done at two phases of the disease cycle: (1) from ascospore inoculum on petals and (2) from disease lesions in stems. A total of 594 unique genotypes was identified by DNA fingerprinting. In each field, a small group of clones represented the majority of the sample, with a large group of clones or genotypes sampled once or twice. Clone frequencies were compared by χ2 tests. The difference in profiles of clone frequencies for the two fields sampled in 1991 was not significant, but in 1992 the difference in profiles was marginally significant, indicating some local population substructure. The difference in profiles of clone frequencies for petals and lesions was not significant in each of the two fields sampled in 1991. In each of the two fields sampled in 1992, however, the difference was highly significant, consistent either with selection for some clones or with waves of immigration during the disease cycle. Nine of the 30 most frequently sampled clones from this study were previously recovered in a macrogeographical sample from western Canada in 1990. For spatial analyses, randomization tests indicated no significant spatial aggregation of either clones on petals or clones from lesions. Also, isolates of a clone on petals were not closer to isolates of the same clone from lesions than could be predicted by chance. Both observations suggest spatial mixing of ascospore inoculum from resident or immigrant sources. 相似文献
7.
Daniel Johansson Karl H. Larsson Cecilia J. Huenchuñir Jens Perus Helena Forslund Lena Kautsky Ricardo T. Pereyra 《Journal of phycology》2011,47(5):990-998
Asexual reproduction by cloning may affect the genetic structure of populations, their potential to evolve, and, among foundation species, contributions to ecosystem functions. Macroalgae of the genus Fucus are known to produce attached plants only by sexual recruitment. Recently, however, clones of attached plants recruited by asexual reproduction were observed in a few populations of Fucus radicans Bergström et L. Kautsky and F. vesiculosus L. inside the Baltic Sea. Herein we assess the distribution and prevalence of clonality in Baltic fucoids using nine polymorphic microsatellite loci and samples of F. radicans and F. vesiculosus from 13 Baltic sites. Clonality was more common in F. radicans than in F. vesiculosus, and in both species it tended to be most common in northern Baltic sites, although variation among close populations was sometimes extensive. Individual clonal lineages were mostly restricted to single or nearby locations, but one clonal lineage of F. radicans dominated five of 10 populations and was widely distributed over 550 × 100 km of coast. Populations dominated by a few clonal lineages were common in F. radicans, and these were less genetically variable than in other populations. As thalli recruited by cloning produced gametes, a possible explanation for this reduced genetic variation is that dominance of one or a few clonal lineages biases the gamete pool resulting in a decreased effective population size and thereby loss of genetic variation by genetic drift. Baltic fucoids are important habitat‐forming species, and genetic structure and presence of clonality have implications for conservation strategies. 相似文献
8.
Peter Mikulíček Matej Kautman Ján Kautman Nicolas B. M. Pruvost 《Journal of Zoological Systematics and Evolutionary Research》2015,53(2):124-132
Coexistence of sperm‐dependent asexual hybrids with their sexual progenitors depends on genetic and ecological interactions between sexual and asexual forms. In this study, we investigate genotypic composition, modes of hybridogenetic gametogenesis and habitat preferences of European water frogs (Pelophylax esculentus complex) in a region of sympatric occurrence. Pelophylax esculentus complex comprises parental species P. ridibundus and P. lessonae, whose primary hybridization leads to hybridogenetic lineages of P. esculentus. Hybrids clonally transmit one parental genome and mate with the other parental species, forming a new generation of hybrids. In the region of western Slovakia, we found syntopic occurrence of diploid and triploid hybrids with P. lessonae, syntopic occurrence of all three taxa as well as the existence of pure P. ridibundus populations. All triploid hybrids were exclusively male possessing one ridibundus and two different lessonae genomes (RLL). Sex ratio in diploid hybrids was substantially female‐biased. Irrespective of the population composition, diploid hybrids excluded the lessonae genome from their germ line and produced ridibundus gametes. Contrarily, RLL males unequivocally eliminated the ridibundus genome and produced diploid lessonae sperms. Perpetuation of RLL males in studied populations is most likely achieved by their mating with diploid hybrid females. The composition of water frog populations is also shaped by taxon‐specific habitat preferences. While P. ridibundus preferred larger water bodies (gravelpits, fishery ponds, dead river arms), P. lessonae was most frequently found in marshes and smaller sandpits. Pelophylax esculentus occupied predominately similar habitats as its sexual host P. lessonae. 相似文献
9.
The insect-pollinated forest tree Tilia cordata Mill. grows today in small fragmented populations in Denmark and other western European countries but was, in prehistoric times, a dominating species and is considered an indicator species for ancient forest. The species is known to propagate both sexually and vegetatively, forming clonal groups. Few studies have been made on the species' population genetics and on how clonality affects the population structure. The aim of this study is to evaluate the Danish gene pool by estimating genetic diversity and differentiation, as well as through exhaustive sampling describe clonal structures in some of the populations. Genetic analysis was carried out using nine nuclear microsatellite markers in nine populations, of which four were exhaustively or partly exhaustively sampled. The markers showed a high degree of genetic diversity but low differentiation between populations, with no geographic-related structure. Clonal structures were found in eight out of the nine populations. In the exhaustively sampled populations, recruitment strategies included both sexual and clonal reproduction with indications that clonality may be enhanced by management and other disturbances. 相似文献
10.
The mode of reproduction of microsporidian parasites has remained puzzling since many decades. It is generally accepted that microsporidia are capable of sexual reproduction, and that some species have switched to obligate asexuality, but such process had never been supported with population genetic evidence. We examine the mode of reproduction of Hamiltosporidium tvaerminnensis and Hamiltosporidium magnivora, two closely related microsporidian parasites of the widespread freshwater crustacean Daphnia magna, based on a set of 129 single‐nucleotide polymorphisms distributed across 16 genes. We analyse 20 H. tvaerminnensis isolates from localities representative of the entire species' geographic distribution along the Skerry Island belt of the Baltic Sea. Five isolates of the sister species H. magnivora were used for comparison. We estimate the recombination rates in H. tvaerminnensis to be at least eight orders of magnitude lower than in H. magnivora and not significantly different from zero. This is corroborated by the higher divergence between H. tvaerminnensis alleles (including fixed heterozygosity), as compared to H. magnivora. Our study confirms that sexual recombination is present in microsporidia, that it can be lost, and that asexuals may become epidemic. 相似文献
11.
In the ocean, large‐scale dispersal and replenishment by larvae is a key process underlying biological changes associated with global warming. On tropical reefs, coral bleaching, degradation of habitat and declining adult stocks are also likely to change contemporary patterns of dispersal and gene flow and may lead to range contractions or expansions. On the Great Barrier Reef, where adjacent reefs form a highly interconnected system, we use allozyme surveys of c. 3000 coral colonies to show that populations are genetically diverse, and rates of gene flow for a suite of five species range from modest to high among reefs up to 1200 km apart. In contrast, 700 km further south on Lord Howe Island, genetic diversity is markedly lower and populations are genetically isolated. The virtual absence of long‐distance dispersal of corals to geographically isolated, oceanic reefs renders them extremely vulnerable to global warming, even where local threats are minimal. 相似文献
12.
Abstract The expected apportionment of genetic diversity in diploid clonal organisms structured in numerous subpopulations is explored. Under the specific assumptions considered, corresponding, for instance, to clonal pathogens infecting a large number of hosts, the co-ancestry between individuals within subpopulations is the only nontrivial quantity. Thus the population structure can be fully described either by F(ST) or F(IS), as F(ST) = -F(IS)/(1 - F(IS)). We show that, for most of the parameter space considered, including simulations where equilibrium is not reached and/or where homoplasy is high, the number of effective migrants is most accurately estimated as Nm = -(1 + F(IS))/4F(IS). We further propose a criterion to test for the absence of cryptic sexual reproduction based on the F-statistics F(IS) and F(ST), which is applied to three previously published empirical data sets. 相似文献
13.
Stacy A. Krueger‐Hadfield 《Evolutionary Applications》2020,13(3):486-499
Biological invasions represent grave threats to terrestrial, aquatic, and marine ecosystems, but our understanding of the role of evolution during invasions remains rudimentary. In marine environments, macroalgae account for a large percentage of invaders, but their complicated life cycles render it difficult to move methodologies and predictions wholesale from species with a single, free‐living ploidy stage, such as plants or animals. In haplodiplontic macroalgae, meiosis and fertilization are spatiotemporally separated by long‐lived, multicellular haploid and diploid stages, and gametes are produced by mitosis, not meiosis. As a consequence, there are unique eco‐evolutionary constraints that are not typically considered in invasions. First, selfing can occur in both monoicious (i.e., hermaphroditic) and dioicious (i.e., separate sexes) haplodiplontic macroalgae. In the former, fertilization between gametes produced by the same haploid thallus results in instantaneous, genome‐wide homozygosity. In the latter, cross‐fertilization between separate male and female haploids that share the same diploid parent is analogous to selfing in plants or animals. Separate sexes, therefore, cannot be used as a proxy for outcrossing. Second, selfing likely facilitates invasions (i.e., Baker's law) and the long‐lived haploid stage may enable purging of deleterious mutations, further contributing to invasion success. Third, asexual reproduction will result in the dominance of one ploidy and/or sex and the loss of the other(s). Whether or not sexual reproduction can be recovered depends on which stage is maintained. Finally, fourth, haplodiplontic life cycles are predicted to be maintained through niche differentiation in the haploid and diploid stages. Empirical tests are rare, but fundamental to our understanding of macroalgal invasion dynamics. By highlighting these four phenomena, we can build a framework with which to empirically and theoretically address important gaps in the literature on marine evolutionary ecology, of which biological invasions can serve as unnatural laboratories. 相似文献
14.
Michael Mogie 《Biological journal of the Linnean Society. Linnean Society of London》1986,28(3):321-329
Biologists have conclusively failed to arrive at a generally acceptable definition of sexual reproduction. Because of this, several reproductive processes are seen as sexual by some authors but as asexual by others. Included among these are automictic methods of reproduction. Automixis describes several reproductive processes whereby a new individual derives from a product or products of a single meiotically dividing cell. Several forms involve an episode of nuclear fusion and it is argued that, because of this, they should be seen as sexual processes irrespective of whether the fusing bodies are differentiated as gametes or are simply meiotic tetrad nuclei. Other forms involve no episode of nuclear fusion and it is argued that, because of this, they should be seen as asexual processes. These latter forms involve the generation of diploid eggs either by restitutional meioses, or by an endomitotic event preceding or following a reductional meiosis, or involve the generation of a diploid embryo by the fusion of cleavage division nuclei in a haploid embryo; in each case the egg develops parthenogenetically. In addition to the disagreement that exists over the reproductive status of automixis, considerable confusion exists over its taxonomic distribution. It is often described as being restricted to a few species of insects, where it is parthenogenetic, but in factde range of taxa, including both isogamous and anisogamous plants and fungi, where it may be either parthenogenetic or non-parthenogenetic. This confusion results both from a failure of many biologists writing on this subject to adequately consider the variation in life-cycles existing between major taxa and from a general failure by botanists and mycologists to distinguish between automixis and autogamous forms of self-fertilization (in which the fusing nuclei derive from different meioses). It is further compounded by a proliferation of synonyms for automictic processes. Thus in a number of publications automictic processes are variously described as being matromorphic, thelytokous, parthenogamic, autogamic or apomictic rather than as being automictic. 相似文献
15.
Unusually high levels of genetic differentiation are often observed between populations of Daphnia (Crustacea: Cladocera) and other cladocerans. Selection and departure from migration–mutation–drift equilibrium have been invoked to explain this fact. However, the null model of neutral genes at equilibrium has not been explicitly stated. Using a simple island model that takes into account the main characteristics of the cyclical parthenogenetic life‐cycle, we show that a high level of differentiation can be obtained for neutral genes at equilibrium if the migration rate during the asexual phase is low and the effective size over the season is reduced, or if mating within clones is common. Recurrent population bottlenecks have a large effect on differentiation and the time to reach equilibrium. Such fluctuating clonal dynamics could be brought about by limitations in the number of clones that hatch and establish themselves each season, or by random associations between neutral and selected genes, as previously suggested in the literature. 相似文献
16.
STANLEY SHOSTAK 《Invertebrate reproduction & development.》2013,57(3):167-178
Buds were collected from hydras fed four days a week on different schedules. Independent of schedule, parents produced the same number of buds per week, but significant differences appeared in the number of buds detaching on particular days, and in the number of digestive cells present in the buds. Groups of buds collected from parents fed the same number of days (from one to three) during the previous four days contained statistically indistinguishable numbers of digestive cells despite the order or sequence of days on which feedings occurred. The number of digestive cells in all the freshly detached buds collected here can be accounted for by the growth of a bud primordium over a four day period of bud development and growth. Such a primordium would have about 3,600 digestive cells and grow at the rate of 0.33 cells per cell per day of feeding. The numbers of tentacles found on freshly detached buds are correlated with the number of feeding days and digestive cells present in the bud. Tentacles, therefore, may also form from primordia consisting originally of a specific number of cells. 相似文献
17.
应用种群累积培养法,就培养液pH值对大乳头水螅（Hydra magnipapillata）的生存、种群增长、无性生殖以及水螅的超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GSH—PX）3种抗氧化酶活力的影响进行了探讨。结果表明,水螅存活的pH上限为10．5,下限为4．0,水螅存活的最适pH范围为5．5～9．5;pH值对水螅种群增长有显著影响,种群密度及种群瞬时增长率均随pH的不同而明显改变。培养15d后,除了pn4．0时水螅种群为负增长外,其他pH梯度下的水螅种群为正增长,其中pH6．5时水螅种群密度最高。以pH6．5为起始点,随着培养液酸性或碱性的增强,水螅种群密度整体都呈递减趋势。水螅SOD活力的转折点在pH6．5,当pH值偏离6．5时（酸性或碱性增强）,水螅SOD活力整体呈明显上升趋势;但水螅GSH—PX和CAT活力的转折点却在pH7．0,当pH值偏离7．0时（酸性或碱性增强）GSH—PX和CAT活力整体呈明显下降趋势。pH6．5时水螅SOD活力最低与pH6．5实验组水螅的无性出芽生殖率最高之间可能存在一定的内在联系。本文研究结果可为实验室培养水螅提供适宜的pH值指标。 相似文献
18.
A. Dia L. Guillou S. Mauger E. Bigeard D. Marie M. Valero C. Destombe 《Molecular ecology》2014,23(3):549-560
Organisms with sexual and asexual reproductive systems benefit from both types of reproduction. Sexual recombination generates new combinations of alleles, whereas clonality favours the spread of the fittest genotype through the entire population. Therefore, the rate of sexual vs. clonal reproduction has a major influence on the demography and genetic structure of natural populations. We addressed the effect of reproductive system on populations of the dinoflagellate Alexandrium minutum. More specifically, we monitored the spatiotemporal genetic diversity during and between bloom events in two estuaries separated by 150 km for two consecutive years. An analysis of population genetic patterns using microsatellite markers revealed surprisingly high genotypic and genetic diversity. Moreover, there was significant spatial and temporal genetic differentiation during and between bloom events. Our results demonstrate that (i) interannual genetic differentiation can be very high, (ii) estuaries are partially isolated during bloom events and (iii) genetic diversity can change rapidly during a bloom event. This rapid genetic change may reflect selective effects that are nevertheless not strong enough to reduce allelic diversity. Thus, sexual reproduction and/or migration may regularly erase any genetic structure produced within estuaries during a bloom event. 相似文献
19.
- The metapopulation theory predicts that the more distant a host population is from other populations, the more challenged will be a parasite to colonise it. We studied parasite prevalence of two parasite taxa across the geographical range of their host in Finland, from more dense host population structure in the south of Finland, towards the northern edge of the host distribution characterised by more isolated populations.
- We found that prevalence of both water mites and gregarines decreased with increasing latitude towards the distribution edge with more isolated population structure of the host damselfly, Coenagrion hastulatum. Furthermore, the prevalences of the two parasite groups were positively correlated.
- The results are discussed in the context of three non‐mutually exclusive hypotheses, explaining why host species have fewer parasites at the edge of their geographic range: (i) unsuitable host hypothesis, (ii) physiological barrier hypothesis and (iii) metapopulation hypothesis.
20.
Abstract. The predominance of sexuality in eukaryotes remains an evolutionary paradox, given the \"two-fold cost of sex\" also known as the \"cost of males.\" [Correction added after online publication 29 January 2009: in the preceding sentence, extraneous words were deleted.] As it requires two sexual parents to reproduce and only one parthenogenetic parent, parthenogens should have twice the reproductive rate compared with their sexual counterparts and their genes should spread twice as fast, if all else is equal. Yet, parthenogenesis is relatively rare and considered an evolutionary dead-end, while sexuality is the dominant form of reproduction in multicellular eukaryotes. Many studies have explored short-term benefits of sex that could outweigh its two-fold cost, but few have compared fecundity between closely related sexuals and parthenogens to first verify that \"all else is equal\" reproductively. We compared six fecundity measures between sexual and parthenogenetic populations of the freshwater snail, Campeloma limum , during a brooding cycle (1 year) across two drainages. Drainages were analyzed separately because of a significant drainage effect. In the Savannah drainage, fecundity was not significantly different between sexuals and parthenogens, even though parthenogens had significantly more empty egg capsules per brood. In the Ogeechee drainage, parthenogens had significantly more egg capsules with multiple embryos and more hatched embryos than sexuals. Taken over 1 year, embryo size was not significantly different between parthenogens and sexuals in either drainage. Given these results and the close proximity of sexual and parthenogenetic populations, it is perplexing why parthenogenetic populations have not completely replaced sexual populations in C. limum. 相似文献