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Complementary sex determination (CSD) is a widespread sex determination mechanism in haplodiploid Hymenoptera. Under CSD, sex is determined by the allelic state of one or multiple CSD loci. Heterozygosity at one or more loci leads to female development, whereas hemizygosity of haploid eggs and homozygosity of diploid eggs results in male development. Sexual (arrhenotokous) reproduction normally yields haploid male and diploid female offspring. Under asexual reproduction (thelytoky), diploidized unfertilized eggs develop into females. Thelytoky is often induced by bacterial endosymbionts that achieve egg diploidization by gamete duplication. As gamete duplication leads to complete homozygosity, endosymbiont-induced thelytokous reproduction is presumed to be incompatible with CSD, which relies on heterozygosity for female development. Previously, we excluded CSD in four Asobara (Braconidae) species and proposed a two-step mechanism for Wolbachia-induced thelytoky in Asobara japonica. Here, we conclusively reject CSD in two cynipid wasp species, Leptopilina heterotoma and Leptopilina clavipes. We further show that thelytoky in L. clavipes depends on Wolbachia titer but that diploidization and feminization steps cannot be separated, unlike in A. japonica. We discuss what these results reveal about the sex determination mechanism of L. clavipes and the presumed incompatibility between CSD and endosymbiont-induced thelytoky in the Hymenoptera.

Hemileia vastatrix is the most important fungal pathogen of coffee and the causal agent of recurrent disease epidemics that have invaded nearly every coffee growing region in the world. The development of coffee varieties resistant to H. vastatrix requires fundamental understanding of the biology of the fungus. However, the complete life cycle of H. vastatrix remains unknown, and conflicting studies and interpretations exist as to whether the fungus is undergoing sexual reproduction. Here we used population genetics of H. vastatrix to infer the reproductive mode of the fungus across most of its geographic range, including Central Africa, Southeast Asia, the Caribbean, and South and Central America. The population structure of H. vastatrix was determined via eight simple sequence repeat markers developed for this study. The analyses of the standardized index of association, Hardy–Weinberg equilibrium, and clonal richness all strongly support asexual reproduction of H. vastatrix in all sampled areas. Similarly, a minimum spanning network tree reinforces the interpretation of clonal reproduction in the sampled H. vastatrix populations. These findings may have profound implications for resistance breeding and management programs against H. vastatrix.

The majority of population genetic theory assumes fully haploid or diploid organisms with obligate sexuality, despite complex life cycles with alternating generations being commonly observed. To reveal how natural selection and genetic drift shape the evolution of haploid-diploid populations, we analyze a stochastic genetic model for populations that consist of a mixture of haploid and diploid individuals, allowing for asexual reproduction and niche separation between haploid and diploid stages. Applying a diffusion approximation, we derive the fixation probability and describe its dependence on the reproductive values of haploid and diploid stages, which depend strongly on the extent of asexual reproduction in each phase and on the ecological differences between them.

PREMISE The distribution of genetic diversity on the landscape has critical ecological and evolutionary implications. This may be especially the case on a local scale for foundation plant species since they create and define ecological communities, contributing disproportionately to ecosystem function. METHODS We examined the distribution of genetic diversity and clones, which we defined first as unique multilocus genotypes (MLG), and then by grouping similar MLGs into multilocus lineages (MLL). We used 186 markers from inter-simple sequence repeats (ISSR) across 358 ramets from 13 patches of the foundation grass Leymus chinensis. We examined the relationship between genetic and clonal diversities, their variation with patch-size, and the effect of the number of markers used to evaluate genetic diversity and structure in this species. RESULTS Every ramet had a unique MLG. Almost all patches consisted of individuals belonging to a single MLL. We confirmed this with a clustering algorithm to group related genotypes. The predominance of a single lineage within each patch could be the result of the accumulation of somatic mutations, limited dispersal, some sexual reproduction with partners mainly restricted to the same patch, or a combination of all three. CONCLUSIONS We found strong genetic structure among patches of L. chinensis. Consistent with previous work on the species, the clustering of similar genotypes within patches suggests that clonal reproduction combined with somatic mutation, limited dispersal, and some degree of sexual reproduction among neighbors causes individuals within a patch to be more closely related than among patches. This article is protected by copyright. All rights reserved.

Cytochimera potato plants, which mixed with diploid and tetraploid cells, could cause the highest and significantly increased biomass yield than the polyploid and diploid potato plants. Polyploidization is an important approach in crop breeding for agronomic trait improvement, especially for biomass production. Cytochimera contains two or more mixed cells with different levels of ploidy, which is considered a failure in whole genome duplication. Using colchicine treatment with diploid (Dip) potato (Solanum chacoense) plantlets, this study generated tetraploid (Tet) and cytochimera (Cyt) lines, which, respectively, contained complete and partial cells with genome duplication. Compared to the Dip potato, we observed remarkably enhanced plant growth and biomass yields in Tet and Cyt lines. Notably, the Cyt potato straw, which was generated from incomplete genome doubling, was of significantly higher biomass yield than that of the Tet with a distinctively altered cell wall composition. Meanwhile, we observed that one layer of the tetraploid cells (about 30%) in Cyt plants was sufficient to trigger a gene expression pattern similar to that of Tet, suggesting that the biomass dominance of Cyt may be related to the proportion of different ploidy cells. Further genome-wide analyses of co-expression networks indicated that down-regulation (against Dip) of spliceosomal-related transcripts might lead to differential alternative splicing for specifically improved agronomic traits such as plant growth, biomass yield, and lignocellulose composition in Tet and Cyt plants. In addition, this work examined that the genome of Cyt line was relatively stable after years of asexual reproduction. Hence, this study has demonstrated that incomplete genome doubling is a promising strategy to maximize biomass production in potatoes and beyond.

Hox genes are highly conserved transcription factors renowned for their roles in the segmental patterning of the embryonic anterior-posterior (A/P) axis. We report functions for Hox genes in A/P tissue segmentation and transverse fission behavior underlying asexual reproduction in adult planarian flatworms, Schmidtea mediterranea. Silencing of each of the Hox family members identifies 5 Hox genes required for asexual reproduction. Among these, silencing of hox3 genes results in supernumerary fission segments, while silencing of post2b eliminates segmentation altogether. The opposing roles of hox3 and post2b in segmentation are paralleled in their respective regulation of fission behavior. Silencing of hox3 increases the frequency of fission behavior initiation while silencing of post2b eliminates fission behavior entirely. Furthermore, we identify a network of downstream effector genes mediating Hox gene functions, providing insight into their respective mechanisms of action. In particular, we resolve roles for post2b and effector genes in the functions of the marginal adhesive organ in fission behavior regulation. Collectively, our study establishes adult stage roles for Hox genes in the regulation of tissue segmentation and behavior associated with asexual reproduction., Hox genes are highly conserved and well-known for their role in segmental patterning during early development. Here, the authors identify an unreported role for Hox genes in the adult tissue patterning and fission behavior required for asexual reproduction in planarian flatworms.

PREMISE Apomixis (asexual reproduction by seed, spore, or egg) has evolved repeatedly across the tree of life. Studies of animals and angiosperms show that apomictic lineages are often evolutionarily short-lived and frequently exhibit different distributions than their sexual relatives. However, apomixis is rare in these groups. Less is known about the role of apomixis in the evolution and biogeography of ferns, in which ~10% of species are apomictic. Apomixis is especially common in the fern genus Pteris (34-39% of species); however, because of the limited taxonomic and geographic sampling of previous studies, the true frequency of apomixis and its associations with geography and phylogeny in this lineage remain unclear. METHODS We used spore analyses of herbarium specimens to determine reproductive mode for 127 previously unsampled Pteris species. Then we leveraged biogeographic and phylogenetic analyses to estimate the global distribution and evolution of apomixis in Pteris. RESULTS Among all Pteris species examined, we found that 21% are exclusively apomictic, 71% are exclusively sexual, and 8% have conflicting reports. Apomixis is unevenly distributed across the range of the genus, with the Paleotropics exhibiting the highest frequency, and has evolved numerous times across the Pteris phylogeny, with predominantly East Asian and South Asian clades containing the most apomictic species. CONCLUSIONS Apomixis arises frequently in Pteris, but apomictic species do not appear to diversify. Species that encompass both apomictic and sexual populations have wider ranges than exclusively sexual or apomictic species, which suggests that sexual and apomictic ferns could occupy separate ecological niches.

Parthenogenesis is a relatively rare event in birds, documented in unfertilized eggs from columbid, galliform, and passerine females with no access to males. In the critically endangered California condor, parentage analysis conducted utilizing polymorphic microsatellite loci has identified two instances of parthenogenetic development from the eggs of two females in the captive breeding program, each continuously housed with a reproductively capable male with whom they had produced offspring. Paternal genetic contribution to the two chicks was excluded. Both parthenotes possessed the expected male ZZ sex chromosomes and were homozygous for all evaluated markers inherited from their dams. These findings represent the first molecular marker-based identification of facultative parthenogenesis in an avian species, notably of females in regular contact with fertile males, and add to the phylogenetic breadth of vertebrate taxa documented to have reproduced via asexual reproduction.

Scleractinian corals feature both sessile and mobile stages and diverse modes of development. In some cases, development can be reversed. Examples include polyp detachment in response to environmental stress (bail-out or polyp expulsion) and reverse metamorphosis, where juveniles detach from the primary skeleton and revert to the mobile stage. Here, we provide aquaria and field evidence of a new form of reverse development: polyp dropout in the solitary cold-water coral Caryophyllia huinayensis. It features tissue retraction and detachment of an entire adult polyp from the skeleton in the putative absence of a stressor. The dropout polyp remains viable and continues to live for many weeks, albeit in a rather collapsed state lacking a well-developed hydroskeleton. We carried out a long-term (37 months) rearing experiment under constant aquaria conditions and found polyp dropout in four out of 83 individuals. Detachment was accompanied by the extrusion of mesenterial filaments through perforations in the body wall. We believe this resulted in the loss of the hydroskeleton, which prevented the dropouts to subsequently resettle or form a new skeleton. As opposed to other known forms of reverse development, the new form is not accompanied by reversible metamorphosis, abandonment of the colonial way of life, nor is it a survival or asexual reproduction strategy. We found field indications of polyp dropout in Patagonian field populations of C. huinayensis, where 1.4 ± 0.8% (mean ± SD, N = 9322) of the polyps of the natural population showed partial detachment indicative of imminent dropout in the putative absence of external impact. Polyp dropout is the first record of polyp detachment in a solitary CWC with possible repercussions for adult coral mobility, evolution and Stanley’s (2003) ‘naked coral’ hypothesis.

In the life cycle of Neopyropia yezoensis, a potential model system for marine macroalgae, both of asexual archeospores and meiosis-related conchospores develop into thalli (gametophyte). To understand this special life phenomenon in macroalgae, we picked out the two kinds of spores (10-30 cells in each sample) and conducted RNA-seq using Smart-seq2. Comparative analysis showed that light capture and carbon fixation associated differentially expressed genes (DEGs) were upregulated in archeospores, thus indicating that archeospores are in a state of rapid vegetative growth. In conchospores, protein synthesis and degradation, especially molecular chaperone, associated DEGs were upregulated, indicating the complex life activities might be occurred in conchospores. There were 68 genes related to DNA replication and repair expressed in conchospores, showing that active DNA replication might occur in conchospores. Moreover, we found that one conchospore specifically expressed DEG (py04595: DNA helicase) was only expressed in diploid stage (conchocelis, sporangial filament) and three archeospore specifically expressed DEGs were only expressed in haploid stage (thalli). These molecular level results indicated that conchospores were closer to diploid, and might be the meiotic mother cells of N. yezoensis. In addition, we found that the knotted-like homeobox gene (PyKNOX), which might relate to the transition of gametophyte from sporophyte, was only expressed in sporophyte generation but not expressed in conchospores, archeospores and thalli, indicating the morphogenesis of gametophyte in N. yezoensis might require the inactivation of PyKNOX.

We studied the impact of flooding and light availability gradients on sexual and asexual reproduction in Lindera melissifolia (Walt.) Blume, an endangered shrub found in floodplain forests of the Mississippi Alluvial Valley (MAV), USA. A water impoundment facility was used to control the duration of soil flooding (0, 45, or 90 days), and shade houses were used to control light availability (high = 72%, intermediate = 33%, or low = 2% of ambient light) received by L. melissifolia established on native soil of the MAV. Sexual reproductive intensity, as measured by inflorescence bud count, fruit set, and drupe production, was greatest in the absence of soil flooding. Ninety days of soil flooding in the year prior to anthesis decreased inflorescence bud counts, and 45 days of soil flooding in the year of anthesis lessened fruit set and drupe production. Inflorescence bud development was the greatest in environments of intermediate light, decreased in high‐light environments, and was absent in low light environments. But low fruit set diminished drupe production in intermediate light environments as compared to high light environments. Asexual reproduction, as measured by development of new ramets, was greatest in the absence of soil flooding and where plants were grown in high or intermediate light. Plants exhibited plasticity in reproductive mode such that soil flooding increased the relative importance of asexual reproduction. The high light environment was most favorable to sexual reproduction, and reproductive mode transitioned to exclusively asexual in the low light environment. Our results raise several implications important to active management for the conservation of this imperiled plant., We studied the impact of flooding and light availability gradients on sexual and asexual reproduction in Lindera melissifolia (Walt.) Blume, an endangered shrub found in floodplain forests of the Mississippi Alluvial Valley, USA. Plants exhibited plasticity in reproductive mode such that soil flooding increased the relative importance of asexual reproduction. The high light environment was most favorable to sexual reproduction, and reproductive mode transitioned to exclusively asexual in the low light environment.

Many organisms can reproduce both asexually and sexually. For cyclical parthenogens, periods of asexual reproduction are punctuated by bouts of sexual reproduction, and the shift from asexual to sexual reproduction has large impacts on fitness and population dynamics. We studied populations of Daphnia dentifera to determine the amount of investment in sexual reproduction as well as the factors associated with variation in investment in sex. To do so, we tracked host density, infections by nine different parasites, and sexual reproduction in 15 lake populations of D. dentifera for 3 years. Sexual reproduction was seasonal, with male and ephippial female production beginning as early as late September and generally increasing through November. However, there was substantial variation in the prevalence of sexual individuals across populations, with some populations remaining entirely asexual throughout the study period and others shifting almost entirely to sexual females and males. We found strong relationships between density, prevalence of infection, parasite species richness, and sexual reproduction in these populations. However, strong collinearity between density, parasitism, and sexual reproduction means that further work will be required to disentangle the causal mechanisms underlying these relationships.

We here analysed the populations’ genetic structure ofCoscinasterias tenuispina,an Atlantic-Mediterranean fissiparous starfish,focusing on the western Mediterranean,to investigate: the distribution and prevalence of genetic variants, the relative importance of asexual reproduction, connectivity across the Atlantic-Mediterranean transition, and the potential recent colonisation of the Mediterranean Sea. Individuals from 11 Atlantic-Mediterranean populations of a previous study added to 172 new samples from five new W Mediterranean sites. Individuals were genotyped at 12 microsatellite loci and their gonads histologically analysed for sex determination. Additionally, four populations were genotyped at two-time points. Results demonstrated genetic homogeneity and low clonal richness within the W Mediterranean, due to the dominance of asuperclone, but large genetic divergence with adjacent areas. The lack of new genotypes recruitment over time, and the absence of females, confirmed that W Mediterranean populations were exclusively maintained by fission and reinforced the idea of its recent colonization. The existence of different environmental conditions among basins and/or density-depend processes could explain this lack of recruitment from distant areas. The positive correlation between clonal richness and heterozygote excess suggests that most genetic diversity is retained within individuals in the form of heterozygosity in clonal populations, which might increase their resilience.

The shells of large benthic foraminifers (LBF) are key contributors to the development and maintenance of coastal landforms in the Pacific as well as to Paleogene and Miocene carbonates deposited along the Neotethys Seaway and tropical Pacific islands. The current study assessed growth and fecundity of two species, Marginopora vertebralis and Amphistegina lobifera, collected from sites in Viti Levu, Fiji, based on shell diameter, shell weight, fecundity, and survival. Specimens were cultured without supplemental nutrients or food for 15 months under controlled laboratory conditions. Physicochemical parameters, including salinity, alkalinity, pH, and temperature, varied by

Intertidal sessile invertebrates experience tough competition for space which they avoid by releasing secondary metabolites (allelochemicals). We investigated the allelopathic interaction between sponge Cinachyrella cf. cavernosa and its neighbour zoanthids Zoanthus sansibaricus over a year on the rocky beach of Anjuna, (Goa) India. A major sterol (β-sitosterol) was isolated from the sponge, and its natural variability was checked in tagged sponges with and without their competitor zoanthids during the reproductive and non-reproductive months of the sponges. The sponge showed significant variability in the production of β-sitosterol owing to its spatial competition and asexual reproduction (budding) as predicted by the multiple regression analysis. Zoanthids are known to have dynamic mutualistic association with their autotrophic endosymbionts’ dinoflagellate (Symbiodinium, known as zooxanthellae), which are directly involved in their physiology. The phytagel™-based field assay of sponge’s bioactive compound (β-sitosterol) was conducted to check its allelopathic impact on Z. sansibaricus and its symbiotic zooxanthellae (Symbiodinium sp.). Results showed significant bleaching (50–80%) in the host Z. sansibaricus, resulting from a decrease in symbiotic zooxanthellae count, cell density, chl a and chl c content. This suggests the role of β-sitosterol as allelochemical of the sponge in preventing the overgrowth of aggressive Z. sansibaricus, possibly by affecting its symbionts. This investigation is not only important to understand the ecological roles of marine-derived allelochemicals but also to allow sustainable bioprospecting of marine resources.

Endosymbiotic bacteria can induce parthenogenesis in many haplo-diploid species, but little is known about their role in asexual reproduction in diplodiploids. Bacteria are essential for reproduction in the asexual lineages of springtails and booklice, and possibly some weevils, but whether they are the causative agent of parthenogenesis remains to be proven. This would require comparing unisexual forms and their closely related bisexual species, but such model species are very rare. Empoasca leafhoppers from the Madeira Archipelago provide an excellent case to test whether bacterial infections can cause parthenogenesis. Here we examined the diversity of the sex-distorting bacteria, Wolbachia, Cardinium, Rickettsia, and Arsenophonus, in three apomictic morphotypes (A, B, C) and three bisexual relatives of Empoasca. Wolbachia of group B was present in all unisexual and bisexual species. Rickettsia were the only bacteria restricted to the three unisexual forms, suggesting an association between infection and asexual reproduction. In addition, we found Asaia for the third time in the Cicadellidae, although this may have little to do with the reproductive mode of its host. Adult females of morphotype C reared on plants watered with tetracycline solution did not result in the production of male offspring. To our knowledge, this is the first study to suggest a possible association between bacterial infection and parthenogenesis in apomictic XO/XX diplodiploid bisexual species based on a range of sex ratio-distorting bacteria.

Citrus black spot (CBS), caused by Phyllosticta citricarpa, is a disease that affects citrus worldwide. In different regions of the world where both mating types occur, reports differ as to whether asexually produced pycnidiospores play an important role in the epidemiology of CBS and fruit infections. Therefore, we investigated the potential role of pycnidiospores in two lemon orchards in South Africa by using microsatellite-based analysis of fruit populations over time (two seasons) and space (distance). The two orchards were situated in the semiarid North West province (NW) and subtropical Mpumalanga province (MP). Each population contained both mating types in 1:1 ratios, and linkage disequilibrium analysis indicated a random mating population. A total of 109 and 94 multilocus genotypes (MLGs) were detected across the two seasons in the NW and MP orchards, respectively. Psex analyses indicated that most MLGs probably resulted from sexual reproduction, but there were six predominant MLGs in each orchard that were probably replicated via asexual reproduction. Each of the predominant MLGs was monomorphic for mating type. In the NW, five predominant and widespread MLGs caused 46 and 44% of the fruit infections in the two seasons, whereas in MP, three MLGs caused 34 and 48% of the infections. Asexual reproduction in both orchards was supported by low MLG evenness values in all populations. In both orchards, distance was not a reliable predictor of population genetic substructuring or season. Populations of P. citricarpa in the MP and NW orchards were significantly genetically differentiated from each other.

During the course of evolution, numerous taxa abandoned canonical sex and reproduced asexually. Examination of the Cobitis hankugensis × Iksookimia longicorpa asexual complex already revealed important evolutionary discoveries tackling phenomena like interspecific hybridization, non-Mendelian inheritance, polyploidy, and asexuality. Yet, as in other similar cases, the investigation is hampered by the lack of easily accessible molecular tools for efficient differentiation among genomotypes. Here, we tested the cross-species amplification of 23 microsatellite markers derived from distantly related species and investigated the extent to which such markers can facilitate the genome identification in the non-model hybrid complex. We found that 21 out of 23 microsatellite markers were amplified in all genomotypes. Five of them could be used for easy diagnostics of parental species and their hybrids due to species-specific amplification profiles. We also noted that three markers, i.e., IC654 and IC783 derived from Cobitis choii Kim et Son, 1984 and Iko_TTA01 from Iksookimia koreensis (Kim, 1975), had dosage-sensitive amplification efficiencies of species-specific alleles. This could be further used for reliable differentiation of genome composition in polyploids. The presently reported study introduces a noninvasive method applicable for the diagnosis of ploidy and genome composition of hybrids, which are not clearly distinguished morphologically. We showed that very detailed information may be obtained even from markers developed in distantly related taxa. Hybridization is being increasingly recognized as a driving force in evolution. Yet, proper detection of hybrids and their ploidy is particularly challenging, especially in non-model organisms. The present paper evaluates the power of microsatellite cross-amplification not only in the identification of hybrid forms but also in estimating their genome dosage on an example of a fish taxon that involves asexuality, hybridization as well as ploidy variation. It thus demonstrates the wide applicability of such cheap and non-invasive tools.

Growth and reproduction are two essential life‐history traits for fungi. Understanding life‐history strategies provides insight into the environmental adaption of species. Here, we investigated the colonial morphology, vegetative growth, and asexual reproduction of the ascomycete fungus Bionectria ochroleuca in response to a variety of environmental conditions. We demonstrated that the increased temperature from 15 to 25°C induced mycelial growth and conidiation in B. ochroleuca. We also found that the optimal temperatures for mycelial growth and conidial formation in this fungus species were 25 and 30°C, respectively. However, as the temperature increased from 25 to 30°C, mycelial growth was suppressed, but the total number of conidia was significantly increased. The shift in light–dark cycles dramatically changed the morphological features of the colonies and affected both vegetative growth and asexual reproduction. Under incubation environments of alternating light and dark (16:8 and 8:16 light:dark cycles), conidiophores and conidia in the colonies formed dense‐sparse rings and displayed synchronous wave structures. When the light duration was prolonged in the sequence of 0, 8, 16, and 24 hr per day, mycelial growth was suppressed, but conidiation was promoted. Together, our results indicate that temperature and light period may trigger a trade‐off between vegetative growth and asexual reproduction in B. ochroleuca.

International audience; A vast diversity of types of life cycles exists in nature, and several theories have been advanced to explain how this diversity has evolved and how each type of life cycle is retained over evolutionary time. Here, we exploited the diversity of life cycles and reproductive traits of the brown algae (Phaeophyceae) to test several hypotheses on the evolution of life cycles. We investigated the evolutionary dynamics of four life-history traits: life cycle, sexual system, level of gamete dimorphism and gamete parthenogenetic capacity. We assigned states to up to 77 representative species of the taxonomic diversity of the brown algal group, in a multi-gene phylogeny. We used maximum likelihood and Bayesian analyses of correlated evolution, while taking the phylogeny into account, to test for correlations between traits, and to investigate the chronological sequence of trait acquisition. Our analyses are consistent with the prediction that diploid growth evolves when sexual reproduction is preferred over asexual reproduction, possibly because it allows the complementation of deleterious mutations. We also found that haploid sex determination is ancestral in relation to diploid sex determination. However, our results could not address whether increased zygotic and diploid growth are associated with increased sexual dimorphism. Our analyses suggest that in the brown algae, isogamous species evolved from anisogamous ancestors, contrary to the commonly reported pattern where evolution proceeds from isogamy to anisogamy.

Two experiments evaluated rooting of blueberry in substrates for use in soilless production systems. Apical and basal semi-hardwood stem cuttings of Vaccinium corymbosum x angustifolium ‘Northland' were rooted in rockwool cubes, shredded rockwool, or 3 perlite:1 sphagnum peat moss (v/v). Cuttings were treated with 0.1% indolebutyric acid (IBA) in 1:1 95% ethyl alcohol: water, 0.1% potassium salt of indolebutyric acid (K-IBA), 1:1 95% ethyl alcohol: water, or water. In Expt. 2, basal stem cuttings of ‘Northland' and V. angustifolium ‘Brunswick' were rooted in the same substrates with the addition of coco coir, treated with 1,000 ppm K-IBA, then fertilized weekly (after rooting began) with water, 75 ppm N from 16-4-17 fertilizer or 4-18-38 and Ca(NO3)2 plus MgSO4 fertilizer, all adjusted to pH 4.0. Rooting percentages were calculated, and rooting quality was assessed using a 6-point visual scale. ‘Northland' roots well (>80%) in peat:perlite and coco coir substrates and acceptably in two rockwool substrates (∼50%). ‘Brunswick' rooted acceptably in peat:perlite and coco coir (27% and 41%, respectively), and very poorly in two rockwool substrates ( Index words: adventitious rooting, auxin, coco coir, hydroponics, indolebutyric acid, rockwool, Vaccinium. Species used: ‘Northland' half-highbush blueberry, Vaccinium corymbosum L. X angustifolium Aiton, ‘Brunswick' low-bush blueberry, V. angustifolium Aiton. Chemicals used: auxin, potassium salt indolebutyric acid, K-IBA; Sigma-Aldrich, St. Louis, MO, USA, auxin, indolebutyric acid, IBA; Sigma-Aldrich, St. Louis, MO, USA, Oasis® 16-4-17 fertilizer, OASIS® Grower Solutions, Kent, OH, USA, ChemGro 4-18-38 fertilizer, ChemGro Hydro-Gardens, Colorado Springs, CO, USA, Ca(NO3)2, Yara North America, Tampa, FL, USA, and MgSO4, PQ Corp., Valley Forge, PA, USA.

Tomato leafminer Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) is a key devastating pest worldwide, it has the capacity to develop on a wide range of Solanaceous plants but tomato (Solanum lycopersicum L.) is considered to be its preferred host. This study was carried out at the Agricultural Scientific Research Centre in Latakia in 2019 to estimate biological parameters of T. absoluta and evaluate the effect of temperature in its development, longevity, reproduction in parthenogenesis. The experiments were carried out at constant temperatures (10, 20, 30˚ C), 60-65% RH, and photoperiod (16L: 8D). Biological parameters were analyzed according to the theory of age-stage two-sex life table by using the computer program TWO-SEX MSchart. The highest value of intrinsic rate of increase (r), the final increase rate (λ), and net reproductive rate (Ro) were 0.0439±0.0028 females/female/day, 1.0449±0.0029, and 7.01±0.8705 females/female/generation, respectively, at 20˚C. The lowest value of net reproductive rate (Ro) was 0.92±0.1250 females/female/generation at 30˚C. Generation time (T) was the longest (44.3±0.203 days) at 20˚C and decreased to 26.38±1.156 days at 30˚C. T. absoluta completed its development at all these temperatures. The results obtained showed that the effect of temperature on the insect development from egg to adult decreased with increased temperature. The shortest development period on egg, larva and pupa development was 3.95±0.149, 11.975±0.075 and 4.95±0.086 days, respectively, at 30˚C. This means that the development time from egg to adult was shorter (20.8±1.151 days) at 30˚C as compared to 34.51±0.127 days at 20˚C, and longest at 10˚C (125.4±1.211 days). The female longevity was longer (61.35±0.25 days) at 20˚C. The highest rate of fecundity was 12.98±1.072 eggs/unmated female, and the lowest was 2.19±0.152 eggs/unmated female at 30˚C. Moreover, the unmated females kept at 10˚C did not lay eggs, and unfertilized eggs (asexually produced eggs) laid by unmated females at 20 or 30˚C did not hatch. The adult pre-oviposition period (APOP) of unmated females was 2.57±0.1368 days at 20˚C and 4.31±0.2629 days at 30˚C, whereas the total APOP of females was 36.86±0.1844 days at 20˚C and 24.21±0.3039 days at 30˚C. Keywords: Tomato leaf miner, Life tables, asexual reproduction, Parthenogenesis, Syria

Apomixis, a type of asexual reproduction in angiosperms, results in progenies that are genetically identical to the mother plant. It is a highly desirable trait in agriculture due to its potential to preserve heterosis of F1 hybrids through subsequent generations. However, no major crops are apomictic. Deciphering mechanisms underlying apomixis becomes one of the alternatives to engineer self-reproducing capability into major crops. Parthenogenesis, a major component of apomixis, commonly described as the ability to initiate embryo formation from the egg cell without fertilization, also can be valuable in plant breeding for doubled haploid production. A deeper understanding of transcriptional differences between parthenogenetic and sexual or non-parthenogenetic eggs can assist with pathway engineering. By conducting laser capture microdissection-based RNA-seq on sexual and parthenogenetic egg cells on the day of anthesis, a de novo transcriptome for the Cenchrus ciliaris egg cells was created, transcriptional profiles that distinguish the parthenogenetic egg from its sexual counterpart were identified, and functional roles for a few transcription factors in promoting natural parthenogenesis were suggested. These transcriptome data expand upon previous gene expression studies and will be a resource for future research on the transcriptome of egg cells in parthenogenetic and sexual genotypes.

During the transition from sexual to asexual reproduction, a suite of reproduction‐related sexual traits become superfluous, and may be selected against if costly. Female functional virginity refers to asexual females resisting to mate or not fertilizing eggs after mating. These traits appear to be among the first that evolve during transitions from sexual to asexual reproduction. The genetic basis of female functional virginity remains elusive. Previously, we reported that female functional virginity segregates as expected for a single recessive locus in the asexual parasitoid wasp Asobara japonica. Here, we investigate the genetic basis of this trait by quantitative trait loci (QTL) mapping and candidate gene analyses. Consistent with the segregation of phenotypes, we found a single QTL of large effect, spanning over 4.23 Mb and comprising at least 131 protein‐coding genes, of which 15 featured sex‐biased expression in the related sexual species Asobara tabida. Two of the 15 sex‐biased genes were previously identified to differ between related sexual and asexual population/species: CD151 antigen and nuclear pore complex protein Nup50. A third gene, hormone receptor 4, is involved in steroid hormone mediated mating behaviour. Overall, our results are consistent with a single locus, or a cluster of closely linked loci, underlying rapid evolution of female functional virginity in the transition to asexuality. Once this variant, causing rejection to mate, has swept through a population, the flanking region does not get smaller owing to lack of recombination in asexuals.

Zymoseptoria tritici, the causal agent of Septoria tritici blotch, is a fungal wheat pathogen that causes significant global yield losses. Within Z. tritici populations, quantitative differences in virulence among different isolates are commonly observed; however, the genetic components that underpin these differences remain elusive. In this study, intraspecific comparative transcriptomic analysis was used to identify candidate genes that contribute to differences in virulence on the wheat cultivar WW2449. This led to the identification of a multicopy gene that was not expressed in the high‐virulence isolate when compared to the medium‐ and low‐virulence isolates. Further investigation suggested this gene resides in a 7.9‐kb transposon. Subsequent long‐read sequencing of the isolates used in the transcriptomic analysis confirmed that this gene did reside in an active Class II transposon, which is composed of four genes named REP9‐1 to ‐4. Silencing and overexpression of REP9‐1 in two distinct genetic backgrounds demonstrated that its expression alone reduces the number of pycnidia produced by Z. tritici during infection. The REP9‐1 gene identified within a Class II transposon is the first discovery of a gene in a transposable element that influences the virulence of Z. tritici. This discovery adds further complexity to genetic loci that contribute to quantitative virulence in this important pathogen., The expression of the gene REP9‐1, which resides in an active Class II transposon, negatively regulates the rate of pycnidia appearance in planta of the wheat pathogen Zymoseptoria tritici.

Phyllosticta citriasiana is the causal agent of citrus tan spot, an important pomelo disease in Asia. At present, there is little or no information on the epidemiology or population structure of P. citriasiana. By using simple sequence repeat markers, we analyzed 94 isolates from three pomelo production regions in southern and southeastern China. The analyses showed high genetic diversity in each of the three geographic populations. A STRUCTURE analysis revealed two genetic clusters among the 94 isolates; one geographic population was dominated by genotypes in one cluster, and the other two geographic populations were dominated by genotypes of the second cluster. P. citriasiana has a heterothallic mating system with two idiomorphs, MAT1-1 and MAT1-2. Analyses using mating type–specific primers revealed that both mating types were present in all three geographic populations, and in all three populations the mating type ratios were in equilibrium. Although the sexual stage of the fungus has not been discovered yet, analyses of allelic associations indicated evidence for sexual and asexual reproduction within and between populations. Despite the observed genetic differentiation between the three geographic populations, evidence for long-distance gene flow was found.

On the macroevolutionary timescale, does trait evolution proceed gradually or by rapid bursts (pulses) separated by prolonged periods of stasis or slow evolution? Although studies have shown pulsed evolution is prevalent in animals, our knowledge about the tempo and mode of evolution across the tree of life is very limited. This long-standing debate calls for a test in bacteria and archaea, the most ancient and diverse forms of life with unique population genetic properties (asexual reproduction, large population sizes, short generation times, high dispersal rates and extensive lateral gene transfers). Using a likelihood-based framework, we analyzed evolutionary patterns of four microbial genomic traits (genome size, genome GC%, 16S rRNA GC% and the nitrogen use in proteins) on a broad macroevolutionary timescale. Our model fitting of phylogenetic comparative data shows that pulsed evolution is not only present, but also prevalent and predominant in microbial genomic trait evolution. Interestingly, for the first time, we detected two distinct types of pulsed evolution (small frequent and large rare jumps) that are predicted by the punctuated equilibrium and quantum evolution theories. Our findings suggest that major bacterial lineages could have originated in quick bursts and pulsed evolution is a common theme across the tree of life despite the drastically different population genetic properties of bacteria, archaea and eukaryotes.

Facultative sexual organisms combine sexual and asexual reproduction within a single life cycle, often switching between reproductive modes depending on environmental conditions. These organisms frequently inhabit variable seasonal environments, where favourable periods alternate with unfavourable periods, generating temporally varying selection pressures that strongly influence life history decisions and hence population dynamics. Due to the rapidly accelerating changes in our global environment today, understanding the dynamics of and genetic changes in facultative sexual populations inhabiting seasonal environments is critical to assess and prepare for additional challenges that will affect such ecosystems. In this study we aimed at obtaining insights of the seasonal population dynamics of the facultative sexual freshwater cnidarian Hydra oligactis through a combination of Restriction-site Associated Sequencing (RAD-Seq) genotyping and the collection of phenotypic data on the reproductive strategy of field-collected hydra strains. We found no significant genetic change during the two years in the study population. Clone lines were detected between seasons and even years, suggesting that clonal lineages can persist for a long time in a natural population. We also found that distinct genotypes differ in sexual reproduction frequency, but these differences did not affect whether genotypes reappeared across samplings. Our study describes changes in population genetic structure across the seasons in a hydra population for the first time, providing key insights into the biology of the species, while also contributing to understanding the population biology of facultative sexual species inhabiting freshwater ecosystems.

Coral transplantation helps to reinstate coral cover in degraded reefs, but the general success of this approach is hampered by limited understanding of how coral-fragment size affects growth and s...

Within the agamic Pilosella complex, apomixis (asexual reproduction through seed) involves apospory, parthenogenesis, and autonomous endosperm development. Observations of reproductive biology in P. brzovecensis throughout four growing seasons in the garden have shown that both tetraploid and pentaploid plants of this species do not produce viable seeds and reproduce exclusively vegetatively by underground stolons. The reasons for the seed development failure were unknown, therefore our research focused on the analysis of reproductive events in the ovules of this taxon. We found that apospory was initiated in the ovules of both cytotypes. Multiple aposporous initial (AI) cells differentiated in close proximity to the megaspore mother cell (MMC) and suppressed megasporogenesis at the stage of early prophase I. However, none of the AI cells was able to further develop into a multi-nucleate aposporous embryo sac (AES) due to the inhibition of mitotic divisions. It was unusual that callose was accumulated in the walls of AI cells and its synthesis was most likely associated with a response to the dysfunction of these cells. Callose is regarded as the isolating factor and its surprising deposition in the ovules of P. brzovecensis may signal disruption of reproductive processes that cause premature termination of the aposporous development pathway and ultimately lead to ovule sterility. The results of our embryological analysis may be the basis for undertaking advanced molecular studies aimed at fully understanding of the causes of female sterility in P. brzovecensis.

Compared with asexual reproduction, sex facilitates the transmission of transposable elements (TEs) from one genome to another, but boosts the efficacy of selection against deleterious TEs. Thus, theoretically, it is unclear whether sex has a positive net effect on TE’s proliferation. An empirical study concluded that sex is at the root of TE’s evolutionary success because the yeast TE load was found to decrease rapidly in approximately 1,000 generations of asexual but not sexual experimental evolution. However, this finding contradicts the maintenance of TEs in natural yeast populations where sexual reproduction occurs extremely infrequently. Here, we show that the purported TE load reduction during asexual experimental evolution is likely an artifact of low genomic sequencing coverages. We observe stable TE loads in both sexual and asexual experimental evolution from multiple yeast data sets with sufficient coverages. To understand the evolutionary dynamics of yeast TEs, we turn to asexual mutation accumulation lines that have been under virtually no selection. We find that both TE transposition and excision rates per generation, but not their difference, tend to be higher in environments where yeast grows more slowly. However, the transposition rate is not significantly higher than the excision rate and the variance of the TE number among natural strains is close to its neutral expectation, suggesting that selection against TEs is at best weak in yeast. We conclude that the yeast TE load is maintained largely by a transposition–excision balance and that the influence of sex remains unclear.

Calmodulin (CaM) plays an important regulatory role in plant growth and development. In this study, on the basis of previous transcriptomic annotation a homolog of CaM gene (Pc-CaM7) was identified from the red alga Phycocalida chauhanii (previously known as Porphyra chauhanii). It encoded a 151 amino acids protein with 4 EF-hand regions, which was the typical structure of calmodulin family proteins. Evolutionary analysis showed that Pc-CaM7 shared conserved orthologous relationships with CaMs from Neoporphyra haitanensis (formerly Pyropia haitanensis), Porphyra umbilicalis, and Gracilariopsis chorda. During the developmental period of P. chauhanii gametophytic germlings from 25- to 50-day-old, the asexual archeospores were continuedly released from the marginal region of blades, followed by the emergence of spermatangia from 40-day-old germlings. Based on quantitative real-time PCR analysis, it showed that expression trend of Pc-CaM7 was correlated with the rule of archeospores’ formation and release, whereas in N. haitanensis without archeospore characteristic, the expression pattern of the orthologous gene (Pha_00404) was different, which increased and reached a plateau during the same developmental period. These findings suggested that Pc-CaM7 may be involved in the process of archeospores formation and release, which may provide a foundation for understanding the molecular mechanisms of asexual reproduction in Bangiales.

The article presents the results of the analysis of available data on the reproduction (sexual reproduction and asexual reproduction or apomixis) of plants of the Pinopsida class. The realization of apomixis in conifers was considered. This method of asexual reproduction is manifested in cases of seed formation’s disruption. A specific type of reproduction in conifers is somatic embryogenesis in in vitro culture. It is shown that the transition of somatic cells to the totipotent and embryogenic state in conifers occurs at the morphogenetic, physiological-biochemical, and molecular genetics levels. The commonality of morphogenetic processes underlying somatic and zygotic embryogenesis is revealed. The position of somatic embryogenesis in the reproduction system of conifers is considered.

The mechanisms of initiation and transmission of apomixis (asexual reproduction through seeds) in natural plant populations are important for understanding the evolution of reproductive variation. Here, we used the phylogenetic diversity of the genus Boechera (Brassicaceae), together with natural diversity in pollen types produced by apomictic lines, to test whether hybridization triggers the transition to asexuality, and whether a 'triploid bridge' is required for the formation of polyploid apomicts. We performed crosses between diploid sexual recipient and diploid apomictic donor lines and tested whether the mating system (interspecific hybridization vs intraspecific outcrossing) or pollen type (haploid vs diploid) influenced the transmission of apomixis from diploid apomictic donors into sexual recipients. We used genetic markers and flow cytometric analyses of embryo and endosperm in seeds to infer the reproductive mode. Within a single generation, initiation of both diploid and polyploid apomixis in sexual Boechera can occur. Diploid apomixis is transmitted through haploid pollen (infectious asexuality) and polyploids can form through multiple pathways. The three functional elements of apomixis occasionally segregate. Variation in pollen ploidy and the segregation of apomixis elements drive reproductive diversity of hybrids and outcrosses and can be utilized for apomixis initiation in crop breeding programs.

Ascospores generated during sexual reproduction are the primary inoculum for the wheat scab fungus Fusarium graminearum. Purine metabolism is known to play important roles in fungal pathogens but its lifecycle stage-specific regulation is unclear. By characterizing the genes involved in purine de novo and salvage biosynthesis pathways, we showed that de novo syntheses of inosine, adenosine and guanosine monophosphates (IMP, AMP and GMP) are important for vegetative growth, sexual/asexual reproduction, and infectious growth, whereas purine salvage synthesis is dispensable for these stages in F. graminearum. Addition of GMP rescued the defects of the Fgimd1 mutant in vegetative growth and conidiation but not sexual reproduction, whereas addition of AMP rescued all of these defects of the Fgade12 mutant, suggesting that the function of de novo synthesis of GMP rather than AMP is distinct in sexual stages. Moreover, Acd1, an ortholog of AMP deaminase, is dispensable for growth but essential for ascosporogenesis and pathogenesis, suggesting that AMP catabolism has stage-specific functions during sexual reproduction and infectious growth. The expression of almost all the genes involved in de novo purine synthesis is downregulated during sexual reproduction and infectious growth relative to vegetative growth. This study revealed that F. graminearum has stage-specific regulation of purine metabolism during infectious growth and sexual reproduction.

Clonal plants can reproduce both sexually and asexually. Selection of reproductive strategies is crucial for the evolution of clonal plants. Nevertheless, little is known about the reproductive strategy of clonal aquatic plants in diverse environments and at different harvest times. In this study, the reproduction of the clonal aquatic plant species Leersia oryzoides (L.) Swartz. was investigated under two different submergence conditions: mesic and flooding in two different years. We collected data concerning specific leaf area (SLA), a growth-related trait, during the growing season in both years. Seed output (total seed mass, seed number and seed mass) and rhizome mass, which reflect sexual reproduction and asexual reproduction, respectively, were measured in the reproductive period. The correlation between sexual reproduction (total seed mass) and asexual propagation (rhizome mass) was subsequently analyzed. The correlations between SLA and each reproductive output—total seed mass and rhizome mass—were explored. Seed output (the seed number and total seed mass) decreased in the second-year harvest (H2) compared to the first-year harvest (H1). Greater seed mass was observed at H2 than at H1 in the flooding treatment. The ratio of sexual to asexual reproductive output increased under flooding and decreased at H2. Generally, the SLA and rhizome mass were not significantly correlated, while a significant negative correlation was detected between SLA and total seed mass across all observations. A nonsignificant correlation between rhizome mass and total seed mass was also detected. A decrease in sexual reproduction can occur over time, although disturbances such as flooding can promote the allocation of reproduction resources to the sexual approach. Leaf functional traits such as SLA may negatively predict the output of sexual reproduction, and the trade-off between SLA and asexual propagation is likely nonexistent. A trade-off between asexual reproduction and sexual reproduction does not exist for L. oryzoides.

Hybridization is one of the major factors contributing to the emergence of highly successful parasites. Hybrid vigour can play an important role in this process, but subsequent rounds of recombination in the hybrid population may dilute its effects. Increased fitness of hybrids can, however, be frozen by asexual reproduction. Here, we identify invasion of a ‘frozen hybrid’ genotype in natural populations of Gyrodactylus turnbulli, a facultatively sexual ectoparasitic flatworm that causes significant damage to its fish host. We resequenced genomes of these parasites infecting guppies from six Trinidad and Tobago populations, and found surprisingly high discrepancy in genome‐wide nucleotide diversity between islands. The elevated heterozygosity on Tobago is maintained by predominantly clonal reproduction of hybrids formed from two diverged genomes. Hybridization has been followed by spread of the hybrids across the island, implying a selective advantage compared with native genotypes. Our results thus highlight that a single outcrossing event may be independently sufficient to cause pathogen expansion.

Because every species has unique attributes relevant to understanding specific aspects of aging, using a diversity of study systems and a comparative biology approach for aging research has the potential to lead to novel discoveries applicable to human health. Monogonont rotifers, a standard model for studies of aquatic ecology, evolutionary biology, and ecotoxicology, have also been used to study lifespan and healthspan for nearly a century. However, because much of this work has been published in the ecology and evolutionary biology literature, it may not be known to the biomedical research community. In this review, we provide an overview of Brachionus rotifers as a model to investigate nutritional and metabolic regulators of aging, with a focus on recent studies of dietary and metabolic pathway manipulation. Rotifers are microscopic, aquatic invertebrates with many advantages as a system for studying aging, including a two-week lifespan, easy laboratory culture, direct development without a larval stage, sexual and asexual reproduction, easy delivery of pharmaceuticals in liquid culture, and transparency allowing imaging of cellular morphology and processes. Rotifers have greater gene homology with humans than do established invertebrate models for aging, and thus rotifers may be used to investigate novel genetic mechanisms relevant to human lifespan and healthspan. The research on caloric restriction; dietary, pharmaceutical, and genetic interventions; and transcriptomics of aging using rotifers provide insights into the metabolic regulators of lifespan and health and suggest future directions for aging research. Capitalizing on the unique biology of Brachionus rotifers, referencing the vast existing literature about the influence of diet and drugs on rotifer lifespan and health, continuing the development of genetic tools for rotifers, and growing the rotifer research community will lead to new discoveries a better understanding of the biology of aging.

Natural plants must actively allocate their limited resources for survival and reproduction. Although vegetative growth, sexual reproduction, asexual reproduction and defense are all basic processes in the life cycle of plants, the strategies used to allocate resources between these processes are poorly understood. These processes are conspicuous in naturally grown Aconitum kusnezoffii Reichb., which makes it a suitable study subject. Here, the morphology, dry matter, total organic carbon, total nitrogen and aconitum alkaloid levels of shoot, principal root (PR) and lateral roots were measured throughout the growing season. Then, transcriptome and metabolite content analyses were performed. We found that vegetative growth began first. After vegetative growth ceased, sexual development began. Flower organ development was accompanied by increased photosynthesis and the PR consumed temporarily stored resources after flower formation. Asexual propagule development initiated earlier than sexual reproduction and kept accumulating resources after that. Development was slow before flower formation, mainly manifesting as increasing length; then, after flower formation it accelerated via enhanced material transport and accumulation. Defense compounds were maintained at low levels before flowering. In particular, the turnover of defense compounds was enhanced before and after flower bud emergence, providing resources for other processes. After flower formation, defense compounds were accumulated. The pattern found herein provides a vivid example for further studies on resource allocation strategies. The exciting finding that the PR, as a more direct storage site for photosynthate, is a buffer unit for resources, and that defense compounds can be reused for other processes, suggests a need to explore potential mechanisms.

Organisms across the tree of life have complex life cycles that include both sexual and asexual reproduction or that are obligately asexual. These organisms include ecologically dominant species that structure many terrestrial and marine ecosystems, as well as many pathogens, pests, and invasive species. We must consider both the evolution and maintenance of these various reproductive modes and how these modes shape the genetic diversity, adaptive evolution, and ability to persist in the species that exhibit them. Thus, having a common framework is a key aspect of understanding the biodiversity that shapes our planet. In the 2019 AGA President’s Symposium, Sex and Asex: The genetics of complex life cycles, researchers investigating a wide range of taxonomic models and using a variety of modes of investigation coalesced around a common theme—understanding not only how such complex life cycles may evolve, but how they are shaped by the evolutionary and ecological forces around them. In this introduction to the Special Issue from the symposium, we give an overview of some of the key ideas and areas of investigation (a common clonal lexicon, we might say) and introduce the breadth of work submitted by symposium participants.

Climate change events and anthropogenic activities (e.g. translocation of non-indigenous species) have been proposed to account for the rise of jellyfish blooms in coastal environments. Bloom-forming scyphozoan jellyfish of the genus Aurelia have successfully invaded new habitats and have caused damaging blooms. In attempting to understand the underlying reasons for their success, researchers have investigated immediate effects of changing environmental conditions (e.g. temperature) on scyphistomae of single/unknown generations, with a particular focus on asexual reproduction. However, it remains unclear how scyphistomae respond to changing conditions over longer time-scales or across generations, and how those responses influence bloom occurrence. Here, we examined the role of transgenerational acclimation in asexual reproduction of A. aurita scyphistomae in a 72 d orthogonal experiment, combining 3 parental with 3 offspring temperatures of 8, 12 and 16°C. The null hypothesis was that the thermal history of the parental (F0) generation will not affect asexual reproduction in the offspring (F1) generation. Our results indicated that, provided with a transgenerational temperature change, parent scyphistomae do modify the reproductive output and timing of offspring. Scyphistomae from ‘cold’ (8°C) parents displayed the greatest reproductive output (2.86 buds per scyphistoma) and earliest budding commencement (23.86 d) at warm temperature (16°C). Scyphistomae from ‘warm’ (16°C) parents displayed the greatest reproductive potential (2.63 buds) at medium temperature (12°C). Cold temperature (8°C) caused considerable inhibition of asexual reproduction in offspring scyphistomae, independent of the parental thermal history. Transgenerational acclimation may benefit potentially invasive jellyfish species facing climate-related and/or human-induced changes in the global marine environment, by facilitating asexual reproduction and subsequent bloom events.

The transition to asexual reproduction is frequent and widespread across the tree of life and constitutes a major life history change. Without sexual reproduction, selection on sexually selected traits is expected to be weaker or absent, allowing the decay and ultimately loss of sexual traits. In this study, we applied an experimental approach to investigate the decay of reproductive traits under asexuality in two asexual populations of the springtail Folsomia candida. Specifically, we compared several key male sexual traits of a sexual population and two distinct parthenogenetic lines. To allow direct comparisons between sexual and asexual individuals we first determined a suite of life history characteristics in the sexual F. candida population, which performs an indirect transfer of sperm packages (spermatophores).To investigate the decay of male sexual traits under asexuality we measured the size of spermatophores, quantified the amount of sperm DNA material, and tested spermatophore attractiveness to females in all three populations. The amount of sperm DNA material in the sperm droplets and the attractiveness of spermatophores were lower in the asexual lines compared to the sexual population. However, the two asexual lines differed in the extent of decay of these traits. Our results are consistent with predictions from neutral mutation accumulation theory, and thus suggest this to be the main evolutionary process underlying the decay of male traits in F. candida.

A growing body of research suggests that many clonal populations maintain genetic diversity even without occasional sexual reproduction. The purpose of our study was to document variation in single-nucleotide polymorphism (SNP) diversity, DNA content, and pathogen susceptibility in clonal lineages of the New Zealand freshwater snail, Potamopyrgus antipodarum. We studied snails that were collected from multiple field sites around a single lake (Lake Alexandrina), as well as isofemale clonal lineages that had been isolated and maintained in the laboratory. We used the kompetitive allele specific PCR (KASP) method to genotype our samples at 46 nuclear SNP sites, and we used flow cytometry to estimate DNA content. We found high levels of SNP diversity, both in our field samples and in our clonal laboratory lines. We also found evidence of high variation in DNA content among clones, even among clones with identical genotypes across all SNP sites. Controlled pathogen exposures of the laboratory populations revealed variation in susceptibility among distinct clonal genotypes, which was independent of DNA content. Taken together, these results show high levels of diversity among asexual snails, especially for DNA content, and they suggest rapid genome evolution in asexuals.

Acoela (Acoelomorpha) represents one of the most spectacular animal taxa with debatable phylogenetic position. Particularly, acoel genus Convolutriloba is of special interest due to the inhabitance mostly in marine aquaria and the development of unique ways of asexual reproduction, while the sexual one is rarely described. The aim of the present work is the ultrastructural investigation of reproductive system in preferably asexually-reproducing acoel Convolutriloba retrogemma, type species of the genus. In all specimens studied, the oocytes were absent, despite the spermatozoa and female copulatory organs (seminal bursa with mouthpiece) were being fully developed. The spermatozoon of C. retrogemma represents an elongated filiform cell with a pair of incorporated axonemes with a formula 9 + 0, axial microtubules and three types of cytoplasmic inclusions. The bursa mouthpiece is composed of matrix cells with the electron-dense sclerotized core surrounding the lumen, and electron-transparent periphery containing most cell organelles, as well as the intercalary (glandular) cells between them. In all individuals studied by electron microscopy, the lumen of the mouthpiece is always locked with a “plug” composed of various cellular elements, including the sclerotized actin fibers, preventing the insemination. The comparative morphology of the reproductive system of Convolutriloba and evolutionary role of asexual reproduction within this genus are discussed.

Parthenogenesis is asexual reproduction without any required participation from males and, as such, is a null model for sexual reproduction. In a comparative context, we can expand our understanding of the evolution and ecology of sex by investigating the consequences of parthenogenesis. In this review, we examine the theoretical predictions of and empirical results on the evolution of asexual reproduction in vertebrates, focusing on recent studies addressing the origins and geographic spread of parthenogenetic lineages and the genomic consequences of an asexual life history. With advances in computational methods and genome technologies, researchers are poised to make rapid and significant progress in studying the origin and evolution of parthenogenesis in vertebrates, thus providing an important perspective on understanding biodiversity patterns of both asexual and sexual populations.