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The cytoplasm of Aegilops kotschyi is known for the induction of male sterility and haploidy in wheat. Both systems originally appeared rather simple, but manipulation of the standard chromosome constitution of the nuclear genome revealed additional interactions. This study shows that while there is little or no allelic variation at the main fertility restorer locus Rfmulti on chromosome arm 1BS, additional genes may also be involved in the nuclear-mitochondrial genome interactions, affecting not only male fertility but also the growth rate, from pollen competition for fertilization and early endosperm divisions all the way to seed size and plant maturity. Some of these effects appear to be of a sporophytic nature; others are gametophytic. Induction of parthenogenesis by a rye inducer in conjunction with the Ae. kotschyi cytoplasm is well known. However, here we show that the cytoplasmic-nuclear interactions affect all aspects of double fertilization: producing maternal haploids from unfertilized eggs, diploids from fertilized eggs or synergids, embryo-less kernels, and fertilized eggs without fertilization of the double nucleus in the embryo sack. It is unclear how frequent the inducers of parthenogenesis are, as variation, if any, is obscured by suppressors present in the wheat genome. Genetic dissection of a single wheat accession revealed five distinct loci affecting the rate of maternal haploid production: four acting as suppressors and one as an enhancer. Only when the suppressing haplotypes are confirmed may it be possible to the identify genetic variation of haploidy inducers, map their position(s), and determine their nature and the mode of action.

Alternative reproductive tactics (ARTs) are thought to be more abundant in males than in females owing to higher fitness variance in males and higher female investment in reproduction, but there are no strong empirical or theoretical studies that support this. Whereas male ARTs tend to act pre-mating (focusing on fertilization), female ARTs can occur at various stages of reproduction (from mate finding to brood care) and form complex networks of decision points. The evolutionary dynamics of female ARTs can be condition- and frequency-dependent, and can be influenced by factors including sexual antagonism and intralocus tactical conflict. Evidence for female ARTs is abundant, and they are more common than is often appreciated. However, their eco-evolutionary drivers are not well understood, calling for future research. It is often argued that anisogamy causes alternative reproductive tactics (ARTs) to be more common in males than females. We challenge this view by pointing out logical flaws in the argument. We then review recent work on the diversity of female ARTs, listing several understudied types such as solitary versus communal breeding and facultative parthenogenesis. We highlight an important difference between male and female ARTs that caused female ARTs to be overlooked: male ARTs tend to focus on successful fertilization, whereas female ARTs occur at many stages of reproduction and often form complex networks of decision points. We propose to study correlated female ARTs as a whole to better understand their drivers and eco-evolutionary dynamics. [ABSTRACT FROM AUTHOR]

Parthenogenesis and interspecific mating are alternative reproductive strategies that species have evolved alternative strategies when the opportunity of sexual reproduction is hindered by the natural environment. However, it is still unclear how to make a choice between parthenogenesis and interspecific mating when females are unable to reproduce sexually with males of the same species.This study mainly investigated the reproductive behaviour of female termites in the absence of male termites of the same species. Here, reproductive behaviours of females Reticulitermes aculabialis (Ra♀) were observed when they encountered a male R. flaviceps (Rf♂) with the absence of male R. aculabialis(Ra♂).The results showed that Ra♀‐Rf♂ tandems were more prevalent and stable compared to Ra♀‐Ra♀ tandems. When a tandem inadvertently broke apart, the female R. aculabialis displayed longer pauses while waiting for male R. flaviceps, but shorter pauses when another female R. aculabialis was involved. Furthermore, there were mating behaviour between female R. aculabialis and males R. flaviceps, resulting in offspring produced in paired Ra♀‐Rf♂ colonies were hybridization between female R. aculabialis and male R. flaviceps.These results suggest that interspecific mating and recombination is an important aspect for the choice of reproduction strategy, which will provide new insights into the trade‐off between gene contribution rate and genetic diversity. [ABSTRACT FROM AUTHOR]

Facultative parthenogenesis is a form of reproduction in which females can either lay unfertilised eggs that typically develop into female offspring only or mate and lay fertilised eggs that develop into male and female offspring. Intriguingly, facultative parthenogens often occur in mixed‐sex populations where reproduction is mostly sexual and all‐female populations where reproduction is asexual. How all‐female populations avoid invasion by males remains unknown. Here, we explored the use of pheromones in male–female communication in a facultatively parthenogenetic stick insect, the peppermint stick insect (Megacrania batesii), and compared chemical signals between females descended from sexually versus parthenogenetically reproducing populations. If parthenogenetic females release less attractive pheromones, this could help explain the persistence of all‐female populations. We found that M. batesii exhibits slight sexual dimorphism in antenna morphology, and behavioural assays provided little evidence that males could locate females solely by volatile pheromones. However, CHC profiles differed substantially between different types of females. Analysis of CHC components indicated a clear genetic difference between females descended from all‐female versus mixed‐sex populations, as well as a maternal effect of female parthenogenetic versus sexual development. Together, our results suggest that males might rely more on close‐range chemical cues to differentiate females, and chemical communication could play a role in the persistence of all‐female populations. [ABSTRACT FROM AUTHOR]

Once infected with parthenogenesis inducing (PI) Wolbachia, the reproductive mode of Trichogramma pretiosum would change from bisexual to thelytokous parthenogenesis; however, male offspring would also appear after maternal females' continuous massive oviposition. Whether there was a relationship between Wolbachia titer and sex determination in T. pretiosum was unclear. In this study, we compared the sex ratio of the offspring of parthenogenetic and bisexual restored lines of T. pretiosum, and measured the Wolbachia titer in parthenogenetic line of T. pretiosum before and after oviposition, in different body parts, as well as at different developmental stages. Results indicated that all the offspring produced by parthenogenetic line females on the 1st day of egg-laying were females, and male offspring were gradually appearing with the increase of females' oviposition age; but the male offspring began to appear on the 1st egg-laying day of bisexual restored line. After oviposition, Wolbachia titer in maternal female of parthenogenetic line was maintained at a lower level compared to those of pre-oviposition females. QRT-PCR results showed that Wolbachia in male offspring was significantly lower than that in female ones; and Wolbachia could be detected in all body parts of female parasitoids, and the titer was highest in abdomen. At different developmental stages, relative Wolbachia titer was higher in eggs and adults than other stages, and the Wolbachia titer in ovaries post-oviposition was significantly lower than that of pre-oviposition. In conclusion, Wolbachia titer is closely related to the sex determination of T. pretiosum. [ABSTRACT FROM AUTHOR]

Summary: The role of maternal tissue in embryogenesis remains enigmatic in many complex organisms. Here, we investigate the contribution of maternal tissue to apical–basal patterning in the kelp embryo.Focussing on Undaria pinnatifida, we studied the effects of detachment from the maternal tissue using microsurgery, staining of cell wall modifications, morphometric measurements, flow cytometry, genotyping and a modified kelp fertilisation protocol synchronising kelp embryogenesis.Detached embryos are rounder and often show aberrant morphologies. When a part of the oogonial cell wall remains attached to the zygote, the apical–basal patterning is rescued. Furthermore, the absence of contact with maternal tissue increases parthenogenesis, highlighting the critical role of maternal signals in the initial stages of development.These results show a key role for the connection to the maternal oogonial cell wall in apical–basal patterning in kelps. This observation is reminiscent of another brown alga, Fucus, where the cell wall directs the cell fate. Our findings suggest a conserved mechanism across phylogenetically distant oogamous lineages, where localised secretion of sulphated F2 fucans mediates the establishment of the apical–basal polarity. In this model, the maternal oogonial cell wall mediates basal cell fate determination by providing an extrinsic patterning cue to the future kelp embryo. [ABSTRACT FROM AUTHOR]

Social insects have developed a broad diversity of nesting and foraging strategies. One of these, inquilinism, occurs when one species (the inquiline) inhabits the nest built and occupied by another species (the host). Obligatory inquilines must overcome strong constraints upon colony foundation and development, due to limited availability of host colonies. To reveal how inquilinism shapes reproductive strategies in a termite host‐inquiline dyad, we carried out a microsatellite marker study on Inquilinitermes inquilinus and its host Constrictotermes cavifrons. The proportion of simple, extended and mixed families was recorded in both species, as well as the presence of neotenics, parthenogenesis and multiple foundations. Most host colonies (95%) were simple families and all were monodomous. By contrast, the inquiline showed a higher proportion of extended (30%) and mixed (5%) families, and frequent neotenics (in 25% of the nests). This results from the simultaneous foundation in host nests of numerous incipient colonies, which, as they grow, may compete, fight, or merge. We also documented the use of parthenogenesis by female–female pairs. In conclusion, the classical monogamous colony pattern of the host species suggests uneventful development of simple foundations dispersed in the environment, in accordance with the wide distribution of their resources. By contrast, the multiple reproductive patterns displayed by the inquiline species reveal strong constraints on foundation sites: founders first concentrate into host nests, then must attempt to outcompete or absorb the neighbouring foundations to gain full control of the resources provided by the host nest. [ABSTRACT FROM AUTHOR]

Ultrasonography is widely used to monitor pregnancy in viviparous species, but it is underutilized as a tool to characterize embryonic development in oviparous species. Currently, a multi-institutional effort is underway to rewild the endangered zebra shark (Stegostoma tigrinum) to locations where this species was previously extirpated by leveraging the reproductive efforts of aquarium sharks as a source of brood stock. Zebra sharks are oviparous and fecund, but a large percentage of their yolked eggs do not result in hatchlings. Therefore, ultrasonography represents a potential tool for distinguishing fertile eggs with developing embryos from degrading eggs, and to diagnose changes in early embryonic development predictive of poor outcomes. The objectives of the current study were to use ultrasonography to assess egg fertility, monitor early embryonic development, and identify morphological indicators that may be predictive of early embryonic mortality. Freshly laid eggs from four female zebra sharks were collected and inventoried daily at Aquarium of the Pacific. Eggs were incubated undisturbed for 2 to 4 weeks and subsequently examined weekly via ultrasound to assess fertility and monitor embryo development. Among 120 fertile eggs, embryos were identified as early as 8 days post-oviposition, with average (±SD) time to first observation at 30 ± 7 days. Morphological and behavioral abnormalities were observed for most embryos (n = 84, 70%) as early as 16 days and up to 95 days post-oviposition. Common abnormalities included: bent or curled tails, vesicle(s) at the base of the yolk stalk, and slow or weak movement. Only one embryo survived to hatch during the study and was genetically-confirmed parthenogenetic, suggesting hatching success for parthenotes is low (<1%). Ultrasonography was demonstrated to be an effective and non-invasive method to determine egg fertility, identify embryos with developmental abnormalities, and monitor embryo growth. [ABSTRACT FROM AUTHOR]

Closely related sexual and parthenogenetic species often show distinct distribution patterns, known as geographical parthenogenesis. Similar patterns, characterized by the existence of separate sexual and parthenogenetic populations across their natural range, can also be found in facultative parthenogens – species in which every female is capable of both sexual and parthenogenetic reproduction. The underlying mechanisms driving this phenomenon in nature remain unclear. Features of the habitat, such as differences in host‐plant phenotypes or niche breadth, could favour sexual or asexual reproductive modes and thus help to explain geographical parthenogenesis in natural insect populations. Megacrania batesii is a facultatively parthenogenetic stick insect that displays geographical parthenogenesis in the wild. We aimed to explore whether sexual and parthenogenetic populations of M. batesii displayed niche differentiation or variations in niche breadth that could explain the separation of the two population types. To do this, we sampled host plants from across the range of M. batesii and quantified phenotypic traits that might affect palatability or accessibility for M. batesii, including leaf thickness, toughness, spike size and density, plant height, and chemical composition. We also quantified host‐plant density, which could affect M. batesii dispersal. We found little evidence of phenotypic differences between host plants supporting sexual versus asexual M. batesii populations, and no difference in host‐plant density or niche breadth between the two population types. Our results suggest that habitat parameters do not play a substantial role in shaping patterns of geographical parthenogenesis in wild populations of M. batesii. Instead, population sex ratio variation could result from interactions between the sexes or dispersal dynamics. [ABSTRACT FROM AUTHOR]

When considering the frequency stability issues brought on by load shifts in a microgrid (μ G) due to a significant integration of fluctuating renewable energy source-based generators and an inherent low inertia, energy storage units (ESUs) are unavoidable. The ESUs can immediately charge or discharge to make up for any shifts in load in the μ G since they react more quickly. This research investigates how a redox flow battery unit (RFBU) impacts the dynamic responses of a standalone μ G (S μ G) in this respect. As the secondary controller, an optimal intelligent model predictive control (iMPC) approach is presented. The cyclical parthenogenesis algorithm is implemented to improve the tuning parameter ( τ w ) in the iMPC cost function to demonstrate an optimal performance of the recommended control approach. The effectiveness of the iMPC approach is contrasted with that of other well-known control approaches. The simulation findings clearly demonstrate the impact of RFBU integration in the S μ G and the capability of the recommended iMPC approach in terms of improved dynamic responses and their transient characteristics. As a consequence, the peak value of the S μ G dynamic response improves by 70.53%, and the settling time improves by 82.26%. The suggested control approach's sensitivity to the S μ G parametric uncertainties is also justified. The closed-loop stability of the suggested approach is also established. The effectiveness of the proposed iMPC approach and the impact of the RFBU integration are then confirmed by statistical analysis. [ABSTRACT FROM AUTHOR]

The stick insects of the genus Clonopsis embody bisexual, parthenogenetic and androgenetic taxa. Clonopsis gallica is an obligate parthenogen with a very wide geographic range, spreading eastwards from Morocco to Tunisia, and across Gibraltar to southern Europe. The body morphology and the egg parameters and pattern are very stable throughout the geographic range, while cytological investigations on follicular mitotic plates and oocyte maturation mechanisms as well as mtDNA findings neatly separated the Moroccan C. gallica collections from the remaining African and European samples, thus revealing a complex phylogenetic scenario. Here we investigated, by two-colour fluorescence in situ hybridization (FISH) of 28S ribosomal and telomeric (TTAGG)n sequences, European C. gallica specimens from three allopatric Italian sites, namely Sicily, Sardinia and Tuscany. We confirmed the variability of mitotic chromosome number and revealed a shared occurrence of colocalized, highly-amplified ribosomal genes and (TTAGG)n interstitial telomeric sequences (ITSs). The labelled sites were constant within the same specimen, but variable in number and chromosome location among specimens, even those coming from the same collecting site. Moreover, the telomeric signals also labelled the centromeric/pericentromeric regions of a few chromosomes, thus showing the presence of another ITS class, generally considered to be the trace of chromosome rearrangements. The finding of different classes of ITSs located on several chromosomes of the complement makes the C. gallica karyotype highly dynamic; its diffuse chromosome repatterning well accounts for the differences between the Moroccan and non-Moroccan populations.

Chaetodactylus krombeini (Acariformes: Astigmata: Chaetodactylidae) mites are kleptoparasites of solitary bees in the genus Osmia and depend on bee hosts for harbourage, nutrition, and dispersal, with infestations increasing morbidity and larval mortality. The life history traits of C. krombeini are unclear, complicating the control efforts of mites in managed bee nests. Mites in the family Chaetodactylidae have a facultative life stage, the heteromorphic deutonymph, used for either dispersal or dormancy when food resources are sparse. The heteromorphic deutonymph life stage is hypothesized to consist only of females, requiring arrhenotokous parthenogenesis to reproduce. This study examined this hypothesis by determining the sex of the adults that developed from each deutonymph morph. Phoretic deutonymphs were isolated after overwintering either with or without a bee host; inert deutonymphs were isolated from field collections from various locations. Mites were individually observed for 14 days, and development was recorded. Mites that reached adulthood were sexed. After 14 days, 32–38% of heteromorphic deutonymphs that reached adulthood were male. These results disprove the previous hypothesis that heteromorphic deutonymphs are exclusively female. The survival and reproductive strategies of C. krombeini are now in question, specifically the role of true arrhenotoky in founding new mite populations. [ABSTRACT FROM AUTHOR]

Parthenogenesis, or virgin birth, describes a mode of reproduction where an egg develops into an offspring without fertilization, and is observed across various vertebrate taxa, excluding mammals. Obligate parthenogenesis, found in around 100 vertebrate species and 1000 invertebrate species, is relatively rare. Conversely, facultative parthenogenesis, where females can reproduce both sexually and parthenogenetically, is observed in some vertebrates, including elasmobranchs. Notably, this phenomenon in elasmobranchs is mainly documented in captivity, allowing for detailed long-term observation. Specifically, this study reports the first case of facultative parthenogenesis in the common smooth-hound shark Mustelus mustelus, a species classified by IUCN as endangered. Here we show that the juvenile M. mustelus were born through parthenogenesis, exhibiting homozygosity at each genetic marker, consistent with terminal fusion automixis. Remarkably, this finding reveals that parthenogenesis can occur annually in these sharks, alternating between two females, and conclusively excludes long-term sperm storage as a cause. Consequently, this enhances our understanding of parthenogenesis in elasmobranchs and highlights the reproductive flexibility of M. mustelus. Overall, these results contribute to our broader understanding of reproductive strategies in elasmobranchs, which could inform conservation efforts for endangered species. [ABSTRACT FROM AUTHOR]

Aim Location Taxon Methods Results and Main Conclusion Understanding the worldwide distribution of species has fascinated scientists at least since Alfred Russel Wallace. Global patterns of belowground biodiversity may fundamentally differ from those of aboveground organisms. Here, we examine the global pattern and potential mechanisms driving the endemism and overlap of a soil microarthropod taxon.Global.Oribatida, Acari.We investigated the global distribution of oribatid mites in five biogeographic regions including North America, South America, Eurasia, Africa and Oceania using a world list on the distribution of ~11,400 described species (including subspecies) at species, genera and family levels.We found that most “endemic” (i.e., only occurring in one of the regions) species (4297) and also genera (143) occurred in Eurasia indicating that this region was the centre of radiation of oribatid mites. Within Eurasia, oribatid mite diversity was highest in Southeast Asia (1975 species) likely reflecting the long tropical history of this region (at least 200 million years), and also high fluctuations in water levels and island formation on the Sunda Shield. On a family level, oribatid mite diversity did not differ between biogeographic regions indicating that oribatid mites are much older than the tropics and older than the existence of Pangaea supporting the view of their origin in the early Palaeozoic. Finally, among the 55 species that occurred in all biogeographic regions nearly 50% reproduce by thelytoky and colonize high latitude ecosystems, indicating that compared to sexual species a disproportionally high number of parthenogenetic species is distributed worldwide suggesting that they possess a general‐purpose genotype. The other ~50% sexuals predominantly occur in tropical/subtropical regions across biogeographic regions supporting the view that resource shortage in tropical regions favours sex. Our findings highlight the importance of biogeographical studies of soil animals to better understand their diversity, distribution and life history strategies. [ABSTRACT FROM AUTHOR]

A male Diachasma muliebre (Musebeck, 1956) (Hymenoptera: Braconidae), an historically reported monophagous, thelytokous parasitoid, was reared from Rhagoletis indifferens Curran, 1932 (Diptera: Tephritidae) puparia. The fly larvae were reared from Prunus emarginata (Douglas ex Hooker) Eaton (Rosaceae) fruit collected in Placer County, California in 2022. An examination of D. muliebre specimens in California collections found four additional males in the California State Collection of Arthropods, the Bohart Museum of Entomology, and the Essig Museum of Entomology. The males were collected over a 60-year period from 1962 to 2022 in Nevada, Placer and Siskiyou Counties some 272 air km apart in northern California. Possible mechanisms explaining the predominately asexual reproduction in D. muliebre and the periodic presence of males are proposed. [ABSTRACT FROM AUTHOR]

Asexual lineages often exhibit broad distributions and can thrive in extreme habitats compared to their sexual counterparts. Several hypotheses can be proposed to explain this pattern. Asexual lineages could be versatile genotypes with wide environmental tolerance, enabling their dispersal and persistence across large geographic areas. Alternatively, asexual genotypes could be ecological specialists that thrive in specific environments and outcompete relative colonizing distantly related with similar conditions in the process. Several aphid species feature widespread obligate asexual lineages, commonly known as 'superclones'. Yet it is often unknown whether these clones are widespread ecological generalists or successful specialists. To explore these hypotheses, we examined climatic niche differentiation among six globally distributed obligate asexual lineages of the cosmopolitan aphid pest, Brachycaudus helichrysi. To ensure that we were investigating the aphid genotype niche and not a by‐product of their association with endosymbionts mediating thermal tolerance, we first verified that clones hosted similar endosymbiont communities. Subsequently, we conducted multivariate analyses on clone occurrence data on a worldwide scale. Our results revealed that, despite their global distribution, B. helichrysi superclones occupy different climatic niches. This study represents the first evidence that aphid superclone distribution can be mediated by distinctive ranges of climatic tolerance. [ABSTRACT FROM AUTHOR]

Parthenogenesis, the development of unfertilized egg cells into embryos, is a key component of apomixis. AtBBM (BABY BOOM), a crucial regulator of embryogenesis in Arabidopsis, possesses the capacity to shift nutritional growth toward reproductive growth. However, the mechanisms underlying AtBBM‐induced parthenogenesis remain largely unexplored in dicot plants. Our findings revealed that in order to uphold the order of sexual reproduction, the embryo‐specific promoter activity of AtBBM as well as repressors that inhibit its expression in egg cells combine to limiting its ability to induce parthenogenesis. Notably, AtRKD5, a RWP‐RK domain‐containing (RKD) transcription factor, binds to the 3′ end of AtBBM and is identified as one of the inhibitory factors for AtBBM expression in the egg cell. In the atrkd5 mutant, we successfully achieved enhanced ectopic expression of AtBBM in egg cells, resulting in the generation of haploid offspring via parthenogenesis at a rate of 0.28%. Furthermore, by introducing chimeric Arabidopsis and rice BBM genes into the egg cell, we achieved a significant 4.6‐fold enhancement in haploid induction through the atdmp8/9 mutant. These findings lay a strong foundation for further exploration of the BBM‐mediated parthenogenesis mechanism and the improvement of haploid breeding efficiency mediated by the dmp8/9 mutant. [ABSTRACT FROM AUTHOR]

The "paradox of sex" refers to the question of why sexual reproduction is maintained in the wild, despite how costly it is compared to asexual reproduction. Because of these costs, one might expect nature to select for asexual reproduction, yet sex seems to be continually selected for. Multiple hypotheses have been proposed to explain this incongruence, including the niche differentiation hypothesis, the Red Queen hypothesis, and accumulation of harmful mutations in asexual species due to inefficient purifying selection. This study focuses on the accumulation of mutations in two terrestrial isopods, Trichoniscus pusillus, which has sexual diploid and parthenogenic triploid forms, and Hyloniscus riparius, an obligately sexual relative. We surveyed sex ratios of both species in an upstate New York population and obtained RNA-seq data from wild-caught individuals of both species to examine within- and between-species patterns of molecular evolution in protein-coding genes. The sex ratio and RNA-seq data together provide strong evidence that this T. pusillus population is entirely asexual and triploid, while the H. riparius population is sexual and diploid. Although all the wild T. pusillus individuals used for sequencing shared identical genotypes at nearly all SNPs, supporting a clonal origin, heterozygosity and SNP density were much higher in T. pusillus than in the sexually reproducing H. riparius. This observation suggests this parthenogenic lineage may have arisen via mating between two divergent diploid lineages. Between-species sequence comparisons showed no evidence of ineffective purifying selection in the asexual T. pusillus lineage, as measured by the ratio of nonsynonymous to synonymous substitutions (dN/dS ratios). Likewise, there was no difference between T. pusillus and H. riparius in the ratios of nonsynonymous to synonymous SNPs overall (pN/pS). However, pN/pS ratios in T. pusillus were significantly higher when considering only SNPs that may have arisen via recent mutation after the transition to parthenogenesis. Thus, these recent SNPs are consistent with the hypothesis that purifying selection is less effective against new mutations in asexual lineages, but only over long time scales. This system provides a useful model for future studies on the evolutionary tradeoffs between sexual and asexual reproduction in nature. [ABSTRACT FROM AUTHOR]

Facultative parthenogenesis (FP) has historically been regarded as rare in vertebrates, but in recent years incidences have been reported in a growing list of fish, reptile, and bird species. Despite the increasing interest in the phenomenon, the underlying mechanism and evolutionary implications have remained unclear. A common finding across many incidences of FP is either a high degree of homozygosity at microsatellite loci or low levels of heterozygosity detected in next-generation sequencing data. This has led to the proposal that second polar body fusion following the meiotic divisions restores diploidy and thereby mimics fertilization. Here, we show that FP occurring in the gonochoristic Aspidoscelis species A. marmoratus and A. arizonae results in genome-wide homozygosity, an observation inconsistent with polar body fusion as the underlying mechanism of restoration. Instead, a high-quality reference genome for A. marmoratus and analysis of whole-genome sequencing from multiple FP and control animals reveals that a post-meiotic mechanism gives rise to homozygous animals from haploid, unfertilized oocytes. Contrary to the widely held belief that females need to be isolated from males to undergo FP, females housed with conspecific and heterospecific males produced unfertilized eggs that underwent spontaneous development. In addition, offspring arising from both fertilized eggs and parthenogenetic development were observed to arise from a single clutch. Strikingly, our data support a mechanism for facultative parthenogenesis that removes all heterozygosity in a single generation. Complete homozygosity exposes the genetic load and explains the high rate of congenital malformations and embryonic mortality associated with FP in many species. Conversely, for animals that develop normally, FP could potentially exert strong purifying selection as all lethal recessive alleles are purged in a single generation. [ABSTRACT FROM AUTHOR]

Potato is the most important non-cereal crop worldwide, and, yet, genetic gains in potato have been traditionally delayed by the crop's biology, mostly the genetic heterozygosity of autotetraploid cultivars and the intricacies of the reproductive system. Novel site-directed genetic modification techniques provide opportunities for designing climate-smart cultivars, but they also pose new possibilities (and challenges) for breeding potato. As potato species show a remarkable reproductive diversity, and their ovules have a propensity to develop apomixis-like phenotypes, tinkering with reproductive genes in potato is opening new frontiers in potato breeding. Developing diploid varieties instead of tetraploid ones has been proposed as an alternative way to fill the gap in genetic gain, that is being achieved by using gene-edited self-compatible genotypes and inbred lines to exploit hybrid seed technology. In a similar way, modulating the formation of unreduced gametes and synthesizing apomixis in diploid or tetraploid potatoes may help to reinforce the transition to a diploid hybrid crop or enhance introgression schemes and fix highly heterozygous genotypes in tetraploid varieties. In any case, the induction of apomixis-like phenotypes will shorten the time and costs of developing new varieties by allowing the multi-generational propagation through true seeds. In this review, we summarize the current knowledge on potato reproductive phenotypes and underlying genes, discuss the advantages and disadvantages of using potato's natural variability to modulate reproductive steps during seed formation, and consider strategies to synthesize apomixis. However, before we can fully modulate the reproductive phenotypes, we need to understand the genetic basis of such diversity. Finally, we visualize an active, central role for genebanks in this endeavor by phenotyping properly genotyped genebank accessions and new introductions to provide scientists and breeders with reliable data and resources for developing innovations to exploit market opportunities. [ABSTRACT FROM AUTHOR]

The bark beetle Ips acuminatus is an important pest in pine-dominated forests of Eurasia. Recently, the frequency of I. acuminatus outbreaks and mortality of host trees have increased, most likely as a result of climate change-related alterations in environmental conditions. Therefore, detailed information on the species' natural history is essential to understand its potential to damage forests and to apply sustainable management measures. We provide a comprehensive overview on the life history of I. acuminatus, focusing on traits that might explain outbreaks and the ability to cause tree mortality. We review its importance for European forestry, outbreak behavior, host plant usage, reproductive biology, temperature-dependent development, diapause and overwintering behavior, and interactions with fungi, bacteria, nematodes and other arthropods. Interestingly, I. acuminatus has a strong nutritional dependency on the fungus Ophiostoma macrosporum, underlined by the presence of a prominent oral mycetangium, a spore-carrying organ, in females, which is not known for other Ips species. Moreover, I. acuminatus can reproduce sexually and asexually (pseudogamy). Additionally, information on the species' evolutionary past provides valuable insights into the origin of certain traits. We present a phylogeny of the genus Ips and examine selected life-history traits in an evolutionary context. Together with its sister species Ips chinensis, I. acuminatus forms a separate clade within Ips. The ancestor of Ips bark beetles originated about 20 million years ago and was a pine-colonizing species inhabiting the Holarctic. Finally, open fields of research are identified to guide future work on this ecologically and economically important pine bark beetle. [ABSTRACT FROM AUTHOR]

Simple Summary: The skin beetle Reesa vespulae is regularly found beyond North America where it originated, having arrived in Europe in the mid-20th century. Initially associated with stored food products, the beetle causes damage in museums by attacking hides, furs, dried plants and zoological collections. Although still only found in a small fraction of museums, it is occasionally present in large numbers. A single female can continue to reproduce, meaning this species can persist over long periods of time. Larvae are trapped more frequently during infestations, suggesting R. vespulae may range widely in search of food. The skin beetle Reesa vespulae is regularly found beyond North America where it originated. The larvae cause considerable concern in museums, as they damage hides or furs in addition to being a special source of damage to collections of dried plants in herbaria or collections of insects and other zoological specimens. Reesa vespulae arrived in Europe in the mid-20th century and was associated mostly with stored food products, but over time, it has become recognised as a museum pest. Although it is still uncommon and may only be observed in a small fraction of museums, when the insect is found in large numbers, it can cause problems. Catches from blunder traps in Austrian museums and from an online database in the UK were used to track changing concern over the insect. As a single female beetle can continue to reproduce because the species is parthenogenetic, its presence can persist over long periods of time. Although small populations in museums are typically found in the adult form, the larval forms are more common where a site is infested by high numbers, perhaps because the larvae and adults must range more widely for food. Although R. vespulae can be controlled using pesticides, it is also possible to kill the larvae within infested materials through freezing or anoxia. [ABSTRACT FROM AUTHOR]

Reproduction is a key feature of all organisms, yet the way in which it is achieved varies greatly across the tree of life. One striking example of this variation is the stick insect genus Bacillus , in which five different reproductive modes have been described: sex, facultative and obligate parthenogenesis, and two highly unusual reproductive modes: hybridogenesis and androgenesis. Under hybridogenesis, the entire genome from the paternal species is eliminated and replaced each generation by mating with the corresponding species. Under androgenesis, an egg is fertilized, but the developing diploid offspring bear two paternal genomes and no maternal genome, as a consequence of unknown mechanisms. Here, we reevaluate the previous descriptions of Bacillus lineages and the proposed F1 hybrid ancestries of the hybridogenetic and obligately parthenogenetic lineages (based on allozymes and karyotypes) from Sicily, where all these reproductive modes are found. We generate a chromosome-level genome assembly for a facultative parthenogenetic species (B. rossius) and combine extensive field sampling with RADseq and mtDNA data. We identify and genetically corroborate all previously described species and confirm the ancestry of hybrid lineages. All hybrid lineages have fully retained their F1 hybrid constitution throughout the genome, indicating that the elimination of the paternal genome in hybridogens is always complete and that obligate parthenogenesis in Bacillus hybrid species is not associated with an erosion of heterozygosity as known in other hybrid asexuals. Our results provide a stepping stone toward understanding the transitions between reproductive modes and the proximate mechanisms of genome elimination. [ABSTRACT FROM AUTHOR]

Parthenogenesis is a form of asexual reproduction in which a gamete (ovum or sperm) develops without being fertilized. Tomer Jordi Chaffer uses parthenogenesis to challenge Don Marquis' future‐like‐ours (FLO) argument against abortion. According to Marquis, (1) what makes it morally wrong to kill us is that it would deprive us of a possible future that we might come to value—a future "like ours" (FLO) and (2) human fetuses are numerically identical to any adult human organism they may develop into, and thus have a FLO. Chaffer contends that if human ova are capable of parthenogenesis, then they would have a FLO, which contraception may deprive them of, but contends this is absurd. Bruce P. Blackshaw challenges Chaffer, contending sexually fertilized embryos are not identical to unfertilized ovum, but this would yield a more absurd implication, that fertilization deprives an ovum of a FLO! Here I show Marquis' account of identity rules out both Chaffer's and Blackshaw's accounts. [ABSTRACT FROM AUTHOR]

The polymitarcyid mayfly Ephoron shigae (Takahashi, 1924) generally propagates via sexual reproduction, but a parthenogenetic-dominant monophyletic strain derived from western Japanese sexual-dominant strains is widely distributed in Japan. This species may provide a case study on distribution patterns of genetic divergence in sexual-dominant and parthenogenetic-dominant strains of aquatic insects. In this study, we sought to characterize the distribution of parthenogenetic-dominant and sexual-dominant strains of E. shigae in eastern Japan and to assess whether there was sex ratio bias among local populations with and without the parthenogenetic strain, as well as the parthenogenetic reproductive success of both strains. We found that in eastern Japan, the parthenogenetic-dominant strain with the cytochrome c subunit I haplotype C1 is more widespread than sexual-dominant strains and that there are sites where both parthenogenetic-dominant and sexual-dominant strains coexist. There was no sex ratio bias at sites where the parthenogenetic-dominant strain was not observed, but at sites with both reproductive strains, the sex ratio was skewed toward females (64–99%), though the degree of bias depended on the relative frequency of the 2 strains. We found no evidence that females of the parthenogenetic-dominant strain mated after emergence; thus, in eastern Japan, females of the parthenogenetic-dominant strain may not mate even when males are present, and they pass through generations by parthenogenesis. The success rates of unfertilized oocytes of the parthenogenetic-dominant strain varied, with developmental success rates of 70% or higher. Oocyte batches with extremely low success rates (<10%) were also observed at 2 of the sites with both strains. Embryo developmental success of unfertilized oocytes in sexual-dominant strains was generally low (<30%), but exceptionally high rates of >90% were observed. At sites with both strains, the degree of developmental success of unfertilized oocytes in the parthenogenetic-dominant strain may be related to its relative frequency. Examining the causes of the distribution of these strains, and how they may change in the future, will provide new perspectives on reproductive modes and geographic parthenogenesis. [ABSTRACT FROM AUTHOR]

A new genus and species, Cretopleciofungivora simpsoni gen. et sp. nov., from the extinct family Pleciofungivoridae (Diptera: Bibionomorpha), is discovered in mid‐Cretaceous Kachin amber. Previously, this family was known only from imprints in sedimentary rocks of the Jurassic and the Lower Cretaceous. Discovery of a representative of Pleciofungivoridae in Kachin amber confirms the presence of the family in the Upper Cretaceous. The new species has a unique structure of fore tarsus, with lobed and extended tarsal segments II to IV, a feature hitherto known only in a few species of extant Sciaroidea. Although not particularly rare, the new species is currently known only from female specimens. Possible reasons for this phenomenon, very unusual in Sciaroidea, are briefly discussed, including parthenogenesis as a potentially plausible hypothesis. [ABSTRACT FROM AUTHOR]

Hybrid parthenogenetic animals are an exceptionally interesting model for studying the mechanisms and evolution of sexual and asexual reproduction. A diploid parthenogenetic lizard Darevskia unisexualis is a result of an ancestral cross between a maternal species Darevskia raddei nairensis and a paternal species Darevskia valentini and presents a unique opportunity for a cytogenetic and computational analysis of a hybrid karyotype. Our previous results demonstrated a significant divergence between the pericentromeric DNA sequences of the parental Darevskia species; however, an in‐depth comparative study of their pericentromeres is still lacking. Here, using target sequencing of microdissected pericentromeric regions, we reveal and compare the repertoires of the pericentromeric tandem repeats of the parental Darevskia lizards. We found species‐specific sequences of the major pericentromeric tandem repeat CLsat, which allowed computational prediction and experimental validation of fluorescent DNA probes discriminating parental chromosomes within the hybrid karyotype of D. unisexualis. Moreover, we have implemented a generalizable computational method, based on the optimization of the Levenshtein distance between tandem repeat monomers, for finding species‐specific fluorescent probes for pericentromere staining. In total, we anticipate that our comparative analysis of Darevskia pericentromeric repeats, the species‐specific fluorescent probes that we found and the pipeline that we developed will form a basis for the future detailed cytogenomic studies of a wide range of natural and laboratory hybrids. Research Highlights: We computationally predicted and experimentally verified fluorescent DNA probes discriminating parental pericentromeric subgenomes in a hybrid parthenogenetic lizard Darevskia unisexualis. We implemented our prediction method as a species‐agnostic Nextflow pipeline. [ABSTRACT FROM AUTHOR]

Copyright of Biology Teaching is the property of East China Normal University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In social insect colonies, selfish behaviour due to intracolonial conflict among members can result in colony-level costs despite close relatedness. In certain termite species, queens use asexual reproduction for within-colony queen succession but rely on sexual reproduction for worker and alate production, resulting in multiple half-clones of a single primary queen competing for personal reproduction. Our study demonstrates that competition over asexual queen succession among different clone types leads to the overproduction of parthenogenetic offspring, resulting in the production of dysfunctional parthenogenetic alates. By genotyping the queens of 23 field colonies of Reticulitermes speratus, we found that clone variation in the queen population reduces as colonies develop. Field sampling of alates and primary reproductives of incipient colonies showed that overproduced parthenogenetic offspring develop into alates that have significantly smaller body sizes and much lower survivorship than sexually produced alates. Our results indicate that while the production of earlier and more parthenogenetic eggs is advantageous for winning the competition for personal reproduction, it comes at a great cost to the colony. Thus, this study highlights the evolutionary interplay between individual-level and colony-level selection on parthenogenesis by queens. [ABSTRACT FROM AUTHOR]

This document summarizes a study on earthworm communities in wildlife sanctuaries in West Bengal, India. The study found that the number of earthworm species varied across the sanctuaries, with one sanctuary being more suitable for earthworm communities based on diversity. Exotic species were identified as indicators in most sanctuaries, except for one where an endemic species was found. The study also observed the range extension of a particular earthworm species in West Bengal and the tolerance of certain species to different environmental factors. The authors suggest further research is needed to understand the genetic variations between parthenogenetic and sexually reproducing colonies of a specific earthworm species. [Extracted from the article]

Summary: Asexual organisms often differ in their geographic distributions from their sexual relatives. This phenomenon, termed geographic parthenogenesis, has long been known, but the underlying factors behind its diverse patterns have been under dispute. Particularly problematic is an association between asexuality and polyploidy in most taxa. Here, we present a new system of geographic parthenogenesis on the tetraploid level, promising new insights into this complex topic.We used flow cytometric seed screen and microsatellite genotyping to characterise the patterns of distribution of sexuals and apomicts and genotypic distributions in Rubus ser. Glandulosi across its range. Ecological modelling and local‐scale vegetation and soil analyses were used to test for niche differentiation between the reproductive groups.Apomicts were detected only in North‐western Europe, sexuals in the rest of the range in Europe and West Asia, with a sharp borderline stretched across Central Europe. Despite that, we found no significant differences in ecological niches. Genotypic richness distributions suggested independence of the reproductive groups and a secondary contact.We argue that unless a niche differentiation (resulting from polyploidy and/or hybridity) evolves, the main factors behind the patterns of geographic parthenogenesis in plants are phylogeographic history and neutral microevolutionary processes, such as clonal turnover. [ABSTRACT FROM AUTHOR]

Brown algae (Phaeophyceae) exhibit a wide diversity of sexual systems, reproductive modes and life histories. The evolution of this diversity has often involved transitions between sexual systems, which may influence genetic diversity and diversification, and phenotypic evolution. This study reports a novel sexual system in kelp. We identified male gametophyte strains of Laminaria pallida that, despite presenting morphological features typical of a male, developed both antheridia and egg-like structures, which suggest an incomplete suppression of femaleness during sexual determination of gametophytes. The sperm released by these variant male gametophytes successfully fertilize eggs produced by female gametophytes, developing into sporophytes with normal morphologies. However, morphologically abnormal sporophytic offspring were formed in isolated variant male gametophytes, indicating that the egg-like structures were not successfully self-fertilized by sperm. The causes of the unsuccessful intragametophytic selfing are unknown, but absence of pheromone production by the egg-like structures is a hypothesis suggested by available evidence. Partial co-sexuality is clearly inherited, as all male gametophyte strains descended from the same sporophyte developed egg-like structures. Further investigation into the genetics and maturation of male partheno-sporophytes will help to estimate the potential effects of this mechanism on natural populations. Morphologically typical male gametophytes in Laminaria pallida developed both antheridia and egg-like structures. Male sexual reproductive ability was retained by partially co-sexual L. pallida gametophytes. Partial co-sexuality appears to be heritable but varies between L. pallida individuals. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hybridization, polyploidy, and apomixis are related to the diversification of angiosperms, generating complex taxonomic relationships between species. Despite the differences in the frequencies of these phenomena, apomixis, the asexual seed production, tends to be frequently associated with hybridization and polyploidy. Apomixis has received more attention due to its potential to preserve desirable phenotypes in agriculture. The joint study of these three phenomena has been little explored, so the main objective of this review was to describe hybridization, polyploidy and apomixis and then analyze how they can be related. A synthesis of the main results of the studies obtained from a specialized literature search, the main patterns that address these three phenomena together, and their evolutionary and ecological consequences are presented.

Abstract In this work we reported injuries caused by the spider mite Oligonychus yothersi on Vitis vinifera leaves and we also investigate the sex ratio of this species under laboratory conditions. To access the aspects regarding reproduction, females were placed individually in arenas made of V. vinifera leaves to oviposit and all progeny were mounted on slides when they reached adulthood to confirm the offspring sex. Our study showed that O. yothersi reproduces by thelytokous /arrhenotokous parthenogenesis, generating low number of males. Additionally, we found vine plants with leaf browning, particularly on the adaxial surface, where mites were usually found.

The coexistence of sexual and asexual lineages is rarely documented in vertebrates. Various ecological and evolutionary mechanisms have been proposed to explain their stable coexistence. Gibel carp (Carassius gibelio), a highly invasive freshwater fish in Europe, is one such example of a sexual and asexual vertebrate, combining gynogenesis (sperm-dependent parthenogenesis) and sexual reproduction. In this study, we focused on vigour-related traits in gynogenetic and sexual forms of gibel carp coexisting in the same habitat, to reveal whether there is a link between parasite load and vigour-related traits reflecting the potential advantage of one reproductive form over another, which may eventually facilitate the obligatory coexistence of sperm-dependent gynogenetic females with sexual males. Using physiological parameters (indexes of somatic condition, energetic condition, and reproductive performance; glucose levels; and erythrocytes-related variables), diploid sexual males, diploid sexual females, and triploid gynogenetic females were found to be differentiated from one another. However, based on immune variables representing innate immunity, specific immunity, and index of immunocompetence, mostly sexual males were found to be weakly differentiated from both groups of females. We revealed different patterns of interactions between parasite abundance and immune variables between sexual and gynogenetic forms. Using parasite assemblage composition, different relationships between parasite assemblage and immunity or physiology in sexual males and sexual females were evidenced, potentially related to male reproduction biology. In contrast, gynogenetic females exhibited the advantage that parasite assemblage composition did not affect their immunity or physiology. Our study suggests that reproduction mode-associated costs of physiology and immunity may facilitate the coexistence of the asexual-sexual complex. We highlight that multiple ecological processes and evolutionary mechanisms contribute to the coexistence of asexual and sexual gibel carp. [ABSTRACT FROM AUTHOR]

Bacteria in the genus Wolbachia have evolved numerous strategies to manipulate arthropod sex, including the conversion of would-be male offspring to asexually reproducing females. This so-called "parthenogenesis induction" phenotype can be found in a number of Wolbachia strains that infect arthropods with haplodiploid sex determination systems, including parasitoid wasps. Despite the discovery of microbe-mediated parthenogenesis more than 30 yr ago, the underlying genetic mechanisms have remained elusive. We used a suite of genomic, computational, and molecular tools to identify and characterize two proteins that are uniquely found in parthenogenesis-inducing Wolbachia and have strong signatures of host-associated bacterial effector proteins. These putative parthenogenesis-inducing proteins have structural homology to eukaryotic protein domains including nucleoporins, the key insect sex determining factor Transformer, and a eukaryotic-like serine–threonine kinase with leucine-rich repeats. Furthermore, these proteins significantly impact eukaryotic cell biology in the model Saccharomyces cerevisiae. We suggest that these proteins are parthenogenesis-inducing factors and our results indicate that this would be made possible by a novel mechanism of bacterial-host interaction. [ABSTRACT FROM AUTHOR]

Summary: In planta haploid induction (HI), which reduces the chromosome number in the progeny after fertilization, has garnered increasing attention for its significant potential in crop breeding and genetic research. Despite the identification of several natural and synthetic HI systems in different plant species, the molecular and cellular mechanisms underlying these HI systems remain largely unknown. This review synthesizes the current understanding of HI systems in plants (with a focus on genes and molecular mechanisms involved), including the molecular and cellular interactions which orchestrate the HI process. As most HI systems can function across taxonomic boundaries, we particularly discuss the evidence for conserved mechanisms underlying the process. These include mechanisms involved in preserving chromosomal integrity, centromere function, gamete communication and/or fusion, and maintenance of karyogamy. While significant discoveries and advances on haploid inducer systems have arisen over the past decades, we underscore gaps in understanding and deliberate on directions for further research for a more comprehensive understanding of in vivo HI processes in plants. [ABSTRACT FROM AUTHOR]

The investigation examines the structure of diploid and polyploid populations within the spined loach group (Cobitis elongatoides-taenia-tanaitica) in the water systems of Western and Central Ukraine, including the Danube River, Dniester River, Southern Bug River, Vistula River, Middle and Upper Dnipro River basins. The study reveals a bipolarity in settlement structure, with a sharp prevalence of either diploids or polyploids, and no discernible geographical trends in spatial distribution. Clonal hybrid polyploids, which make up 70 % of the individuals studied in the region, are most common in settlements along the main river channels, as well as in the middle and lower reaches of first and second-order tributaries. Populations where diploid specimens of the parent species are predominant are located in accessory systems, tributaries of the third and higher orders, upper reaches of first and second-order tributaries, and lakes. This spatial segregation arises from historical circumstances rather than ecological preferences, primarily due to the distance from water corridors through which polyploids invaded in the 1960s-1970s. The displacement of diploid individuals by clonal hybrid polyploids is a universal phenomenon. This is due to the advantages of parthenogenetic reproduction and higher survival rates of polyploids in modern environmental situations. [ABSTRACT FROM AUTHOR]

Wolbachia is a group of bacteria that is known to infect many arthropods and nematodes. It is one of the most common parasitic microbes and is possibly the most common reproductive parasite in the biosphere. The bacterium is best known for its ability to manipulate host reproductive biology where it can induce cytoplasmic incompatibility, parthenogenesis, feminization and male-killing. In the present study, onion thrips (Thrips tabaci Lindeman) were collected from 9 locations in India along with melon thrips (Thrips palmi Karny) and chilli thrips (Scirtothrips dorsalis). From the molecular level detection by using 16s rDNA, the Wolbachia infection has been detected in the onion thrips collected from 6 locations out of 9. Melon thrips and chilli thrips samples were also found to be infected by Wolbachia. The phylogenetic analysis revealed that all detected Wolbachia samples showed that all were distantly related to the previously known Wolbachia samples. [ABSTRACT FROM AUTHOR]

Harvestmen are a major arachnid order that has experienced a dramatic increase in biological knowledge in the 21st century. The publication of the book Harvestmen: The Biology of Opiliones in 2007 stimulated the development of many behavioral studies. Although the book is relatively recent, our understanding of the reproductive biology of harvestmen is already outdated due to the fast accumulation of new data. Our goal is to provide an updated review of the subject to serve as a benchmark for the following years. In the pre-copulatory phase, we explore the evolution of facultative parthenogenesis, the factors that may affect the types of mating system, and the role of nuptial gifts in courtship. Regarding the copulatory phase, harvestmen are unique arachnids because they have aflagellate spermatozoa and a penis with complex morphology. We discuss the implications of these two features for sperm competition and cryptic female choice. In the post-copulatory phase, we connect oviposition site selection and climate conditions to the widespread occurrence of resource defense polygyny, alternative reproductive tactics, and sexual dimorphism in several clades of tropical harvestmen. Finally, we present the different forms of parental care in the order, and discuss the benefits and costs of this behavior, which can be performed either by females or males. Throughout the review, we indicate gaps in our knowledge and subjects that deserve further studies. Hopefully, the information synthesized here will stimulate researchers worldwide to embrace harvestmen as a study system and to improve our effort to unravel the mysteries of their reproductive biology. [ABSTRACT FROM AUTHOR]

Ultrasonography is widely used to monitor pregnancy in viviparous species, but it is underutilized as a tool to characterize embryonic development in oviparous species. Currently, a multi-institutional effort is underway to re-wild the endangered zebra shark (Stegostoma tigrinum) to locations where this species was previously extirpated by leveraging the reproductive efforts of aquarium sharks as a source of brood stock. Zebra sharks are oviparous and fecund, but a large percentage of their yolked eggs do not result in hatchlings. Therefore, ultrasonography represents a potential tool for distinguishing fertile eggs with developing embryos from degrading eggs, and to diagnose changes in early embryonic development predictive of poor outcomes. The objectives of the current study were to use ultrasonography to assess egg fertility, monitor early embryonic development, and identify morphological indicators that may be predictive of early embryonic mortality. Freshly laid eggs from four female zebra sharks were collected and inventoried daily at Aquarium of the Pacific. Eggs were incubated undisturbed for 2 to 4 weeks and subsequently examined weekly via ultrasound to assess fertility and monitor embryo development. Among 120 fertile eggs, embryos were identified as early as 8 days post-oviposition, with average (±SD) time to first observation at 30 ± 7 days. Morphological and behavioral abnormalities were observed for most embryos (n = 84, 70%) as early as 16 days and up to 95 days post-oviposition. Common abnormalities included: bent or curled tails, vesicle(s) at the base of the yolk stalk, and slow or weak movement. Only one embryo survived to hatch during the study and was genetically-confirmed parthenogenetic, suggesting hatching success for parthenotes is low (

The “paradox of sex” refers to the question of why sexual reproduction is maintained in the wild, despite how costly it is compared to asexual reproduction. Because of these costs, one might expect nature to select for asexual reproduction, yet sex seems to be continually selected for. Multiple hypotheses have been proposed to explain this incongruence, including the niche differentiation hypothesis, the Red Queen hypothesis, and accumulation of harmful mutations in asexual species due to inefficient purifying selection. This study focuses on the accumulation of mutations in two terrestrial isopods, Trichoniscus pusillus, which has sexual diploid and parthenogenic triploid forms, and Hyloniscus riparius, an obligately sexual relative. We surveyed sex ratios of both species in an upstate New York population and obtained RNA-seq data from wild-caught individuals of both species to examine within- and between-species patterns of molecular evolution in protein-coding genes. The sex ratio and RNA-seq data together provide strong evidence that this T. pusillus population is entirely asexual and triploid, while the H. riparius population is sexual and diploid. Although all the wild T. pusillus individuals used for sequencing shared identical genotypes at nearly all SNPs, supporting a clonal origin, heterozygosity and SNP density were much higher in T. pusillus than in the sexually reproducing H. riparius. This observation suggests this parthenogenic lineage may have arisen via mating between two divergent diploid lineages. Between-species sequence comparisons showed no evidence of ineffective purifying selection in the asexual T. pusillus lineage, as measured by the ratio of nonsynonymous to synonymous substitutions (dN/dS ratios). Likewise, there was no difference between T. pusillus and H. riparius in the ratios of nonsynonymous to synonymous SNPs overall (pN/pS). However, pN/pS ratios in T. pusillus were significantly higher when considering only SNPs that may have arisen via recent mutation after the transition to parthenogenesis. Thus, these recent SNPs are consistent with the hypothesis that purifying selection is less effective against new mutations in asexual lineages, but only over long time scales. This system provides a useful model for future studies on the evolutionary tradeoffs between sexual and asexual reproduction in nature.

This article discusses the successful generation of haploid plants in foxtail millet through the expression of the dandelion PARTHENOGENESIS (PAR) gene in egg cells. Haploid induction is a valuable technique in crop breeding, and this study demonstrates its feasibility in foxtail millet, a significant multigrain crop. The researchers used a heterologous expression system to introduce the PAR gene into foxtail millet and observed haploid induction in six out of eleven transgenic lines. The haploid plants exhibited distinct characteristics and complete loss of fertility. This research provides insights into the potential application of haploid induction in foxtail millet breeding programs. [Extracted from the article]

The Wolbachia strain that infects the parasitoid wasp Encarsia formosa induces female-producing parthenogenesis. A new study shows that a Wolbachia -encoded gene has replaced the use of the ancestral wasp homologue that normally controls sexual reproduction, resulting in parthenogenesis. [ABSTRACT FROM AUTHOR]

The endemic North American praying mantid, Brunneria borealis Scudder (1896), is obligatorily parthenogenic and wingless. The species is both geographically widespread, distributed over an essentially continuous pericoastal range of more than 2,400 km from eastern Texas to central North Carolina, and abundant in early-stage successional old fields. We used mitochondrial cytochrome oxidase I (COI) analysis to examine the genetic similarities among specimens of this insect and collected from 7 states along this range of distribution. We found no variations in the mitochondrial COI gene, which suggests that this wide geographic distribution of the species is surprisingly recent. We hypothesize that its obligatory parthenogenic status may be an accident of colonization of North America by a single facultative parthenogenic female, and the subsequent distribution was most likely achieved by inadvertent human transport. [ABSTRACT FROM AUTHOR]

The Strongyloides clade, to which the parasitic nematode genus Strongyloides belongs, contains taxa with diverse lifestyles, ranging from free-living to obligate vertebrate parasites. Reproductive strategies are also diverse in this group of nematodes, employing not only sexual reproduction but also parthenogenesis, making it an attractive group to study genome adaptation to specific conditions. An in-depth understanding of genome evolution, however, has been hampered by fragmented genome assemblies. In this study, we generated chromosome-level genome assemblies for two Strongyloides species and the outgroup species Rhabditophanes diutinus using long-read sequencing and high‐throughput chromosome conformation capture (Hi-C). Our synteny analyses revealed a clearer picture of chromosome evolution in this group, suggesting that a functional sex chromosome has been maintained throughout the group. We further investigated sex chromosome dynamics in the lifecycle of Strongyloides ratti and found that bivalent formation in oocytes appears to be important for male production in the mitotic parthenogenesis. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'. [ABSTRACT FROM AUTHOR]