With a few rare exceptions, the vast majority of animals reproduce sexually 1–3. Some species have, however, evolved alternative modes of reproduction by shifting from classical bisexuality to ...unorthodox reproductive systems, like parthenogenesis, gynogenesis, or hybridogenesis 4, 5. Under hybridogenesis, both the maternal and paternal genomes are expressed in somatic tissues, whereas the germline is purely maternal. Recently, a form of hybridogenesis at the level of the society has been reported in some ants, where purebred females develop into reproductive queens and interlineage hybrids into sterile workers 6. Here, we report a unique case of social hybridogenesis in the desert ant Cataglyphis hispanica. Workers are produced exclusively from interbreeding between two distinct genetic lineages, whereas male and female sexuals are produced by asexual reproduction through parthenogenesis. As a consequence, all workers are pure hybridogens, and only maternal genes are perpetuated from one generation to the next. Thus, queens of C. hispanica use sexual reproduction for colony growth, whereas they reproduce asexually through parthenogenesis for germline production.
► Genetic analyses reveal a unique form of social hybridogenesis in the ant C. hispanica ► Nonreproductive workers are all interlineage hybrids ► Male and female sexuals develop from asexual reproduction ► Only the maternal genome is perpetuated across generation
Abstract
Recent research has shown that many cold-adapted species survived the last glacial maximum (LGM) in northern refugia. Whether this evolutionary history has had consequences for their genetic ...diversity and adaptive potential remains unknown. We sampled 14 populations of Carex limosa, a sedge specialized to bog ecosystems, along a latitudinal gradient from its Scandinavian core to the southern lowland range-margin in Germany. Using microsatellite and experimental common-garden data, we evaluated the impacts of global climate change along this gradient and assessed the conservation status of the southern marginal populations. Microsatellite data revealed two highly distinct genetic groups and hybrid individuals. In our common-garden experiment, the two groups showed divergent responses to increased nitrogen/phosphorus (N/P) availability, suggesting ecotypic differentiation. Each group formed genetically uniform populations at both northern and southern sampling areas. Mixed populations occurred throughout our sampling area, an area that was entirely glaciated during the LGM. The fragmented distribution implies allopatric divergence at geographically separated refugia that putatively differed in N/P availability. Molecular data and an observed low hybrid fecundity indicate the importance of clonal reproduction for hybrid populations. At the southern range-margin, however, all populations showed effects of clonality, lowered fecundity and low competitiveness, suggesting abiotic and biotic constraints to population persistence.
Recent reports in model plant species have highlighted a role for DNA methylation pathways in the regulation of the somatic-to-reproductive transition in the ovule, suggesting that apomixis (asexual ...reproduction through seeds) likely relies on RdDM downregulation. Our aim was therefore to explore this hypothesis by characterizing genes involved in DNA methylation in the apomictic grass Eragrostis curvula. We explored floral transcriptomes to identify homologs of three candidate genes, for which mutations in Arabidopsis and maize mimic apomixis (AtAGO9/ZmAGO104, AtCMT3/ZmDMT102/ZmDMT105, and AtDDM1/ZmCHR106), and compared both their spatial and temporal expression patterns during reproduction in sexual and apomictic genotypes. Quantitative expression analyses revealed contrasting expression patterns for the three genes in apomictic vs sexual plants. In situ hybridization corroborated these results for two candidates, EcAGO104 and EcDMT102, and revealed an unexpected ectopic pattern for the AGO gene during germ line differentiation in apomicts. Although our data partially support previous results obtained in sexual plant models, they suggest that rather than an RdDM breakdown in the ovule, altered localization of AtAGO9/ZmAGO104 expression is required for achieving diplospory in E. curvula. The differences in the RdDM machinery acquired during plant evolution might have promoted the emergence of the numerous apomictic paths observed in plants.
Vallisneria natans
(Lour.) Hara is a typical macrophyte engineering plant frequently applied in water restoration projects. This study treated
V. natans
with Gibberellin (GA), and measured its growth ...features and nutrient element allocation as it grew in high, medium, and low fertility substrates. With GA treatment,
V. natans
leaf length, leaf biomass, and total biomass increased significantly (
p
< 0.05), while total concentrations of nitrogen, phosphorus, and soluble sugar in the roots and leaves increased in all substrates, except root total phosphorus values which notably (
p
< 0.05) decreased in low-phosphorus substrate. Moreover, GA treatment significantly (
p
< 0.05) decreased the number of ramets while increasing their total biomass, which indicates that this plant hormone substantially affected
V. natans
asexual reproduction. Substrate available phosphorous (AP) concentrations positively impacted plant growth in a significant manner (
p
< 0.05), and substrate NO
3
−
concentrations decreased significantly (
p
< 0.05) as the plant grew.
V. natans
growth increased substrate Eh while significantly (
p
< 0.05) decreasing substrate NO
3
−
concentrations. It can be concluded that GA might be applied effectively to waterbody restoration projects by improving the growth status of the plant, and that substrate fertility is critical to enhancing both the growth and nutrient conditions of any plant treated with GA.
Knowledge and estimates of species richness at all scales are biased both by our understanding of the evolutionary processes shaping diversity and by the methods used to delineate the basic units of ...diversity. DNA taxonomy shows that diversity may be underestimated by traditional taxonomy, especially for microscopic animals. The effects of such hidden diversity are usually overlooked in ecological studies. Here, we estimate hidden diversity in bdelloid rotifers, a group of microscopic animals. We analyse cryptic diversity using a coalescent approach to infer taxonomical units from phylogenetic trees. Cryptic diversity was measured for eight traditional species of bdelloid rotifers and the results compared to that of the monogonont rotifer
Brachionus plicatilis species complex, which is well studied and for which cross-mating experiments have been performed to explicitly define some of the species boundaries. A taxonomic inflation of up to 34 potential cryptic taxa was found in bdelloids. Cryptic taxa within each traditional species may be spatially isolated, but do not have narrower ecological niches. The species deemed as generalists exhibit the highest cryptic diversity. Cryptic diversity based on molecular characterization is commonly found in animals; nevertheless, the amount of cryptic diversity in bdelloids is much higher than in other groups analysed so far, maybe because of their peculiar parthenogenetic reproduction, other than microscopic size. We discuss this hypothesis in the light of the available empirical evidence from other groups of microscopic invertebrates, such as tardigrades and mites, which share size, habitat heterogeneity, potential for dispersal, and/or parthenogenetic reproduction.
A distinctive group of species historically classified within Pertusaria subgenus Pionospora have been treated at the genus level under the name Variolaria, and more recently Marfloraea. Recent work ...has shown that Lepra is the oldest available name for this group. A nomenclatural summary of the members of the group that occur in North America north of Mexico is presented, including formal new combinations for the epithets that have not already been transferred to Lepra (i.e., P. andersoniae, P. commutata, P. floridiana, P. hypothamnolica, P. multipunctoides, V. pustulata, P. subdactylina, P. trachythallina, P. ventosa and P. waghornei). A key to the species occurring in the region is also presented.
Monostroma nitidum, a monostromatic green algae (MGA) with high economic value, is distributed worldwide. Life cycle often serves as a fundamental criterion for taxonomic classification. Most ...researchers consider the life cycle of M. nitidum to involve dimorphic alternation of generations, although the possibility of a monomorphic asexual life cycle remains unclear. In this study, tufA and 18S rDNA sequences were employed as molecular markers, complemented by morphological analysis, to classify and identify MGA in two distinct habitats: Hailing Island reefs (YJ) and Naozhou Island reefs (ZJ). The results of tufA and 18S rDNA sequence analysis revealed that all samples from YJ and ZJ clustered to the same branch (M. nitidum clade) with high bootstrap support and genetic distances of less than 0.000 and 0.005, respectively. However, morphological observations indicated significant differences in the external morphology of the YJ and ZJ samples, although both initially exhibited a filament‐blade form during early development. The life cycle of the ZJ samples exhibited typical dimorphic alternation of generations, whereas the YJ samples only produced biflagellate asexual gametes with negative phototaxis. Gametes of the YJ samples directly developed into new gametophytes without undergoing the sporophyte stage. Consequently, the YJ and ZJ samples were classified as monomorphic asexual and dimorphic sexual M. nitidum, respectively. These findings provide evidence supporting the monomorphic asexual life cycle of M. nitidum for the classification of MGA.
This study employed molecular markers and morphological studies of two populations of Monostroma nitidum collected from YJ and ZJ. The results revealed no obvious differences in tufA and 18S rDNA sequences between the two populations, although there were extremely significant differences in morphological characteristics. M. nitidum collected from YJ exhibited only a monomorphic asexual life cycle, while samples collected from ZJ followed the typical dimorphic alternation of generations. The results of this study demonstrate that an asexual life cycle is insufficient as the only classification of monostromatic green algae at the genus level. M. nitidum has both sexual and asexual life cycles. The emergence of asexual M. nitidum is the result of environmental selection, they are secondary and have lost the capacity for sexual reproduction for the second time over a long evolutionary period.
Questions
Bryophytes are a common plant component of the mining‐threatened ironstone outcrops called Cangas, although quite neglected. Aiming to improve conservation strategies for this Brazilian ...landscape, here we ask: (a) are there differences in species composition, richness and abundance and the role of reproduction (i.e., sexual and asexual expression, and reproductive success) among bryophyte communities of Cangas; and (b) do abiotic and geographic factors influence species composition on these outcrops?
Location
Eight Canga sites in the Quadrilátero Ferrífero (QF) of the state of Minas Gerais, southeast Brazil.
Methods
We sampled eight Canga sites for bryophyte species composition, richness, abundance, and reproduction (i.e., sexual and asexual expression, reproductive success) using 18 4‐m2 plots per site. Similarities in species composition among sites were assessed by cluster analysis; differences in richness, abundance, and reproduction parameters were tested by ANOVA; and the correlations between species composition and climatic variables, altitude, and geographical distance were tested by the Mantel test.
Results
The Canga sites had unique species compositions of bryophytes, with only liverwort richness and abundance differing significantly among sites. Nonetheless, there were floristic similarities among certain geographically close sites, and bryophyte composition was not completely explained by either environmental variables or geographical distance. Additionally, sexual, and asexual reproduction did not differ among Cangas.
Conclusions
Cangas of the Brazilian QF have unique bryophyte communities (i.e., high beta diversity), especially for liverworts. Liverwort composition was found to be strongly affected by threats to Cangas, especially in areas disturbed by intensive fire. We hypothesize that the local landscape and microclimate have a greater influence on bryophyte diversity than regional aspects. Therefore, future conservation efforts on Cangas must emphasize local diversity and the functionality of liverworts and mosses in different habitats, combined with enhanced protection of Conservation Units.
This is the first study to assess bryophyte diversity among Brazilian Cangas, a very harsh environment threatened by anthropogenic disturbances, such as iron ore mining. Due to the local vegetational heterogeneity in Cangas and the regional singularity of each sampling site, we verified a high beta diversity of bryophytes with a high species richness, especially of liverworts in vegetation islands that were not exposed to intense fire cycles.
Speciation in fungi Giraud, Tatiana; Refrégier, Guislaine; Le Gac, Mickaël ...
Fungal genetics and biology,
06/2008, Volume:
45, Issue:
6
Journal Article
Peer reviewed
In this review on fungal speciation, we first contrast the issues of species definition and species criteria and show that by distinguishing the two concepts the approaches to studying the speciation ...can be clarified. We then review recent developments in the understanding of modes of speciation in fungi. Allopatric speciation raises no theoretical problem and numerous fungal examples exist from nature. We explain the theoretical difficulties raised by sympatric speciation, review the most recent models, and provide some natural examples consistent with speciation in sympatry. We describe the nature of prezygotic and postzygotic reproductive isolation in fungi and examine their evolution as functions of temporal and of the geographical distributions. We then review the theory and evidence for roles of cospeciation, host shifts, hybridization, karyotypic rearrangement, and epigenetic mechanisms in fungal speciation. Finally, we review the available data on the genetics of speciation in fungi and address the issue of speciation in asexual species.
Autophagy is ubiquitously present in eukaryotes. During this process, intracellular proteins and some waste organelles are transported into lysosomes or vacuoles for degradation, which can be reused ...by the cell to guarantee normal cellular metabolism. However, the function of autophagy-related (ATG) proteins in oomycetes is rarely known. In this study, we identified an autophagy-related gene,
encoding a 514-amino-acid protein in
which is the most destructive pathogen of litchi. The transcriptional level of
was relatively higher in mycelium, sporangia, zoospores and cysts. We generated
knockout mutants using CRISPR/Cas9 technology. The
Δ
mutants were significantly impaired in autophagy and vegetative growth. We further found that the Δ
mutants displayed decreased branches of sporangiophore, leading to impaired sporangium production. PlATG6a is also involved in resistance to oxidative and salt stresses, but not in sexual reproduction. The transcription of peroxidase-encoding genes was down-regulated in Δ
mutants, which is likely responsible for hypersensitivity to oxidative stress. Compared with the wild-type strain, the Δ
mutants showed reduced virulence when inoculated on the litchi leaves using mycelia plugs. Overall, these results suggest a critical role for PlATG6a in autophagy, vegetative growth, sporangium production, sporangiophore development, zoospore release, pathogenesis and tolerance to salt and oxidative stresses in
.
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