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FIGURE 2 in Crassula ×mortii (Crassulaceae subfam. Crassuloideae), a new natural hybrid between C. perforata and C. rubricaulis from South Africa's southern Cape

FIGURE 2. Crassula ×mortii from Montagu Pass, Western Cape Province, South Africa. A. Habit. B. Inflorescence lateral view. C. Inflorescence dorsal view. D. Leafy shoot. E. Mark Mort (1969–) while conducting fieldwork in South Africa. Scale bars: A: 30 mm; B: 3 mm; C: 3 mm; D 7 mm. Photographs by the authors (A–D) and Jenny Archibald (E).

FIGURE 1. A. Crassula perforata habit, with leaf pairs basally fused. B. Crassula perforata inflorescence. C. Crassula rubricaulis habit with leaves basally cuneate. D. Crassula rubricaulis inflorescence. E in Crassula ×mortii (Crassulaceae subfam. Crassuloideae), a new natural hybrid between C. perforata and C. rubricaulis from South Africa's southern Cape

FIGURE 1. A. Crassula perforata habit, with leaf pairs basally fused. B. Crassula perforata inflorescence. C. Crassula rubricaulis habit with leaves basally cuneate. D. Crassula rubricaulis inflorescence. E. Leafy shoots of C. perforata (left), C. ×mortii (centre), and C. rubricaulis (right), all from Montagu Pass. Scale bars: A: 7 cm; B: 9 mm; C: 45 mm; D 4.5 mm; E: 8 mm. Photographs: Neil R. Crouch.

FIGURE 3 in Carex ×payettei, a new hybrid of Carex sect. Racemosae described from subarctic Quebec, Canada (Cyperaceae)

FIGURE 3. Distribution range of the studied parental species and hybrid in the Northern Québec and Labrador (north of 54°N). A, Carex atratiformis. B, Carex ×payettei. C, Carex media. Maps provided by the Flore nordique project, Herbier Louis-Marie (QFA), Laval University.

FIGURE 2 in Carex ×payettei, a new hybrid of Carex sect. Racemosae described from subarctic Quebec, Canada (Cyperaceae)

FIGURE 2. Perigynium beaks of the studied parental species and hybrid, in three vertical rows. A, Carex atratiformis (QFA 240451). B, Carex ×payettei (CAN 152624). C, Carex media (QFA 240538). Arrows indicate sharp barbs on the margins of the perigynium beak of Carex ×payettei.

FIGURE 2 in Calanthe × yarlungzangboensis, a new natural hybrid in genus Calanthe (Orchidaceae) from China

FIGURE 2. Bayesian tree from the nrITS, plastid rbcL and matK. The numbers near the nodes are Bayesian posterior probabilities and bootstrap percentage (PP, BP, BP). The portions of Calanthe tree based on (A) plastid DNA and (B) nrITS are shown in the top left ML MP corner.

FIGURE 1 in Calanthe × yarlungzangboensis, a new natural hybrid in genus Calanthe (Orchidaceae) from China

FIGURE 1. Photos of 14 species of Calanthe. A. C. griffithii; B. C. × yarlungzangboensis; C. C. tricarinata; D. C. brevicornu; E. C. herbacea; F. C. nipponica; G. C. alismatifolia; H. C. metoensis; I. C. puberula; J. C. masuca; K. C. plantaginea; L. C. densiflora; M. C. davidii; N. C. mannii.

FIGURE 5 in Calanthe × yarlungzangboensis, a new natural hybrid in genus Calanthe (Orchidaceae) from China

FIGURE 5. Calanthe ×yarlungzangboensis. A. individual; B. front view of flower; C. ovary and column; D. pollinia; E. sepals and petals. (Drawn by Li-Jie Zhu)

FIGURE 4 in Calanthe × yarlungzangboensis, a new natural hybrid in genus Calanthe (Orchidaceae) from China

FIGURE 4. Calanthe ×yarlungzangboensis. A. habitat; B. habit; C. individual; D. front view of flower; E. vertical view of flower; F. peduncle and floral bract; G. ovary and lip; H. perianth and bract; I. lip and column; J. pollinia.

Allopatry, hybridization, and reproductive isolation in Arctostaphylos: phenology and field morphology

Premise of the study: Hybridization plays a key role in introgressive adaptation, speciation, and adaptive radiation as a source of evolutionary innovation. Hybridization is considered common in Arctostaphylos, yet species boundaries are retained in stands containing multiple species. Arctostaphylos contains diploids and tetraploids, and recent phylogenies indicate two clades; we hypothesize combinations of these traits limit or promote hybridization rates. Methods: We statistically analyzed co-occurrence patterns of species by clade membership and ploidy level from 87-0.1 ha plots. We sampled multiple sites to analyze for percent hybridization based on morphology. Finally, phenophases were analyzed by scoring herbarium sheets for a large number of taxa from both clades as well as tetraploids, and second, surveying three field sites over two years for divergence in phenological stages between co-occurring taxa. Key results: Most taxa in Arctostaphylos are allopatric relative to other congenerics. When two taxa co-occur, the patterns are a diploid with a tetraploid, or two diploids from different clades. When three taxa co-occur, the pattern is two diploids from different clades and a tetraploid. Field and herbarium data both indicate flowering phenology is displaced between diploids from the two clades; one of the diploid clades and tetraploids overlap considerably. Conclusions: The two deep clades in Arctostaphylos are genetically distant, with hybrids rare or non-existent when taxa co-occur. Reproductive isolation between clades is enhanced by displaced flowering phenology for co-occurring species. Within clades, taxa appear to have few reproductive barriers other than an allopatric distribution or different ploidy levels.

Dataset: lhp1 FLC-Venus time course imaging – Hybrid protein assembly-histone modification mechanism for PRC2-based epigenetic switching and memory

The histone modification H3K27me3 plays a central role in Polycomb-mediated epigenetic silencing. H3K27me3 recruits and allosterically activates Polycomb Repressive Complex 2 (PRC2), which adds this modification to nearby histones, providing a read/write mechanism for inheritance through DNA replication. However, for some PRC2 targets, a purely histone-based system for epigenetic inheritance may be insufficient. We address this issue at the Polycomb target Flowering Locus C (FLC) in Arabidopsis thaliana, as a narrow nucleation region of only ~three nucleosomes within FLC mediates epigenetic state switching and subsequent memory over many cell cycles. To explain the memory's unexpected persistence, we introduce a mathematical model incorporating extra protein memory storage elements with positive feedback that persist at the locus through DNA replication, in addition to histone modifications. Our hybrid model explains many features of epigenetic switching/memory at FLC and encapsulates generic mechanisms that may be widely applicable.

opencc-by-4.0Apr 2021View details →

Multiple Sclerosis lesions detection by a hybrid Watershed-Clustering algorithm

Computer Aided Diagnosis (CAD) systems have been developing in the last years with the aim of helping the diagnosis and monitoring of several diseases. We present a novel CAD system based on a hybrid Watershed-Clustering algorithm for the detection of lesions in Multiple Sclerosis. Magnetic Resonance Imaging scans (FLAIR sequences without gadolinium) of 20 patients affected by Multiple Sclerosis with hyperintense lesions were studied. The CAD system consisted of the following automated processing steps: images recording, automated segmentation based on the Watershed algorithm, detection of lesions, extraction of both dynamic and morphological features, and classification of lesions by Cluster Analysis. The investigation was performed on 316 suspect regions including 255 lesion and 61 non-lesion cases. The Receiver Operating Characteristic analysis revealed a highly significant difference between lesions and non-lesions; the diagnostic accuracy was 87% (95% CI: 0.83–0.90), with an appropriate cut-off of 192.8; the sensitivity was 77% and the specificity was 87%. In conclusion, we developed a CAD system by using a modified algorithm for automated image segmentation which may discriminate MS lesions from non-lesions. The proposed method generates a detection out-put that may be support the clinical evaluation.

Species divergence and repeated ancient hybridization in a Sulawesian lake system

An increasing volume of empirical studies demonstrated that hybridization between distant lineages may have promoted speciation in various taxa. However, the timing, extent, and direction of introgressive hybridization remain unknown in many cases. Here, we report a possible case in which repeated hybridization promoted divergence of Oryzias ricefishes (Adrianichthyidae) on Sulawesi, an island of Wallacea. Four Oryzias species are endemic to the Malili Lake system in central Sulawesi, which is composed of five tectonic lakes; of these, one lake is inhabited by two species. Morphological and population genomic analyses of genome-wide single-nucleotide polymorphisms revealed that these two sympatric species are phylogenetically sister to but substantially reproductively isolated from each other. Analyses of admixture and comparison of demographic models revealed that the two sympatric species experienced several substantial introgressions from outgroup populations that probably occurred soon after they had secondary contact with each other in the lake. However, the ratio of migrants from the outgroups was estimated to be different between the two species, which is consistent with the hypothesis that these introgressions aided their divergence or prevented them from forming a hybrid swarm. Repeated lake fragmentations and fusions may have promoted diversification of this freshwater fish species complex that is endemic to this ancient lake system.

Weak coupling among barrier loci and waves of neutral and adaptive introgression across an expanding hybrid zone

Hybridization can serve as an evolutionary stimulus, but we have little understanding of introgression at early stages of hybrid zone formation. We analyze reproductive isolation and introgression between a range-limited and a widespread species. Reproductive barriers are estimated based on differences in flowering time, ecogeographic distributions, and seed set from crosses. We find an asymmetrical mating barrier due to cytonuclear incompatibility that is consistent with observed clusters of coincident and concordant tension zone clines (barrier loci) for mtDNA haplotypes and nuclear SNPs. These groups of concordant clines are spread across the hybrid zone, resulting in weak coupling among barrier loci and extensive introgression. Neutral clines had nearly equal introgression into both species' ranges, while putative cases of adaptive introgression had exceptionally wide clines with centers shifted towards one species. Analyses of cline shape indicate that secondary contact was initiated within the last 800 generations with the per-generation dispersal between 200 and 400 meters, and provide some of the first estimates of the strength of selection required to account for observed levels of adaptive introgression. The weak species boundary between these species appears to be in early stages of dissolution, and ultimately will precipitate genetic swamping of the range-limited species.

opencc-zeroOct 2021View details →

Banks grass mite (Acari: Tetranychidae) suppression may add to the benefit of drought-tolerant corn hybrids exposed to water-stress

Spider mite (Acari: Tetranychidae) outbreaks are common on corn grown in the arid West. Hot and dry conditions reduce mite development time, increase fecundity, and accelerate egg hatch. Climate change is predicted to increase drought incidents and produce more intense temperature patterns. Together, these environmental shifts may cause more frequent and severe spider mite infestations. Spider mite management is difficult as many commercially-available acaricides are ineffective due to the development of resistance traits in field mite populations. Therefore, alternative approaches to suppress outbreaks are critically needed. Drought-tolerant plant hybrids alleviate the challenges of growing crops in water-limited environments; yet, it is unclear if drought-tolerant hybrids exposed to water-stress affects mite outbreaks under these conditions. We conducted a greenhouse experiment to evaluate the effect of drought-tolerant corn hybrids on Banks grass mite, a primary pest of corn, under optimal irrigation and water-stress irrigation. This was followed by a 2-year field study investigating the effect of drought-tolerant corn hybrids exposed to the same irrigation treatments on Banks grass mite artificially infested on hybrids and resident spider mite populations. Results showed that water-stressed drought-tolerant hybrids had significantly lower Banks grass mite and resident spider mite populations than water-stressed drought-susceptible hybrids. Interestingly, water-stressed drought-tolerant hybrids had equal Banks grass mite populations to drought-susceptible and drought-tolerant hybrids under optimal irrigation. We posit that planting drought-tolerant hybrids may suppress spider mite outbreaks in water-challenged areas.

opencc-by-4.0Oct 2021View details →

Raw data for "Multi-Length Scale Structure of 2D/3D Dion–Jacobson Hybrid Perovskites Based on an Aromatic Diammonium Spacer"

Raw solid-state NMR data (Bruker format), and optical and XRD data (Microsoft Excel format).

opennotspecifiedOct 2021View details →

FIGURE 1 in Citrus × pubinervia, a new natural hybrid species from central China

FIGURE 1. Main morphological characters of C. × pubinervia and its related species: C. trifoliata A. Fruits, A. Leaves; C. × polytrifolia 1 2 B. Fruits, B. Leaves; C. × pubinervia. C. Fruits, C. Leaves, C. Anatomy of flowers, C. Flowering branch, C. Cross section of young 1 2 1 2 3 4 5 fruit.

opennotspecifiedOct 2021View details →

FIGURE 2 in Citrus × pubinervia, a new natural hybrid species from central China

FIGURE 2. Citrus × pubinervia D. G. Zhang & Z. H. Xiang, Y. Wu. A. Flowering branch, B. Stamens and pistil, C. A petal, D. Fruit and its cross section (drawing by Jianing Yang).

opencc-by-4.0Dec 2018View details →

Hybrid Illumina/PacBio assembly of a virome from the Rhode River at the Smithsonian Environmental Research Center (SERC).

Hybrid Illumina/PacBio assembly of a virome from the Rhode River at the Smithsonian Environmental Research Center (SERC). This dataset was used in the following publication: https://www.frontiersin.org/articles/10.3389/fmicb.2018.03053/full.

opencc-zeroNov 2022View details →

Genotypes of cave, surface and hybrid Astyanax mexicanus

Genetic divergence in the presence of gene flow has been well documented, but there is little information on the specific factors maintaining divergence. The present study investigates this in the Mexican tetra (Astyanax mexicanus), an excellent model for studying this question because surface and cave populations differ markedly in phenotype and genotype, but are interfertile. Previous population studies documented significant gene flow among cave and surface populations but they focused on analyses of neutral markers, whose evolutionary dynamics likely differ from those of genes involved in cave adaptation. The present study advances our understanding of this question by focusing specifically on the genetics responsible for eye and pigmentation reduction, signature traits of cave populations. Direct observations of two cave populations over the course of 63 years verify that surface fish frequently move into the caves and even hybridize with the cavefish. Importantly, however, historical records show that surface alleles for pigmentation and eye size do not persist, but are rapidly eliminated from the cave gene pool. It has been argued that the regression of eyes and pigmentation was driven by drift, but the results of this study suggest that strong selection actively eliminates surface alleles from the cave populations.