Perceived Visual Direction near an Occluder

When an opaque object occludes a more distant object, the two eyes often see different parts of the distant object. Hering s laws of visual direction make an interesting prediction for this situation: the part seen by both eyes should be seen in a different direction than the part seen by one eye. We examined whether this prediction holds by asking observers to align a vertical monocular line segment with a nearby vertical binocular segment. We found it necessary to correct the alignment data for vergence errors, which were measured in a control experiment, and for monocular spatial distortions, which were also measured in a control experiment. Settings were reasonably consistent with Hering's laws when the monocular and binocular targets were separated by 30 arcmin or more. Observers aligned the targets as if they were viewing them from one eye only when they were separated by 2 arcmin; this behavior is consistent with an observation reported by Erkelens and colleagues. The same behavior was observed when the segments were horizontal and when no visible occluder was present. Perceived visual direction when the two eyes see different parts of a distant target is assigned in a fashion that minimizes, but does not eliminate, distortions of the shape of the occluded object

An analysis of binocular slant contrast

When a small frontoparallel surface (a test strip) is surrounded by a larger slanted surface (an inducer), the test strip is perceived as slanted in the direction opposite to the inducer. This has been called the depth-contrast effect, but we call it the slant-contrast effect. In nearly all demonstrations of this effect, the inducers slant is specified by stereoscopic signals, and other signals, such as the texture gradient, specify that it is frontoparallel. We present a theory of slant estimation that determines surface slant via linear combination of various slant estimators; the weight of each estimator is proportional to its reliability. The theory explains slant contrast because the absolute slant of the inducer and the relative slant between test strip and inducer are both estimated with greater reliability than the absolute slant of the test strip. The theory predicts that slant contrast will be eliminated if the signals specifying the inducers slant are consistent with one another. It also predicts reversed slant contrast if the inducers slant is specified by nonstereoscopic signals rather than by stereo signals. These predictions were tested and confirmed in three experiments. The first showed that slant contrast is greatly reduced when the stereo- and nonstereo-specified slants of the inducer are made consistent with one another. The second showed that slant contrast is eliminated altogether when the stimulus consists of real planes rather than images on a display screen. The third showed that slant contrast is reversed when the nonstereo-specified slant of the inducer varies and the stereo-specified slant is zero. We conclude that slant contrast is a byproduct of the visual systems reconciliation of conflicting information while it attempts to determine surface slant

Nomenclature and taxonomy of Croton glabellus L. (Euphorbiaceae), a widespread Caribbean species

The application of the names Croton glabellus, C. lucidus, and Phyllanthus glabellus has been confusing since the earliest publications that used them. After a thorough review of these publications and corresponding herbarium specimens, we clarify the nomenclatural confusion surrounding these names and their taxonomy. We identify a new name, Phyllanthus glabellus Fawc. & Rendle, that was inadvertently made. We make the new combination Croton glabellus subsp. polytrichus, and we designate lectotypes for Astrocasia tremula, Croton subsect. Astraeopsis, C. glandulifer, C. lucidus var. polytrichus, and C. spicatus.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146901/1/tax605029.pd

A revised infrageneric classification and molecular phylogeny of New World Croton (Euphorbiaceae)

Croton (Euphorbiaceae) is a large and diverse group of plants that is most species‐rich in the tropics. We update the infrageneric classification of the New World species of Croton with new evidence from phylogenetic analyses of DNA sequence data from all three genomes. The relationships of species that were previously placed in conflicting positions by nuclear and chloroplast data, such as C. cupreatus, C. poecilanthus, and C. setiger, are further resolved by adding the nuclear EMB2765 and mitochondrial rps3 genes to the molecular sampling. Analyses of rps3 reveal an accelerated rate of evolution within Croton subg. Geiseleria, the only one of the four subgenera that contains numerous herbaceous, annual species. We provide morphological descriptions, species lists, and a key to the 31 sections and 10 subsections recognized in the New World. New taxa that we describe include C. sects. Alabamenses, Argyranthemi, Cordiifolii, Corinthii, Cupreati, Luetzelburgiorum, Nubigeni, Olivacei, Pachypodi, Prisci, and C. subsects. Cubenses, Jamaicenses, and Sellowiorum. Additional transfers are made to the ranks of subgenus, section, and subsection. A total of 712 species of Croton are currently recognized for the New World, with 702 of them assigned here to section.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146834/1/tax603013.pd

Phylogeny and biogeography of Croton alabamensis (Euphorbiaceae), a rare shrub from Texas and Alabama, using DNA sequence and AFLP data

Croton alabamensis (Euphorbiaceae s.s. ) is a rare plant species known from several populations in Texas and Alabama that have been assigned to var. texensis and var. alabamensis , respectively. We performed maximum parsimony, maximum likelihood, and Bayesian analyses of DNA sequences from the nuclear ribosomal internal transcribed spacer (ITS) and 5.8S regions and chloroplast trn L- trn F regions from collections of the two varieties of C. alabamensis and from outgroup taxa. C. alabamensis emerges alone on a long branch that is sister to Croton section Corylocroton and the Cuban endemic genus Moacroton . Molecular clock analysis estimates the split of C. alabamensis from its closest relatives in sect. Corylocroton at 41 million years ago, whereas the split of the two varieties of C. alabamensis occurred sometime in the Quaternary. Amplified fragment length polymorphism (AFLP) analyses were performed using two selective primer pairs on a larger sampling of accessions (22 from Texas, 17 from Alabama) to further discriminate phylogenetic structure and quantify genetic diversity. Using both neighbour joining and minimum evolution, the populations from the Cahaba and Black Warrior watersheds in Alabama form two well-separated groups, and in Texas, geographically distinct populations are recovered from Fort Hood, Balcones Canyonlands, and Pace Bend Park. Most of the molecular variance is accounted for by variance within populations. Approximately equal variance is found among populations within states and between states (varieties). Genetic distance between the Texas populations is significantly less than genetic distance between the Alabama populations. Both sequence and AFLP data support the same relationships between the varieties of C. alabamensis and their outgroup, while the AFLP data provide better resolution among the different geographical regions where C. alabamensis occurs. The conservation implications of these findings are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72311/1/j.1365-294X.2006.02970.x.pd

Sectional rearrangement of arborescent clades of Croton (Euphorbiaceae) in South America: Evolution of arillate seeds and a new species, Croton domatifer

Most of the arborescent Croton species in the New World were treated by Webster as belonging either to C. sect. Cyclostigma Griseb. or C. sect. Luntia (Neck. ex Raf.) G.L. Webster. The circumscription of C. sect. Cyclostigma has been treated recently. In this paper we focus on C. sect. Luntia, which was subdivided by Webster into two subsections, C. subsect. Matourenses and subsect. Cuneati. Using chloroplast trnL‐F and nuclear ITS DNA sequence data, morphology and a broader sampling of additional Croton lineages, we found that the two subsections are not closely related and form distinct monophyletic groups. Substantial morphological differences support the molecular data. A taxonomic recircumscription of the two subsections, elevated to sectional level, is proposed. A key and taxonomic revision, with new synonyms, is provided for C. sect. Cuneati; together with the description of a new species from the coastal mountains of Venezuela, Croton domatifer. The new species is the only one in the genus known to possess leaf domatia. We infer that species in the Cuneati clade have lost the typical Croton caruncle, and some of them have evolved a different, specialized type of aril. We hypothesize that the arillate seeds are an adaptation to dispersal by fish in the Orinoco and Amazon river basins.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147226/1/tax594014.pd

La posición sistemática de Cubanthus y otras especies arbustivas endémicas de Euphorbia (Euphorbiaceae) en Cuba

Cubanthus (Euphorbiaceae) has traditionally been recognized as a small genus of three similar species restricted to Cuba and Hispaniola. In this study we used DNA sequence data from the nuclear ITS and chloroplast ndhF gene regions to investigate its systematic position and the position of four other shrubby Euphorbia species endemic to Cuba: E. cubensis, E. helenae, E. munizii, and E. podocarpifolia. The results demonstrate that all of these taxa belong to a well-supported Antillean clade nested within Euphorbia that also includes E. punicea and E. gymnonota. For that reason, we treat Cubanthus as a section of Euphorbia instead of a separate genus. Euphorbia sect. Adenorima is relegated to a synonym of sect. Cubanthus. New names are proposed for Cubanthus brittonii and Cubanthus linearifolius (Euphorbia millspaughii and E. scutiformis, respectively), and a new combination is made for Cubanthus umbelliformis (Euphorbia umbelliformis). Section Cubanthus belongs to clade C of Euphorbia and is part of a New World assemblage that includes members of sections Euphorbiastrum, Pteroneurae, Portulacastrum, Stachydium, and the former genus Pedilanthus. Based on both the molecular results and morphological differences, two subsections are proposed: subsect. Cubanthus and subsect. Moa. The molecular phylogeny supports the hypothesis that section Cubanthus radiated entirely within the Antilles and the nearby Bahamian archipelago.Cubanthus (Euphorbiaceae) ha sido tradicionalmente reconocido como un género de tres especies muy similares entre sí y endémicas de las islas de Cuba y La Española. En este estudio se emplearon datos de secuencias de ADN tanto nuclear (ITS) como del cloroplasto (ndhF) para investigar la posición sistemática de Cubanthus y de cuatro especies arbustivas de Euphorbia endémicas de Cuba: E. cubensis, E. helenae, E. munizii, y E. podocarpifolia. Los resultados muestran que todas las especies analizadas pertenecen a un clado Antillano anidado en Euphorbia, al cual también pertenecen E. punicea y E. gymnonota. Por tal razón, tratamos a Cubanthus como una sección de Euphorbia en lugar de un género distinto. Euphorbia sección Adenorima se relega como sinónimo de la sección Cubanthus. Se proponen nuevos nombres para Cubanthus brittonii y C. linearifolius (Euphorbia millspaughii y E. scutiformis, respectivamente) y una nueva combinación para Cubanthus umbelliformis (Euphorbia umbelliformis). La sección Cubanthus pertenece al clado C de Euphorbia y es parte de un grupo del Nuevo Mundo que incluye miembros de las secciones Euphorbiastrum, Pteroneurae, Portulacastrum, Stachydium y del anteriormente reconocido género Pedilanthus. Basado en los resultados moleculares y las diferencias morfológicas, se proponen dos subsecciones: subsección Cubanthus y subsección Moa. La filogenia molecular sustenta la hipótesis de que la sección Cubanthus surgió y se diversificó en Las Antillas y el Archipiélago de Las Bahamas

Croton laceratoglandulosus (Euphorbiaceae s.s. ), a new glandular-stipulate species from Brazil and Bolivia, and its systematic position based on molecular analysis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72371/1/j.1095-8339.2008.00844.x.pd

Phylogeny, Adaptive Radiation, and Historical Biogeography in Bromeliaceae: Insights from an Eight-Locus Plastid Phylogeny

Premise: Bromeliaceae form a large, ecologically diverse family of angiosperms native to the New World. We use a bromeliad phylogeny based on eight plastid regions to analyze relationships within the family, test a new, eight-subfamily classification, infer the chronology of bromeliad evolution and invasion of different regions, and provide the basis for future analyses of trait evolution and rates of diversification. Methods: We employed maximum-parsimony, maximum-likelihood, and Bayesian approaches to analyze 9341 aligned bases for four outgroups and 90 bromeliad species representing 46 of 58 described genera. We calibrate the resulting phylogeny against time using penalized likelihood applied to a monocot-wide tree based on plastid ndhF sequences and use it to analyze patterns of geographic spread using parsimony, Bayesian inference, and the program S-DIVA. Results: Bromeliad subfamilies are related to each other as follows: (Brocchinioideae, (Lindmanioideae, (Tillandsioideae, (Hechtioideae, (Navioideae, (Pitcairnioideae, (Puyoideae, Bromelioideae))))))). Bromeliads arose in the Guayana Shield ca. 100 million years ago (Ma), spread centrifugally in the New World beginning ca. 16-13 Ma, and dispersed to West Africa ca. 9.3 Ma. Modern lineages began to diverge from each other roughly 19 Ma. Conclusions: Nearly two-thirds of extant bromeliads belong to two large radiations: the core tillandsioids, originating in the Andes ca. 14.2 Ma, and the Brazilian Shield bromelioids, originating in the Serro do Mar and adjacent regions ca. 9.1 Ma

Platform adaptive trial of novel antivirals for early treatment of COVID-19 In the community (PANORAMIC): protocol for a randomised, controlled, open-label, adaptive platform trial of community novel antiviral treatment of COVID-19 in people at increased risk of more severe disease

Introduction: There is an urgent need to determine the safety, effectiveness and cost-effectiveness of novel antiviral treatments for COVID-19 in vaccinated patients in the community at increased risk of morbidity and mortality from COVID-19. // Methods and analysis: PANORAMIC is a UK-wide, open-label, prospective, adaptive, multiarm platform, randomised clinical trial that evaluates antiviral treatments for COVID-19 in the community. A master protocol governs the addition of new antiviral treatments as they become available, and the introduction and cessation of existing interventions via interim analyses. The first two interventions to be evaluated are molnupiravir (Lagevrio) and nirmatrelvir/ritonavir (Paxlovid). Eligibility criteria: community-dwelling within 5 days of onset of symptomatic COVID-19 (confirmed by PCR or lateral flow test), and either (1) aged 50 years and over, or (2) aged 18–49 years with qualifying comorbidities. Registration occurs via the trial website and by telephone. Recruitment occurs remotely through the central trial team, or in person through clinical sites. Participants are randomised to receive either usual care or a trial drug plus usual care. Outcomes are collected via a participant-completed daily electronic symptom diary for 28 days post randomisation. Participants and/or their Trial Partner are contacted by the research team after days 7, 14 and 28 if the diary is not completed, or if the participant is unable to access the diary. The primary efficacy endpoint is all-cause, non-elective hospitalisation and/or death within 28 days of randomisation. Multiple prespecified interim analyses allow interventions to be stopped for futility or superiority based on prespecified decision criteria. A prospective economic evaluation is embedded within the trial. // Ethics and dissemination: Ethical approval granted by South Central–Berkshire REC number: 21/SC/0393; IRAS project ID: 1004274. Results will be presented to policymakers and at conferences, and published in peer-reviewed journals. // Trial registration number: ISRCTN30448031; EudraCT number: 2021-005748-31