Dated historical biogeography of the temperate Loliinae (Poaceae, Pooideae) grasses in the northern and southern hemispheres

Divergence times and biogeographical analyses have been conducted within the Loliinae, one of the largest subtribes of temperate grasses. New sequence data from representatives of the almost unexplored New World, New Zealand, and Eastern Asian centres were added to those of the panMediterranean region and used to reconstruct the phylogeny of the group and to calculate the times of lineage-splitting using Bayesian approaches. The traditional separation between broad-leaved and fine-leaved Festuca species was still maintained, though several new broad-leaved lineages fell within the fine-leaved clade or were placed in an unsupported intermediate position. A strong biogeographical signal was detected for several Asian-American, American, Neozeylandic, and Macaronesian clades with different affinities to both the broad and the fine-leaved Festuca. Bayesian estimates of divergence and dispersal-vicariance analyses indicate that the broad-leaved and fine-leaved Loliinae likely originated in the Miocene (13My) in the panMediterranean-SW Asian region and then expanded towards C and E Asia from where they colonized the New World. Further expansions in America (10-3.8My) showed a predominant migratory route from North to South (N America<-->the Andes<-->Patagonia). This late Tertiary scenario of successive colonizations and secondary polyploid radiations in the southern hemisphere from the northern hemisphere was accompanied by occasional transcontinental long-distance dispersal events between South America and New Zealand. Multiple Pliocene dispersal events (3.6-2.5My) from the near SW European and NW African continents gave rise to the Macaronesian Loliinae flora, while a more recent Pleistocene origin (2-1My) is hypothesized for the high polyploid lineages that successfully colonized newly deglaciated areas in both hemispheres.     

Around the world in 10 million years: biogeography of the nearly cosmopolitan true toads (Anura: Bufonidae)

Aim The species‐rich family of true toads (Anura: Bufonidae) has been the focus of several earlier studies investigating the biogeography of geographically widespread taxa. Herein, we employ newly developed Bayesian divergence estimate methods to investigate the biogeographical history of this group. Resulting age estimates are used to test several key temporal hypotheses including that the origin of the bufonid clade pre‐dates Gondwanan vicariance (~105 million years ago, Ma). Area cladograms are also invoked to investigate the geographical origin of the family. Location Worldwide, except the Australia–New Guinea plate, Madagascar and the Antarctic. Methods A phylogenetic hypothesis of the relationships among true toads was derived from analysis of 2521 bp of DNA data including fragments from three mitochondrial (12S, tRNA^val, 16S) and two nuclear (RAG‐1, CXCR‐4) genes. Analysis of multiple, unlinked loci with a Bayesian method for estimating divergence times allowed us to address the timing and biogeographical history of Bufonidae. Resulting divergence estimates permitted the investigation of alternative vicariance/dispersal scenarios that have been proposed for true toads. Results Our area cladogram resulting from phylogenetic analysis of DNA data supports a South American origin for Bufonidae. Divergence estimates indicate that the family originated earlier than had been suggested previously (78–99 Ma). The age of the enigmatic Caribbean clade was dated to the late Palaeocene–early Eocene. A return of bufonids to the New World in the Eocene was followed by rapid diversification and secondary expansion into South America by the early Oligocene (Rupelian). Main conclusions The South American origin of Bufonidae in the Upper Cretaceous was followed by relatively rapid expansion and radiation around the globe, ending with a return to the Americas via a Eurasian/North American land bridge in the Eocene. Though the exact route of this dispersal (Beringia or North Atlantic) remains unclear, an argument is made for the less frequently invoked North Atlantic connection. The origin of the enigmatic Caribbean lineage was found to be consistent with colonization following the bolide impact at the K/T boundary. These findings provide the first, firm foundation for understanding true toad divergence times and their truly remarkable and global radiation.     

Sympathovagal Balance,Nighttime Blood Pressure,and QT Intervals in Normotensive Obese Women

Objective : We describe associations among the heart‐rate‐corrected QT (QTc) interval, QTc dispersion (QTc‐d), circadian BP variation, and autonomic function in obese normotensive women and the effect of sustained weight loss. Research Methods and Procedures : In 71 obese (BMI = 37.14 ± 2.6 kg/m²) women, 25 to 44 years of age, circadian BP variations (24‐hour ambulatory BP monitoring), autonomic function (power spectral analysis of RR interval oscillations), and cardiac repolarization times (QTc‐d and QTc interval) were recorded at baseline and after 1 year of a multidisciplinary program of weight reduction. Results : Compared with nonobese age‐matched women (n = 28, BMI = 23 ± 2.0 kg/m²), obese women had higher values of QTc‐d (p < 0.05) and QTc (p < 0.05), an altered sympathovagal balance (ratio of low‐frequency/high‐frequency power, p < 0.01), and a blunted nocturnal drop in BP (p < 0.01). In obese women, QTc‐d and the QTc interval correlated with diastolic nighttime BP (p < 0.01) and sympathovagal balance (p < 0.01). Waist‐to‐hip ratio, free fatty acids, and plasma insulin levels correlated with QT intervals and reduced nocturnal drops in both systolic and diastolic BP and sympathovagal balance (p < 0.01). After 1 year, obese women lost at least 10% of their original weight, which was associated with decrements of QTc‐d (p < 0.02), the QTc interval (p < 0.05), nighttime BP (p < 0.01), and sympathovagal balance (p < 0.02). Discussion : Sustained weight loss is a safe method to ameliorate diastolic nighttime BP drop and sympathetic overactivity, which may reduce the cardiovascular risk in obese women.     

Measuring agreement of multivariate discrete survival times using a modified weighted kappa coefficient

Summary .  Assessing agreement is often of interest in clinical studies to evaluate the similarity of measurements produced by different raters or methods on the same subjects. We present a modified weighted kappa coefficient to measure agreement between bivariate discrete survival times. The proposed kappa coefficient accommodates censoring by redistributing the mass of censored observations within the grid where the unobserved events may potentially happen. A generalized modified weighted kappa is proposed for multivariate discrete survival times. We estimate the modified kappa coefficients nonparametrically through a multivariate survival function estimator. The asymptotic properties of the kappa estimators are established and the performance of the estimators are examined through simulation studies of bivariate and trivariate survival times. We illustrate the application of the modified kappa coefficient in the presence of censored observations with data from a prostate cancer study.     

Temporal patterns of diversification and microendemism in Eastern Highland endemic barcheek darters (Percidae: Etheostomatinae)

Eastern North America is the location of the world's most species-rich temperate freshwater fish fauna. Hypotheses regarding the geographic and temporal scale of teleost diversification in this region have not been broadly investigated using absolute divergence time estimates among the constituent lineages. This study used time-calibrated molecular phylogenies estimated from mitochondrial and nuclear genes to investigate the temporal and geographic signatures of diversification within barcheek darters, a clade of allopatrically distributed species endemic to the Eastern Highlands. Results from divergence time estimates using an uncorrelated lognormal model suggest that the barcheek darters are an ancient group with a crown node estimate of 16.3 mya, 95% highest posterior density (HPD): [12.4, 20.5], and the clade is characterized by substantial intraspecific divergence times within several species. In particular, the Caney Fork endemic Etheostoma basilare comprises five strongly supported and deeply divergent clades with a most recent common ancestor estimated at 8.0 mya, 95% HPD: [5.6, 10.7]. These results are concordant with the hypothesis that geologically stable areas of eastern North America have facilitated both the generation and preservation of lineages across a substantial breadth of evolutionary time, and that allopatric speciation in darters has occurred at much smaller spatial scales than previously realized.     

An application of the active time model to multiple concurrent variable-interval schedules

The current experiment investigates whether an active time model can account for anomalous results that have emerged from multiple schedule, concurrent variable-interval (VI) VI experiments. The model assumes that (1) during concurrent VI VI training pigeons learn a function that relates time since the most immediate response, i.e., active time, to changeover probabilities and (2) that molar preference is the result of an interaction between inter-response time frequencies and the learned active time changeover functions. Pigeons were trained under a concurrent VI 30-s VI 30-s schedule and a concurrent VI 60-s VI 60-s schedule. Probes were conducted in which VI 30-s and VI 60-s stimuli were paired. During these probes, birds allocated choices equally to the stimuli. The active time model accurately fit individual subject data. In contrast data were not fit by a variant of scalar expectancy theory proposed by Gibbon [Gibbon, J., 1995. Dynamics of time matching: arousal makes better seem worse. Psychon. Bull. Rev. 2, 208-215].     

ZT和2iP对3个南方高丛蓝浆果优选系丛生枝增殖及生长的影响

研究了不同质量浓度ZT和2iP对南方高丛蓝浆果(Vaccinium corymbosum hybrids)优选系A47、A119和A167丛生枝的增殖倍数、质量、含水量和长度的影响.结果表明,在0.5～3.0 mg·L~(-1)质量浓度范围内,随ZT质量浓度提高,3个优选系丛生枝的总增殖倍数、有效增殖倍数、鲜质量、干质量、含水量及总长度均呈增加趋势,而平均长度则呈下降趋势.在2.5～15.0 mg·L~(-1)质量浓度范围内,随2iP质量浓度提高,3个优选系丛生枝的总增殖倍数和含水量先增加后下降,在2iP质量浓度为5.0～10.0 mg·L~(-1)时达到峰值;有效增殖倍数、总长度和平均长度一直呈下降趋势;鲜质量和干质量无明显的变化规律.在改良WPM培养基中添加2.0～3.0 mg·L~(-1) ZT或5.0～10.0 mg·L~(-1) 2iP可使3个南方高丛蓝浆果优选系丛生枝有较高的增殖倍数,而添加0.5～1.0 mg·L~(-1) ZT或2.5 mg·L~(-1) 2iP可使丛生枝生长较好.此外,优选系A47和A167丛生枝的增殖倍数显著高于优选系A119.     

Perturbation expansions of multilocus fixation probabilities for frequency-dependent selection with applications to the Hill-Robertson effect and to the joint evolution of helping and punishment

Natural populations are of finite size and organisms carry multilocus genotypes. There are, nevertheless, few results on multilocus models when both random genetic drift and natural selection affect the evolutionary dynamics. In this paper we describe a formalism to calculate systematic perturbation expansions of moments of allelic states around neutrality in populations of constant size. This allows us to evaluate multilocus fixation probabilities (long-term limits of the moments) under arbitrary strength of selection and gene action. We show that such fixation probabilities can be expressed in terms of selection coefficients weighted by mean first passages times of ancestral gene lineages within a single ancestor. These passage times extend the coalescence times that weight selection coefficients in one-locus perturbation formulas for fixation probabilities. We then apply these results to investigate the Hill-Robertson effect and the coevolution of helping and punishment. Finally, we discuss limitations and strengths of the perturbation approach. In particular, it provides accurate approximations for fixation probabilities for weak selection regimes only (Ns?1), but it provides generally good prediction for the direction of selection under frequency-dependent selection.     

Mathematical modelling of radiotherapy strategies for early breast cancer

Targeted intraoperative radiotherapy (Targit) is a new concept of partial breast irradiation where single fraction radiotherapy is delivered directly to the tumour bed. Apart from logistic advantages, this strategy minimizes the risk of missing the tumour bed and avoids delay between surgery and radiotherapy. It is presently being compared with the standard fractionated external beam radiotherapy (EBRT) in randomized trials. In this paper we present a mathematical model for the growth and invasion of a solid tumour into a domain of tissue (in this case breast tissue), and then a model for surgery and radiation treatment of this tumour. We use the established linear-quadratic (LQ) model to compute the survival probabilities for both tumour cells and irradiated breast tissue and then simulate the effects of conventional EBRT and Targit. True local recurrence of the tumour could arise either from stray tumour cells, or the tumour bed that harbours morphologically normal cells having a predisposition to genetic changes, such as a loss of heterozygosity (LOH) in genes that are crucial for tumourigenesis, e.g. tumour suppressor genes (TSGs). Our mathematical model predicts that the single high dose of radiotherapy delivered by Targit would result in eliminating all these sources of recurrence, whereas the fractionated EBRT would eliminate stray tumour cells, but allow (by virtue of its very schedule) the cells with LOH in TSGs or cell-cycle checkpoint genes to pass on low-dose radiation-induced DNA damage and consequently mutations that may favour the development of a new tumour. The mathematical model presented here is an initial attempt to model a biologically complex phenomenon that has until now received little attention in the literature and provides a 'proof of principle' that it is possible to produce clinically testable hypotheses on the effects of different approaches of radiotherapy for breast cancer.