Pseudoroegneria spicata (Poaceae: Triticeae) is an abundant, allogamous species widely adapted to the temperate, semiarid steppe and open woodland regions of western North America. Amplified fragment length polymorphism (AFLP), model-based Bayesian clustering, and other methods of hypothesis testing were used to investigate genetic diversity and population structure among 565 P. spicata plants ...

BACKGROUND Previous cytological and single copy nuclear genes data suggested the St and Y genome in the StY-genomic Elymus species originated from different donors: the St from a diploid species in Pseudoroegneria and the Y from an unknown diploid species, which are now extinct or undiscovered. However, ITS data suggested that the Y and St genome shared the same progenitor although rather few S...

Theories based on competition for resources predict a monotonic negative relationship between population density and individual biomass in plant populations. They do not consider the role of facilitative interactions, which are known to be important in high stress environments. Using an individual-based 'zone-of-influence' model, we investigated the hypothesis that the balance between facilitat...

We describe near-IR imaging data for a sample of 23 Class I sources in the Taurus-Auriga dark clouds. Combining our data with previous photometry, we detect brightness variations of 0.1–0.5 mag in many sources. The near-IR morphologies are consistent with millimeter continuum measurements. Most ( 60%) of the sample are true protostars; the rest may be objects in transition between Class I and C...

We examine the implications of a beat frequency modulated model of T Tauri accretion. In particular we show that measurements of the variability of accretion generated lines can be used in conjunction with existing photometry to obtain a measurement of the underlying photospheric and disc ux. This provides an independent way of checking spectral energy distribution modelling. In addition, we sh...

the aim of this research was to investigate the effect of index species, astragalusammodendron on the associated plants of agropyron tauri and bromus tomentellus fromdifferent aspects in shazand rangeland in southwest of markazi province. the effects ofspecies density and distribution pattern and then index species on the soil properties werestudied. based on the randomized – systematic method,...

Protostars are precursors to the nearly fully assembled T-Tauri and Herbig Ae/Be type stars undergoing quasi-static contraction towards the zero-age main sequence; they are in the process of acquiring the majority of their stellar mass. Although numerous young stars with spatially extended envelope-like structures appear to fit this description, their high extinction has inhibited observers fro...