Penalized likelihood analysis of previously published chloroplast DNA (cpDNA) ndhF sequences suggests that the central-southern Andean genus Chaetanthera diverged ca. 16.5 million years (my) ago, well before the uplift of the Andes to their present heights. Penalized likelihood analysis based on new nuclear ribosomal DNA (rDNA) internal transcribed spacer (ITS) sequences indicates that the most...

Current theory presumes that natural selection on vascular traits is controlled by a trade-off between efficiency and safety of hydraulic architecture. Hence, traits linked to efficiency, such as vessel diameter, should show biogeographic patterns; but critical tests of these predictions are rare, largely owing to confounding effects of environment, tree size and phylogeny. Using wood sampled f...

m a r Terrigenous sediments from Ceara Rise in the western ropical Atlantic Ocean record Pleistocene Amazon Basin cliate variability. Iron oxides and oxyhydroxides in this region riginate mainly from chemically leached Amazon lowland oils. Concentrations of goethite and hematite in the terrignous fraction consistently peak during transitions from lacial to interglacial periods, suggesting an in...

Dust storms are catastrophic natural disasters that beside other disasters frequency occur in the arid and semiaridregions worldwide. Drought occurrence, climate aridity, dryness of the Hamoun Lake cause strong winds to below.These conditions have been prepared for dust storms in Sistan region. The damages to Sistan society have beenmeasured using different criteria. The result shows that, peak...

isfahan province is located in the center of iran and has arid and semi-arid climate. in recent years, water shortage has increased in this region and has affected crop production. wheat is one of the most important crops of the province. in the present research, an index (dei) has been developed for drought evaluation using long term climatic data through application of principle components an...

Climate change is increasing mean temperatures and in the eastern Mediterranean is expected to decrease annual precipitation. The resulting increase in aridity may be too rapid for adaptation of tree species unless their gene pool already possesses variation in drought resistance. Vulnerability to embolism, estimated by the pressure inducing 50% loss of xylem hydraulic conductivity (P 50), is s...

Aridification is often considered a major driver of long-term ecological change and hominin evolution in eastern Africa during the Plio-Pleistocene; however, this hypothesis remains inadequately tested owing to difficulties in reconstructing terrestrial paleoclimate. We present a revised aridity index for quantifying water deficit (WD) in terrestrial environments using tooth enamel δ18O values,...

Genetic variation is often arrayed in latitudinal or altitudinal clines, reflecting either adaptation along environmental gradients, migratory routes, or both. For forest trees, climate is one of the most important drivers of adaptive phenotypic traits. Correlations of single and multilocus genotypes with environmental gradients have been identified for a variety of forest trees. These correlat...

Genetic variation is often arrayed in latitudinal or altitudinal clines, reflecting either adaptation along environmental gradients, migratory routes, or both. For forest trees, climate is one of the most important drivers of adaptive phenotypic traits. Correlations of single and multilocus genotypes with environmental gradients have been identified for a variety of forest trees. These correlat...

Broad-scale comparisons of birds indicate the possibility of adaptive modification of basal metabolic rate (BMR) and total evaporative water loss (TEWL) in species from desert environments, but these might be confounded by phylogeny or phenotypic plasticity. This study relates variation in avian BMR and TEWL to a continuously varying measure of environment, aridity. We test the hypotheses that ...