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The functional composition of plant communities in montane regions has been studied for decades, and most recent analyses find that environmentally favourable landscapes at lower altitudes tend to be dominated by species with resource-acquisitive traits, while more resource-conservative taxa dominate higher-altitude communities. However, it is unclear the extent to which this pattern is driven by co-gradient variation within clades or changes in clade representation across the gradient. To test for co-gradient variation, species composition, phylogenetic structure and functional traits were quantified for 97 species within the plant family Melastomataceae at five locations across a 2500-m altitudinal gradient along Volcán Barva in Costa Rica. Average melastome leaf force to punch, specific leaf area and leaf size vary with altitude, while four other functional traits do not. Taxonomic dissimilarity between communities was correlated with altitudinal difference, while phylogenetic dissimilarity was correlated with altitudinal dissimilarity only when measured with a metric that emphasizes shallow turnover of the tips of the phylogeny. These results highlight how species turnover may be more pronounced than functional or phylogenetic variation along altitudinal gradients. In addition, these results highlight the conservation value of lowland tropical forests, which here harbour a disproportionate amount of phylogenetic and functional diversity.
We report major new insights from recent research at the Powars II Paleoindian red ocher quarry (48PL330). We salvaged more than 7,000 artifacts from Powars II between 2014 and 2016 by screening redeposited sediment from the talus slope below the intact portion of the site. Clovis artifacts dominate the diagnostic artifact assemblage, including 53 Clovis points, 33 preforms, and artifacts associated with a previously unrecognized blade core industry. We report the first radiocarbon dates from the site, determined from dating bone tools, which indicate Cody-aged use (ca. >10,000 cal BP). Further, salvage efforts discovered a previously unknown toolstone source from which many of the Clovis artifacts were produced. The Powars II Clovis points most resemble early Paleoindian points from the far Northern Plains and were likely both produced and discarded in the red ocher quarry after hunting, as evidenced by preform production and the presence of impact fractures on many used points. Given these production and discard patterns, Powars II holds some of the best evidence archaeologists currently have for Paleoindian ritualism related to hunting.
Colliding ring galaxies provide a remarkable testbed for the study of star formation in perturbed galaxies. In the process of passing through a disk system, a small perturbing galaxy generates a density wave of stars and gas which expands into the host disk. This triggers a wave of star formation. As the star forming wave passes through the host galaxy, progressively older burst populations may be found interior to the ring. As part of a multiwavelength study of ring galaxies, we have performed optical and infrared imaging using the Kitt Peak 2.1m telescope. These images are used to explore the relation between stellar density wave amplitude and star formation rate. Color gradients are searched for which would indicate the presence of an aging burst population interior to the ring.
The rapid spread of glyphosate-resistant sourgrass populations generates concern in the agricultural production sector in Brazil. Nonetheless, there is not much information related to the frequency and dispersion of sourgrass throughout recent years. We investigated the frequency and dispersion of glyphosate-resistant sourgrass populations in Brazilian agricultural regions as part of a larger-scale weed resistance monitoring study. A discriminatory rate of 960 g ae ha−1 of glyphosate was used on plants at the 2- to 3-tiller stage, originating from 2,593 populations of sourgrass sampled in 329 counties in 14 Brazilian states between 2012 and 2015. The dispersion of sourgrass populations originated in western Paraná State, next to the Paraguay border, where the first resistance case was reported. Its dispersion to the central region of Brazil, mainly in soybean-producing areas, is most likely a consequence of agricultural equipment movement and wind-mediated dispersal. Glyphosate-resistant sourgrass populations were found in every geographical region across all Brazilian states tested. These data highlight the importance of an appropriate weed resistance monitoring program to track the evolution and dispersion of resistance to mitigate these issues by focusing efforts regionally and raising awareness among stakeholders in each region.
Studies have long noted the influence of stone package size and reduction intensity on lithic assemblage composition, particularly in the form of flake size distributions. However, it remains difficult to distinguish objectively the effect of either factor in archaeological contexts without controlling for the variation in one of the two variables. Here we report on an experimental study designed to test the null hypotheses that original stone size and reduction intensity have no impact on the size distribution of lithic flake debris produced during core reduction. Results indicate statistically significant influence from original stone size but not reduction intensity, although the effects from the former are low enough to be considered trivial. In reviewing a sequence of archaeological assemblages from a Middle Paleolithic site, all exhibit an excess of smallsized materials in comparison to the experimental data. When exceptionally high frequencies of the smaller size classes occur, taphonomic processes are clearly responsible.
We have been conducting multi-color observations of a sample of classical ring galaxies with the aim of using them to study the formation and evolution of massive stars. We compare theoretical predictions for the expected color of the material inside the rings assuming that massive stars are created in the wake of the expanding wave. We present ground based data for VIIZw466 and HST data for IIZw28 and the Cartwheel which show strong color gradients.
Gd2TixZr2−xO7 (x = 0 to 2) pyrochlore was irradiated by 30 MeV C60 clusters, which provide an extremely high ionizing energy density. High-resolution transmission electron microscopy revealed a complex ion-track structure in Gd2Ti2O7 and Gd2TiZrO7, consisting of an amorphous core and a shell of a disordered, defect-fluorite structure. As compared with the irradiation by 1.5 GeV U ions with the highest energy loss, the track structure is consistent with tracks created by monoatomic swift heavy ions, but the diameters (with the entire diameter of 17 nm for Gd2Ti2O7 and 15 nm for Gd2TiZrO7) are significantly larger due to the much smaller velocity and higher energy density of the C60 ions. Ion tracks created by monoatomic ions are challenging to describe by HRTEM, as the boundary between disordered fluorite and pyrochlore matrix is less distinct. However, the C60 irradiation shows a clearly resolved ion track with completely crystalline, disordered, defect-fluorite structure around an amorphous core. Based on the distinct boundaries of the track morphology, inelastic thermal-spike calculations were used to describe the track size and extract critical energy densities for the interpretation of the complex core–shell morphologies for the different pyrochlore compositions.
In 2011 we carried out the first systematic survey to determine the density and abundance of endemic forest primates in Siberut National Park, in the Mentawai Islands of West Sumatra, Indonesia. Distance sampling was employed to survey 18 transects located systematically throughout the Park, yielding a total survey effort of 192 km and 285 observations of primates for data analysis. From density estimates for the four resident primate species, the Siberut langur Presbytis siberu, the pig-tailed snub-nosed langur Simias concolor, Kloss's gibbon Hylobates klossii and the Siberut macaque Macaca siberu, we extrapolated a total population of c. 51,000 primates within the Park. We conclude that Siberut National Park is of major significance for the continued survival of Siberut's endemic primates, and provide recommendations to help ensure that it will continue to function as a refuge for primates.
Assessment of error and uncertainty is a vital component of both natural and social science. Empirical research involves dealing with all kinds of errors and uncertainties, yet there is significant variance in how such results are dealt with. Contributors to this volume present case studies of research practices across a wide spectrum of scientific fields, including experimental physics, econometrics, environmental science, climate science, engineering, measurement science and statistics. They compare methodologies and present the ingredients needed for an overarching framework applicable to all.