Are changes in remotely sensed canopy cover associated to changes in vegetation structure,diversity, and composition in recovered tropical shrublands?

The recovery of vegetation cover is a process that has important implications for the conservation of biodiversity and ecosystem services. Generally, the recovery of vegetation cover is documented over large areas using remote sensing, and it is often assumed that ecosystem properties and processes recover along with remotely sensed canopy cover. Here we analyze and compare the structure, composition, and diversity of trees and shrubs among plots established in a stratified random sampling design over four remotely sensed canopy cover change (CCC) categories defined according to a gradient in the percent of canopy cover. Plots were located in the Lake Cuitzeo basin (Mexico), where canopy recovery associated with agricultural abandonment has occurred in recent decades (1975–2000). We found that diversity measures, basal area, tree and shrub density, ground-truthed canopy cover, and mean plant height increased with increasing CCC category. However, Shannon index (H′) was lower in the CCC category with the most closed canopy cover category than in plots apparently not affected by agriculture. Furthermore, ordination analyses showed that composition of dominant species were not associated with CCC categories. Our results suggest that canopy closure in our study area is not associated with the recovery of species diversity, and does not result in similar species dominance as in sites not affected by agriculture.     

Pollination of the cycad <Emphasis Type="Italic">Zamia incognita</Emphasis> A. Lindstr. &amp; Idárraga by <Emphasis Type="Italic">Pharaxonotha</Emphasis> beetles in the Magdalena Medio Valley,Colombia: a mutualism dependent on a specific pollinator and its significance for conservation

The genus Zamia (Zamiaceae: Cycadales) exhibits its greatest diversity in Colombia and is highly threatened by habitat loss, extraction for ornamental plant trade, and mining, among other factors. One of the most important considerations for the effective conservation of Zamia is its highly specialized reproductive biology. Despite the importance of pollination for the populations’ viability, no studies have examined the pollination process of cycads in Colombia. Herein, we describe the pollination process of Zamia incognita A. Lindstr. & Idárraga, in a natural population. Exclusion experiments were performed by selectively excluding wind, beetles, both, or neither, which demonstrated that Pharaxonotha beetles are effective pollinators of Zamia incognita and that wind does not play any role as pollen vector. By following beetles marked with fluorescent dyes and directly observing beetle movements on and into female cones and micropyles, we confirmed that Pharaxonotha sp. is the effective pollinator of Z. incognita. The beetles traveled a maximum dispersal distance from a male to female cone of nearly 22 m and a minimum distance of 5 m. We found Pharaxonotha beetles in male cones, where they complete their life cycle. Cones produce heat in a circadian pattern associated with the elongation of the cones and pollen shedding. The increase in cones’ temperature appears to play an important role in beetle attraction. We suggest that pollination droplets on the micropyles would be a reward to pollinators. We also discuss the relationship of this Zamia species with other insects, which have important consequences for the conservation of web interactions.     

Genetic diversity and spatial structure of the Rufous‐throated Antbird (Gymnopithys rufigula), an Amazonian obligate army‐ant follower

Amazonian understory antbirds are thought to be relatively sedentary and to have limited dispersal ability; they avoid crossing forest gaps, and even narrow roads through a forest may limit their territories. However, most evidence for sedentariness in antbirds comes from field observations and plot‐based recapture of adult individuals, which do not provide evidence for lack of genetic dispersal, as this often occurs through juveniles. In this study, we used microsatellite markers and mitochondrial control‐region sequences to investigate contemporary and infer historical patterns of genetic diversity and structure of the Rufous‐throated Antbird (Gymnopithys rufigula) within and between two large reserves in central Amazonia. Analyses based on microsatellites suggested two genetically distinct populations and asymmetrical gene flow between them. Within a population, we found a lack of genetic spatial autocorrelation, suggesting that genotypes are randomly distributed and that G. rufigula may disperse longer distances than expected for antbirds. Analyses based on mitochondrial sequences did not recover two clear genetic clusters corresponding to the two reserves and indicated the whole population of the Rufous‐throated Antbird in the region has been expanding over the last 50,000 years. Historical migration rates were low and symmetrical between the two reserves, but we found evidence for a recent unilateral increase in gene flow. Recent differentiation between individuals of the two reserves and a unilateral increase in gene flow suggest that recent urban expansion and habitat loss may be driving changes and threatening populations of Rufous‐throated Antbird in central Amazonia. As ecological traits and behavioral characteristics affect patterns of gene flow, comparative studies of other species with different behavior and ecological requirements will be necessary to better understand patterns of genetic dispersal and effects of urban expansion on Amazonian understory antbirds.     

Molecular data and distribution dynamics indicate a recent and incomplete separation of manakins species of the genus Antilophia (Aves: Pipridae) in response to Holocene climate change

To determine a hypothetical scenario that accounts for the diversification of the two species of the genus Antilophia, we conducted multilocus molecular comparisons and species distribution modeling for the two taxa, which have distinct male plumage coloration patterns and allopatric geographic distributions, despite the high degree of genetic similarity indicated by recent studies. Three mitochondrial and three nuclear fragments were analyzed. The results indicate clear differences in the genetic diversity of the two species, but with ample sharing of haplotypes in all the markers analyzed, reflecting the absence of reciprocal monophyly, presumably due to the relatively recent and still incomplete separation of the two species. The paleoclimatic distribution models, together with the observed genetic profile indicate a recent process of divergence by geographic isolation in the ancestral populations of the two species. This scenario coincides with the recent climatic events of the South American dry diagonal, which involves the gallery forests of the Cerrado biome and the cloud forest enclaves of the seasonal tropical dry forest of the Caatinga between the late Pleistocene and the mid Holocene.     

Digoxin reduces the mutagenic effects of Mitomycin C in human and rodent cell lines

Digoxin is a drug widely used to treat heart failure and studies have demonstrated its potential as anticancer agent. In addition, digoxin presents the potential to interact with a series of other compounds used in medicine. The aim of the present study was to evaluate in vitro the cytotoxicity, genotoxicity and mutagenicity of digoxin and its potential to interact with the mutagen Mitomycin C (MMC). The cytotoxicity of digoxin was assessed by employing the MTT method and the comet assay was performed to assess the genotoxicity of this medicine in CHO-K1 and HeLa cell lines. Besides, the cytokinesis-block micronucleus assay was performed to assess the mutagenicity and the antimutagenicity of this drug. The Ames assay was also performed with TA98 and TA100 strains of S. typhimurium. Results showed that digoxin was cytotoxic, genotoxic and mutagenic for HeLa and CHO-K1 cell lines at concentrations many times higher than those observed in human therapeutic conditions. Nevertheless, an antimutagenic effect against the mutagen MMC was observed on both cell lines in concentrations near those used therapeutically in humans. This chemoprotective effect observed is an interesting finding that should be better explored regarding its impact in anticancer chemotherapy.     

Crystal structure of the UBR‐box from UBR6/FBXO11 reveals domain swapping mediated by zinc binding

The UBR‐box is a 70‐residue zinc finger domain present in the UBR family of E3 ubiquitin ligases that directly binds N‐terminal degradation signals in substrate proteins. UBR6, also called FBXO11, is an UBR‐box containing E3 ubiquitin ligase that does not bind N‐terminal signals. Here, we present the crystal structure of the UBR‐box domain from human UBR6. The dimeric crystal structure reveals a unique form of domain swapping mediated by zinc coordination, where three independent protein chains come together to regenerate the topology of the monomeric UBR‐box fold. Analysis of the structure suggests that the absence of N‐terminal residue binding arises from the lack of an amino acid binding pocket.     

Genetic Variation in FABP4 and Evaluation of Its Effects on Beef Cattle Fat Content

FABP4 is a protein primarily expressed in adipocytes and macrophages that plays a key role in fatty acid trafficking and lipid hydrolysis. FABP4 gene polymorphisms have been associated with meat quality traits in cattle, mostly in Asian breeds under feedlot conditions. The objectives of this work were to characterize FABP4 genetic variation in several worldwide cattle breeds and evaluate possible genotype effects on fat content in a pasture-fed crossbred (Angus-Hereford-Limousin) population. We re-sequenced 43 unrelated animals from nine cattle breeds (Angus, Brahman, Creole, Hereford, Holstein, Limousin, Nelore, Shorthorn, and Wagyu) and obtained 22 single nucleotide polymorphisms (SNPs) over 3,164?bp, including four novel polymorphisms. Haplotypes and linkage disequilibrium analyses showed a high variability. Five SNPs were selected to perform validation and association studies in our crossbred population. Four SNPs showed well-balanced allele frequencies (minor frequency?>?0.159), and three showed no significant deviations from Hardy-Weinberg proportions. SNPs showed significant effects on backfat thickness and fatty acid composition (P?相似文献   

The Melanosome: An Ideal Model to Study Cellular Differentiation

Melanosomes provide an intriguing model for study at many levels. In part this is due to their unique structure and function, but also in part to their involvement in pigmentary diseases and as a model to study basic cellular mechanisms of organelle biogenesis. Recent studies have elucidated the full proteome of the melanosome and the metabolic and molecular lesions involved in a number of pigmentary diseases have been resolved. This paper summarizes recent advances in the field in these areas.     

Sleep-Wake Patterns of Student Workers and Non-Workers

Adolescents usually exhibit late sleep phase and irregular sleep patterns. As a result, they do not get enough sleep and report daytime sleepiness. This condition could be aggravated in working students who have a more limited time for sleep. In this survey, we investigated the impact of evening classes and employment on the sleep patterns of adolescents. We compared female (n = 17) and male (n = 14) non-worker students to female (n = 28) and male (n = 20) worker students who attended the same high school. The volunteers (aged 17.4 years ± 11 months) answered a sleep log during a 16-day period. Worker students slept and woke up earlier, had a shorter nocturnal sleep length and a shorter daily (nocturnal plus diurnal) sleep length compared to non-working pupils. The four groups of students delayed sleep onset time on weekends, but only worker students delayed wake-up time on Sundays. The wake-up time was similar among groups on Sundays. While student workers tended to increase the sleep length in the weekends, non-working students increased it on Mondays and/or Tuesdays. The results showed that sleep schedules and sleep length were different according to the work status. Going to bed later on Saturday by the four groups of students suggests the influence of social activities, while a later wake-up time on Sundays could result from a shorter sleep length on workdays.