Koch K.A.,219 Hodson Hall |
Quiram G.L.,Evolution and Behavior |
Venette R.C.,U.S. Department of Agriculture
Urban Forestry and Urban Greening | Year: 2010
Oak wilt, caused by the invasive fungal pathogen Ceratocystis fagacearum (Bretz) Hunt, is a serious and fatal disease of oaks, Quercus spp., with red oaks (section Lobatae) generally being more susceptible than white oaks (section Quercus). Oak wilt was first recognized in North America in 1944 and has since been confirmed in 24 eastern, midwestern, and southern states. The purpose of this paper is to review relevant literature on the efficacy of oak wilt treatment options. Root disruption, sanitation, and chemical control methods have been used most often to manage the disease. Root disruption has primarily focused on severing root grafts between oaks. Sanitation has focused on removal and proper disposal of potential spore-producing trees. Chemical control has focused on the use of systemic triazole fungicides. Efficacy of treatments can vary significantly, for example from 54% to 100% for root graft barriers. Educational programs can increase prevention efforts, detection, compliance with recommended management methods, and overall efficacy. Our review confirms that management programs should address underground and overland spread and include an educational component.
Voss R.S.,American Museum of Natural History |
Jansa S.A.,Evolution and Behavior |
Jansa S.A.,University of Minnesota
Biological Reviews | Year: 2012
Mammals that prey on venomous snakes include several opossums (Didelphidae), at least two hedgehogs (Erinaceidae), several mongooses (Herpestidae), several mustelids, and some skunks (Mephitidae). As a group, these taxa do not share any distinctive morphological traits. Instead, mammalian adaptations for ophiophagy seem to consist only in the ability to resist the toxic effects of snake venom. Molecular mechanisms of venom resistance (as indicated by biochemical research on opossums, mongooses, and hedgehogs) include toxin-neutralizing serum factors and adaptive changes in venom-targeted molecules. Of these, toxin-neutralizing serum factors have received the most research attention to date. All of the toxin-neutralizing serum proteins discovered so far in both opossums and mongooses are human α1B-glycoprotein homologs that inhibit either snake-venom metalloproteinases or phospholipase A2 myotoxins. By contrast, adaptive changes in venom-targeted molecules have received far less attention. The best-documented examples include amino-acid substitutions in mongoose nicotinic acetylcholine receptor that inhibit binding by α-neurotoxins, and amino-acid substitutions in opossum von Willebrand factor (vWF) that are hypothesized to weaken the bond between vWF and coagulopathic C-type lectins. Although multiple mechanisms of venom resistance are known from some species, the proteomic complexity of most snake venoms suggests that the evolved biochemical defences of ophiophagous mammals are likely to be far more numerous than currently recognized. Whereas most previous research in this field has been motivated by the potential for medical applications, venom resistance in ophiophagous mammals is a complex adaptation that merits attention from comparative biologists. Unfortunately, evolutionary inference is currently limited by ignorance about many relevant facts that can only be provided by future research. © 2012 The Authors. Biological Reviews © 2012 Cambridge Philosophical Society.
He Z.,University of Oklahoma |
Piceno Y.,Lawrence Berkeley National Laboratory |
Deng Y.,University of Oklahoma |
Xu M.,University of Oklahoma |
And 9 more authors.
ISME Journal | Year: 2012
One of the major factors associated with global change is the ever-increasing concentration of atmospheric CO 2. Although the stimulating effects of elevated CO 2 (eCO 2) on plant growth and primary productivity have been established, its impacts on the diversity and function of soil microbial communities are poorly understood. In this study, phylogenetic microarrays (PhyloChip) were used to comprehensively survey the richness, composition and structure of soil microbial communities in a grassland experiment subjected to two CO 2 conditions (ambient, 368 p.p.m., versus elevated, 560 p.p.m.) for 10 years. The richness based on the detected number of operational taxonomic units (OTUs) significantly decreased under eCO 2. PhyloChip detected 2269 OTUs derived from 45 phyla (including two from Archaea), 55 classes, 99 orders, 164 families and 190 subfamilies. Also, the signal intensity of five phyla (Crenarchaeota, Chloroflexi, OP10, OP9/JS1, Verrucomicrobia) significantly decreased at eCO 2, and such significant effects of eCO 2 on microbial composition were also observed at the class or lower taxonomic levels for most abundant phyla, such as Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes and Acidobacteria, suggesting a shift in microbial community composition at eCO 2. Additionally, statistical analyses showed that the overall taxonomic structure of soil microbial communities was altered at eCO 2. Mantel tests indicated that such changes in species richness, composition and structure of soil microbial communities were closely correlated with soil and plant properties. This study provides insights into our understanding of shifts in the richness, composition and structure of soil microbial communities under eCO 2 and environmental factors shaping the microbial community structure. © 2012 International Society for Microbial Ecology All rights reserved.
Venom is a complex mixture of proteins and other toxic chemicals produced by animals such as snakes and spiders, either to incapacitate their prey or to defend against predators. The influence of positive selection (the process by which a protein changes rapidly over evolutionary time scales) in expanding and diversifying animal venoms is widely recognized. This process was hypothesized to result from an evolutionary chemical arms race, in which the invention of potent venom in the predatory animals and the evolution of venom resistance in their prey animals, exert reciprocal selection pressures. In contrast to positive selection, the role of purifying selection (also known as negative selection, which is the selective removal of deleterious genetic changes from a population) has rarely been considered in venom evolution. Moreover, venom research has mostly neglected ancient animal groups in favor of focusing on venomous snakes and cone snails, which are both "young" animal groups that originated only recently in evolutionary timescales, approximately 50 million years ago. Consequently, it was concluded that venom evolution is mostly driven by positive selection. In the new study, Dr. Yehu Moran at the Hebrew University's Department of Ecology, Evolution and Behavior and the guest scientist Dr. Kartik Sunagar examined numerous venom genes in different animals in order to unravel the unique evolutionary strategies of toxin gene families. The researchers analyzed and compared the evolutionary patterns of over 3500 toxin sequences from 85 gene families. These toxins spanned the breadth of the animal kingdom, including ancient venomous groups such as centipedes, scorpions, spiders, coleoids (octopus, cuttlefish and squids) and cnidarians (jellyfish, sea anemones and hydras). Unexpectedly, despite their long evolutionary histories, ancient animal groups were found to have only accumulated low variation in their toxins. The analysis also revealed a striking contrast between the evolution of venom in ancient animal groups as compared to evolutionarily "young" animals. It also highlighted the significant role played by purifying selection in shaping the composition of venoms. According to Dr. Yehu Moran, "Our research shows that while the venoms of ancient lineages evolve more slowly through purifying selection, the venoms in more recent lineages diversify rapidly under the influence of positive selection." The findings enable the postulation of a new theory of venom evolution. According to this theory, toxin-producing genes in young venomous groups that enter a novel ecological niche, experience a strong influence of positive selection that diversifies their toxins, thus increasing their chances to efficiently paralyze relevant prey and predatory species in the new environment. However, in the case of the ancient venomous groups, where the venom is already "optimized" and highly suitable for the ecological niche, the venom's rate of accumulating variations slows down under the influence of purifying selection, which preserves the potent toxins generated previously. The proposed "two-speed" mode of venom evolution highlights the fascinating evolutionary dynamics of this complex biochemical cocktail, by showing for the first time the significant roles played by different forces of natural selection in shaping animal venoms. According to Drs. Moran and Sunagar, "The 'two-speed' mode of evolution of animal venoms involves an initial period of expansion, resulting in the rapid diversification of the venom arsenal, followed by longer periods of purifying selection that preserve the now potent toxin pharmacopeia. However, species that have entered the stage of purification and fixation may re-enter the period of expansion if they experience a major shift in ecology and/or environment." More information: Kartik Sunagar et al. The Rise and Fall of an Evolutionary Innovation: Contrasting Strategies of Venom Evolution in Ancient and Young Animals, PLOS Genetics (2015). DOI: 10.1371/journal.pgen.1005596
What accounts for this dramatic divergence in the two insects' development? Within the last decade, many scientists have come to believe that DNA methylation—a mode of genetic regulation in which chemical tags turn genes on or off—is involved. However, this explanation doesn't hold up to scrutiny, according to new findings from Rockefeller University published on January 21 in Current Biology. The researchers studied DNA methylation in clonal raider ants, Cerapachys biroi, which can switch between performing either brood care or egg-laying. When comparing methylation patterns in the brains of workers and queens, they found no overall differences. "Discovering that there is no evidence to support methylation as a reason why two ants can behave so differently was, on the one hand, a little sobering," says senior author Daniel Kronauer, assistant professor and head of Rockefeller's Laboratory of Social Evolution and Behavior. "On the other hand, this finding could be really important for those who want to understand the evolution of social behavior and the function of DNA methylation in insects." Previous research had found methylation differences in the brains of insect queens and workers—making many scientists believe these differences cause the animals to take on different social roles. "It was a great story, and everyone ran with it," says Peter Oxley, a co-first author and postdoc in the lab. But these previous studies looked at average levels of methylation within a sample of each insect type—taking, for instance, a group of worker ants, mixing their DNA together, and measuring the average amount of methylation among all their brains. These experiments consistently found differences between worker and queen insects—but that test alone won't tell you if the difference is significant, explains Kronauer. The average amount of methylation present in one group will most likely differ from the average amount present in another group. To be meaningful, those differences must be consistent across multiple groups of workers and queens. To take that extra step, members of Kronauer's team—including co-first author Romain Libbrecht, who at the time was a postdoc in Kronauer's lab and presently works at the University of Lausanne, in Switzerland—measured methylation levels from multiple samples of ants performing brood care or laying eggs. In these experiments, the distinctions found in previous research didn't hold up. The team did see differences in methylation between samples; however, these differences were equivalent between samples of workers, as well as between samples of queens. "It dawned on us that there was really nothing there," Kronauer says. It's not that methylation doesn't do anything at all—in fact, the researchers found that it is primarily associated with genes that serve crucial functions for workers and queens alike, suggesting that DNA methylation might contribute to the stable expression of so-called household genes. And, Kronauer notes, "we can't say for sure there is no difference in methylation between queens and workers. What our study does show is that the current evidence is inconclusive. That does not rule out the possibility that future studies with even higher resolution and more statistical power could find such differences." Explore further: Genome of clonal raider ant provides promising model to study social evolution and behavior More information: Romain Libbrecht et al. Robust DNA Methylation in the Clonal Raider Ant Brain, Current Biology (2016). DOI: 10.1016/j.cub.2015.12.040 , www.cell.com/current-biology/abstract/S0960-9822(15)01571-7