Loyd S.J.,University of California at Los Angeles |
Loyd S.J.,University of Southern California |
Loyd S.J.,California State University, Fullerton |
Corsetti F.A.,University of Southern California |
And 8 more authors.
Precambrian Research | Year: 2015
The Wonoka-Shuram Anomaly represents the largest negative carbon isotope excursion recognized in the geologic record and is associated with the emergence and diversification of metazoan life ca. 580 million years ago (Ma). The origin of the anomaly is highly debated, with interpretations ranging from primary to diagenetic, each having unique and potentially transformative implications for early life. Here, we apply carbonate clumped isotope thermometry to three sections expressing the anomaly in order to constrain mineral formation temperatures and thus directly calculate water oxygen isotope compositions (δ18Ow) with which carbonate minerals equilibrated. With δ18Ow known, it is possible to address previous hypotheses for the origin of the anomaly. In each section, precipitation temperatures correlate positively with reconstructed δ18Ow. Previous hypotheses, based on the covariance of δ18Ocarb vs. δ13Ccarb (uncorrected for temperature effects), suggested a meteoric diagenetic origin for the anomaly. However, reconstructed δ18Ow values do not covary with carbon isotope compositions (δ13Ccarb) within anomaly facies. Rather, the oxygen isotope and temperature data are consistent with carbonate recrystallization and equilibration under increasingly rock-buffered conditions. Based on simple modeling and comparison to modern formation fluids, recrystallization may have occurred in an environment far removed from the initial depositional or early diagenetic regime. In addition, although clumped isotope temperatures vary significantly and reach elevated values consistent with burial diagenesis, it is unclear to what degree, if at all, carbon isotope values were reset during recrystallization. Ultimately, these new data indicate that Wonoka-Shuram-aged carbonates experienced equilibration with fluids under increasingly closed-system conditions. The clumped isotope data do not provide a means to distinguish previous hypotheses outright, but provide additional context for the evaluation of geochemical signatures within these ancient carbonate rocks. © 2015 Elsevier B.V. Source
Spinks P.Q.,University of California at Davis |
Spinks P.Q.,Institute of the Environment and Sustainability |
Thomson R.C.,University of California at Davis |
Zhang Y.,CAS Kunming Institute of Zoology |
And 3 more authors.
Molecular Phylogenetics and Evolution | Year: 2012
Turtles are currently the most endangered major clade of vertebrates on earth, and Asian box turtles (Cuora) are in catastrophic decline. Effective management of this diverse turtle clade has been hampered by human-mediated, and perhaps natural hybridization, resulting in discordance between mitochondrial and nuclear markers and confusion regarding species boundaries and phylogenetic relationships among hypothesized species of Cuora. Here, we present analyses of mitochondrial and nuclear DNA data for all 12 currently hypothesized species to resolve both species boundaries and phylogenetic relationships. Our 15-gene, 40-individual nuclear data set was frequently in conflict with our mitochondrial data set; based on its general concordance with published morphological analyses and the strength of 15 independent estimates of evolutionary history, we interpret the nuclear data as representing the most reliable estimate of species boundaries and phylogeny of Cuora. Our results strongly reiterate the necessity of using multiple nuclear markers for phylogeny and species delimitation in these animals, including any form of DNA "barcoding", and point to Cuora as an important case study where reliance on mitochondrial DNA can lead to incorrect species identification. © 2012 Elsevier Inc. Source
In the southern part of the state, the California newt—Taricha torosa — has been showing up at breeding grounds nearly 20 percent underweight on average. The drastic change has UCLA evolutionary biologist Gary Bucciarelli concerned. "They look really emaciated," said Bucciarelli, a postdoctoral researcher with UCLA Institute of the Environment and Sustainability. "You can see the vertebrae and ribs of individuals. They don't look like they are in healthy breeding condition." Bucciarelli, who has studied the species since 2010, believes the problem is related to dry, hot weather from the drought and climate change, although more information is needed to determine an exact cause. "I've studied these newts across California, from San Diego to Mendocino County," he said. "You see a very different picture when you look up north. They're not showing these signs of lack of nourishment or whatever may be happening." California newts spend most of the year on land, staying underground to keep cool and moist—a must for amphibians. From January to May, they emerge to breed in streams. However, if there isn't enough rain, they might not come out at all. The species is highly poisonous, containing the same neurotoxin as pufferfish, yet it is not clear how newts get their toxin. If consumed, it is deadly to humans and other creatures—causing numbness, vomiting, decreased blood pressure and paralysis. However, a garter snake that preys on the newt has apparently evolved tolerance to the toxin. And, while evolution is typically a slow process, some researchers argue that toxicity and resistance are co-evolving, said Bucciarelli, whose research has drawn attention to this possibility. A toxic arms race with a snake would top the list of most species' concerns, but amphibians are highly susceptible to human impacts. Because they spend time on land and in water, changes to either environment affect them. This vulnerability came to global attention in the early 21st century when a climate-linked pathogenic fungus killed large numbers of Central and South American amphibians. "At that time, they really became the canary in the coal mine for climate change," Bucciarelli said. Researchers believe individual California newts can live up to 30 or 40 years, which is a long time for an amphibian. That makes the species useful in determining how changes in climate might affect other wildlife. Bucciarelli laughs when other researchers tell him about the difficulty of the fieldwork they do. "Birds fly. They're hard to find. You've got to trap them." The newt, on the other hand, returns to same breeding locations year after year. They don't even swim away. "They're quite inquisitive. They don't mind coming to the water surface to see what's going on." Bucciarelli catches them by hand to take measurements and tissue samples—one for DNA and another for toxicity. He also assesses their general breeding characteristics. In just five days, he can sample 30 breeding localities from L.A. to Mendocino. Laura Patterson is the statewide amphibian and reptile coordinator for California Department of Fish and Wildlife, which monitors the effects of the drought on wildlife. Not surprisingly, species that rely on marshes, creeks and other freshwater places are the most at risk. The agency helps create recovery plans for endangered and threatened species. It also focuses on protecting species—like the newt — that have not yet reached critical status. "It can be a monumental effort to improve species to a point where they no longer need protection," Patterson said. "It's a lot cheaper to be proactive and protect habitat ahead of time." That's where research from Bucciarelli and other scientists comes in. They partner with local, state and federal agencies to fill gaps in knowledge, enabling conservation authorities to create more effective plans. As Southern California moves further into the drought, Bucciarelli plans to keep working with land management agencies to improve protection for amphibians in the L.A. area.
Quiros D.C.,California Air Resources Board |
Quiros D.C.,Institute of the Environment and Sustainability |
Zhang S.,California Air Resources Board |
Sardar S.,California Air Resources Board |
And 12 more authors.
Environmental Science and Technology | Year: 2015
The California Air Resources Board (ARB) adopted the low emission vehicle (LEV) III particulate matter (PM) standards in January 2012, which require, among other limits, vehicles to meet 1 mg/mi over the federal test procedure (FTP). One possible alternative measurement approach evaluated to support the implementation of the LEV III standards is integrated particle size distribution (IPSD), which reports real-time PM mass using size distribution and effective density. The IPSD method was evaluated using TSI's engine exhaust particle sizer (EEPS, 5.6-560 nm) and gravimetric filter data from more than 250 tests and 34 vehicles at ARB's Haagen-Smit Laboratory (HSL). IPSD mass was persistently lower than gravimetric mass by 56-75% over the FTP tests and by 81-84% over the supplemental FTP (US06) tests. Strong covariance between the methods suggests test-to-test variability originates from actual vehicle emission differences rather than measurement accuracy, where IPSD offered no statistical improvement over gravimetric measurement variability. © 2015 American Chemical Society. Source
Over time, some species become more tolerant of humans' presence, but the extent to which they do is largely driven by the type of environment in which the animals live and by the animal's body size, according to a comprehensive new analysis. Researchers led by Daniel Blumstein, a professor and chair of ecology and evolutionary biology in the UCLA College, analyzed 75 studies conducted over the past half-century of 212 animal species—mostly birds, but also mammals and lizards. The scientists estimated species' tolerance to human disturbance by comparing how far away from humans an animal would have to be before it fled—a statistic called "flight initiation distance." The paper was published today in Nature Communications. Although Blumstein said the first finding was to be expected, he was initially surprised by the effect of body size because substantial evidence has shown that larger animals are most often more disturbed by people than smaller animals are. The analysis is one of a series of studies by Blumstein and colleagues addressing questions about wild animals' fear responses to humans and how humans' presence in animal habitats might be altering those responses. The new analysis showed that larger animals are more likely to be disturbed in more remote areas by people, but if the human–animal interactions are mostly benign, and if the animals can tolerate people, larger species eventually learn that people are not very threatening. "This new finding flips previous recommendations about large-bodied species being more vulnerable to the presence of humans, and shows that large-bodied species are more tolerant," said Blumstein, the study's senior author and a member of the Institute of the Environment and Sustainability. "It is likely costly for animals to respond fearfully to people that are not harming them. The key question to ask now is which species can tolerate humans enough so as to habituate to them." Other factors, such as birds' diet, the openness of their habitats, and the number of eggs they lay, had some impact on species' tolerance to human visits, but not as much as urban-rural differences and body size differences, the researchers report. Diogo Samia, the first author of the study, said smaller bird species included in the analysis were hummingbirds, while the larger species included pelicans and black-backed gulls. The researchers' findings could ultimately help shape wildlife conservation practices. The paper notes, for example, that protecting smaller birds might be more dependent on creating environments that reduce human disturbance. The paper also suggested that ecotourism—which has been said to be dangerous to animal species in general—might be less harmful to larger birds than previously thought because larger animals are more likely to be able to tolerate human disturbance. Explore further: Underground ants can't take the heat: Climage change models may not look closely enough at microhabitats More information: Diogo S. M. Samia et al. Increased tolerance to humans among disturbed wildlife, Nature Communications (2015). DOI: 10.1038/ncomms9877