1,867 research outputs found
Patterns of tree species composition and richness across the principal biomes of lowland tropical South America and their underlying environmental drivers
Get PDFLowland tropical South America encompasses some of the most species-rich and
threatened ecosystems in the world, spanning across countries such as Brazil, Bolivia,
Colombia, Ecuador, Peru and Venezuela, which are known for their biodiversity.
However, due to its incredible environmental and ecological complexity and that
most of its area has yet to be scientifically studied in any depth, controversy
surrounds its biomes’ identities, the limits of their geographic and environmental
distributions and estimates of their tree species richness. The main objective of this
thesis is to study the phytogeography of lowland Tropical South America by delimiting
its biomes through a floristic approach, by investigating these biomes’ environmental
controls and dynamics and by assessing their tree species richness and endemism. In
order to fulfil this objective, we have employed a dataset of thoroughly checked tree
species checklists, the NeoTropTree (NTT) dataset, which covers more than 8000
locations across South, Central and southern North America and encompasses
occurrence records for more than 12000 tree species.
Firstly, I defined and mapped the main biomes in lowland tropical South America
(LTSA) through the means of a hierarchical clustering analysis based on tree species
composition associated with an a priori classification of 4103 NTT sites into
vegetation types. I then proceeded to map these biomes geographically and to assess
their environmental overlaps (both climatic and edaphic) through a classification tree
approach (random forest analysis). I was able to delimit five main biomes in LTSA:
Amazon Forest, Atlantic Forest, Chaco, Savanna and Seasonally Dry Tropical Forest
(SDTF). I also show that there is an important environmental overlap amongst
biomes. Error rates for site classification into biome using solely environmental data
ranged from 19-21% when only climate was considered and 16-18% when I also took
edaphic variables into account. I conclude that it is viable and advisable to use tree
species composition to determine biome identity, at least within individual
continents. In the case of LTSA, there is high biome heterogeneity at small spatial
scales, which explains why it is so challenging to use climatic and/or interpolation
based edaphic data, or remotely-sensed imagery, to map tropical biomes. Because of
this, I then conclude that biome delimitation using floristic information may enable
more efficient biome conservation and management efforts.
Secondly, I investigated the environmental controls distinguishing biome limits for
two regions of LTSA with high biome heterogeneity – eastern Brazil and Bolivia. To
this end, I selected 182 NTT sites in these two regions, collected detailed soil data
from the field and extracted climate and fire data from publicly available GIS data
layers. I assigned these sites to one of three states based on their tree species
composition: moist forest (including both Atlantic and Amazon Forests), SDTF or
savanna. Selected environmental variables were organized into three distinct
categories describing functional environmental regime: water availability, soil fertility
and fire, and their significance as predictors of biome identity was assessed within a
structural equation modelling framework. I found that environmental controls
behind biome distribution differ between the two studied areas and according to the
biomes involved. I concluded that water availability, soil fertility and fire are all
important determinants of biome limits. Amongst the three categories, water
availability was the most important one in determining biome identity at our study
sites, with soil fertility differentiating eastern Brazil SDTFs from the other biomes, and
fire representing an important determinant of savanna’s environmental limits.
Thirdly, I estimated and compared tree species richness and endemism levels of
LTSA’s main biomes using NTT’s tree species checklists and incidence (i.e.,
occurrence) data. To do so, I extracted tree species information for 4540 sites
registered in NeoTropTree distributed across four biomes: Amazon Forest, Atlantic
Forest, Savanna and SDTF. I first compared how tree species accumulated with
number of sites sampled for biomes and then estimated biomes’ total tree species
richness using non-parametric approaches (species extrapolation curves). I also
estimated the number of endemic tree species to these areas with two approaches:
indicator species analyses and absolute unique/shared species counts. I was able to
show that the Amazon Forest is the most tree species-rich environment in LTSA,
followed by the Atlantic Forest, Savannas and then SDTFs. In relation to endemism
levels, the Amazon and Atlantic Forests’ tree flora are mainly composed of endemic
tree species whereas that is not the case for the savanna and SDTF. The estimation
of total tree species richness through extrapolation curves revealed that around 94%
of the tree flora of the Amazon forest, the Atlantic forest and the SDTF have already
been recorded. According to the same analysis, only around 70% of the savannah tree
flora has been recorded. However, this pattern might be related to the high number
of biome intrusions into this biome. The differences in richness and endemism
between the moist (Amazon and Antlantic forests) and drier biomes (savanna and
SDTF) suggest that drought-sensitivity and biogeographic history are drivers of tree
species distribution in LTSA.
Finally, by integrating biome delimitation based on floristic composition with
knowledge on these environments’ environmental correlates and tree species
richness, I was able to describe LTSA’s main phytogeographic features in a way that
has never been done before, drawing attention to its complexities and performing
novel cross-biome comparisons. My study shows that LTSA’s biomes are interspersed
across geographic space, especially in the Dry Diagonal located between the Amazon
and Atlantic Forests, and that environmental controls driving these ecosystems’
distributions can vary according to the biomes being considered and the geographic
location. I also show that LTSA’s most tree species-rich biomes are the ones with the
highest quantity of endemic tree species and that taxonomic expeditions to the
Amazon Forest can potentially lead to more species being described in these
environments. To summarize, I was able to highlight LTSA’s main floristic patterns
and link them to environmental drivers and tree species richness, thereby
substantially transforming how these biomes are perceived by biodiversity scientists
and conservationists
Kyle Haselden
No full textKyle Emerson Haselden, D.D., Class of 1934, was a distinguished Baptist minister, author and editor. He authored three books, including 'The Racial Problem in Christian Perspective' published in 1959. He was also the editor of 'The Christian Century.' He is a Charter Member of the Furman University Hall of Fame
First person – Kyle Wegner
No full textFirst Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Kyle Wegner is first author on ‘Edar is a downstream target of beta-catenin and drives collagen accumulation in the mouse prostate’, published in BIO. Kyle is a PhD candidate in the lab of Chad M. Vezina at the University of Wisconsin-Madison, investigating principles of toxicology and urology to evaluate mechanisms of urinary dysfunction in aging men
005 - Kyle Singer
No full textI highlight the importance of flaws, trauma, and repression by evoking concepts of “the unconscious” through surrealist methodologies. Considering all that is suppressed/repressed within my psyche to form the culturally accepted version of myself, and by examining the distance between my identity, and the repressed self. Engaging the viewers through superabundance, tackling issues of consumerism with construction that grapples with the excess of daily life. I question aesthetic value, moral responsibility, and political agency in my efforts to sublimate the abject. The abject touches on the fragility of our boundaries and the spatial distinction between our interiority and exteriority. My art stems from an insatiable appetite for new materials and compulsive ways I can explore new methods and processes. The impetus for my work is a cultural and political critique imbued with my own flavor of cynicism and disillusionment. I endeavor to destabilize perceptions by creating overwhelming masses of matter and meaning; meant to be all-consuming. This non-hierarchical kind of making causes a slow unraveling of my work allowing for an unpredictable composition and use of materials.The abject deals with a vast array of issues such as marginalized people, mortality, boundaries, and repulsion. It is usually used to describe the human reaction to horror and threatens to breakdown meaning by causing the loss of distinction between subject and object; between self and other. In an era of mass displacement due to natural and political disasters, this conceptually interest me and seem particularly relevant. The abject calls into question hierarchical values that allows for the dispersion and displacement of people: whether it be refugees, or low in-come families pushed out by gentrification. In the age of information, we have become incredibly efficient at codifying people and separating them from their personhood and seeing them only as replaceable objects with a set value; as a cluster of information to be used and exploited for profits. I plan to continue exploring the possibilities of media combination and new technologies. I am currently working with laser cutting, 3D printing, 3D scanning and the CNC machine. I am trying to explore new ways of misusing the machinery as a chance operation that allows the ebbs, flows, and limitations of the process itself to become a way of making. These new processes drastically change the way we think about construction and the possibilities of form. It blurs the boundaries between the hand-made and the mass-produced, dovetailing nicely with my ideas of consumerist cultural critique.College of Liberal Arts - Highest Achievement - Visual and Performing Arts
Gods, Spirits, People: Resource Collection
No full textThis collection of primary sources on Gods, Spirits, People in the early modern period accompanies the Gods, Spirits, People chapter. Curated Dr Andrew Redden and Dr Kyle Jackson, University of Liverpool.Collection of primary sourcesThis collection of primary sources on Gods, Spirits, People in the early modern period accompanies the Gods, Spirits, People chapter found at https://kora.kpu.ca/islandora/object/kora:579 and https://liverpooluniversitypress.manifoldapp.org/read/untitled-493687ea-d192-4880-b61e-19bd082917ba/section/0b9435bf-9209-45e7-bf35-81be5a2c3da
Linoleic acid causes greater weight gain than saturated fat without hypothalamic inflammation in the male mouse
No full textA significant change in the Western diet, concurrent with the obesity epidemic, was a substitution of saturated fatty acids with polyunsaturated, specifically linoleic acid (LA). Despite increasing investigation on type as well as amount of fat, it is unclear which fatty acids are most obesogenic. The objective of this study was to determine the obesogenic potency of LA vs. saturated fatty acids and the involvement of hypothalamic inflammation. Forty-eight mice were divided into four groups: low-fat or three high-fat diets (HFDs, 45% kcals from fat) with LA comprising 1%, 15% and 22.5% of kilocalories, the balance being saturated fatty acids. Over 12 weeks, bodyweight, body composition, food intake, calorimetry, and glycemia assays were performed. Arcuate nucleus and blood were collected for mRNA and protein analysis. All HFD-fed mice were heavier and less glucose tolerant than control. The diet with 22.5% LA caused greater bodyweight gain, decreased activity, and insulin resistance compared to control and 1% LA. All HFDs elevated leptin and decreased ghrelin in plasma. Neuropeptides gene expression was higher in 22.5% HFD. The inflammatory gene Ikk was suppressed in 1% and 22.5% LA. No consistent pattern of inflammatory gene expression was observed, with suppression and augmentation of genes by one or all of the HFDs relative to control. These data indicate that, in male mice, LA induces obesity and insulin resistance and reduces activity more than saturated fat, supporting the hypothesis that increased LA intake may be a contributor to the obesity epidemic.Peer reviewe
Woody plant distributions along an Amazon-to-Andes elevation gradient: evolutionary trends and tendencies
Get PDFWith high taxonomic turnover and exceptional levels of endemism, tropical montane forests are one of the most biodiverse ecosystems on the planet. The taxa within these forests frequently occupy narrow elevational ranges, and display upslope migration rates insufficient to track predicted temperature increases. Consequently, tropical montane forests and the diversity within them are expected to be susceptible to declines in abundance and potential extinction under ongoing environmental change. Substantial changes to biodiversity patterns across elevation may have significant consequences for the carbon and nutrient cycles as well as the regulation of hydrological processes provided by these forests.
In this thesis I examine the diversity and distribution trends of woody plants across a tropical montane forest elevation gradient on the Amazonian flank of the Peruvian Andes, stretching from 425 to 3625 m asl. I consider the influence of the major environmental changes which occur over elevation, such as decreasing temperature. A particular focus is on the transitions which occur at the cloud-base ecotone, above which forests are defined by frequent and prolonged cloud immersion. I apply an evolutionary perspective, using phylogenetic approaches throughout this research. Closely related evolutionary lineages are frequently similar in terms of their ecology and functional characteristics, yet the influence of this tendency on the elevational distribution pattern of woody plants within tropical montane forest has received limited attention
Using census data from a network of one-hectare plots, in combination with phylogenetic information, covering a breadth of vascular plant diversity, from angiosperms and gymnosperms to pteridophyte tree ferns, I investigate the influence of evolutionary heritage on elevational distribution trends at the genus level. I further employ these plot data to reflect on the differences between taxonomic and phylogenetic richness patterns across elevation. A deeper consideration of the way variation in the evolutionary age structure of communities can influence diversity trends is also undertaken. In order to test the consistency of elevational patterns between genus and species scales, I conducted independent and detailed sampling within the tribe Miconieae (Melastomataceae), along the same gradient. Within Miconieae, I also measured functional leaf-traits associated with species resource-investment strategies, allowing investigation of the potential mechanistic processes underlying distribution trends across elevation.
I reveal a tendency for closely related woody plant lineages to occupy similar mean elevations and display phylogenetic clustering both above and below the cloud-base ecotone. A few exceptional lineages are able to occupy broad elevations, yet they are not each other’s closest evolutionary relatives. I further show that, across both taxonomic and phylogenetic measures, the diversity of mid-elevation tropical montane forests may rival, or even exceed that found in the tropical lowlands, especially when the full evolutionary history of lineages is represented. Deviation among diversity measures is driven by variation in the evolutionary age structure of communities across elevation. Older evolutionary lineages are more numerous at middle to high elevations, while many evolutionarily younger lineages are restricted to distributions at lower elevation. Utilising Miconieae as a test lineage, I show that elevational diversity and distribution patterns at the species-level largely echo genus-level trends. Lastly, I reveal that closely related species tend to have similar functional leaf trait values, with certain traits displaying elevational trends. Amongst measured traits, only specific leaf area (SLA) appears to share an evolutionary correlation with species’ elevational distributions. It may be that unmeasured traits or resource investment strategies unrelated to SLA, are more significant drivers of species constrained elevational distributions.
Overall, the work presented in this thesis adds to the body of evidence demonstrating that evolutionary factors, such as niche conservatism, form an important lens through which to understand the spatial organisation of biodiversity. I demonstrate that the broad relevance of evolutionary processes applies to woody plant distributions within unique and vulnerable tropical montane forests and may prove important to our understanding of the ecological response of this system to ongoing global environmental change
209 - Kyle Matthew Nardi
No full textIncludes bibliographical references.Atmospheric rivers (ARs), narrow corridors of high atmospheric water vapor transport, influence large regions of the West Coast of North America, from southern California to British Columbia and Alaska. Regardless of location, areas influenced by landfalling ARs face various threats and disruptions from excessive rainfall and associated runoff. Therefore, improving forecasts of AR occurrence and characteristics is of great importance to those responsible for protecting life and property. When providing the public with outlooks and warnings related to ARs, forecasters must confront the challenge of assessing the output of different numerical weather prediction (NWP) models. Specifically, forecasters must understand how performance varies across different time scales, geographical regions, and individual models. Prior work, such as Wick et al. (2013), has examined the forecast skill
of several NWP models at different lead times, yet as models are continuously updated, a fresh perspective on AR forecast performance is desired. This study aims to assess how different weather forecast models perform at varying lead times and for distinct regions of the West Coast of North America. Re-forecasts from several operational NWP models, obtained from the International S2S Project Database, are run out to approximately 60 days. An atmospheric river detection algorithm is applied to the model output in order to quantify how the models handle such features. The study examines atmospheric river re-forecasts for the West Coast of North America as well as three non-overlapping sub-regions along the coast. The first sub-region extends from southern California to the Oregon border. The second sub-region covers the Pacific Northwest from southern Oregon to the northern extent of Vancouver Island. The third and final sub-region consists of the coasts of British Columbia and southeastern Alaska. Together, these regions represent a large fraction of the AR landfall locations for western North America. Model performance is studied through the lens of AR occurrence, intensity, and location. Results indicate variations in re-forecast skill as a function of lead time, geographic region, and model used. A desired near-term outcome of this work is an increased awareness of both the utility and limitations of NWP models in the prediction of atmospheric river events at short, medium, and long-range leads. A desired long-term outcome is the use of these results as a bridge to understanding what gives rise to the differing characters of atmospheric rivers over the northeast Pacific and how models can improve their depictions of such features
From problems of citizenship to questions of action
No full textThis thesis is a methodological evaluation of thequestion–or problem –of citizenship that explores this concept’s limits,the consequences of citizenship’s overextension,and the potential of analternative question of action for political inquiry. Through thisprocess, the thesis intervenes within citizenship studies’dominant theoretical concerns with the everyday and the constitutive other, asserting that they both maintain the citizen as the defining term of the political. It argues that this conceptualization of politics is produced by the question of citizenship, and is expressed in its assumptions of separation that reduce political action to citizenship.In contrast, aquestion of action provides an alternative engagement with politics by limiting the concept of citizenship itself to avoid defining the political and action through this term.The conclusion briefly explores posing a question of action and enumerates some potential research avenues for its actualization.M.A.Includes bibliographical referencesby Kyle Loewe
Regulation of gene expression by 17β-estradiol in the arcuate nucleus of the mouse through ERE-dependent and ERE-independent mechanisms
No full text17β-Estradiol (E2) modulates gene expression in the hypothalamic arcuate nucleus (ARC) to control homeostatic functions. In the ARC, estrogen receptor (ER) α is highly expressed and is an important contributor to E2's actions, controlling gene expression through estrogen response element (ERE)-dependent and -independent mechanisms. The objective of this study was to determine if known E2-regulated genes are regulated through these mechanisms. The selected genes have been shown to regulate homeostasis and have been separated into three subsections: channels, receptors, and neuropeptides. To determine if ERE-dependent or ERE-independent mechanisms regulate gene expression, two transgenic mouse models, an ERα knock-out (ERKO) and an ERα knock-in/knock-out (KIKO), which lacks a functional ERE binding domain, were used in addition to their wild-type littermates. Females of all genotypes were ovariectomized and injected with oil or estradiol benzoate (E2B). Our results suggest that E2B regulates multiple genes through these mechanisms. Of note, Cacna1g and Kcnmb1 channel expression was increased by E2B in WT females only, suggesting an ERE-dependent regulation. Furthermore, the NKB receptor, Tac3r, was suppressed by E2B in WT and KIKO females but not ERKO females, suggesting that ERα-dependent, ERE-independent signaling is necessary for Tac3r regulation. The adrenergic receptor Adra1b was suppressed by E2B in all genotypes indicating that ERα is not the primary receptor for E2B's actions. The neuropeptide Tac2 was suppressed by E2B through ERE-dependent mechanisms. These results indicate that E2B activates both ERα-dependent and independent signaling in the ARC through ERE-dependent and ERE-independent mechanisms to control gene expression.Peer reviewe
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