254 research outputs found
Morphological Divergence and Flow-Induced Phenotypic Plasticity in a Native Fish from Anthropogenically Altered Stream Habitats
Understanding population-level responses to human-induced changes to habitats can elucidate the evolutionary consequences of rapid habitat alteration. Reservoirs constructed on streams expose stream fishes to novel selective pressures in these habitats. Assessing the drivers of trait divergence facilitated by these habitats will help identify evolutionary and ecological consequences of reservoir habitats. We tested for morphological divergence in a stream fish that occupies both stream and reservoir habitats. To assess contributions of genetic-level differences and phenotypic plasticity induced by flow variation, we spawned and reared individuals from both habitats types in flow and no flow conditions. Body shape significantly and consistently diverged in reservoir habitats compared with streams; individuals from reservoirs were shallower bodied with smaller heads compared with individuals from streams. Significant population-level differences in morphology persisted in offspring but morphological variation compared with field-collected individuals was limited to the head region. Populations demonstrated dissimilar flow-induced phenotypic plasticity when reared under flow, but phenotypic plasticity in response to flow variation was an unlikely explanation for observed phenotypic divergence in the field. Our results, together with previous investigations, suggest the environmental conditions currently thought to drive morphological change in reservoirs (i.e., predation and flow regimes) may not be the sole drivers of phenotypic change
Geophysical Evolution During Rocky Planet Formation
Progressive astronomical characterization of planet-forming disks and rocky
exoplanets highlight the need for increasing interdisciplinary efforts to
understand the birth and life cycle of terrestrial worlds in a unified picture.
Here, we review major geophysical and geochemical processes that shape the
evolution of rocky planets and their precursor planetesimals during planetary
formation and early evolution, and how these map onto the astrophysical
timeline and varying accretion environments of planetary growth. The evolution
of the coupled core-mantle-atmosphere system of growing protoplanets diverges
in thermal, compositional, and structural states to first order, and ultimately
shapes key planetary characteristics that can discern planets harboring clement
surface conditions from those that do not. Astronomical campaigns seeking to
investigate rocky exoplanets will require significant advances in laboratory
characterization of planetary materials and time- and spatially-resolved
theoretical models of planetary evolution, to extend planetary science beyond
the Solar System and constrain the origins and frequency of habitable worlds
like our own.Comment: 37 pages, 10 figures; under review for publication as a chapter in
Protostars and Planets VII, University of Arizona Press; comments welcome;
figures available at https://osf.io/rcjt
The Cepheid Period-Luminosity Relation at Mid-Infrared Wavelengths: I. First-Epoch LMC Data
We present the first mid-infrared Period-Luminosity (PL) relations for Large
Magellanic Cloud (LMC) Cepheids. Single-epoch observations of 70 Cepheids were
extracted from Spitzer IRAC observations at 3.6, 4.5, 5.8 and 8.0 microns,
serendipitously obtained during the SAGE (Surveying the Agents of a Galaxy's
Evolution) imaging survey of the LMC. All four mid-infrared PL relations have
nearly identical slopes over the period range 6 - 88 days, with a small scatter
of only +/-0.16 mag independent of period for all four of these wavelengths. We
emphasize that differential reddening is not contributing significantly to the
observed scatter, given the nearly two orders of magnitude reduced sensitivity
of the mid-IR to extinction compared to the optical. Future observations,
filling in the light curves for these Cepheids, should noticeably reduce the
residual scatter. These attributes alone suggest that mid-infrared PL relations
will provide a practical means of significantly improving the accuracy of
Cepheid distances to nearby galaxies.Comment: 19 pages, 4 figures, 1 table, Accepted for publication in the
Astrophysical Journa
Understanding the spatial dimension of youth intergroup contact in a post-accord society
Understanding how to promote better social relations between groups in divided societies is vital for peacebuilding efforts. Building on the substantial body of research on intergroup contact theory and everyday multiculturalism, the present research aimed to examine how youth in the divided society of Belfast, Northern Ireland, experience social interactions in everyday urban spaces. Ten youth aged 16–18 (n = 2 Protestant females, one Protestant male, four Catholic females, two Catholic males, and one mixed religious background male) were recruited to take part in the research. Everyday contact experiences were explored using photovoice, a participatory method. Following engagement with a series of photography workshops and tasks, youth took part in focus group discussions and later, walking interviews (n = 3) to discuss the factors that influence their social interactions. Five main themes explaining youth contact experiences in context were uncovered: geographical and socioeconomic constraints on space use; group-based spatial cognitions, emotions, and behavior; lived experience and social discourses; markers of identity; and intergroup norms. Taken together, findings highlight key individual and structural processes through which public spaces become used or not by young people from different community backgrounds. Implications for research and practice for promoting intergroup contact and peace in socially divided societies are discussed
Application of an Equilibrium Vaporization Model to the Ablation of Chondritic and Achondritic Meteoroids
We modeled equilibrium vaporization of chondritic and achondritic materials
using the MAGMA code. We calculated both instantaneous and integrated element
abundances of Na, Mg, Ca, Al, Fe, Si, Ti, and K in chondritic and achondritic
meteors. Our results are qualitatively consistent with observations of meteor
spectra.Comment: 8 pages, 4 figures; in press, Earth, Moon, and Planets, Meteoroids
2004 conference proceeding
Evolution of a Sexually Dimorphic Trait in a Broadly Distributed Topminnow (Fundulus Olivaceus)
Understanding the interaction between sexual and natural selection within variable environments is crucial to our understanding of evolutionary processes. The handicap principle predicts females will prefer males with exaggerated traits provided those traits are indicators of male quality to ensure direct or indirect female benefits. Spatial variability in ecological factors is expected to alter the balance between sexual and natural selection that defines the evolution of such traits. Male and female blackspotted topminnows (Fundulidae: Fundulus olivaceus) display prominent black dorsolateral spots that are variable in number across its broad range. We investigated variability in spot phenotypes at 117 sites across 13 river systems and asked if the trait was sexually dimorphic and positively correlated with measures of fitness (condition and gonadosomatic index [GSI]). Laboratory and mesocosm experiments assessed female mate choice and predation pressure on spot phenotypes. Environmental and community data collected at sampling locations were used to assess predictive models of spot density at the individual, site, and river system level. Greater number of spots was positively correlated with measures of fitness in males. Males with more spots were preferred by females and suffered greater mortality due to predation. Water clarity (turbidity) was the best predictor of spot density on the drainage scale, indicating that sexual and natural selection for the trait may be mediated by local light environments
Evolution of a Sexually Dimorphic Trait In a Broadly Distributed Topminnow (\u3ci\u3eFundulus olivaceus\u3c/i\u3e)
Understanding the interaction between sexual and natural selection within variable environments is crucial to our understanding of evolutionary processes. The handicap principle predicts females will prefer males with exaggerated traits provided those traits are indicators of male quality to ensure direct or indirect female benefits. Spatial variability in ecological factors is expected to alter the balance between sexual and natural selection that defines the evolution of such traits. Male and female blackspotted topminnows (Fundulidae: Fundulus olivaceus) display prominent black dorsolateral spots that are variable in number across its broad range. We investigated variability in spot phenotypes at 117 sites across 13 river systems and asked if the trait was sexually dimorphic and positively correlated with measures of fitness (condition and gonadosomatic index [GSI]). Laboratory and mesocosm experiments assessed femalemate choice and predation pressure on spot phenotypes. Environmental and community data collected at sampling locations were used to assess predictive models of spot density at the individual, site, and river system level. Greater number of spots was positively correlated with measures of fitness in males. Males with more spots were preferred by females and suffered greater mortality due to predation. Water clarity (turbidity) was the best predictor of spot density on the drainage scale, indicating that sexual and natural selection for the trait may be mediated by local light environments
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