Habitat fragmentation and species diversity in competitive communities

Habitat loss is one of the key drivers of the ongoing decline of biodiversity. However, ecologists still argue about how fragmentation of habitat (independent of habitat loss) affects species richness. The recently proposed habitat amount hypothesis posits that species richness only depends on the total amount of habitat in a local landscape. In contrast, empirical studies report contrasting patterns: some find positive and others negative effects of fragmentation per se on species richness. To explain this apparent disparity, we devise a stochastic, spatially explicit model of competitive species communities in heterogeneous habitats. The model shows that habitat loss and fragmentation have complex effects on species diversity in competitive communities. When the total amount of habitat is large, fragmentation per se tends to increase species diversity, but if the total amount of habitat is small, the situation is reversed: fragmentation per se decreases species diversity.Peer reviewe

A Library of Integrated Spectra of Galactic Globular Clusters

We present a new library of integrated spectra of 40 Galactic globular clusters, obtained with the Blanco 4-m telescope and the R-C spectrograph at the Cerro Tololo Interamerican Observatory. The spectra cover the range ~ 3350 -- 6430 A with ~ 3.1 A (FWHM) resolution. The spectroscopic observations and data reduction were designed to integrate the full projected area within the cluster core radii in order to properly sample the light from stars in all relevant evolutionary stages. The S/N values of the flux-calibrated spectra range from 50 to 240/A at 4000 A and from 125 to 500/A at 5000 A. The selected targets span a wide range of cluster parameters, including metallicity, horizontal-branch morphology, Galactic coordinates, Galactocentric distance, and concentration. The total sample is thus fairly representative of the entire Galactic globular cluster population and should be valuable for comparison with similar integrated spectra of unresolved stellar populations in remote systems. For most of the library clusters, our spectra can be coupled with deep color-magnitude diagrams and reliable metal abundances from the literature to enable the calibration of stellar population synthesis models. In this paper we present a detailed account of the observations and data reduction. The spectral library is publicly available in electronic format from the National Optical Astronomical Observatory website.Comment: 39 Pages, including 2 tables and 15 Figures. To appear in the Astrophysical Journal, Supplement Serie

The relative importance of local and regional processes to metapopulation dynamics

Metapopulation dynamics - patch occupancy, colonization and extinction - are the result of complex processes at both local (e.g. environmental conditions) and regional (e.g. spatial arrangement of habitat patches) scales. A large body of work has focused on habitat patch area and connectivity (area-isolation paradigm). However, these approaches often do not incorporate local environmental conditions or fully address how the spatial arrangement of habitat patches (and resulting connectivity) can influence metapopulation dynamics. Here, we utilize long-term data on a classic metapopulation system - the Glanville fritillary butterfly occupying a set of dry meadows and pastures in the angstrom land islands - to investigate the relative roles of local environmental conditions, geographic space and connectivity in capturing patch occupancy, colonization and extinction. We defined connectivity using traditional measures as well as graph-theoretic measures of centrality. Using boosted regression tree models, we find roughly comparable model performance among models trained on environmental conditions, geographic space or patch centrality. In models containing all of the covariates, we find strong and consistent evidence for the roles of resource abundance, longitude and centrality (i.e. connectivity) in predicting habitat patch occupancy and colonization, while patch centrality (connectivity) was relatively unimportant for predicting extinction. Relative variable importance did not change when geographic coordinates were not considered and models underwent spatially stratified cross-validation. Together, this suggests that the combination of regional-scale connectivity measures and local-scale environmental conditions is important for predicting metapopulation dynamics and that a stronger integration of ideas from network theory may provide insight into metapopulation processes.Peer reviewe

Video Assisted Thoracic Surgery for Indeterminate Pulmonary Nodules

The approach to patients with indeterminate pulmonary nodules is poorly defined. Should every pulmonary nodule be biopsied, is needle biopsy adequate, and other questions are challenges. Video assisted thoracic surgery or thoracoscopy has added a new diagnostic possibility which is evaluated in this paper. Fifty-five patients underwent thoracoscopy for diagnosis of a solitary pulmonary nodule. There were few complications and mortality was zero. A definitive diagnosis was obtained in all patients, although one required a second thoracoscopic wedge resection and 10 required conversion to an open thoracotomy

Drone Measurements of Solar-Induced Chlorophyll Fluorescence Acquired with a Low-Weight DFOV Spectrometer System

Solar induced chlorophyll fluorescence (SIF) emitted from plant canopies is now retrievable from space. In addition, SIF is now also routinely measured from fixed tower platforms. However there is a scale gap between temporally continuous tower measurements and spatially coarse satellite retrievals that is now being bridged by drone technology. Drone retrievals of SIF can be used to help unravel the structural and species component dependencies that occur across space on the scale of meters in heterogeneous vegetation types. Also when flown at sufficient altitude, drones can be used to simulate, and potentially validate satellite retrievals of SIF. We flew a dual field of view spectrometer system, the Piccolo doppio, above a boreal forest with the aim of retrieving SIF. Our flights were designed to assess both spatial heterogeneity of SIF driven by changes in vegetation cover type and to simulate satellite pixels by flying at a relatively high altitude.Peer reviewe

The diverse nature of island isolation and its effect on land bridge insular faunas

Aim: Isolation is a key factor in island biology. It is usually defined as the distance to the geographically nearest mainland, but many other definitions exist. We explored how testing different isolation indices affects the inference of impacts of isolation on faunal characteristics. We focused on land bridge islands and compared the relationships of many spatial and temporal (i.e., through time) isolation indices with community‐, population‐ and individual‐level characteristics (species richness, population density and body size, respectively). Location: Aegean Sea islands, Greece. Time period: Current. Taxon: Many animal taxa. Methods: We estimated 21 isolation indices for 205 islands and recorded species richness data for 15 taxa (invertebrates and vertebrates). We obtained body size data for seven lizard species and population density data for three. We explored how well indices predict each characteristic, in each taxon, by conducting a series of ordinary least squares regressions (controlling for island area when needed) and a meta‐analysis. Results: Isolation was significantly (and negatively) associated with species richness in 10 of 15 taxa. It was significantly (and positively) associated with body size in only one of seven species and was not associated with population density. The effect of isolation on species richness was much weaker than that of island area, regardless of the index tested. Spatial indices generally out‐performed temporal indices, and indices directly related to the mainland out‐performed those related mainly to neighbouring islands. No index was universally superior to others, including the distance to the geographically nearest mainland. Main conclusions: The choice of index can alter our perception of the impacts of isolation on biological patterns. The nearly automatic, ubiquitous use of distance to the geographically nearest mainland misrepresents the complexity of the effects of isolation. We recommend the simultaneous testing of several indices that represent different aspects of isolation, in order to produce more constructive and thorough investigations and avoid imprecise inference

Terrestrial Alteration Mineral Assemblages in the NWA 10416 Olivine Phyric Shergottite

We report on the alteration history of the olivine-phyric, highly depleted (HD) shergottite, Northwest Africa (NWA) 10416, paying particular attention to the origin of the aqueous alteration seen affecting the meteorite’s olivine megacrysts. The rock’s interior displays 1 mm, zoned, altered olivine megacrysts set in a groundmass of clinopyroxene, unzoned olivine, and interstitial plagioclase and maskelynite. Synchrotron micro X-ray diffraction (µ-XRD) and transmission electron microscopy (TEM) show that plagioclase and maskelynite have been partially replaced by kaolinite. The relict olivine megacryst cores display a unique concentric colouration for Martian meteorites, having central amber-coloured zones surrounded by a brown mantle zone, with the rims remaining clear and unaltered. This colouration is a result of fluid alteration and partial replacement, with hydration. TEM analysis revealed the ∼200 nm scale banded and largely amorphous nature of the alteration, but with some (∼ 20%) relict crystalline olivine patches. Although the coloured olivine zones show cation and anion site vacancies compared to stoichiometric olivine, a relict igneous compositional trend is preserved in the megacrysts, from Mg-rich altered cores (Mg# = 76) to unaltered stoichiometric rims (Fo53). Synchrotron Fe-K X-ray absorption near-edge structure (XANES) analysis revealed that the coloured zones of the megacryst have different Fe oxidation values. High ferric contents are present in the brown mantle zones (Fe3+/ΣFe ≤ 0.92) and the amber zones (Fe3+/ΣFe ≤ 0.30), whereas the clear rims are ferrous. This suggests alteration occurred in an oxidising environment and that the sharp contrast in colour of the megacryst (brown to clear) is a record of a relict fluid reaction front. In order to test the terrestrial or extraterrestrial origin of the alteration, olivine material from a shock-melt vein was analysed by TEM. The analysis revealed 0.952 nm curved d-spacing’s from clay alteration undisturbed by any shock effects, strongly suggesting a terrestrial origin. The d-spacing values most likely represent a collapsed saponite or vermiculite, showing that in some places olivine has been replaced by crystalline clay. Oxygen isotope analysis of bulk (Δ17O = 0.309 ± 0.009 (2σ) ‰) and amber-coloured megacryst material (= 0.271 ± 0.002 (2σ) ‰), are also consistent with terrestrial alteration. We propose a model in which, during the meteorite’s time in Northwest Africa, low-temperature, likely acidic, groundwater exploited fractures. The fluid altered the olivine megacrysts in a way that was controlled by the pre-existing, igneous compositional zonation, with Mg-rich olivine being more susceptible to alteration in this fluid environment. The plagioclase and maskelynite were also altered to a high degree. After the alteration event it is likely that NWA 10416 had a significant residence time in Northwest Africa, accounting for terrestrial calcite and the dehydration of some clay phases

The structure of galactic disks: Studying late-type spiral galaxies using SDSS

Using imaging data from the SDSS survey, we present the g' and r' radial stellar light distribution of a complete sample of ~90 face-on to intermediate inclined, nearby, late-type (Sb-Sdm) spiral galaxies. The surface brightness profiles are reliable (1sigma uncertainty less than 0.2 mag) down to mu=~27magsqarcsec. Only ~10% of all galaxies have a normal/standard purely exponential disk down to our noise limit. The surface brightness distribution of the rest of the galaxies is better described as a broken exponential. About 60% of the galaxies have a break in the exponential profile between ~1.5-4.5 times the scalelength followed by a downbending, steeper outer region. Another ~30% shows also a clear break between ~4.0-6.0 times the scalelength but followed by an upbending, shallower outer region. A few galaxies have even a more complex surface brightness distribution. The shape of the profiles correlates with Hubble type. Downbending breaks are more frequent in later Hubble types while the fraction of upbending breaks rises towards earlier types. No clear relation is found between the environment, as characterised by the number of neighbours, and the shape of the profiles of the galaxies.Comment: LaTeX, 69 pages, 213 (very low resolution) figures, A&A accepted. Second version to match the accepted one including all referee's comments. Version with full resolution figures (highly recommended, but with 7.6MB) available at http://www.astro.rug.nl/~pohlen/pohlenSDSS.pd

Interseismic quiescence and triggered slip of active normal faults of Kīlauea Volcano's south flank during 2001-2018

The mobile south flank of Kīlauea Volcano hosts two normal fault systems, the Koa'e fault system (KFS) and the Hilina fault system (HFS). In historical time, at least three M>6.5 earthquakes have occurred on the basal detachment of the Kīlauea Volcano's south flank, with the most recent being the 4 May 2018 M6.9 earthquake. Here we analyze kinematic Global Positioning System data collected from 2001 to 2017 and interferometric synthetic aperture radar data before, during, and after the 2018 M6.9 earthquake to determine the crustal motion across the HFS and KFS faults. Our results indicate that the HFS faults did not significantly slip during the interseismic period from 2007 to 2011. Despite its substantial magnitude, interferometric synthetic aperture radar (InSAR) data show that the 2018 M6.9 earthquake triggered subcentimeter level slip along sections of the previously mapped HFS branches. Up to 20 cm of offset occurred on what appears to be a newly formed (or previously unknown) fault near the eastern end of the HFS. During the 3 months following the M6.9 earthquake, up to ~30 cm of slip occurred along the KFS, which helps accommodate rapid large‐scale subsidence of Kīlauea's summit region as large volumes of summit reservoir magma fed the lower East Rift Zone eruption. The HFS appears to activate only in concert with large earthquakes on the basal detachment. The KFS, on the other hand, moves both seismically during small local earthquakes and aseismically in response to nearby earthquakes and caldera subsidence