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Heterogeneity in the density of spotted hyaenas in Hluhluwe-iMfolozi Park, South Africa

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Animal population sizes and trends, as well as their distributions, are essential information to the understanding and conservation of ecosystems. During this study in Hluhluwe-iMfolozi Park, South Africa, a spotted hyaena Crocuta crocuta Erxleben, 1777 (Hyaenidae) population was surveyed by attracting individuals with pre-recorded sounds. The hyaena population (excluding cubs) is substantially larger (321 individuals) than the previous estimate of 200 and this population is the second largest protected population 2 in South Africa. Average hyaena density, at 0.357 individuals/km(2), was relatively high compared to other southern African conservation areas, and range from 0 to 1.25 individuals/km(2) across sampling stations. For short periods, spatial heterogeneity in density was marked at small and large spatial scales, but decreased when averaged over a longer period. This heterogeneity may be important in promoting the coexistence of other large and mobile carnivores in Hluhluwe-iMfolozi Park by creating potential dynamic competition refugia in space and time. Furthermore, heterogeneity of hyaena density at smaller scales should influence studies investigating the avoidance of hyaenas by competitively inferior carnivores.

Stone Shamans and Flying Deer of Northern Mongolia: Deer Goddess of Siberia or Chimera of the Steppe?

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Mongolia's Bronze Age deer stones are one of the most striking expressions of early monumental art in Central Asia, yet their age, origins, relationships, and meaning remain obscure. Speculation about Scythian connections has stimulated recent research in Mongolia that has begun to peel away their mysteries and reveals connections to Scytho-Siberian and northern art. Radiocarbon-dated horse skulls indicate pre-Scythian ages of "classic Mongolian" deer stones as well as firm association with the Late Bronze Age khirigsuur [kurgan] burial mound complex.

Mars Reconnaissance Orbiter observations of light-toned layered deposits and associated fluvial landforms on the plateaus adjacent to Valles Marineris

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We have used data from the Mars Reconnaissance Orbiter to study 30-80 m thick light-toned layered deposits on the plateaus adjacent to Valles Marineris at five locations: (1) south of Ius Chasma, (2) south of western Melas Chasma, (3) south of western Candor Chasma, (4) west of Juventae Chasma, and (5) west of Ganges Chasma. The beds within these deposits have unique variations in brightness, color, mineralogy, and erosional properties that are not typically observed in light-toned layered deposits within Valles Marineris or many other equatorial areas on Mars. Reflectance spectra indicate these deposits contain opaline silica and Fe-sulfates, consistent with low-temperature, acidic aqueous alteration of basaltic materials. We have found valley or channel systems associated with the layered deposits at all five locations, and the volcanic plains adjacent to Juventae, Ius, and Ganges exhibit inverted channels composed of light-toned beds. Valleys, channels, and light-toned layering along the walls of Juventae and Melas Chasmata are most likely coeval to the aqueous activity that affected the adjacent plateaus and indicate some hydrological activity occurred after formation of the chasmata. Although the source of water and sediment remains uncertain, the strong correlation between fluvial landforms and light-toned layered deposits argues for sustained precipitation, surface runoff, and fluvial deposition occurring during the Hesperian on the plateaus adjacent to Valles Marineris and along portions of chasmata walls.

Interspecific variation in susceptibility to fungal pathogens in seeds of 10 tree species in the neotropical genus Cecropia

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1. Species differences in susceptibility to pathogens acting at early life history stages may strongly influence the abundance and distribution of tropical trees. Here, we test the susceptibility of 10 congeners of the pioneer genus Cecropia to fungal seed and seedling pathogens and compare interspecific differences in intrinsic seed defences with survival. 2. Pathogens were experimentally removed through fungicide addition and/or autoclave sterilization of forest soil to determine the relative importance of fungal versus other microbial pathogens. Treatments were applied during a 4-month seed incubation (pre-emergence) phase or during an 8-week germination phase to distinguish between seed and seedling mortality. 3. Overall, seedling emergence after incubation in fungicide-treated, autoclaved soil was twice that in live soil, with significant positive effects of fungicide for six of 10 species. Pathogen infection occurred while seeds were quiescent in soil; fungicide addition during germination had no effect on emergence. Seedling emergence after burial ranged from 6 to 58%, indicating large interspecific variation in the capacity for Cecropia seeds to persist in the seed bank. Neither interspecific variation in survivorship, nor the relative strength of fungicide effects on survivorship was correlated with seed defence traits. 4. For four species, measurements of fungicide effects on emergence were coupled with direct measurements of the fungal and bacterial infection of seeds and seedlings. For two species, fungicide addition resulted in lower fungal infection rates and higher emergence success. However, Cecropia peltata, the species with the highest overall emergence success, also had the highest fungal infection rate. This suggests that either C. peltata was infected by a different suite of fungi than other congeners, or that fungi had low pathogenicity when colonizing this host species. 5. Synthesis. Our study shows strong interspecific variation in seed survival and susceptibility to fungal infection among congeneric tree species with similar life history. These differences are likely to influence recruitment success from the soil seed bank and may play a role in species coexistence.

A new approach to trenching experiments for measuring root-rhizosphere respiration in a lowland tropical forest

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Soil respiration in tropical forests is a major source of atmospheric CO2. The ability to partition soil respiration into its individual components is becoming increasingly important to predict the effects of disturbance on CO2 efflux from the soil as the responses of heterotrophic and autotrophic respiration to change are likely to differ. However, current field methods to partition respiration suffer from various methodological artefacts; root-rhizosphere respiration is particularly difficult to estimate. We used trenched subplots to estimate root-rhizosphere respiration in large-scale litter addition (L+), litter removal (L-) and control (CT) plots in a lowland tropical semi-evergreen forest in Panama. We took a new approach to trenching by making measurements immediately before-and-after trenching and comparing them to biweekly measurements made over one year. Root-rhizosphere respiration was estimated to be 38%, 17% and 27% in the CT, L+, and L- plots, respectively, from the measurements taken immediately before and one day after trenching in May-June 2007. Biweekly measurements over the following year provided no estimates of root-rhizosphere respiration for the first seven months due to decomposition of decaying roots. We were also unable to estimate root-rhizosphere respiration during the dry season due to differences in soil water content between trenched and untrenched soil. However, biweekly measurements taken during the early rainy season one year after trenching (May-June 2008) provided estimates of root-rhizosphere respiration of 39%, 24% and 36% in the CT, L+, and L- plots, respectively, which are very similar to those obtained during the first day after trenching. We suggest that measurements taken immediately before and one day after root excision are a viable method for a rapid estimation of root-rhizosphere respiration without the methodological artefacts usually associated with trenching experiments.

Difference in larval type explains patterns of nonsynonymous substitutions in two ancient paralogs of the histone H3 gene in sea stars

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SUMMARY Paralogous genes frequently show differences in patterns and rates of substitution that are typically attributed to different selection regimes, mutation rates, or local recombination rates. Here, two anciently diverged paralogous copies of the histone H3 gene in sea stars, the tandem-repetitive early-stage gene and a newly isolated gene with lower copy number that was termed the "putative late-stage histone H3 gene" were analyzed in 69 species with varying mode of larval development. The two genes showed differences in relative copy number, overall substitution rates, nucleotide composition, and codon usage, but similar patterns of relative nonsynonymous substitution rates, when analyzed by the dN/dS ratio. Sea stars with a nonpelagic and nonfeeding larval type (i.e., brooding lineages) were observed to have dN/dS ratios that were larger than for nonbrooders but equal between the two paralogs. This finding suggested that demographic differences between brooding and nonbrooding lineages were responsible for the elevated dN/dS ratios observed for brooders and refuted a suggestion from a previous analysis of the early-stage gene that the excess nonsynonymous substitutions were due to either (1) gene expression differences at the larval stage between brooders and nonbrooders or (2) the highly repetitive structure of the early-stage histone H3 gene.

Analysis of ordinary chondrites using powder X-ray diffraction: 1. Modal mineral abundances

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Abstract2013Powder X-ray diffraction (XRD) is used to quantify the modal abundances (in wt%) of 18 H, 17 L, and 13 LL unbrecciated ordinary chondrite falls, which represents the complete petrologic range of equilibrated ordinary chondrites (types 420136). The XRD technique presents an effective alternative to traditional methods for determining modal abundances, such as optical point counting and electron microprobe phase (EMP) mapping. The majority of chondrite powders in this study were previously prepared for chemical characterization from 8 to 20 g of material, which is consistent with the suggested mass (10 g) necessary to provide representative sampling of ordinary chondrites. Olivine and low-Ca pyroxene are the most abundant phases present, comprising one-half to three-fourths of total abundances, while plagioclase, high-Ca pyroxene, troilite, and metal comprise the remaining XRD-measured mineralogy. Pigeonite may also be present in some samples, but it is fitted using a high-Ca pyroxene standard, so exact abundances cannot be measured directly using XRD. Comparison of XRD-measured abundances with calculated Cross, Iddings, Pirsson, Washington (CIPW) normative abundances indicates that systematic discrepancies exist between these two data sets, particularly in olivine and high-Ca pyroxene. This discrepancy is attributed to the absence of pigeonite as a possible phase in the CIPW normative mineralogy. Oxides associated with pigeonite are improperly allocated, resulting in overestimated normative olivine abundances and underestimated normative high-Ca pyroxene abundances. This suggests that the CIPW norm is poorly suited for determining mineralogical modal abundances of ordinary chondrites.

What&#39s in a Name?

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Migration of endpoints of two genes relative to boundaries between regions of the plastid genome in the grass family (Poaceae)

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Overlapping genes occur widely in microorganisms and in some plastid genomes, but unique properties are observed when such genes span the boundaries between single-copy and repeat regions. The termini of ndhH and ndhF, situated near opposite ends of the small single-copy region (SSC) in the plastid genomes of grasses (Poaceae), have migrated repeatedly into and out of the adjacent inverted-repeat regions (IR). The two genes are transcribed in the same direction, and the 5' terminus of ndhH extends into the IR in some species, while the 3' terminus of ndhF extends into the IR in others. When both genes extend into the IR, portions of the genes overlap and are encoded by the same nucleotide positions. Fine-scale mapping of the SSC-IR junctions across a sample of 92 grasses and outgroups, integrated into a phylogenetic analysis, indicates that the earliest grasses resembled the related taxa Joinvillea (Joinvilleaceae) and Ecdeiocolea (Ecdeiocoleaceae), with ca. 180 nucleotides of ndhH extending into the IR, and with ndhF confined to the SSC. This structure is maintained in early-diverging grass lineages and in most species of the BEP clade. In the PACMAD clade, ndhH lies completely or nearly completely within the SSC, and ca. 20 nucleotides of ndhF extend into the IR. The nucleotide substitution rate has increased in the PACMAD clade in the portion of ndhH that has migrated into the SSC.

Electric fishes of the genus Sternarchorhynchus (Teleostei, Ostariophysi, Gymnotiformes); phylogenetic and revisionary studies

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Analysis of 88 characters of external and internal body systems yielded a phylogenetic reconstruction of the Neotropical electric knifefish genus Sternarchorhynchus (Apteronotidae; Gymnotiformes). The results support a hypothesis of Sternarchorhynchus as the sister group to Platyurosternarchus. A series of synapomorphies, many involving major innovations of the neurocranium, jaws, suspensorium, and associated systems that permit an unusual mode of grasp-suction feeding, support the monophyly of both genera. Synapomorphies largely resolve relationships within Sternarchorhynchus with basal nodes strongly supported by characters pertinent to prey capture and initial processing of food items. These possible key innovations may provide Sternarchorhynchus with a competitive advantage over other clades of the Apteronotidae and account for the species diversity of the genus in Neotropical rivers. Adaptive radiation in Sternarchorhynchus was analysed. Habitat preference transitions repeatedly occurred in the genus between deep-river channel dwelling species and rheophilic species with preferences for higher energy setting including rapids and swift-flowing fluviatile settings. Twenty-two species of Sternarchorhynchus are described as new based on samples that originated in the smaller rivers draining into the Golfo de Paria, the Marowijne and Essequibo River basins, the Río Orinoco and in particular the Amazon River basin. The 32 species in Sternarchorhynchus make it the most speciose genus in the Apteronotidae. No claim to original US government works. Journal compilation © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159, 2232013371.

The ancient pit-dwellers of Yezo

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