276 research outputs found
An analysis of precipitation isotope distributions across Namibia using historical data
Global precipitation isoscapes based on the Global Network for Isotopes in Precipitation (GNIP) network are an important toolset that aid our understanding of global hydrologiccycles. Although the GNIP database is instrumental in developing global isoscapes, data coverage in some regions of hydrological interest (e.g., drylands) is low or non-existent thus the accuracy and relevance of global isoscapes to these regions is debatable. Capitalizing on existing literature isotope data, we generated rainfall isoscapes for Namibia (dryland) using the cokriging method and compared it to a globally fitted isoscape (GFI) downscaled to country level. Results showed weak correlation between observed and predicted isotope values in the GFI model (r2 < 0.20) while the cokriging isoscape showed stronger correlation (r2 = 0.67). The general trend of the local cokriging isoscape is consistent with synoptic weather systems (i.e., influences from Atlantic Ocean maritime vapour, Indian Ocean maritime vapour, Zaire Air Boundary, the Intertropical Convergence Zone and Tropical Temperate Troughs) and topography affecting the region. However, because we used the unweighted approach in this method, due to data scarcity, the absolute values could beimproved in future studies. A comparison of local meteoric water lines (LMWL) constructed from the cokriging and GFI suggested that the GFI model still reflects the global averageeven when downscaled. The cokriging LMWL was however more consistent with expectations for an arid environment. The results indicate that although not ideal, for data deficientregions such as many drylands, the unweighted cokriging approach using historical local data can be an alternative approach to modelling rainfall isoscapes that are more relevantto the local conditions compared to using downscaled global isoscapes
Evidence of reproductive isolation confirms that Apis andreniformis (Smith, 1858) is a separate species from sympatric Apis florea (Fabricius, 1787).
The species Apis andreniformis (Smith, 1858), the small dwarf honey bee of South-east Asia, is recognized as a valid biological species. This recognition is based on distinctive endophallus characteristics in comparison with sympatric Apis florea (Fabricius, 1787). Additionally, scanning electron microscope images of drone basitarsi are presented, as are preliminary comparisons of wing venation
Genetic structure of drone congregation areas of Africanized honeybees in southern Brazil
As yet, certain aspects of the Africanization process are not well understood, for example, the reproductive behavior of African and European honeybees and how the first Africanized swarms were formed and spread. Drone congregation areas (DCAs) are the ideal place to study honeybee reproduction under natural conditions since hundreds of drones from various colonies gather together in the same geographical area for mating. In the present study, we assessed the genetic structure of seven drone congregations and four commercial European-derived and Africanized apiaries in southern Brazil, employing seven microsatellite loci for this purpose. We also estimated the number of mother-colonies that drones of a specific DCA originated from. Pairwise comparison failed to reveal any population sub-structuring among the DCAs, thus indicating low mutual genetic differentiation. We also observed high genetic similarity between colonies of commercial apiaries and DCAs, besides a slight contribution from a European-derived apiary to a DCA formed nearby. Africanized DCAs seem to have a somewhat different genetic structure when compared to the European
Modeling the isotopic evolution of snowpack and snowmelt : Testing a spatially distributed parsimonious approach
This work was funded by the NERC/JPI SIWA project (NE/M019896/1) and the European Research Council ERC (project GA 335910 VeWa). The Krycklan part of this study was supported by grants from the Knut and Alice Wallenberg Foundation (Branch-points), Swedish Research Council (SITES), SKB and Kempe foundation. The data and model code is available upon request. Authors declare that they have no conflict of interest. We would like to thank the three anonymous reviewers for their constructive comments that improved the manuscript.Peer reviewedPublisher PD
Taking the Sector Seriously: Data, Developments, and Drivers of Intrasectoral Earnings Inequality
The politics and administration of institutional chang
Drone aggregation behavior in the social wasp Vespula germanica (Hymenoptera: Vespidae): Effect of kinship and density
Inbreeding can have negative consequences on population viability because of the reduced fitness of the progeny. In general, most species have developed mechanisms to minimize inbreeding such as dispersal and kin avoidance behavior. In the eusocial Hymenoptera, related individuals typically share a common nest and have relatively short mating periods, this could lead to inbreeding, and because of their single?locus complementary sex determination system, it may generate diploid males that could result in infertile triploid progeny representing a cost for the colony. Vespula germanica, is an eusocial wasp that has invaded many parts of the world, despite likely facing a reduced genetic pool during the arrival phases. We ask whether male wasp display specific aggregation behavior that favors genetic diversity, key to reduce inbreeding. Through a set of laboratory experiments, we investigated the effects of drone nestmateship and density on the aggregation behavior of V. germanica drones. We show that drones avoid aggregating with their nestmates at all densities while non-nestmates are avoided only at high densities. This suggests that lek genetic diversity and density could be regulated through drone behavior and in the long run minimize inbreeding favoring invasion success.Fil: Masciocchi, Maité. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Angeletti, Bárbara. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Corley, Juan Carlos. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Martinez Von Ellrichshausen, Andres Santiago. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentin
Inter-laboratory comparison of cryogenic water extraction systems for stable isotope analysis of soil water
For more than two decades, research groups in hydrology, ecology, soil
science, and biogeochemistry have performed cryogenic water extractions (CWEs) for
the analysis of δ2H and δ18O of soil water.
Recent studies have shown that extraction conditions (time, temperature, and
vacuum) along with physicochemical soil properties may affect extracted soil
water isotope composition. Here we present results from the first worldwide
round robin laboratory intercomparison. We test the null hypothesis that, with
identical soils, standards, extraction protocols, and isotope analyses,
cryogenic extractions across all laboratories are identical. Two standard
soils with different physicochemical characteristics along with deionized
(DI) reference water of known isotopic composition were shipped to 16
participating laboratories. Participants oven-dried and rewetted the soils to
8 and 20 % gravimetric water content (WC), using the deionized reference
water. One batch of soil samples was extracted via predefined extraction
conditions (time, temperature, and vacuum) identical to all laboratories; the
second batch was extracted via conditions considered routine in the
respective laboratory. All extracted water samples were analyzed for
δ18O and δ2H by the lead laboratory (Global
Institute for Water Security, GIWS, Saskatoon, Canada) using both a laser and an
isotope ratio mass spectrometer (OA-ICOS and IRMS, respectively). We rejected
the null hypothesis. Our results showed large differences in retrieved
isotopic signatures among participating laboratories linked to soil type and
soil water content with mean differences compared to the reference water ranging from
+18.1 to −108.4 ‰ for δ2H and +11.8 to
−14.9 ‰ for δ18O across all laboratories. In
addition, differences were observed between OA-ICOS and IRMS isotope data.
These were related to spectral interferences during OA-ICOS analysis that are
especially problematic for the clayey loam soils used. While the types of
cryogenic extraction lab construction varied from manifold systems to single
chambers, no clear trends between system construction, applied extraction
conditions, and extraction results were found. Rather, observed differences
in the isotope data were influenced by interactions between multiple factors
(soil type and properties, soil water content, system setup, extraction
efficiency, extraction system leaks, and each lab's internal accuracy). Our
results question the usefulness of cryogenic extraction as a standard for
water extraction since results are not comparable across laboratories. This
suggests that defining any sort of standard extraction procedure applicable
across laboratories is challenging. Laboratories might have to establish
calibration functions for their specific extraction system for each natural
soil type, individually.</p
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