Conservation requires reliable estimates of a species' population and their spatial distribution. Knowledge of large‐scale habitat use and population trends in common hippopotamus (Hippopotamus ...amphibius; hereafter hippo) in wetland ecosystems is limited, with no studies of hippo populations in the Okavango Delta (the Delta), Botswana.
We examined the drivers of long‐term trends and spatial patterns in the Delta's hippo population, using 13 years of aerial surveys (1996–2018) informing on the potential impacts of changes in inflow, flooding patterns and rainfall on hippo populations.
We estimated temporal changes in hippo populations and relationships with rainfall and inflow. We also examined how spatially explicit hippo counts related to flood and surface water extent and vegetation class at different scales.
The Delta's hippo population has increased, probably due to increasing long‐term rainfall and inflow, following a period of severe drought/low flooding. Hippos were positively associated with areas with high variation in flooding and negatively associated with broad‐scale surface water extent, indicating hippos avoided permanent swamps and main channels, probably due to water depth, lack of nearby grazing, and thick riparian vegetation. At a fine scale, hippos relied on large lagoons for daytime refuge.
The most recent population estimate indicates that Botswana has the third highest hippo population in Africa, reflecting the importance of the Delta. Reductions in inflow and rainfall from climate change and water resource development would threaten these hippo populations by reducing grazing availability, lagoon sizes, and seasonal swamps. Ongoing monitoring of hippos should continue as they represent a good indicator for the entire floodplain ecosystem.
Stepping to recover balance is an important way we avoid falling. However, when faced with obstacles in the step path, we must adapt such reactions. Physical obstructions are typically detected ...through vision, which then cues step modification. The present study describes a novel method to assess visually prompted step inhibition in a reactive balance context. In our task, participants recovered balance by quickly stepping after being released from a supported forward lean. On rare trials, however, an obstacle blocked the stepping path. The timing of vision relative to postural perturbation was controlled using occlusion goggles to regulate task difficulty. Furthermore, we explored step suppression in our balance task related to inhibitory capacity measured at the hand using a clinically feasible handheld device (ReacStick). Our results showed that ReacStick and step outcomes were significantly correlated in terms of successful inhibition (r = 0.57) and overall reaction accuracy (r = 0.76). This study presents a novel method for assessing rapid inhibition in a dynamic postural context, a capacity that appears to be a necessary prerequisite to a subsequent adaptive strategy. Moreover, this capacity is significantly related to ReacStick performance, suggesting a potential clinical translation.
Angiosperms have dominated the Earth's vegetation since the mid-Cretaceous (90 million years ago), providing much of our food, fibre, medicine and timber, yet their origin and early evolution have ...remained enigmatic for over a century. One part of the enigma lies in the difficulty of identifying the earliest angiosperms; the other involves the uncertainty regarding the sister group of angiosperms among extant and fossil gymnosperms. Here we report a phylogenetic analysis of DNA sequences of five mitochondrial, plastid and nuclear genes (total aligned length 8,733 base pairs), from all basal angiosperm and gymnosperm lineages (105 species, 103 genera and 63 families). Our study demonstrates that Amborella, Nymphaeales and Illiciales-Trimeniaceae-Austrobaileya represent the first stage of angiosperm evolution, with Amborella being sister to all other angiosperms. We also show that Gnetales are related to the conifers and are not sister to the angiosperms, thus refuting the Anthophyte Hypothesis. These results have far-reaching implications for our understanding of diversification, adaptation, genome evolution and development of the angiosperms.
Ecologists describe plant distribution using direct gradient analysis, by which a tolerance curve of species abundance is described along an environmental gradient (any environmental variable that ...affects plant distribution). Soil moisture is generally the gradient in low-relief areas that explains the most variation. Traditional direct gradient analyses have used terrain structure (i.e., transects up or down hillslopes) as a correlate to soil moisture. Here we use a numerical tectonic and geomorphic process-based landscape development model to create two landscapes with different geomorphic characteristics: (1) to demonstrate the influence of geomorphic processes on soil moisture patterns and plant distribution and (2) to evaluate the effectiveness of transects in describing moisture gradients and tolerance curves on landscapes dominated by creep or overland flow. We use a topographic index to approximate the distribution of soil moisture as it is determined by the shape of these different landscapes. Transects are placed on hillslopes in each model landscape and used to construct tolerance curves.
Results show that transect methods that use the distance from the channel to the ridgeline as an approximation of soil moisture create variable tolerance curves for the same plant both within a single landscape and between different landscapes. The reason for these differences is that transects do not take into account the three-dimensional landscape form that explains water movement. Landscapes have regions of convexity and flow path divergence and regions of concavity and flow path convergence that, along with hillslope length, determine contributing area. In addition, hillslope curvature results in varying capacities to retain water. However, when the topographic index is used instead of hillslope transect position, tolerance curves from the same and different landscapes reflect the differences the topographic structure has on soil moisture. We thus show that traditional methods of direct gradient analysis are not always adequate as they do not tend to consider that soil moisture depends on hillslope length, curvature, and slope. Furthermore, we show that within and between landscapes there are differences in spatial distributions of soil moisture that are reflections of the geomorphic processes that created them.
Epigenetic differences exist between trauma-exposed individuals with and without post-traumatic stress disorder (PTSD). It is unclear whether these epigenetic differences pre-exist, or arise ...following, trauma and PTSD onset.
In pre- and post-trauma samples from a subset of Detroit Neighborhood Health Study participants, DNA methylation (DNAm) was measured at DNA methyltransferase 1 (DNMT1), DNMT3A, DNMT3B and DNMT3L. Pre-trauma DNAm differences and changes in DNAm from pre- to post-trauma were assessed between and within PTSD cases (n = 30) and age-, gender- and trauma exposure-matched controls (n = 30). Pre-trauma DNAm was tested for association with post-trauma symptom severity (PTSS) change. Potential functional consequences of DNAm differences were explored via bioinformatic search for putative transcription factor binding sites (TFBS).
DNMT1 DNAm increased following trauma in PTSD cases (p = 0.001), but not controls (p = 0.067). DNMT3A and DNMT3B DNAm increased following trauma in both cases (DNMT3A: p = 0.009; DNMT3B: p < 0.001) and controls (DNMT3A: p = 0.002; DNMT3B: p < 0.001). In cases only, pre-trauma DNAm was lower at a DNMT3B CpG site that overlaps with a TFBS involved in epigenetic regulation (p = 0.001); lower pre-trauma DNMT3B DNAm at this site was predictive of worsening of PTSS post-trauma (p = 0.034). Some effects were attenuated following correction for multiple hypothesis testing.
DNAm among trauma-exposed individuals shows both longitudinal changes and pre-existing epigenetic states that differentiate individuals who are resilient versus susceptible to PTSD. These distinctive DNAm differences within DNMT loci may contribute to genome-wide epigenetic profiles of PTSD.
We investigated the physiological response of the endangered Tidewater Goby Eucyclogobius newberryi to the presence of Threespine Sticklebacks Gasterosteus aculeatus (native to California) and ...Rainwater Killifish Lucania parva (nonnative). A fully factorial experimental design was used to examine species assemblage effects on juvenile fish over a 28-d period. Growth characteristics (weight, SL, and relative condition factor K ) and stress hormone levels (cortisol) were assessed under ample food conditions and at a salinity of 15‰. Weight and SL of Tidewater Goby increased throughout the experiment; growth did not differ in relation to fish assemblage treatment, but significant differences in growth were observed between sampling dates within the experiment. Rainwater Killifish exhibited marginal increases in weight, SL, and K ₙ, but these increases were not different among assemblage treatments or over time. For Threespine Sticklebacks, weight and SL increased during the final 2 weeks of the experiment, resulting in significant differences over the entire experimental period; however, growth characteristics of this species did not differ among assemblage treatments. Cortisol levels in all three species were not significantly affected by assemblage treatment. The present results indicate that juvenile Tidewater Goby are not adversely affected by native Threespine Sticklebacks or nonnative Rainwater Killifish under stable abiotic conditions in the absence of food limitation.
The relative contribution of central and peripheral mechanisms to the generation and maintenance of allograft tolerance is of considerable interest. Here, we present new evidence that regulatory T ...cells (Foxp3+) maintain skin and heart allograft tolerance in mixed hematopoietic chimeric mice. Transient depletion of both donor‐ and recipient‐derived Foxp3+ cells was necessary and sufficient to induce decisive rejection of long‐accepted skin and heart allografts. In contrast, stable hematopoietic chimerism remained, and there was no detectable induction of donor‐specific reactivity to hematopoietic cells. Foxp3+ cell depletion did not result in the rejection of skin grafts of only MHC‐disparate donors (B6.C‐H2d/bByJ), indicating that MHC antigens were not the target in the graft. We conclude that two different mechanisms of tolerance are present in mixed chimeras. Hematopoietic chimerism, resistant to Foxp3+ depletion, is probably due to deletional tolerance to MHC antigens, as supported by previous studies. In contrast, regulatory tolerance mechanisms involving Foxp3+ cells are required to control reactivity against non‐MHC antigens not present on hematopoietic lineages.
The authors show that dual mechanisms of tolerance are induced by mixed hematopoietic chimerism in mice: maintenance of tolerance of heart and skin allografts is dependent on Foxp3+ cells to regulate the response to non‐MHC antigens; in contrast, tolerance of MHC antigens on hematopoietic cells and skin grafts is independent of Foxp3 regulation, consistent with deletional mechanisms.
Detailed radiative transfer simulations of kilonovae are difficult to apply directly to observations; they only sparsely cover simulation parameters, such as the mass, velocity, morphology, and ...composition of the ejecta. On the other hand, semianalytic models for kilonovae can be evaluated continuously over model parameters, but neglect important physical details which are not incorporated in the simulations, thus introducing systematic bias. Starting with a grid of two-dimensional anisotropic simulations of kilonova light curves covering a wide range of ejecta properties, we apply adaptive learning techniques to iteratively choose new simulations and produce high-fidelity surrogate models for those simulations. These surrogate models allow for continuous evaluation across model parameters while retaining the microphysical details about the ejecta. Using a code formultimessenger inference developed by our group, we demonstrate how to use our interpolated models to infer kilonova parameters. Comparing to inferences using simplified analytic models, we recover different ejecta properties. We discuss the implications of this analysis which is qualitatively consistent with similar previous work using detailed ejecta opacity calculations and which illustrates systematic challenges for kilonova modeling. An associated data and code release provides our interpolated light-curve models, interpolation implementation which can be applied to reproduce our work or extend to new models, and our multimessenger parameter inference engine.
Magnetotelluric data were used to study the lithosphere structure of the Southern Oklahoma Aulacogen (SOA). Inversion of the data revealed two low resistivity anomalies beneath the SOA. The first is ...located in the depth range 0–90 km in the crust and upper lithospheric mantle. The second extends from a depth 100 km to the base of the lithospheric mantle and extends away from the SOA to the ends of the profile. The cause of low resistivity anomalies is discussed in relation to the tectonic evolution of the region and recent laboratory experiments on rock conductivity. The first anomaly is attributed to the combination of (a) water present in mantle minerals and (b) the formation of hydrous mineral phases by interactions between a plume and the lithosphere during rifting. Grain size reduction and fabric alignment from deformation during the Ancestral Rocky Mountain (ARM) orogeny may have also contributed to the low resistivity. This enrichment phase may have mechanically weakened the lithosphere and allowed deformation to occur during the ARM orogeny. The low resistivity of the deeper anomaly is attributed to a fluorine‐enriched phlogopite layer that is also coincident with an observed seismic mid‐lithosphere discontinuity (MLD). A lithosphere keel of mantle minerals enriched in water underlies this layer and may have formed by accretion of the plume head to the lower lithosphere after rifting, which also rethickened the lithosphere to its present‐day depths. The MLD may then reflect a melt layer along a paleo lithosphere‐asthenosphere boundary entombed during the accretion.
Plain Language Summary
Earth's tectonic plates result from modification by past and present tectonic processes such as rifting and plumes. Processes that occurred in the past can be understood by present day studies of these processes that are active today. Geophysical imaging is a key part of these investigations as it provides information about subsurface structure. One method that is widely used is magnetotellurics (MT) which provides information about electrical resistivity. This parameter is sensitive to the presence of fluids and past metamorphism. The Southern Oklahoma Aulacogen is a failed rift located in the central USA. After the rifting occurred, compression formed the Ancestral Rocky Mountains (ARMs). This study uses MT data to understand how past tectonic events modified the North American Plate in this region. The results show that the lithosphere beneath the rift has a low electrical resistivity relative to the surrounding region. This suggests that metamorphism changed the composition of lithosphere and made it weaker. When later tectonic events caused compression, this weakening allowed the ARM to form. These results help us to understand how rifts and plumes modify plates at the present.
Key Points
A 2‐D magnetotelluric model of the Southern Oklahoma Aulacogen in the USA is compared with regional geochemical and mineral physics data
After rifting, an enriched plume may have been accreted to the lithosphere and increased the lithospheric thickness to its current value
Metasomatism during rifting rheologically weakened the lithosphere, allowing deformation during the Ancestral Rocky Mountain orogeny
Transfrontier wildlife corridors can be successful conservation tools, connecting protected areas and reducing the impact of habitat fragmentation on mobile species. Urban wildlife corridors have ...been proposed as a potential mitigation tool to facilitate the passage of elephants through towns without causing conflict with urban communities. However, because such corridors are typically narrow and close to human development, wildlife (particularly large mammals) may be less likely to use them. We used remote-sensor camera traps and global positioning system collars to identify the movement patterns of African elephants Loxondonta africana through narrow, urban corridors in Botswana. The corridors were in three types of human-dominated land-use designations with varying levels of human activity: agricultural, industrial and open-space recreational land. We found that elephants used the corridors within all three land-use designations and we identified, using a model selection approach, that season, time of day and rainfall were important factors in determining the presence of elephants in the corridors. Elephants moved more slowly through the narrow corridors compared with their movement patterns through broader, wide-ranging corridors. Our results indicate that urban wildlife corridors are useful for facilitating elephants to pass through urban areas.
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