Species richness is greatest in the tropics, and much of this diversity is concentrated in mountains. Janzen proposed that reduced seasonal temperature variation selects for narrower thermal ...tolerances and limited dispersal along tropical elevation gradients Janzen DH (1967) Am Nat 101:233–249. These locally adapted traits should, in turn, promote reproductive isolation and higher speciation rates in tropical mountains compared with temperate ones. Here, we show that tropical and temperate montane stream insects have diverged in thermal tolerance and dispersal capacity, two key traits that are drivers of isolation in montane populations. Tropical species in each of three insect clades have markedly narrower thermal tolerances and lower dispersal than temperate species, resulting in significantly greater population divergence, higher cryptic diversity, higher tropical speciation rates, and greater accumulation of species over time. Our study also indicates that tropical montane species, with narrower thermal tolerance and reduced dispersal ability, will be especially vulnerable to rapid climate change.
In traumatic brain injury (TBI), a diversity of brain resident and peripherally derived myeloid cells have the potential to worsen damage and/or to assist in healing. We define the heterogeneity of ...microglia and macrophage phenotypes during TBI in wild-type (WT) mice and Ccr2−/− mice, which lack macrophage influx following TBI and are resistant to brain damage. We use unbiased single-cell RNA sequencing methods to uncover 25 microglia, monocyte/macrophage, and dendritic cell subsets in acute TBI and normal brains. We find alterations in transcriptional profiles of microglia subsets in Ccr2−/− TBI mice compared to WT TBI mice indicating that infiltrating monocytes/macrophages influence microglia activation to promote a type I IFN response. Preclinical pharmacological blockade of hCCR2 after injury reduces expression of IFN-responsive gene, Irf7, and improves outcomes. These data extend our understanding of myeloid cell diversity and crosstalk in brain trauma and identify therapeutic targets in myeloid subsets.
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•TBI elevates distinct phenotypes of microglia, macrophages, and dendritic cells•Ccr2 deficiency alters cell proportions and reduces ISG expression in microglia•TBI induces crosstalk between microglia and circulating monocytes•Preclinical translational studies to target human CCR2 after TBI improves outcomes
By single-cell RNA sequencing of traumatically injured and normal brains from wild-type and Ccr2−/− mice, Somebang et al. define microglia, macrophage, and dendritic cell phenotypes in TBI. Targeting mouse and/or human CCR2 reduces specific TBI brain CNS myeloid compartments, dampens type I interferon responses, and improves cognition after TBI.
Janzen's extension of the climate variability hypothesis (CVH) posits that increased seasonal variation at high latitudes should result in greater temperature overlap across elevations, and favour ...wider thermal breadths in temperate organisms compared to their tropical counterparts.
We tested these predictions by measuring stream temperatures and thermal breadths (i.e. the difference between the critical thermal maximum and minimum) of 62 aquatic insect species from temperate (Colorado, USA) and tropical (Papallacta, Ecuador) streams spanning an elevation gradient of c. 2000 m.
Temperate streams exhibited greater seasonal temperature variation and overlap across elevations than tropical streams, and as predicted, temperate aquatic insects exhibited broader thermal breadths than tropical insects. However, elevation had contrasting effects on patterns of thermal breadth. In temperate species, thermal breadth decreased with increasing elevation because CTMAX declined with elevation while CTMIN was similar across elevations. In tropical insects, by contrast, CTMAX declined less sharply than CTMIN with elevation, causing thermal breadth to increase with elevation.
These macrophysiological patterns are consistent with the narrower elevation ranges found in other tropical organisms, and they extend Janzen's CVH to freshwater streams. Furthermore, because lowland tropical aquatic insects have the narrowest thermal breadths of any region, they may be particularly vulnerable to short‐term extreme changes in stream temperature.
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To compare survival rates and age at death among very preterm infants in 10 national and regional neonatal networks.
A cohort study of very preterm infants, born between 24 and 29 weeks' gestation ...and weighing <1500 g, admitted to participating neonatal units between 2007 and 2013 in the International Network for Evaluating Outcomes of Neonates. Survival was compared by using standardized ratios (SRs) comparing survival in each network to the survival estimate of the whole population.
Network populations differed with respect to rates of cesarean birth, exposure to antenatal steroids and birth in nontertiary hospitals. Network SRs for survival were highest in Japan (SR: 1.10; 99% confidence interval: 1.08-1.13) and lowest in Spain (SR: 0.88; 99% confidence interval: 0.85-0.90). The overall survival differed from 78% to 93% among networks, the difference being highest at 24 weeks' gestation (range 35%-84%). Survival rates increased and differences between networks diminished with increasing gestational age (GA) (range 92%-98% at 29 weeks' gestation); yet, relative differences in survival followed a similar pattern at all GAs. The median age at death varied from 4 days to 13 days across networks.
The network ranking of survival rates for very preterm infants remained largely unchanged as GA increased; however, survival rates showed marked variations at lower GAs. The median age at death also varied among networks. These findings warrant further assessment of the representativeness of the study populations, organization of perinatal services, national guidelines, philosophy of care at extreme GAs, and resources used for decision-making.
Species are a fundamental unit of biodiversity that are delimited via genetic data and coalescent-based methods with increasing frequency. Despite the widespread use of coalescent-based species ...delimitation, we do not fully understand the sensitivity of these methods to potential sources of bias and violations of their underlying assumptions. One implicit assumption of coalescent-based species delimitation is that geographic sampling is adequate and representative of genetic variation among populations within the lineage of interest. Yet exhaustive geographic sampling is logistically difficult, if not impossible, for many taxa that span large geographic expanses or occupy remote regions. Here, we examine the impact of geographic sampling on the output of Bayes-factor delimitation with SNAPP, a popular coalescent-based species delimitation pipeline. First, we demonstrate the problematic nature of sparse geographic sampling and isolation by distance for species delimitation using simulated data sets of populations connected by different levels of gene flow. We then examine whether similar trends are present in an empirical dataset of Andesiops mayflies (Ephemeroptera: Baetidae) from a high elevation transect in the Ecuadorian Andes. In both the simulated and empirical analyses, we systematically exclude geographically intermediate sites to quantify the impact of geographic sampling and isolation by distance on coalescent-based species delimitation. We find that removing intermediate sites with genetically admixed individuals incorrectly favors multi-species delimitation scenarios. Oversplitting is especially pronounced when isolation by distance is strong, but exists even when gene flow among neighboring populations is relatively high. These findings highlight the importance of adequate geographic sampling in species delimitation and urge caution in interpreting the output of such methods when species' distributions are sparsely sampled and in systems characterized by strong patterns of isolation by distance.
Individual animals should adjust diets according to food availability. We used DNA metabarcoding to construct individual-level dietary timeseries for elephants from two family groups in Kenya varying ...in habitat use, social position and reproductive status. We detected at least 367 dietary plant taxa, with up to 137 unique plant sequences in one fecal sample. Results matched well-established trends: elephants tended to eat more grass when it rained and other plants when dry. Nested within these switches from 'grazing' to 'browsing' strategies, dietary DNA revealed seasonal shifts in food richness, composition and overlap between individuals. Elephants of both families converged on relatively cohesive diets in dry seasons but varied in their maintenance of cohesion during wet seasons. Dietary cohesion throughout the timeseries of the subdominant 'Artists' family was stronger and more consistently positive compared to the dominant 'Royals' family. The greater degree of individuality within the dominant family's timeseries could reflect more divergent nutritional requirements associated with calf dependency and/or priority access to preferred habitats. Whereas theory predicts that individuals should specialize on different foods under resource scarcity, our data suggest family bonds may promote cohesion and foster the emergence of diverse feeding cultures reflecting links between social behaviour and nutrition.
Applications of DNA barcoding include identifying species, inferring ecological and evolutionary relationships between species, and DNA metabarcoding. These applications require reference libraries ...that are not yet available for many taxa and geographic regions. We collected, identified, and vouchered plant specimens from Mpala Research Center in Laikipia, Kenya, to develop an extensive DNA‐barcode library for a savanna ecosystem in equatorial East Africa. We amassed up to five DNA barcode markers (rbcL, matK, trnL‐F, trnH–psbA, and ITS) for 1,781 specimens representing up to 460 species (~92% of the known flora), increasing the number of plant DNA barcode records for Africa by ~9%. We evaluated the ability of these markers, singly and in combination, to delimit species by calculating intra‐ and interspecific genetic distances. We further estimated a plant community phylogeny and demonstrated its utility by testing if evolutionary relatedness could predict the tendency of members of the Mpala plant community to have or lack “barcode gaps”, defined as disparities between the maximum intra‐ and minimum interspecific genetic distances. We found barcode gaps for 72%–89% of taxa depending on the marker or markers used. With the exception of the markers rbcL and ITS, we found that evolutionary relatedness was an important predictor of barcode‐gap presence or absence for all of the markers in combination and for matK, trnL‐F, and trnH–psbA individually. This plant DNA barcode library and community phylogeny will be a valuable resource for future investigations.
Intermittent streams are globally ubiquitous and represent a large percentage of stream networks. As climate change in many arid regions increases the frequency and intensity of drying disturbances, ...it is important to understand how aquatic biota will respond to such disturbances and how it would impact aquatic biodiversity. To address these topics, we sampled 10 stream reaches in the Sycamore Creek basin, an arid‐land stream in central Arizona (USA), with reach‐scale flow regimes ranging from perennial to highly intermittent. We sampled aquatic macroinvertebrates during 4 seasons to explore seasonal variability in community structure through flowing and drying phases. We also collected continuous flow data with remote data loggers to explore the impacts of intermittency and distance to perennial refuges on species richness, taxonomic composition and trait composition. Overall, richness was lower at intermittent reaches than perennial reaches, and richness values increased linearly as flow duration increased. We found no relationship between richness and distance to the nearest perennial refuge. Community assemblages differed significantly by season but were not distinct between perennial and intermittent reaches. Trait composition was also distinct between seasons and flow regimes, with traits such as a lack of diapause, longer life span and predatory feeding behaviours being indicators for perennial reaches. As climate change alters natural flow regimes, understanding the responses of macroinvertebrate community structure to drying disturbances in arid‐land streams can provide insight on aquatic community responses to climate change at larger scales.
Do hotspots of plant biodiversity translate into hotspots in the abundance and diversity of large mammalian herbivores? A common expectation in community ecology is that the diversity of plants and ...animals should be positively correlated in space, as with the latitudinal diversity gradient and the geographic mosaic of biodiversity. Whether this pattern ‘scales down’ to landscape-level linkages between the diversity of plants or the activities of highly mobile megafauna has received less attention. We investigated spatial associations between plants and large herbivores by integrating data from a plant-DNA-barcode phylogeny, camera traps, and a comprehensive map of woody plants across the 1.2-km2 Mpala Forest Global Earth Observatory (ForestGEO) plot, Kenya. Plant and large herbivore communities were strongly associated with an underlying soil gradient, but the richness of large herbivore species was negatively correlated with the richness of woody plants. Results suggest thickets and steep terrain create associational refuges for plants by deterring megaherbivores from browsing on otherwise palatable species. Recent work using dietary DNA metabarcoding has demonstrated that large herbivores often directly control populations of the plant species they prefer to eat, and our results reinforce the important role of megaherbivores in shaping vegetation across landscapes.
BACKGROUNDNephrogenic rests (NR) may represent precursor lesions for Wilms tumor (WT), but their clinical course is not fully understood and no guidelines for treatment exist. This study sought to ...evaluate the outcomes of pediatric patients with NRs related to traditional chemotherapy and surgery. METHODSA PRISMA-P-compliant literature search was conducted in MEDLINE, Embase, CINAHL, Web of Science, COCHRANE, and SCOPUS from inception to June 2021. Clinical questions regarding the treatment of NRs, including chemotherapy and surgery, were developed in the population, intervention, comparison, and outcome format. RESULTSTwenty-five studies including 1445 patients met inclusion criteria for evaluating chemotherapy compared to observation for NRs. Eighteen studies including 1392 patients met inclusion criteria for evaluating the role of surgery for NRs. Patients with isolated NRs who underwent observation progressed to WT 33% of the time; chemotherapy reduced the rate of WT to 3.9%. Observation of multiple NRs and diffuse hyperplastic perilobar nephroblastomatosis (DHPLN) led to progression to WT 50% and 100% of the time, respectively. Chemotherapy reduced the rate of WT to 34% for multiple NRs and 46% for DHPLN. Surgery for isolated NRs reduced the risk of WT development from 23.7% in patients with incomplete excision to 3.3% with complete excision; however, 96% of patients with incompletely excised NRs had bilateral disease. CONCLUSIONSObservation with close surveillance for isolated NRs is safe. Treatment with chemotherapy is recommended for patients with multiple NRs and DHPLN. Surgical management of NRs should focus on renal function preservation. LEVEL OF EVIDENCETreatment study, Level III.
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