Edaphic adaptation maintains the coexistence of two cryptic species on serpentine soils

• Premise of the study: Divergent edaphic adaptation can contribute to reproductive isolation and coexistence between closely related species, yet we know little about how small-scale continuous edaphic gradients contribute to this phenomenon. We investigated edaphic adaptation between two cryptic species of California wildflower, Lasthenia californica and L. gracilis (Asteraceae), which grow in close parapatry on serpentine soil. • Methods: We reciprocally transplanted both species into the center of each species’ habitat and the transition zone between species. We quantified multiple components of fitness and used aster models to predict fitness based on environmental variables. We sampled soil across the ridge throughout the growing season to document edaphic changes through time. We sampled naturally germinating seedlings to determine whether there was dispersal into the adjacent habitat and to help pinpoint the timing of any selection against migrants. • Key results: We documented within-serpentine adaptation contributing to habitat isolation between close relatives. Both species were adapted to the edaphic conditions in their native region and suffered fitness trade-offs when moved outside that region. However, observed fitness values did not perfectly match those predicted by edaphic variables alone, indicating that other factors, such as competition, also contributed to plant fitness. Soil water content and concentrations of calcium, magnesium, sodium, and potassium were likely drivers of differential fitness. Plants either had limited dispersal ability or migrants experienced early-season mortality outside their native region. • Conclusions: Demonstrating that continuous habitats can support differently adapted, yet closely related, taxa is important to a broader understanding of how species are generated and maintained in nature

A survey of nuclear ribosomal internal transcribed spacer substitution rates across angiosperms: an approximate molecular clock with life history effects

BACKGROUND: A full understanding of the patterns and processes of biological diversification requires the dating of evolutionary events, yet the fossil record is inadequate for most lineages under study. Alternatively, a molecular clock approach, in which DNA or amino acid substitution rates are calibrated with fossils or geological/climatic events, can provide indirect estimates of clade ages and diversification rates. The utility of this approach depends on the rate constancy of molecular evolution at a genetic locus across time and across lineages. Although the nuclear ribosomal internal transcribed spacer region (nrITS) is increasingly being used to infer clade ages in plants, little is known about the sources or magnitude of variation in its substitution rate. Here, we systematically review the literature to assess substitution rate variation in nrITS among angiosperms, and we evaluate possible correlates of the variation. RESULTS: We summarize 28 independently calibrated nrITS substitution rates ranging from 0.38 × 10(-9 )to 8.34 × 10(-9 )substitutions/site/yr. We find that herbaceous lineages have substitution rates almost twice as high as woody plants, on average. We do not find any among-lineage phylogenetic constraint to the rates, or any effect of the type of calibration used. Within life history categories, both the magnitude of the rates and the variance among rates tend to decrease with calibration age. CONCLUSION: Angiosperm nrITS substitution rates vary by approximately an order of magnitude, and some of this variation can be attributed to life history categories. We make cautious recommendations for the use of nrITS as an approximate plant molecular clock, including an outline of more appropriate phylogenetic methodology and caveats against over interpretation of results. We also suggest that for lineages with independent calibrations, much of the variation in nrITS substitution rates may come from uncertainty in calibration date estimates, highlighting the importance of accurate and/or multiple calibration dates

Above- and Below-Ground Functional Trait Coordination in the Neotropical Understory Genus \u3cem\u3eCostus\u3c/em\u3e

The study of plant functional traits and variation among and within species can help illuminate functional coordination and trade-offs in key processes that allow plants to grow, reproduce and survive. We studied 20 leaf, above-ground stem, below-ground stem and fine-root traits of 17 Costus species from forests in Costa Rica and Panama to answer the following questions: (i) Do congeneric species show above-ground and below-ground trait coordination and trade-offs consistent with theory of resource acquisition and conservation? (ii) Is there correlated evolution among traits? (iii) Given the diversity of habitats over which Costus occurs, what is the relative contribution of site and species to trait variation? We performed a principal components analysis (PCA) to assess for the existence of a spectrum of trait variation and found that the first two PCs accounted for 21.4 % and 17.8 % of the total trait variation, respectively, with the first axis of variation being consistent with a continuum of resource-acquisitive and resource-conservative traits in water acquisition and use, and the second axis of variation being related to the leaf economics spectrum. Stomatal conductance was negatively related to both above-ground stem and rhizome specific density, and these relationships became stronger after accounting for evolutionary relatedness, indicating correlated evolution. Despite elevation and climatic differences among sites, high trait variation was ascribed to individuals rather than to sites. We conclude that Costus species present trait coordination and trade-offs that allow species to be categorized as having a resource-acquisitive or resource-conservative functional strategy, consistent with a whole-plant functional strategy with evident coordination and trade-offs between above-ground and below-ground function. Our results also show that herbaceous species and species with rhizomes tend to agree with trade-offs found in more species-rich comparisons

Sympatric serpentine endemic Monardella (Lamiaceae) Species Maintain Habitat Differences Despite Hybridization

Ecological differentiation and genetic isolation are thought to be critical in facilitating coexistence between related species, but the relative importance of these phenomena and the interactions between them are not well understood. Here, we examine divergence in abiotic habitat affinity and the extent of hybridization and introgression between two rare species of Monardella (Lamiaceae) that are both restricted to the same serpentine soil exposure in California. Although broadly sympatric, they are found in microhabitats that differ consistently in soil chemistry, slope, rockiness and vegetation. We identify one active hybrid zone at a site with intermediate soil and above-ground characteristics, and we document admixture patterns indicative of extensive and asymmetric introgression from one species into the other. We find that genetic distance among heterospecific populations is related to geographic distance, such that the extent of apparent introgression is partly explained by the spatial proximity to the hybrid zone. Our work shows that plant species can maintain morphological and ecological integrity in the face of weak genetic isolation, intermediate habitats can facilitate the establishment of hybrids, and that the degree of apparent introgression a population experiences is related to its geographic location rather than its local habitat characteristics

Flexible Drought Deciduousness in a Neotropical Understory Herb

PREMISE OF THE STUDY Adaptive divergence across environmental gradients is a key driver of speciation. Precipitation seasonality gradients are common in the tropics, yet drought adaptation is nearly unexplored in neotropical understory herbs. We examine two recently diverged neotropical spiral gingers, one adapted to seasonal drought and one reliant on perennial water, to uncover the basis of drought adaptation. METHODS We combine ecophysiological trait measurements in the field and greenhouse with experimental and observational assessment of real-time drought response to determine how Costus villosissimus (Costaceae) differs from C. allenii to achieve drought adaptation. KEY RESULTS We find that drought-adapted C. villosissimus has several characteristics indicating flexible dehydration avoidance via semi-drought-deciduousness and a fast economic strategy. Although the two species do not differ in water use efficiency, C. villosissimus has a more rapid growth rate, lower leaf mass per area, lower stem density, higher leaf nitrogen, and a strong trend of greater light-saturated photosynthetic rates. These fast economic strategy traits align with both field-based observations and experimental dry-down results. When faced with drought, C. villosissimus displays facultative drought-deciduousness, losing lower leaves during the dry season and rapidly growing new leaves in the wet season. CONCLUSIONS We reveal a drought adaptation strategy that has not, to our knowledge, previously been documented in tropical herbs. This divergent drought adaptation evolved recently and is an important component of reproductive isolation between C. villosissimus and C. allenii, indicating that adaptive shifts to survive seasonal drought may be an underappreciated axis of neotropical understory plant diversification

Physical Activity Reduces Hippocampal Atrophy in Elders at Genetic Risk for Alzheimer\u27s Disease

We examined the impact of physical activity (PA) on longitudinal change in hippocampal volume in cognitively intact older adults at varying genetic risk for the sporadic form of Alzheimer\u27s disease (AD). Hippocampal volume was measured from structural magnetic resonance imaging (MRI) scans administered at baseline and at an 18-month follow-up in 97 healthy, cognitively intact older adults. Participants were classified as High or Low PA based on a self-report questionnaire of frequency and intensity of exercise. Risk status was defined by the presence or absence of the apolipoprotein E-epsilon 4 (APOE-ε4) allele. Four subgroups were studied: Low Risk/High PA (n = 24), Low Risk/Low PA (n = 34), High Risk/High PA (n = 22), and High Risk/Low PA (n = 17). Over the 18 month follow-up interval, hippocampal volume decreased by 3% in the High Risk/Low PA group, but remained stable in the three remaining groups. No main effects or interactions between genetic risk and PA were observed in control brain regions, including the caudate, amygdala, thalamus, pre-central gyrus, caudal middle frontal gyrus, cortical white matter (WM), and total gray matter (GM). These findings suggest that PA may help to preserve hippocampal volume in individuals at increased genetic risk for AD. The protective effects of PA on hippocampal atrophy were not observed in individuals at low risk for AD. These data suggest that individuals at genetic risk for AD should be targeted for increased levels of PA as a means of reducing atrophy in a brain region critical for the formation of episodic memories

Orphan Gpr182 suppresses ERK-mediated intestinal proliferation during regeneration and adenoma formation

Orphan GPCRs provide an opportunity to identify potential pharmacological targets, yet their expression patterns and physiological functions remain challenging to elucidate. Here, we have used a genetically engineered knockin reporter mouse to map the expression pattern of the Gpr182 during development and adulthood. We observed that Gpr182 is expressed at the crypt base throughout the small intestine, where it is enriched in crypt base columnar stem cells, one of the most active stem cell populations in the body. Gpr182 knockdown had no effect on homeostatic intestinal proliferation in vivo, but led to marked increases in proliferation during intestinal regeneration following irradiation-induced injury. In the ApcMin mouse model, which forms spontaneous intestinal adenomas, reductions in Gpr182 led to more adenomas and decreased survival. Loss of Gpr182 enhanced organoid growth efficiency ex vivo in an EGF-dependent manner. Gpr182 reduction led to increased activation of ERK1/2 in basal and challenge models, demonstrating a potential role for this orphan GPCR in regulating the proliferative capacity of the intestine. Importantly, GPR182 expression was profoundly reduced in numerous human carcinomas, including colon adenocarcinoma. Together, these results implicate Gpr182 as a negative regulator of intestinal MAPK signaling–induced proliferation, particularly during regeneration and adenoma formation

Diabetes and disordered eating behaviours in a community-based sample of Australian adolescents

Background People with diabetes have been shown to be at risk for disordered eating compared to their non-diabetic peers. However, the majority of studies have been conducted in relatively small samples drawn from clinical diabetes settings or registries. Community-based samples are required to better understand disordered eating behaviours in this population. In a large community-based population sample of Australian adolescents, this study aimed to (1) investigate disordered eating behaviours in adolescents reporting a diagnosis of diabetes compared to their non-diabetic peers and (2) test associations between disordered eating behaviours and insulin restriction. Methods Secondary school students (n = 4854; mean (SD) age 14.4 (1.6) years; 47% boys) completed an online survey, including self-reported presence of diabetes, demographics, weight status, substance use, insulin restriction and disordered eating behaviours. Clinically meaningful cut-offs for disordered eating behaviours were generated for analysis. Results Disordered eating behaviours, specifically self-induced vomiting (diabetes 19.2%, no diabetes 3.3%; p <  0.001), laxative use (diabetes 15.4%, no diabetes 2.1%; p <  0.001), use of cigarettes (diabetes 26.9%, no diabetes 4.3%; p <  0.001) and other drugs (diabetes 28.9%, no diabetes 4.0%; p <  0.001), cleanse/detox (diabetes 30.8%, no diabetes 10.5%; p <  0.001) and extreme weight loss diets (diabetes 13.5%, no diabetes 4.7%; p <  0.003) were higher in those reporting a diagnosis of diabetes. In addition, 17% of those with diabetes reported frequent insulin restriction (≥ once per week), and insulin restriction was associated with more frequent disordered eating behaviours. Conclusion There was a high rate of disordered eating behaviours in adolescents with diabetes compared to their peers without diabetes. The findings of this study may have the potential to inform future health promotion, prevention, and early intervention approaches for those with comorbid diabetes and disordered eating behaviours. Future longitudinal studies are required to evaluate disordered eating behaviours in those with diabetes over time in community-based samples

Evidence of Natural Bluetongue Virus Infection among African Carnivores

Bluetongue is an International Office of Epizootics List A disease described as the century\u27s most economically devastating affliction of sheep. Bluetongue (BLU) viruses were thought to infect only ruminants, shrews, and some rodents, but recently, inadvertent administration of BLU virus-contaminated vaccine resulted in mortality and abortion among domestic dogs. We present evidence of natural BLU virus infection among African carnivores that dramatically widens the spectrum of susceptible hosts. We hypothesize that such infection occurred after ingestion of meat and organs from BLU virus infected prey species. The effect of BLU virus on endangered carnivores such as the cheetah and African wild dog requires urgent investigation. Also, the role of carnivores in the epizootiology of this disease needs elucidation

Promoting students’ interest through culturally sensitive curricula in higher education

Previous studies have emphasized culturally sensitive curricula in the context of enhancing minoritized students’ education. We examined the relationship between second-year higher education students’ perceptions of the cultural sensitivity of their curriculum and both majoritized and minoritized students’ interest in their course. A total of 286 (228 F) students rated the cultural sensitivity of their curriculum on six scales using a revised version of the Culturally Sensitive Curricula Scales (CSCS-R), the perceived quality of their relationships with teachers, and their interest. The CSCS-R widened the construct with two new scales and showed better reliability. Ethnic minority students (n = 99) perceived their curriculum as less culturally sensitive than White students (n = 182), corroborating previous findings. Black students perceived their curriculum as less culturally sensitive than Asian students. There were no significant differences between ethnic minority and White students on interest or perceived quality of relationships with teachers. Five dimensions of cultural sensitivity (Diversity Represented, Positive Depictions, Challenge Power, Inclusive Classroom Interactions, Culturally Sensitive Assessments) and perceived quality of relationships with teachers predicted interest. Ethnicity did not. Ensuring curricula and assessments represent diversity positively, challenge power and are inclusive may support students’ interest while reflecting an increasingly diverse society