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Ecologically mediated selection against hybrids, caused by hybrid phenotypes fitting poorly into available niches, is typically viewed as distinct from selection caused by epistatic Dobzhansky-Muller hybrid incompatibilities. Here, we show how selection against transgressive phenotypes in hybrids manifests as incompatibility. After outlining our logic, we summarize current approaches for studying ecology-based selection on hybrids. We then quantitatively review QTL-mapping studies and find traits differing between parent taxa are typically polygenic. Next, we describe how verbal models of selection on hybrids translate to phenotypic and genetic fitness landscapes, highlighting emerging approaches for detecting polygenic incompatibilities. Finally, in a synthesis of published data, we report that trait transgression-and thus possibly extrinsic hybrid incompatibility in hybrids-escalates with the phenotypic divergence between parents. We discuss conceptual implications and conclude that studying the ecological basis of hybrid incompatibility will facilitate new discoveries about mechanisms of speciation., (Copyright © 2024 Cold Spring Harbor Laboratory Press; all rights reserved.)

Interactions between alleles and across environments play an important role in the fitness of hybrids and are at the heart of the speciation process. Fitness landscapes capture these interactions and can be used to model hybrid fitness, helping us to interpret empirical observations and clarify verbal models. Here, we review recent progress in understanding hybridization outcomes through Fisher's geometric model, an intuitive and analytically tractable fitness landscape that captures many fitness patterns observed across taxa. We use case studies to show how the model parameters can be estimated from different types of data and discuss how these estimates can be used to make inferences about the divergence history and genetic architecture. We also highlight some areas where the model's predictions differ from alternative incompatibility-based models, such as the snowball effect and outlier patterns in genome scans., (Copyright © 2024 Cold Spring Harbor Laboratory Press; all rights reserved.)

When divergent populations interbreed, their alleles are brought together in hybrids. In the initial F1 cross, most divergent loci are heterozygous. Therefore, F1 fitness can be influenced by dominance effects that could not have been selected to function well together. We present a systematic study of these F1 dominance effects by introducing variable phenotypic dominance into Fisher's geometric model. We show that dominance often reduces hybrid fitness, which can generate optimal outbreeding followed by a steady decline in F1 fitness, as is often observed. We also show that "lucky" beneficial effects sometimes arise by chance, which might be important when hybrids can access novel environments. We then show that dominance can lead to violations of Haldane's Rule (reduced fitness of the heterogametic F1) but strengthens Darwin's Corollary (F1 fitness differences between cross directions). Taken together, results show that the effects of dominance on hybrid fitness can be surprisingly difficult to isolate, because they often resemble the effects of uniparental inheritance or expression. Nevertheless, we identify a pattern of environment-dependent heterosis that only dominance can explain, and for which there is some suggestive evidence. Our results also show how existing data set upper bounds on the size of dominance effects. These bounds could explain why additive models often provide good predictions for later-generation recombinant hybrids, even when dominance qualitatively changes outcomes for the F1., (© 2022 The Authors. Evolution published by Wiley Periodicals LLC on behalf of The Society for the Study of Evolution.)

Spicier food in hot countries has been explained in terms of natural selection on human cultures, with spices with antimicrobial effects considered to be an adaptation to increased risk of foodborne infection. However, correlations between culture and environment are difficult to interpret, because many cultural traits are inherited together from shared ancestors, neighbouring cultures are exposed to similar conditions, and many cultural and environmental variables show strong covariation. Here, using a global dataset of 33,750 recipes from 70 cuisines containing 93 different spices, we demonstrate that variation in spice use is not explained by temperature and that spice use cannot be accounted for by diversity of cultures, plants, crops or naturally occurring spices. Patterns of spice use are not consistent with an infection-mitigation mechanism, but are part of a broader association between spice, health, and poverty. This study highlights the challenges inherent in interpreting patterns of human cultural variation in terms of evolutionary pressures., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

When divergent populations form hybrids, hybrid fitness can vary with genome composition, current environmental conditions, and the divergence history of the populations. We develop analytical predictions for hybrid fitness, which incorporate all three factors. The predictions are based on Fisher's geometric model, and apply to a wide range of population genetic parameter regimes and divergence conditions, including allopatry and parapatry, local adaptation, and drift. Results show that hybrid fitness can be decomposed into intrinsic effects of admixture and heterozygosity, and extrinsic effects of the (local) adaptedness of the parental lines. Effect sizes are determined by a handful of geometric distances, which have a simple biological interpretation. These distances also reflect the mode and amount of divergence, such that there is convergence toward a characteristic pattern of intrinsic isolation. We next connect our results to the quantitative genetics of line crosses in variable or patchy environments. This means that the geometrical distances can be estimated from cross data, and provides a simple interpretation of the "composite effects." Finally, we develop extensions to the model, involving selectively induced disequilibria, and variable phenotypic dominance. The geometry of fitness landscapes provides a unifying framework for understanding speciation, and wider patterns of hybrid fitness., (© 2020 The Authors. Evolution published by Wiley Periodicals LLC on behalf of The Society for the Study of Evolution.)

Language diversity is distributed unevenly over the globe. Intriguingly, patterns of language diversity resemble biodiversity patterns, leading to suggestions that similar mechanisms may underlie both linguistic and biological diversification. Here we present the first global analysis of language diversity that compares the relative importance of two key ecological mechanisms - isolation and ecological risk - after correcting for spatial autocorrelation and phylogenetic non-independence. We find significant effects of climate on language diversity, consistent with the ecological risk hypothesis that areas of high year-round productivity lead to more languages by supporting human cultural groups with smaller distributions. Climate has a much stronger effect on language diversity than landscape features, such as altitudinal range and river density, which might contribute to isolation of cultural groups. The association between biodiversity and language diversity appears to be an incidental effect of their covariation with climate, rather than a causal link between the two.

A growing number of studies seek to identify predictors of broad-scale patterns in human cultural diversity, but three sources of non-independence in human cultural variables can bias the results of cross-cultural studies. First, related cultures tend to have many traits in common, regardless of whether those traits are functionally linked. Second, societies in geographical proximity will share many aspects of culture, environment and demography. Third, many cultural traits covary, leading to spurious relationships between traits. Here, we demonstrate tractable methods for dealing with all three sources of bias. We use cross-cultural analyses of proposed associations between human cultural traits and parasite load to illustrate the potential problems of failing to correct for these three forms of statistical non-independence. Associations between parasite stress and sociosexuality, authoritarianism, democracy and language diversity are weak or absent once relatedness and proximity are taken into account, and parasite load has no more power to explain variation in traditionalism, religiosity and collectivism than other measures of biodiversity, climate or population size do. Without correction for statistical non-independence and covariation in cross-cultural analyses, we risk misinterpreting associations between culture and environment., Competing Interests: We declare we have no competing interests.

What role does speaker population size play in shaping rates of language evolution? There has been little consensus on the expected relationship between rates and patterns of language change and speaker population size, with some predicting faster rates of change in smaller populations, and others expecting greater change in larger populations. The growth of comparative databases has allowed population size effects to be investigated across a wide range of language groups, with mixed results. One recent study of a group of Polynesian languages revealed greater rates of word gain in larger populations and greater rates of word loss in smaller populations. However, that test was restricted to 20 closely related languages from small Oceanic islands. Here, we test if this pattern is a general feature of language evolution across a larger and more diverse sample of languages from both continental and island populations. We analyzed comparative language data for 153 pairs of closely-related sister languages from three of the world's largest language families: Austronesian, Indo-European, and Niger-Congo. We find some evidence that rates of word loss are significantly greater in smaller languages for the Indo-European comparisons, but we find no significant patterns in the other two language families. These results suggest either that the influence of population size on rates and patterns of language evolution is not universal, or that it is sufficiently weak that it may be overwhelmed by other influences in some cases. Further investigation, for a greater number of language comparisons and a wider range of language features, may determine which of these explanations holds true.

History: In February 2013, 5 patients in an intensive care unit (ICU) were found to have positive blood cultures with Ralstonia pickettii within one week. Because all patients got intravenous therapy, improper work of a staff member was suspected. Some days later, a 6th patient was found with a positive blood culture of Ralstonia pickettii in another department of the hospital., Investigations: Hygienic investigations showed no evidence of failures in preparation of intravenous therapy. All patients were on different intravenous drugs, but every patient had received glucose 5 % and magnesium. We examined samples of glucose and magnesia as well as samples from environment. RESULTS AND COURSE: Glucose and magnesium samples were examined by membrane filter method. Ralstonia pitteckii was detected in some Magnesium vials. We concluded, that contamination of Magnesium vials might have been the reason for blood stream infection of patients. Pharmacists and authorities were informed and all vials were collected and replaced by vials from another company. Later a nationwide recall of Magnesium vials was performed by the producing company. No further Ralstonia pickettii was found in blood cultures in our hospital., Conclusion: Unusual pathogens in blood cultures should lead to reflection of rarer causes such as contamination of medicines., (© Georg Thieme Verlag KG Stuttgart · New York.)

The aim of our study was to assess the effect of oral and rectal stool softeners on dark-lumen magnetic resonance (MR) colonography without bowel cleansing. Ten volunteers underwent MR colonography without colonic cleansing. A baseline examination was performed without oral or rectal administration of stool softeners. In a second set, volunteers ingested 60 ml of lactulose 24 h prior to MR examination. In a third examination, water as a rectal enema was replaced by a solution of 0.5%-docusate sodium (DS). A fourth MR examination was performed, in conjunction with both oral administration of lactulose and rectal application of DS. A T1-weighted data set was acquired at scanning times of 0, 5 and 10 min after colonic filling. A fourth data set was acquired 75 s after i.v. injection of contrast agent. Signal intensity of stool was calculated for all colonic segments. Without oral ingestion of lactulose or rectal enema with DS stool signal intensity was high and did not decrease over time. However, lactulose and DS caused a decrease in stool signal intensity. Both substances together led to a decreasing signal intensity of feces. Combination of lactulose and DS provided the lowest signal intensity of stool. Thus, feces could hardly be distinguished from dark rectal enema allowing for the assessment of the colonic wall.

To assess the effect of the osmolarity for small bowel distension in MRI, ten volunteers ingested at two separate occasions negative oral contrast agents with different quantity and osmolarity: (1) a water solution combined with 2.0% sorbitol and 0.2% locus bean gum (LBG) with a quantity of 1500 ml and an osmolarity of 148 mOsmol/l, (2) a water solution combined with 2.0% sorbitol and 2.0% barium sulphate with a quantity of 1000 ml and an osmolarity of 194 mOsmol/l. Small bowel distension was quantified on coronal 2D-TrueFISP images by measuring the small bowel diameters. There were no statistically significant differences in mean small bowel diameter between both contrast agents. The mean small bowel distension was 19.2 mm after ingestion of 1500 ml of sorbitol-LBG solution and 19.0 mm after ingestion of 1000-ml sorbitol-barium sulphate solution. Furthermore, all volunteers found the ingestion of 1000-ml solution more pleasant than the 1500-ml solution. The ingestion of 1000 ml of sorbitol-barium sulphate solution led to a sufficient small bowel distension compared to 1500 ml of sorbitol-LBG solution. The side effect rate of both solutions was low. Based on these data, we recommend a quantity of 1000 ml of sorbitol-barium sulphate solution as an alternative for 1500-ml sorbitol-LBG solution for optimal bowel distension.

Purpose: To optimize the dose of a hydro solution containing 2.5% mannitol and 0.2% locust bean gum (LBG) for small bowel MRI in terms of bowel distension and patient acceptance., Materials and Methods: A total of 10 healthy volunteers ingested a hydro solution containing 2.5% mannitol and 0.2% LBG. Four different volumes (1500, 1200, 1000, and 800 ml) were assessed on four different examination days. Small bowel distension was quantified on coronal two-dimensional TrueFISP images by measuring the diameter of eight bowel loops throughout the jejunum and the ileum. In addition, volunteer acceptance was evaluated for every single examination by using a questionnaire., Results: Optimal distension was obtained with either, 1000, 1200, or 1500 ml, with no statistically significant differences in distension between these groups. Administration of 800 ml led to significantly less distension of the small bowel. Significantly less side effects were noted using either 800 or 1000 ml compared to using larger volumes., Conclusion: We recommend a dose of 1000 ml mannitol/LBG solution as an oral contrast agent for optimal bowel distension and minimal side effects., (Copyright 2004 Wiley-Liss, Inc.)

The purpose of this study was to compare two osmotic carbohydrate sugar alcohols (mannitol 2.5% and sorbitol 2.5%, 2.0%, and 1.5% watery solutions) in combination with 0.2% locust bean gum (LBG) for small bowel distension for MR imaging. Small bowel distension was quantified on coronal 2D TrueFISP images by measuring the diameters of 16 small bowel loops in each of 12 healthy subjects (age range 31-55 years). Additionally, the grade of small bowel distension was rated qualitatively. Patient acceptance concerning nausea, vomiting, flatulence, and diarrhea was noted for each solution, and all results were compared by a Wilcoxon test or t test, respectively. The ingestion of water combined with LBG and either 2.5% mannitol or 2.0% sorbitol showed the best distension of the small bowel. The lowest side effect rate was observed following ingestion of sorbitol in a concentration of 2.0 and 1.5%. Based on these data, we recommend a combination of LBG and 2% sorbitol use for optimal bowel distension and minimal side effects resulting in enhanced patient acceptance.

The authors qualitatively and quantitatively assessed a solution containing 0.2% locust bean gum (LBG) and 2.5% mannitol (mannitol-LBG) dissolved in water to provide a negative oral contrast material in dual-modality positron emission tomography (PET)/computed tomography (CT) scanning. PET/CT was performed in 60 patients with cancer after oral administration of barium, water, or mannitol-LBG. Qualitative and quantitative analyses were conducted to determine bowel distention and a potential influence of the contrast agents on the PET data. Intestinal distention with mannitol-LBG proved superior to that with water or barium. Findings at both quantitative and qualitative analysis revealed apparently increased tracer uptake in the small bowel with barium in comparison to that with mannitol-LBG or water. Mannitol-LBG may, therefore, be used as a negative oral contrast agent at PET/CT scanning because it provides excellent bowel distention while avoiding contrast material-induced PET artifacts., (Copyright RSNA, 2004)

Effect on small-bowel distention of additives to water as contrast agents for magnetic resonance (MR) imaging was assessed. Oral contrast agents included water and water in combination with mannitol, a bulk fiber laxative, locust bean gum, and a combination of mannitol and locust bean gum. Filling of the small bowel was quantified on coronal images obtained with two-dimensional true fast imaging with steady-state precession sequence; bowel diameters were measured. Ingestion of water with locust bean gum and mannitol provided the best distention of the small bowel. MR imaging of the small bowel with oral administration of water can be improved with addition of osmotic and nonosmotic substances that lead to decreased water resorption.