A Trip Back Home: Resistance to Herbivores of Native and Non-Native Plant Populations of Datura stramonium.

When colonizing new ranges, plant populations may benefit from the absence of the checks imposed by the enemies, herbivores, and pathogens that regulated their numbers in their original range. Therefore, rates of plant damage or infestation by natural enemies are expected to be lower in the new range. Exposing both non-native and native plant populations in the native range, where native herbivores are present, can be used to test whether resistance mechanisms have diverged between populations. Datura stramonium is native to the Americas but widely distributed in Spain, where populations show lower herbivore damage than populations in the native range. We established experiments in two localities in the native range (Mexico), exposing two native and two non-native D. stramonium populations to natural herbivores. Plant performance differed between the localities, as did the abundance of the main specialist herbivore, Lema daturaphila. In Teotihuacán, where L. daturaphila is common, native plants had significantly more adult beetles and herbivore damage than non-native plants. The degree of infestation by the specialist seed predator Trichobaris soror differed among populations and between sites, but the native Ticumán population always had the lowest level of infestation. The Ticumán population also had the highest concentration of the alkaloid scopolamine. Scopolamine was negatively related to the number of eggs deposited by L. daturaphila in Teotihuacán. There was among-family variation in herbivore damage (resistance), alkaloid content (scopolamine), and infestation by L. daturaphila and T. soror, indicating genetic variation and potential for further evolution. Although native and non-native D. stramonium populations have not yet diverged in plant resistance/constitutive defense, the differences between ranges (and the two experimental sites) in the type and abundance of herbivores suggest that further research is needed on the role of resource availability and adaptive plasticity, specialized metabolites (induced, constitutive), and the relationship between genealogical origin and plant defense in both ranges.

Genomic and chemical evidence for local adaptation in resistance to different herbivores in Datura stramonium.

Because most species are collections of genetically variable populations distributed to habitats differing in their abiotic/biotic environmental factors and community composition, the pattern and strength of natural selection imposed by species on each other's traits are also expected to be highly spatially variable. Here, we used genomic and quantitative genetic approaches to understand how spatially variable selection operates on the genetic basis of plant defenses to herbivores. To this end, an F2 progeny was generated by crossing Datura stramonium (Solanaceae) parents from two populations differing in their level of chemical defense. This F2 progeny was reciprocally transplanted into the parental plants' habitats and by measuring the identity by descent (IBD) relationship of each F2 plant to each parent, we were able to elucidate how spatially variable selection imposed by herbivores operated on the genetic background (IBD) of resistance to herbivory, promoting local adaptation. The results highlight that plants possessing the highest total alkaloid concentrations (sum of all alkaloid classes) were not the most well-defended or fit. Instead, specific alkaloids and their linked loci/alleles were favored by selection imposed by different herbivores. This has led to population differentiation in plant defenses and thus, to local adaptation driven by plant-herbivore interactions.

Selection on tropane alkaloids in native and non-native populations of Datura stramonium.

Theories of plant invasion based on enemy release in a new range assume that selection exerted by specialist herbivores on defence traits should be reduced, absent, or even selected against in the new environment. Here, we measured phenotypic selection on atropine and scopolamine concentration of Datura stramonium in eight native (Mexico) and 14 non-native (Spain) populations. Native populations produced between 20 and 40 times more alkaloid than non-native populations (atropine: 2.0171 vs. 0.0458 mg/g; scopolamine: 1.004 vs. 0.0488 mg/g, respectively). Selection on alkaloids was negative for atropine and positive for scopolamine concentration in both ranges. However, the effect sizes of selection gradients were only significant in the native range. Our results support the assumption that the reduction of plant defence in the absence of the plant's natural enemies in invasive ranges is driven by natural selection.

Natural selection drives chemical resistance of Datura stramonium.

Plant resistance to herbivores involves physical and chemical plant traits that prevent or diminish damage by herbivores, and hence may promote coevolutionary arm-races between interacting species. Although Datura stramonium's concentration of tropane alkaloids is under selection by leaf beetles, it is not known whether chemical defense reduces seed predation by the specialist weevil, Trichobaris soror, and if it is evolving by natural selection. We measured infestation by T. soror as well as the concentration of the plants' two main tropane alkaloids in 278 D. stramonium plants belonging to 31 populations in central Mexico. We assessed whether the seed predator exerted preferences on the levels of both alkaloids and whether they affect plant fitness. Results show great variation across populations in the concentration of scopolamine and atropine in both leaves and seeds of plants of D. stramonium, as well as in the intensity of infestation and the proportion of infested fruits by T. soror. The concentration of scopolamine in seeds and leaves are negatively associated across populations. We found that scopolamine concentration increases plant fitness. Our major finding was the detection of a positive relationship between the population average concentrations of scopolamine with the selection differentials of scopolamine. Such spatial variation in the direction and intensity of selection on scopolamine may represent a coevolutionary selective mosaic. Our results support the view that variation in the concentration of scopolamine among-populations of D. stramonium in central Mexico is being driven, in part, by selection exerted by T. soror, pointing an adaptive role of tropane alkaloids in this plant species.

Adaptive divergence in resistance to herbivores in Datura stramonium.

Defensive traits exhibited by plants vary widely across populations. Heritable phenotypic differentiation is likely to be produced by genetic drift and spatially restricted gene flow between populations. However, spatially variable selection exerted by herbivores may also give rise to differences among populations. To explore to what extent these factors promote the among-population differentiation of plant resistance of 13 populations of Datura stramonium, we compared the degree of phenotypic differentiation (P ST) of leaf resistance traits (trichome density, atropine and scopolamine concentration) against neutral genetic differentiation (F ST) at microsatellite loci. Results showed that phenotypic differentiation in defensive traits among-population is not consistent with divergence promoted by genetic drift and restricted gene flow alone. Phenotypic differentiation in scopolamine concentration was significantly higher than F ST across the range of trait heritability values. In contrast, genetic differentiation in trichome density was different from F ST only when heritability was very low. On the other hand, differentiation in atropine concentration differed from the neutral expectation when heritability was less than or equal to 0.3. In addition, we did not find a significant correlation between pair-wise neutral genetic distances and distances of phenotypic resistance traits. Our findings reinforce previous evidence that divergent natural selection exerted by herbivores has promoted the among-population phenotypic differentiation of defensive traits in D. stramonium.

Natural selection on plant resistance to herbivores in the native and introduced range.

When plants are introduced into new regions, the absence of their co-evolved natural enemies can result in lower levels of attack. As a consequence of this reduction in enemy pressure, plant performance may increase and selection for resistance to enemies may decrease. In the present study, we compared leaf damage, plant size and leaf trichome density, as well as the direction and magnitude of selection on resistance and plant size between non-native (Spain) and native (Mexico) populations of Datura stramonium. This species was introduced to Spain about five centuries ago and constitutes an ideal system to test four predictions of the enemy release hypothesis. Compared with native populations, we expected Spanish populations of D. stramonium to have (i) lower levels of foliar damage; (ii) larger plant size; (iii) lower leaf trichome density that is unrelated to foliar damage by herbivores; and (iv) weak or no selection on resistance to herbivores but strong selection on plant size. Our results showed that, on average, plants from non-native populations were significantly less damaged by herbivores, were less pubescent and were larger than those from native populations. We also detected different selection regimes on resistance and plant size between the non-native and native ranges. Positive selection on plant size was detected in both ranges (though it was higher in the non-native area), but consistent positive selection on relative resistance was detected only in the native range. Overall, we suggest that changes in selection pressure on resistance and plant size in D. stramonium in Spain are a consequence of 'release from natural enemies'.

Selection mosaic exerted by specialist and generalist herbivores on chemical and physical defense of Datura stramonium.

Selection exerted by herbivores is a major force driving the evolution of plant defensive characters such as leaf trichomes or secondary metabolites. However, plant defense expression is highly variable among populations and identifying the sources of this variation remains a major challenge. Plant populations are often distributed across broad geographic ranges and are exposed to different herbivore communities, ranging from generalists (that feed on diverse plant species) to specialists (that feed on a restricted group of plants). We studied eight populations of the plant Datura stramonium usually eaten by specialist or generalist herbivores, in order to examine whether the pattern of phenotypic selection on secondary compounds (atropine and scopolamine) and a physical defense (trichome density) can explain geographic variation in these traits. Following co-evolutionary theory, we evaluated whether a more derived alkaloid (scopolamine) confers higher fitness benefits than its precursor (atropine), and whether this effect differs between specialist and generalist herbivores. Our results showed consistent directional selection in almost all populations and herbivores to reduce the concentration of atropine. The most derived alkaloid (scopolamine) was favored in only one of the populations, which is dominated by a generalist herbivore. In general, the patterns of selection support the existence of a selection mosaic and accounts for the positive correlation observed between atropine concentration and plant damage by herbivores recorded in previous studies.

Insuficiencia renal aguda en enfermos críticos sometidos a tratamiento intensivo / Acute renal insufficiency in critical patients subitted to intensive treatment

La IRA constituye una causa importante de morbilidad y mortalidad en pacientes críticos; por dicho motivo, fue valorada prospectivamente la función renal de 84 pacientes admitidos en la Unidad de Cuidados Intensivos mediante la determinación seriada de creatinina sérica durante 7 a 14 días; se consideró como indicador diagnóstico de IRA el aumento de ésta por encima del 25% de sus cifras basales. Todos los pacientes tenían al ingreso creatinina *132,6mmol/L y sus edades oscilaban entre 15 y 86 años con igual proporción para ambossexos. Los datos se procesaron estadísticamente mediante el empleo de paquetes de programas Microstat. La IRA se presentó en 18 casos (21,42%) . Los pacientes quirúrgicos mostraron mayor frecuencia en la aparición de IRA(X*=14,8p<0,005). Sólo un paciente requirió depuración extrarenal(hemodiálisis). Todos los enfermos con IRA conservaron diuresis. La proporción de enfermos que fallecen es significativamente superior (p<0,0005) en el grupo con IRA y no influye en éstos últimos al parecer, la edad con la mortalidad (X*=7,33 p>0,1), lo que indica que existen otros factores que intervienen en el deceso. Según esta serie, existe una estimación probabilística general de 0,14 a 0,31 de que cualquier enfermo que requiera cuidados intensivos desarrolle IRA

Alteraciones psicopatológicas en el transplante renal / Physiopathological changes in Kidney transplantation

El trasplante renal (TR) ha devenido en forma estable de tratamiento para la nefropatía terminal; sin embargo, puede asociarse a fracasos y complicaciones que indiscutiblemente socavan la estabilidad psíquica del receptor. La aparición de trastornos psiquiátricos de envergadura en estos enfermos ha sido motivo de diversas comunicaciones. Con el fin de establecer la frecuencia y tipo de dichas alteraciones fueron estudiados 44 pacientes con TR primario y función útil (creatinina sérica 350mmol/l y no menos de 30 días de evolución del injerto sin apoyo dialítico) cuyas edades oscilaban entre los 15 y 55 años, en quienes se aplicó una batería de pruebas psicológicas constituídas por HTP, Bender, Wais verbal, IPAT, Zung y Rotter, y una encuesta formularia creada al efecto. Entre los conflictos ambientales la propia enfermedad renal, los de índole económico y los familiares fueron los más relevantes. Las pruebas psicológicas mostraron una elevada frecuencia a nivel no psicótico de ansiedad, depresión, inseguridad, organicidad y preocupación por la salud. A su vez, las manifestaciones psicopatológicas fueron: ansiedad, depresión, insomnio y disfunción sexual. En 30 enfermos se estableció algún diagnóstico psiquiátrico, destacándose entre otros, los de reacción situacional y retraso mental ligero. Más de las 3/4 partes de los pacientes había logrado reincorporación laboral total al momento del estudio. Los autores consideran útil y necesario la presencia sistemática de un equipo de salud mental integrado a los programas nacionales de diálisis y trasplante

Trombosis de cava inferior. Presentación de un caso asintomático en fase aguda / Thrombosis of the inferior vena cava. Presentation of an asymptomatic case in acute phase

Después de una breve introducción en que los autores hacen hincapié en las complicaciones inmediatas y mediatas de las trombosis venosas, enfatizando el porqué de los posibles errores diagnósticos y la relativa frecuencia de las mismas en nuestro medio, pasan a detallar la clasificación anatomoclínica de las trombosis de cava inferior en un joven de 16 años, asintomático en la fase aguda, que debuta por sus complicaciones mediatas. Se establece de forma gráfica la secuencia del estudio clínico y angiográfico que permite concluir el diagnóstico acertado (AU)