Evolution of a genetic polymorphism with climate change in a Mediterranean landscape

Many species show changes in distribution and phenotypic trait variation in response to climatic warming. Evidence of genetically based trait responses to climate change is, however, less common. Here, we detected evolutionary variation in the landscape-scale distribution of a genetically based chemical polymorphism in Mediterranean wild thyme (Thymus vulgaris) in association with modified extreme winter freezing events. By comparing current data on morph distribution with that observed in the early 1970s, we detected a significant increase in the proportion of morphs that are sensitive to winter freezing. This increase in frequency was observed in 17 of the 24 populations in which, since the 1970s, annual extreme winter freezing temperatures have risen above the thresholds that cause mortality of freezing-sensitive morphs. Our results provide an original example of rapid ongoing evolutionary change associated with relaxed selection (less extreme freezing events) on a local landscape scale. In species whose distribution and genetic variability are shaped by strong selection gradients, there may be little time lag associated with their ecological and evolutionary response to long-term environmental change.Ongoing changes in regional climates are pushing many species to shift their distribution toward higher latitudes and altitudes (1–7). Such changes in species distribution, with an expansion in previously hostile areas and contraction in areas becoming less favorable, can occur rapidly both in plants and animals (2, 3, 5, 6). As a result, major changes in community composition due to differential migration rates may occur (8). Indeed, habitat fragmentation may prevent many species from showing such a distributional response to climate change. As a result, only those species that can respond by phenotypic plasticity or genetically based local adaption will persist (9). In animal and plant species, phenotypic plasticity of phenological traits can allow individuals to adjust to climate change (1, 10, 11). In addition to changes in distribution and plasticity, an evolutionary response to climate change may occur if species evolve a genetically based adaptation to climate change (12, 13). It is important to distinguish this genetic response from a plastic response of individuals if we are to fully understand the evolutionary potential of species to evolve with climate change (14). Adaptive trait variation in relation to climate change has been shown in the classic study of Drosophila (15, 16) and in experimental and natural populations of a small number of plant species (17–20). However, in some cases, the evolutionary response to climate change may be slow due to genetic constraints (21) causing a time lag between the environmental change and an observed evolutionary response. Understanding how species track climate change by genetically based adaptive trait variation and which traits facilitate the evolution of such adaption is important; such issues determine which species may persist locally and which may shift their distribution (22, 23).In this study, we test for an evolutionary response of a genetic polymorphism in essential oil composition in Mediterranean wild thyme, Thymus vulgaris, to reduced selection associated with a warming of extreme winter freezing events over a sharp spatial climatic gradient. Our study was done in and around the Saint Martin-de-Londres basin (43°48′N, 03°46′E), which covers an area of ∼80 km² and whose southern limits are ∼20 km north of Montpellier in the Mediterranean climate region of southern France. The center of the basin (lowest altitude, 145 m) is surrounded by calcareous hills, ranging from 300 to 658 m. The study area has a Mediterranean climate with summer drought but also severe winter freezing temperatures within the basin as a result of a dramatic temperature inversion (Fig. 1). In this area, there are six different chemotypes that are the expression of a genetically controlled polymorphism in T. vulgaris (24). Two phenolic chemotypes (carvacrol and thymol) are largely dominant on the slopes outside of the basin on stony soils above 250-m elevation and four nonphenolic chemotypes (linalool, thuyanol-4, α-terpineol, and geraniol) occur within the basin below 200-m elevation on deeper, more humid soils (25–27), where they experience the winter temperature inversion. There is thus a sharp cline in chemotype frequency over only 3–5 km that goes from 100% of either phenolic or nonphenolic chemotypes to 100% of the other form, with a narrow transitional zone (Fig. 2). In short, nonphenolic chemotypes show marked adaptation to habitats, which in the past have frequently experienced extreme freezing temperatures in early winter, whereas phenolic chemotypes are sensitive to intense early-winter freezing and occur in habitats where extreme summer drought can exclude nonphenolic chemotypes (28, 29).Open in a separate windowFig. 1.Coldest annual temperature from 1955 to 2010 at the weather station of Saint Martin-de-Londres (filled squares), which occurs in the zone dominated by freezing-tolerant nonphenolic chemotypes, and from 1970 to 2010 at the Centre d''Ecologie Fonctionnelle et Evolutive–Centre National de la Recherche Scientifique experimental gardens on the northern periphery of Montpellier (open circles), where natural thyme populations are dominated by freezing-sensitive phenolic chemotypes.Open in a separate windowFig. 2.Spatial distribution and chemical composition of sampled thyme populations in the early 1970s and the 36 populations that were resampled in the present study along six transects. The chemical composition of resampled populations indicated on the map is that which was observed in the initial study. Black circles, phenolic populations; open circles, nonphenolic populations; gray circles, mixed populations. On each transect, the six populations are connected by a dashed line and are represented by a slightly larger circle than populations that were not resampled in the present study.In the part of the study area where nonphenolic chemotypes dominated populations in the early 1970s, extreme winter temperatures have become less severe (Fig. 1) with a significant increase in temperature of extreme freezing events (r = 0.36, n = 56, P < 0.01). In the 20 y before and during the initial study, winter temperatures fell below levels (−15 °C in December) that would exclude phenolic chemotypes from sites dominated by nonphenolic chemotypes (29) on five occasions. In the 16 y following the initial study, three such events were recorded. In the last 20 y, no such extreme events have been recorded in the zone dominated by nonphenolic chemotypes. The last extreme freezing event that could impact the composition of thyme populations occurred 25 y ago.Here, we test the hypothesis that phenolic chemotypes (thymol and carvacrol) now occur in sites where they were previously absent or have increased their frequency in transitional sites due to a relaxation of selection normally associated with extreme early-winter freezing temperatures. To do so, we compared the chemotype composition of populations observed in the early 1970s (26) to that in 2009–2010 for 36 populations sampled along six transects. Each transect is <10 km long, each containing six populations, with two “phenolic,” “mixed,” and “nonphenolic” populations (Fig. 2). To provide an indication of whether population-level changes are due to within-population adaptation or migration among populations, we also examine whether any increases in the abundance of phenolic chemotypes are primarily in nonphenolic or mixed populations that are spatially the closest to preexisting phenolic populations.     

Substance P receptor immunodetection in the spinal cord: comparative use of direct anti-receptor antibody and anti-complementary peptide antibody

The immunolocalization of substance P (SP) receptors was compared in the rat spinal cord using either a direct anti-substance P NK1-receptor antibody (anti-SPR) or an anticomplementary peptide antibody (anti-CP). The first antibody recognizes an intracellular epitope, the C-terminal tail of the NK1-receptor. The second antibody recognizes an extracellular epitope located at or near the ligand-binding domain because anti-CP antibody and SP were previously shown to compete for binding to the receptor. At the light microscope level, it was observed that anti-CP antibody labels both laminae I and II of the dorsal horn, while anti-SPR antibody labels exclusively lamina I, except at the lumbar level. This could suggest that spinal NK1 receptors are heterogeneous. Anti-SPR antibodies may recognize an NK1 receptor subclass confined to lamina I. Conversely, anti-CP antibody may recognize either another receptor subclass or two different subclasses present in laminae I and II. At the electron microscope level, labeling was localized either on the intracellular or the extracellular face of the plasma membrane depending on the location of the epitope recognized by both antibodies on the transmembrane receptor. However, using either antibody, the ultrastructural labeling was found at non-junctional sites, suggesting that SP may act in a non-synaptic manner on all putative receptor subclasses.     

Effect of theophylline and other drugs on rabbit renal cyclic nucleotide phosphodiesterase, 5'-nucleotidase and adenosine deaminase.

The effect of theophylline and several other drugs on cyclic AMP and cyclic GMP phosphodiesterase, 5′-nucleotidase and adenosine deaminase was tested in homogenates of rabbit renal cortex and medulla.Theophylline was a competitive inhibitor of cyclic nucleotide phosphodiesterase, a non-competitive inhibitor of 5′-nucleotidase and alkaline phosphatase but did not influence adenosine deaminase. Cyclic AMP and cyclic GMP hydrolysis were inhibited to an equal extent by theophylline, furosemide, caffeine, 3-isobutyl-methylxanthine, and SQ 20006. Dipyridamol, ZK 62.711, Ro 20-1724 and ICI 63.197 inhibited cyclic AMP hydrolysis in at least ten times lower concentrations than cyclic GMP hydrolysis. Conversely, M &; B 22948 and dilazep were more potent as inhibitors of cyclic GMP than of cyclic AMP hydrolysis.All the diuretic agents tested (furosemide, ethacrynic acid, chlorthalidone, cyclopentiazide and theophylline) inhibited 5′-nucleotidase at 1 mM concentration or lower.Of the drugs tested at 1 mM concentration only dipyridamol and chlorthalidone produced significant (30 per cent) inhibition of adenosine deaminase activity.     

Familial polycythemia caused by high oxygen affinity hemoglobin. 2nd world case of hemoglobin J Providence

The cas observed in Auvergne and reported here raises the aetiological problem of polycythaemias. Young subjects with polycythaemia should be investigated for congenital anomaly of oxygen transport by measuring P50 and 2,3-DPG, which provides information on the oxygen-carrying capacity of haemoglobin. When confronted with familial polycythaemia due to high oxygen affinity haemoglobin, clinicians must know that a cause-effect relationship is not always demonstrable since other factors, such as tobacco-smoking in this particular case, may intervene.     

Localized pulmonary pseudo-tumoral form of Wegener's disease and fulminating evolution. Apropos of a case

A case of Wegener's granulomatosis starting as a localized pseudo-tumoral lung lesion and following a fulminating course is reported. The histological diagnosis required thoracotomy. New pulmonary lesions developed post-operatively, together with severe renal failure which was responsible for the patient's death 5 weeks after the thoracotomy. The authors describe the lesions characteristic of the disease and their pathogenesis and discuss the relationship between Wegener's syndrome and other granulomatous angiitis.     

Influence of hormone replacement therapy on the accuracy of screening mammography

The use of hormone replacement therapy (HRT) is currently a subject of debate because of the possibility of an increase in the incidence of breast cancer and difficulties associated with breast cancer detection. The objective of this study was to determine the influence of HRT on specificity and sensitivity in a breast cancer screening program. We found that although specificity was significantly lower in menopausal women who had ever used or were currently using HRT (93.3%) compared to HRT nonusers (94.8%) at the expense of a greater number of recalls (6.9% versus 5.6%), this difference seems to be clinically irrelevant. There were no significant differences with regard to the number of invasive procedures (2.5% in the HRT versus 2.1% in the control group). We conclude that the slight decrease in sensitivity of screening mammography in HRT users is not clinically significant in our setting, and in any case, false positives (recalled women) are diagnosed correctly with additional imaging studies without the need for invasive procedures. Most women given HRT are candidates to participate in population breast cancer screening campaigns.