Phylogeographical footprints of the Strait of Gibraltar and Quaternary climatic fluctuations in the western Mediterranean: a case study with the greater white-toothed shrew, Crocidura russula (Mammalia: Soricidae).

We used mitochondrial cyt b sequences to investigate the phylogenetic relationships of Crocidura russula (sensu lato) populations across the Strait of Gibraltar, western Europe, Maghreb, and the Mediterranean and Atlantic islands. This revealed very low genetic divergence between European and Moroccan populations. The application of a molecular clock previously calibrated for shrews suggested that the separation of European from Moroccan lineages occurred less than 60 000 bp, which is at least 5 million years (Myr) after the reopening of the Strait of Gibraltar. This means that an overwater dispersal event was responsible for the observed phylogeographical structure. In contrast, genetic analyses revealed that Moroccan populations were highly distinct from Tunisian ones. According to the molecular clock, these populations separated about 2.2 million years ago (Ma), a time marked by sharp alternations of dry and humid climates in the Maghreb. The populations of the Mediterranean islands Ibiza, Pantelleria, and Sardinia were founded from Tunisian populations by overwater dispersal. In conclusion, overwater dispersal across the Strait of Gibraltar, probably assisted by humans, is possible for small terrestrial vertebrates. Moreover, as in Europe, Quaternary climatic fluctuations had a major effect on the phylogeographical structure of the Maghreb biota.

Triassic stratigraphic evolution of the Arabian-Greater India embayment of the southern Tethys margin

An exceptional, tectonically remarkably unaffected, nearly 200 m-thick continuous section of hemipelagic and turbiditic sediments, covering most of the Triassic is described from the Batain Complex of north-eastern Oman. According to conodont and radiolarian data the sequence spans the late Scythian to the early Norian, a time period of nearly 30 M. Coupled with a high resolution stratigraphy, the lithostratigraphy, sedimentology, as well as sequence and isotope stratigraphy of the section are documented. For the Triassic of the Batain Plain we propose the new name Sal Formation, which replaces the formerly used Matbat Formation, and subdivide it into three new members. The Sal Formation was deposited on the proximal continental margin of northeastern Arabia and records various depositional environments. The lower member is interpreted as the distal part of a homoclinal ramp which evolves to a distally steepened ramp during time of deposition of the middle member. The upper member displays a toe of slope position which is indicated by an increase of proximal turbidites. These sediments form part of a segment of the Neo-Tethyan embayment between Arabia and India. The stratigraphic analysis indicates highly varying sedimentation rates from a minimum of 2 m/M gamma around the Anisian/Ladinian boundary up to 15 m/M gamma during the Lower and Upper Triassic. Sequence-stratigraphically, the Sal section is subdivided into six third order cycles which are biochronologically well integrated into the global Triassic cycle chart. The mixed siliciclastic-calcareous upper member of the Sal Formation typically shows highstand related carbonate shedding. It is, therefore, an important test case for sequence-stratigraphic controlled carbonate export to mixed basin fills. The well developed sequence stratigraphic cycles are mirrored in the isotope patterns. Additionally, the carbon and oxygen isotope data from the Sal Formation record the same chemostratigraphic marker at the Spathian/Anisian boundary known from other Tethyan sections.

Plasticity in sex allocation in the plant Mercurialis annua is greater for hermaphrodites sampled from dimorphic than from monomorphic populations.

Plants are notoriously variable in gender, ranging in sex allocation from purely male through hermaphrodite to purely female. This variation can have both a genetic and an adaptive plastic component. In gynodioecious species, where females co-occur with hermaphrodites, hermaphrodites tend to shift their allocation towards greater maleness when growing under low-resource conditions, either as a result of hermaphrodites shifting away from an expensive female function, or because of enhanced siring advantages in the presence of females. Similarly, in the androdioecious plant Mercurialis annua, where hermaphrodites co-exist with males, hermaphrodites also tend to enhance their relative male allocation under low-resource conditions. Here, we ask whether this response differs between hermaphrodites that have been evolving in the presence of males, in a situation analogous to that supposed for gynodioecious populations, vs. those that have been evolving in their absence. We grew hermaphrodites of M. annua from populations in which males were either present or absent under different levels of nutrient availability and compared their reaction norms. We found that, overall, hermaphrodites from populations with males tended to be more female than those from populations lacking males. Importantly, hermaphrodites' investment in pollen and seed production was more plastic when they came from populations with males than without them, reducing their pollen production at low resource availability and increasing their seed production at high resource availability. These results are consistent with the hypothesis that plasticity in sex allocation is enhanced in hermaphrodites that have likely been exposed to variation in mating opportunities due to fluctuations in the frequency of co-occurring males.

Sex-specific selective pressures on body mass in the greater white-toothed shrew, Crocidura russula.

The direction, intensity and shape of viability-, sexual- and fecundity selection on body mass were investigated in a natural population of the greater white-toothed shrew (Crocidura russula), combining parentage assignment through molecular techniques and mark-recapture data over several generations. A highly significant stabilizing viability selection was found in both sexes, presumably stemming from the constraints imposed by their insectivorous habits and high metabolic costs. Sexual selection, directional in both sexes, was twice as large in males than in females. Our results suggest that body mass matters in this context by facilitating the acquisition and defense of a breeding territory. No fecundity selection could be detected. The direction of sexual size dimorphism (SSD) was in agreement with the observed pattern of selective pressures: males were heavier than females, because of stronger sexual selection. SSD intensity, however, was low compared with other mammals, because of the low level of polygyny, the active role of females in territory defense and the intensity of stabilizing viability selection.

Reactive rise in blood pressure upon cuff inflation : cuff inflation at the arm causes a greater rise in pressure than at the wrist in hypertensive patients

Résumé en français: Il est admis que l'inflation d'une manchette à pression au niveau du bras engendre une augmentation réactionnelle de la tension artérielle qui peut être le résultat d'une gêne lors de l'inflation et peut diminuer la précision de la mesure. Dans cette étude, nous comparons séquentiellement l'augmentation de la tension artérielle lorsque la manchette à pression est positionnée au niveau du bras et au niveau du poignet. Nous avons étudié un collectif de 34 participants normotendus et 34 patients hypertendus. Chacun d'eux était équipé de deux manchettes à pression, l'une au niveau du bras et l'autre au niveau du poignet. Nous avons randomisé l'ordre d'inflation des manchettes ainsi que la pression d'inflation maximale (180mmHg versus 240mmHg). Trois mesures étaient effectuées pour chaque pression d'inflation maximale, ceci au bras comme poignet, et leur séquence était également randomisée. En parallèle, un enregistrement continu de la tension artérielle avait lieu au niveau du majeur de la main opposée à l'aide d'un photoplethysmographe. Cette valeur était considérée comme la valeur de tension artérielle au repos. Pour les participants normotendus, aucune différence statistiquement significative n'a pu être mise en évidence en lien avec la position de la manchette à pression, ceci indépendamment de la pression d'inflation maximale. Variation de la pression systolique à 180 mmHg: 4.3+/-3.0 mmHg au bras et 3.7+/-2.9 mmHg au poignet (p=ns), à 240 mmHg: 5.5+/-3.9 au bras et 4.2+/-2.7 mmHg au poignet (p=0.052). En revanche, concernant les patients hypertendus, une augmentation significative de la tension artérielle a été mise en évidence entre le bras et le poignet. Ceci pour les valeurs de tension artérielle systolique et diastolique et quelle que soit la pression d'inflation maximale utilisée. Augmentation de la pression artérielle systolique 6.513.5 mmHg au bras et 3.812.1mmHg au poignet pour une pression d'inflation maximale de 180 mmHg (p<0.01) et respectivement 6.413.5 mmHg et 4.713.0 mmHg pour 240 mmHg (p=0.01). L'augmentation des valeurs de tension artérielle était indépendante de la valeur tensionnelle de base. Ces résultats montrent que les patients hypertendus réagissent significativement moins à l'inflation d'une manchette ä pression lorsque celle-ci est positionnée au niveau du poignet par rapport au bras, ceci indépendamment des valeurs de tension artérielle de base des patients. Nous pouvons donc suggérer que l'inflation d'une manchette à pression cause moins de désagrément lorsqu'elle est placée au niveau du poignet, notamment chez les patients hypertendus et qu'elle peut être une alternative à la mesure standard au niveau du bras.

A constitutively active mutant of the alpha 1B-adrenergic receptor can cause greater agonist-dependent down-regulation of the G-proteins G9 alpha and G11 alpha than the wild-type receptor.

Rat 1 fibroblasts transfected to express either the wild-type hamster alpha 1B-adrenergic receptor or a constitutively active mutant (CAM) form of this receptor resulting from the alteration of amino acid residues 288-294 to encode the equivalent region of the human beta 2-adrenergic receptor were examined. The basal level of inositol phosphate generation in cells expressing the CAM alpha 1B-adrenergic receptor was greater than for the wild-type receptor, The addition of maximally effective concentrations of phenylephrine or noradrenaline resulted in substantially greater levels of inositol phosphate generation by the CAM alpha 1B-adrenergic receptor, although this receptor was expressed at lower steady-state levels than the wild-type receptor. The potency of both phenylephrine and noradrenaline to stimulate inositol phosphate production was approx. 200-fold greater at the CAM alpha 1B-adrenergic receptor than at the wild-type receptor. In contrast, endothelin 1, acting at the endogenously expressed endothelin ETA, receptor, displayed similar potency and maximal effects in the two cell lines. The sustained presence of phenylephrine resulted in down-regulation of the alpha subunits of the phosphoinositidase C-linked, pertussis toxin-insensitive, G-proteins G9 and G11 in cells expressing either the wild-type or the CAM alpha 1B-adrenergic receptor. The degree of down-regulation achieved was substantially greater in cells expressing the CAM alpha 1B-adrenergic receptor at all concentrations of the agonist. However, in this assay phenylephrine displayed only a slightly greater potency at the CAM alpha 1B-adrenergic receptor than at the wild-type receptor. There were no detectable differences in the basal rate of G9 alpha/G11 alpha degradation between cells expressing the wild-type or the CAMalpha 1B-adrenergic receptor. In both cell lines the addition of phenylephrine substantially increased the rate of degradation of these G-proteins, with a greater effect at the CAM alpha 1B-adrenergic receptor. The enhanced capacity of agonist both to stimulate second-messenger production at the CAM alpha 1B-adrenergic receptor and to regulate cellular levels of its associated G-proteins by stimulating their rate of degradation is indicative of an enhanced stoichiometry of coupling of this form of the receptor to G9 and G11.

Disentangling reasons for low Y chromosome variation in the greater white-toothed shrew (Crocidura russula).

Y chromosome variation is determined by several confounding factors including mutation rate, effective population size, demography, and selection. Disentangling these factors is essential to better understand the evolutionary properties of the Y chromosome. We analyzed genetic variation on the Y chromosome, X chromosome, and mtDNA of the greater white-toothed shrew, a species with low variance in male reproductive success and limited sex-biased dispersal, which enables us to control to some extent for life-history effects. We also compared ancestral (Moroccan) to derived (European) populations to investigate the role of demographic history in determining Y variation. Recent colonization of Europe by a small number of founders (combined with low mutation rates) is largely responsible for low diversity observed on the European Y and X chromosomes compared to mtDNA. After accounting for mutation rate, copy number, and demography, the Y chromosome still displays a deficit in variation relative to the X in both populations. This is possibly influenced by directional selection, but the slightly higher variance in male reproductive success is also likely to play a role, even though the difference is small compared to that in highly polygynous species. This study illustrates that demography and life-history effects should be scrutinized before inferring strong selective pressure as a reason for low diversity on the Y chromosome.

Range expansion of the greater white-toothed shrew Crocidura russula in Switzerland results in local extinction of the bicoloured white-toothed shrew C-leucodon

The distribution limits of Crocidura russula (Hermann, 1780) and C. leucodon (Hermann, 1780) were investigated during an interval of 25 years in the bottom of the Rhone valley above Lake Geneva, Switzerland (total data set: 105 spatio-temporal occurrences, 1137 shrews). In 1975, the contact zone between the two species was situated in the region of Martigny. In 1999/2000, new sampling revealed three results: (1) The contact zone showed an upward shift of about 25 km. (2) In the expanded range of C. russula, the resident species has totally disappeared (confirmed by owl pellets analysis). (3) This demonstrates a dominance of C, russula over C. leucodon. Three hypotheses which may explain the range expansion of C. russula were evaluated: (1) habitat modification favouring linear dispersal due to the construction of a highway; (2) temporal event favoured by climate fluctuations, or (3) ongoing postglacial colonisation of Europe. Hypothesis 1 was rejected, because the progression of the shrews anticipated the construction. Hypothesis 3 received only weak support because range limits of C. russula in the region of Nice have been stable for thousands of years. Therefore hypothesis 2, admitting that ongoing climate change has facilitated range expansion, is the most probable.

Individual reproductive success and effective population size in the greater white-toothed shrew Crocidura russula.

In order to investigate the determinants of effective population size in the socially monogamous Crocidura russula, the reproductive output of 44 individuals was estimated through genetic assignment methods. The individual variance in breeding success turned out to be surprisingly high, mostly because the males were markedly less monogamous than expected from previous behavioural data. Males paired simultaneously with up to four females and polygynous males had significantly more offspring than monogamous ones. The variance in female reproductive success also exceeded that of a Poisson distribution (though to a lesser extent), partly because females paired with multiply mated males weaned significantly more offspring. Polyandry also occurred occasionally, but only sequentially (i.e. without multiple paternity of litters). Estimates of the effective to census size ratio were ca. 0.60, which excluded the mating system as a potential explanation for the high genetic variance found in this shrew's populations. Our data suggest that gene flow from the neighbourhood (up to one-third of the total recruitment) is the most likely cause of the high levels of genetic diversity observed in this shrew's subpopulations.

Nonshivering thermogenesis capacity associated to mitochondrial DNA haplotypes and gender in the greater white-toothed shrew, Crocidura russula.

A selection gradient was recently suggested as one possible cause for a clinal distribution of mitochondrial DNA (mtDNA) haplotypes along an altitudinal transect in the greater white-toothed shrew, Crocidura russula (Ehinger et al. 2002). One mtDNA haplotype (H1) rare in lowland, became widespread when approaching the altitudinal margin of the distribution. As H1 differs from the main lowland haplotype by several nonsynonymous mutations (including on ATP6), and as mitochondria play a crucial role in metabolism and thermogenesis, distribution patterns might stem from differences in the thermogenic capacity of different mtDNA haplotypes. In order to test this hypothesis, we measured the nonshivering thermogenesis (NST) associated with different mtDNA haplotypes. Sixty-two shrews, half of which had the H1 haplotype, were acclimated in November at semioutdoor conditions and measured for NST throughout winter. Our results showed the crucial role of NST for winter survival in C. russula. The individuals that survived winter displayed a higher significant increase in NST during acclimation, associated with a significant gain in body mass, presumably from brown fat accumulation. The NST capacity (ratio of NST to basal metabolic rate) was exceptionally high for such a small species. NST was significantly affected by a gender x haplotype interaction after winter-acclimation: females bearing the H1 haplotype displayed a better thermogenesis at the onset of the breeding season, while the reverse was true for males. Altogether, our results suggest a sexually antagonistic cyto-nuclear selection on thermogenesis.

North-African house martins endure greater haemosporidian infection than their European counterparts

Afro-Palearctic migrant species are exposed to parasites at both breeding and over-wintering grounds. The house martin Delichon urbicum is one such migratory species facing high instances of blood parasite infection. In an attempt to determine whether breeding European house martins harbour similar blood parasite communities to populations breeding in North Africa, birds were sampled at their breeding grounds in Switzerland and Algeria. Moreover, haemosporidian prevalence and parasite communities were compared to published data sets on Spanish and Dutch breeding populations. This study furthermore wanted to establish whether co-infection with multiple genera or lineages of parasites had negative effects on host body condition. Breeding house martins caught in Algeria showed a higher prevalence of avian haemosporidian parasites than did European populations. Swiss house martins showed a prevalence comparable to that of Spanish and Dutch populations. There were slight differences in the haemosporidian community between European and North-African populations in terms of composition and abundance of each lineage. Similar to the Dutch house martins, but in contrast to the Spanish population, infection status and number of genera of parasites infecting single hosts did not inFLuence Swiss house martin body condition.

Wide-pulse-high-frequency neuromuscular stimulation of triceps surae induces greater muscle fatigue compared with conventional stimulation.

We compared the extent and origin of muscle fatigue induced by short-pulse-low-frequency [conventional (CONV)] and wide-pulse-high-frequency (WPHF) neuromuscular electrical stimulation. We expected CONV contractions to mainly originate from depolarization of axonal terminal branches (spatially determined muscle fiber recruitment) and WPHF contractions to be partly produced via a central pathway (motor unit recruitment according to size principle). Greater neuromuscular fatigue was, therefore, expected following CONV compared with WPHF. Fourteen healthy subjects underwent 20 WPHF (1 ms-100 Hz) and CONV (50 μs-25 Hz) evoked isometric triceps surae contractions (work/rest periods 20:40 s) at an initial target of 10% of maximal voluntary contraction (MVC) force. Force-time integral of the 20 evoked contractions (FTI) was used as main index of muscle fatigue; MVC force loss was also quantified. Central and peripheral fatigue were assessed by voluntary activation level and paired stimulation amplitudes, respectively. FTI in WPHF was significantly lower than in CONV (21,717 ± 11,541 vs. 37,958 ± 9,898 N·s P<0,001). The reductions in MVC force (WPHF: -7.0 ± 2.7%; CONV: -6.2 ± 2.5%; P < 0.01) and paired stimulation amplitude (WPHF: -8.0 ± 4.0%; CONV: -7.4 ± 6.1%; P < 0.001) were similar between conditions, whereas no change was observed for voluntary activation level (P > 0.05). Overall, our results showed a different motor unit recruitment pattern between the two neuromuscular electrical stimulation modalities with a lower FTI indicating greater muscle fatigue for WPHF, possibly limiting the presumed benefits for rehabilitation programs.

Social organization and mating system of free-ranging, greater white-toothed shrews, Crocidura russula

Indirect evidence from trapping suggests that Crocidura russula is less solitary and territorial than other shrews. To study the social organization and mating system, free-ranging adult and juvenile C. russula were tracked simultaneously throughout the year using a radioactive tracking technique. Coincident rest, coincident activity and home range overlap were measured. During winter, all individuals used the same communal nest and spent on average 84% of their total rest in coincident rest. This led to a large home range overlap (52% on average). Coincident activity was low (2% on average). At the onset of the reproductive season the females became, territorial and shared their nest with only one male. During pair formation, coincident activity and home range overlap were significantly greater between than within sexes. The social organization of C. russula appeared to be strongly influenced by season and differed in this respect from the other species in the genus Sorex which are territorial throughout the year.

Inbreeding in the greater white-toothed shrew, Crocidura russula.

We combined mark-and-recapture studies with genetic techniques of parentage assignment to evaluate the interactions between mating, dispersal, and inbreeding, in a free-ranging population of Crocidura russula. We found a pattern of limited and female-biased dispersal, followed by random mating within individual neighborhoods. This results in significant inbreeding at the population level: mating among relatives occurs more often than random, and F(IT) analyses reveal significant deficits in heterozygotes. However, related mating partners were not less fecund, and inbred offspring had no lower lifetime reproductive output. Power analyses show these negative results to be quite robust. Absence of phenotypic evidence of inbreeding depression might result from a history of purging: local populations are small and undergo disequilibrium gene dynamics. Dispersal is likely caused by local saturation and (re)colonization of empty breeding sites, rather than inbreeding avoidance.