Biogeographical comparison of the emergent macrophyte, Sagittaria platyphylla in its native and introduced ranges

Understanding why some plant species become invasive is important to predict and prevent future weed threats and identify appropriate management strategies. Many hypotheses have been proposed to explain why plants become invasive, yet few studies have quantitatively compared plant and population parameters between native and introduced range populations to gain an objective perspective on the causes of plant invasion. The present study uses a biogeographical field survey to compare morphological and reproductive traits and abundance between the native range (USA) and two introduced ranges (Australia and South Africa) of Sagittaria platyphylla (Engelm.) J.G. Sm (Alismataceae), a highly invasive freshwater macrophyte. Introduced and native populations differed in sexual reproductive output with the number of achenes per fruiting head and individual achene weight found to be 40% and 50% greater in introduced populations respectively. However, no other morphological traits were found to be consistently different between the native and both introduced ranges, especially after taking into account differences in environmental conditions between the three ranges. Although populations in introduced regions were larger and occupied greater percentage cover, no differences in plant density were evident. Our results suggest that, apart from sexual reproduction, many of the trait patterns observed in S. platyphylla are influenced by environmental and habitat conditions within the native and invaded ranges. We conclude that the enemy release hypothesis best explains the results observed for sexual reproduction. In particular, we hypothesise that a release from natural enemies, specifically a pre-dispersal seed predator, may induce reproductive plasticity in S. platyphylla

Could enemy release explain invasion success of Sagittaria platyphylla in Australia and South Africa?.

Sagittaria platyphylla (delta arrowhead) is an emergent aquatic macrophyte native to southeastern United States of America that has been introduced into Australia and South Africa as an ornamental pond and aquarium plant. Compared to plants in the native range, S. platyphylla in the introduced range have greater reproductive capacity and form extensive infestations that dominate shallow waterbodies. One explanation for the invasive success of S. platyphylla in introduced countries is that plants are devoid of biotic pressures that would regulate population abundance in their native range (the enemy release hypothesis). We previously reported on field surveys that documented the number of pathogens and insect herbivores associated with S. platyphylla in native and introduced ranges. Here, we quantify the damage caused by these natural enemies to S. platyphylla in the two ranges. As predicted, damage to plants caused by pathogens and insect herbivores was much greater in the native than the introduced range at both the plant and population level. In introduced regions herbivory was low (less than 10%) in every plant part, while in North America insect damage to fruiting heads was 46% (of fruiting heads attacked), damage to leaves was between 33 to 57%, and internal herbivore damage to petioles and the inflorescence scapes was 56% and 43% respectively. Pathogen damage to leaves was between 39 to 57% of leaves per plant affected, compared to 9% in Australia and 8% in South Africa. This lack of biotic resistance from herbivores and disease may have facilitated S. platyphylla invasion in Australia and South Africa

Effects of aging and type 2 diabetes on resting and post occlusive hyperemia of the forearm; the impact of rosiglitazone

BACKGROUND: Both Diabetes and ageing are associated with reduced vascular endothelial function. The exact relationship between the 2 and any improvements from the insulin sensitizer rosiglitazone have not been explored. METHODS: Thirty controls and sixteen subjects with type 2 diabetes participated in a series of experiments to examine the interrelationships between age, diabetes and endothelial cell function. In subjects with diabetes, the insulin sensitizer rosiglitazone (RSG), a drug also known to improve vascular function, was administered for 3 months to see how it altered these relationships. Resting forearm flows (RF) and blood flows after 4 min of vascular occlusion (PF) were measured as an index of endothelial cell function. RESULTS: RF, measured by venous occlusion plethysmography, was negatively correlated to both age and diabetes. Administration of RSG for 3 months was associated with an increase in the blood flow response to venous occlusion so that it was not significantly different than that of age matched controls. Total PF in control subjects, compared to subjects with diabetes, averaged 56.58 +/- 12.57 and 13.6 +/- 8.01 cc/100 cc tissue per min respectively, and were significantly different (p < 0.01). After 3 months on RSG, differences between PF in the two groups were no longer evident. CONCLUSION: These studies suggest a different mechanism causing a reduction in vascular reactivity with aging and diabetes

Suivi de la salinité et de l'état trophique de l'Etang de l'Or. Rapport d'étude 1992

[Notes_IRSTEA]graph., tabl.Observation de l'étang de l'Or : modele de salinité et impact des pompages. Comportement général de la qualité de l'eau de l'étang

BIOGÉOGRAPHIE DU SILURE GLANE (SILURUS GLANIS) : CAUSES HYDROGRAPHIQUES, CLIMATIQUES ET ANTHROPIQUES.

La répartition actuelle du silure glane (Silurus glanis) en France et en Europe résulte de la combinaison de facteurs à la fois hydrographiques, climatiques et anthropiques. Des données paléontologiques montrent que l'espèce faisait partie de l'ichtyofaune française (bassin du Rhône) avant d'être éliminée par les glaciations. Le réchauffement climatique qui a suivi (10 000 av. JC) et l'existence d'interconnexions entre, d'une part, des tributaires de la mer Noire et de la mer Caspienne et d'autre part ceux de la mer Baltique et de la mer du Nord lui ont permis de rapidement coloniser le Nord de l'Europe occidentale. Deux périodes de transplantations-introductions de l'espèce, à but économique, sont identifiées. Une première vague d'introductions hors du bassin danubien semble avoir eu lieu dès le Moyen-Age (lacs de Suisse), suivie par une deuxième période débutant vers 1800, et se poursuivant actuellement. Les effets combinés de ces introductions et des dégradations du milieu d'origine anthropique ont induit un décalage de l'aire de distribution vers le Sud et le Sud-Est de l'Europe (Italie, Espagne), tandis que ne subsistent en Suède, Carélie, Russie et Estonie que des populations relictuelles. Les résultats présentés ici, pourraient aussi concerner d'autres espèces de poissons (Percidés, Cyprinidés), qui, après avoir bénéficié pendant les glaciations des refuges constitués par les bassins de la mer Noire et de la mer Caspienne, ont pu (re-) colonisé l'Europe continentale, de manière « naturelle » et avec l'aide de l'Homme

Titrated safe extubation: application of an original strategy for safe management of perioperative glottis edema with severe upper airway obstruction.

Sir: Usual approach to traumatic laryngeal oedema with glottis obstruction can be harmful. Long-term orotracheal intubation and a prolonged stay of airway exchange catheters (AECs) could make the patient suffer new lesions [1]; therefore bed immobility and ICU stay could be prolonged. Airway emergencies during tracheal extubation phase are still associated with death or brain damage, indicating that additional management strategies are required to improve patient safety [2]. We report the application of new approach to safe extubation in a case of iatrogenic upper airways obstruction

L'étang de Terrenzana (Haute Corse) : caractérisation écologique du site en vue de sa gestion

[Notes_IRSTEA]tabl., fig.Cette étude porte sur l'étang de Terrenzana en Corse. Elle use à caractériser l'état actuel du site, à en défini les potentialités et les modalités de gestion envisageables. Ce rapport résulte d'une campagne de terrain et d'une enquête aupres des divers intervenants menées en 1986 par le CEMAGREF. Une comparaison rapide avec l'étang de Santa Giulia a été réalisée