How is the invasive gorse Ulex europaeus pollinated during winter? A lesson from its native range

Many examples of plant-insect interactions have shown that selection from herbivores can act on flowering and fruiting phenology. In Ulex europaeus (Fabaceae), escaping seed predation resulted in extended, but variable flowering periods, with some plants flowering from autumn until spring and others flowering only in spring. The present study aims at understanding how gorses can have a high reproductive success during winter despite harsh climatic conditions and low number of pollinators. We measured pollen production, flower size and seed production in spring and winter, and compared the different seasons. The pollination success of flowers was high in both seasons. The flowers produced as much pollen, and were of comparable size in spring and winter, but they stayed open twice as long in winter than in spring. The high pollination rate we observed was thus due to the longer opening period of flowers and the high attractiveness of flowers during winter. However, pod abortion was higher in winter, with 43% of the flowers in winter and 75% in spring producing ripe pods. Antagonistic selective pressures exerted by biotic and abiotic interactions may, therefore, have lead to the observed flowering polymorphism, and allow U.europaeus to thrive in various climates, thus, increasing its invasiveness in different countrie

Seed predation in Ulex europaeus: a geographic and temporal mosaic of interactions

The interactions between plants and their parasites usually involve several species and present high level of variation in space and time. According to the geographic mosaic theory of coevolution, this may lead to population differentiation, large polymorphism and local maladaptation. Here we explore whether the temporal and spatial variation of the interaction between gorse (Ulex europaeus) and its seed predators can explain the polymorphism observed within and among populations of its native range. Indeed, gorse individuals present a polymorphism of flowering and fruiting phenology, and large variability for their susceptibility to seed predation. We performed a regular monitoring of five populations localised in Brittany (France) over five consecutive years. We observed the flowering and fruiting phenology of the gorses, and measured pods infestation rates by their two main seed predators, the weevil Exapion ulicis and the moth Cydia succedana. Flowering phenotypes and between year evolution of parasitism rates were conserved from year to year. Parasitism rates by weevils and moths increased over the fruiting period, and were negatively correlated one to another. Long flowering plants were more attacked by weevils, while short-flowering plants were more attacked by moths. However, the majority of the weevil larvae did not develop into adults, either because they were still at an immature stage at pod maturity, or because they were attacked by a parasitoid wasp. Year-to-year variations in the infestation rates by the two seed predators were very high, and depended on the population but not on the microclimatic conditions. These variations can thus explain the maintenance of the within populations polymorphism of gorse phenology and susceptibility to seed predation

Benefit of surgery after chemoradiotherapy in stage IIIB (T4 and/or N3) non–small cell lung cancer

AbstractObjective: The purpose of this study was to evaluate postchemoradiotherapy surgery in stage IIIB non–small cell lung cancer. Methods: Forty patients with stage IIIB non–small cell lung cancer were included in this phase II study. A preoperative diagnosis of stage IIIB cancer was based on mediastinoscopy or a thoracotomy in all patients. Induction treatment included two cycles of cisplatin (100 mg/m2, day 1), 5-fluorouracil (1 g/m2, days 1-3), and vinblastine (4 mg/m2, day 1) combined with 42 Gy of hyperfractionated radiotherapy delivering 21 Gy in two sessions. Patients with a clinical response were offered surgery. Results: The minimum follow-up for survivors was 48 months. Thirty patients had a T4 lesion and 18 had N3 disease. Twenty-nine patients (73%) had a clinical objective tumor response after induction treatment. These 29 patients underwent thoracotomy, and a complete resection was performed in 23 (58%). Two postoperative deaths occurred (7%). Four patients had a pathologic complete response at the time of surgery (10%). The 5-year survival is 19% for the overall population. When only patients who had persistent viable tumor cells at surgery are considered (n = 25), the 5-year survival is 28%. The 5-year survival is 42% for patients having no mediastinal lymph node involvement at the time of surgery and being treated with complete resection. Conclusion: This study shows that surgery, when feasible, is associated with a 28% long-term survival for patients in whom chemoradiotherapy alone fails to control disease

Invasive Plants and Enemy Release: Evolution of Trait Means and Trait Correlations in Ulex europaeus

Several hypotheses that attempt to explain invasive processes are based on the fact that plants have been introduced without their natural enemies. Among them, the EICA (Evolution of Increased Competitive Ability) hypothesis is the most influential. It states that, due to enemy release, exotic plants evolve a shift in resource allocation from defence to reproduction or growth. In the native range of the invasive species Ulex europaeus, traits involved in reproduction and growth have been shown to be highly variable and genetically correlated. Thus, in order to explore the joint evolution of life history traits and susceptibility to seed predation in this species, we investigated changes in both trait means and trait correlations. To do so, we compared plants from native and invaded regions grown in a common garden. According to the expectations of the EICA hypothesis, we observed an increase in seedling height. However, there was little change in other trait means. By contrast, correlations exhibited a clear pattern: the correlations between life history traits and infestation rate by seed predators were always weaker in the invaded range than in the native range. In U. europaeus, the role of enemy release in shaping life history traits thus appeared to imply trait correlations rather than trait means. In the invaded regions studied, the correlations involving infestation rates and key life history traits such as flowering phenology, growth and pod density were reduced, enabling more independent evolution of these key traits and potentially facilitating local adaptation to a wide range of environments. These results led us to hypothesise that a relaxation of genetic correlations may be implied in the expansion of invasive species

How is the invasive gorse Ulex europaeus pollinated during winter? A lesson from its native range

Many examples of plant-insect interactions have shown that selection from herbivores can act on flowering and fruiting phenology. In Ulex europaeus (Fabaceae), escaping seed predation resulted in extended, but variable flowering periods, with some plants flowering from autumn until spring and others flowering only in spring. The present study aims at understanding how gorses can have a high reproductive success during winter despite harsh climatic conditions and low number of pollinators. We measured pollen production, flower size and seed production in spring and winter, and compared the different seasons. The pollination success of flowers was high in both seasons. The flowers produced as much pollen, and were of comparable size in spring and winter, but they stayed open twice as long in winter than in spring. The high pollination rate we observed was thus due to the longer opening period of flowers and the high attractiveness of flowers during winter. However, pod abortion was higher in winter, with 43% of the flowers in winter and 75% in spring producing ripe pods. Antagonistic selective pressures exerted by biotic and abiotic interactions may, therefore, have lead to the observed flowering polymorphism, and allow U. europaeus to thrive in various climates, thus, increasing its invasiveness in different countries

Une plante envahissante dans un écosystème insulaire : l'ajonc Ulex europaeus sur l'île de La Réunion.

communication oral

Une plante envahissante dans un écosystème insulaire : l'ajonc Ulex europaeus sur l'île de La Réunion.

communication oral

Flowering strategies and the invasiveness of gorse (Ulex europaeus L., Fabaceae).

Communication oral

Role of biotic and anthropogenic factors in the invasiveness of gorse

Poste

Genetic divergence and ecological specialization of seed weevils (Exapion spp.) on gorses (Ulex spp.).

1. Reproductive isolation of sympatric populations may result from divergent selection of populations in different environments, and lead to ecological specialisation. In Brittany (France), the gorse Ulex europaeus (Fabaceae, Genisteae), may be encountered in sympatry with one of the two other gorse species present: U. gallii and U. minor. A recent study based on morphological identification of seed predators of gorse has shown that two weevil species (Curculionoidea, Apionidae) infest gorse pods at different seasons and have different host ranges: Exapion ulicis infests U. europaeus in spring, whereas E. lemovicinum infests U. gallii and U. minor in autumn. Weevil populations may thus have diverged in sympatry. 2. As morphological identification of weevils is often difficult and some of the characters used may exhibit individual or environmental variation, mitochondrial and nuclear sequences of weevils collected within pods of the three gorse species in 10 populations of Brittany were used to reconstruct their phylogeny. 3. The results reveal that species differentiation based on morphological characters is confirmed by the two molecular data sets, showing that E. ulicis and E. lemovicinum are distinct species, and suggesting the absence of host races. Finally, E. ulicis was able to use U. gallii and U. minor pods in spring in some years in some populations, which appeared to depend on the availability of pods present during its reproductive period. 4. Divergence between E. ulicis and E. lemovicinum may have resulted from temporal isolation of reproductive periods of weevil populations followed by specialisation of insects to host phenology