Experimental investigation of the effect of spatial aggregation on reproductive success in a rewardless orchid

Plant reproductive success within a patch may depend on plant aggregation through pollinator attraction. For rewardless plants that lack rewards for pollinators, reproductive success may rely strongly on the learning abilities of pollinators. These abilities depend on relative co-flowering rewarding and rewardless plant species spatial distributions. We investigated the effect of aggregation on the reproductive success of a rewardless orchid by setting up 16 arrays in a factorial design with two levels of intraspecific aggregation for both a rewardless orchid and a rewarding co-flowering species. Our results show that increasing aggregation of both species negatively influenced the reproductive success of the rewardless plants. To our knowledge, this is the first experimental study demonstrating negative effects of aggregation on reproductive success of a rewardless species due both to its own spatial aggregation and that of a co-flowering rewarding species. We argue that pollinator learning behaviour is the key driver behind this resul

Carry-over effects of bumblebee associative learning in changing plant communities leads to increased costs of foraging

Flower visitors learn to avoid food-deceptive plants and to prefer rewarding ones by associating floral cues to rewards. As co-occurring plant species have different phenologies, cue-reward associations vary over time. It is not known how these variations affect flower visitors' foraging costs and learning. We trained bumblebees of two colonies to forage in a community of deceptive and rewarding artificial inflorescences whose flower colours were either similar or dissimilar. We then modified the community composition by turning the rewarding inflorescences into unrewarding and adding rewarding inflorescences of a novel flower colour. In the short term, bees trained to similar rather than dissimilar inflorescences experienced higher costs of foraging (decreased foraging speed and accuracy) in the novel community. The colonies differed in their speed-accuracy trade-off. In the longer term, bees adapted their foraging behaviour to the novel community composition by increasingly visiting the novel rewarding inflorescence

Inventaire de la population naturelle de latanier rouge (Latania lontaroides) de la ravine Balthazar (La Possession - île de La Réunion) (Arecales : Arecaceae)

Résumé : Le latanier rouge ou latanier de La Réunion (Latania lontaroides (Gaertn.) H.E. Moore) est un palmier (famille des Arécacées) endémique de La Réunion inféodé au secteur semi-sec et aux régions côtières sèches (secteur ouest à nord-ouest) à humides (secteur sud) de l'île. L’espèce est aujourd’hui confinée à quelques stations isolées à effectifs réduits à tout au plus quelques individus dans son milieu naturel. Elle est officiellement considérée comme en danger critique d’extinction par l’Union Internationale pour la Conservation de la Nature. Grâce à Elysé Assani et Fabris Themyr, de la commune de La Possession, l’existence d’une population à priori non connue des institutions impliquées dans la sauvegarde de la flore et des habitats a été simultanément indiquée au Parc national de La Réunion, à l’Office National des Forêts et au Conservatoire Botanique de Mascarin. L’étude d’inventaire conservatoire présentée dans cet article démontre que la population en question est très certainement d’origine sauvage et qu’elle est à ce titre hautement exceptionnelle à l’échelle mondiale. Cette étude met en exergue les caractéristiques biologiques et écologiques de la population, les nombreuses menaces qui pèsent sur celle-ci et propose des actions urgentes de conservation afin de sauvegarder tant sur le plan ex situ que in situ les composantes génétiques et phénotypiques de ce patrimoine naturel d’exception. Une opération de restauration écologique partagée entre les différents acteurs sus-mentionnés devra très rapidement être mise en œuvre. Abstract: The red latanier or La Reunion's latanier (Latania lontaroides (Gaertn.) H.E. Moore) is a palm tree (Arecaceae) endemic to La Reunion, restricted to the semi-dry sector and the dry-to-wet coastal areas (west to northwest and southern sector) of the island. The species is now confined to a few isolated sites with at most a few individuals in their natural environment. It is officially classified as critically endangered by the International Union for Conservation of Nature. Thanks to Elysé Assani and Fabris Themyr (La Possession), the existence of a population, a priori unknown by institutions involved in the preservation of flora and habitats, was simultaneously shown to the Parc national de La Réunion, to the Office National des Forêts and to the Conservatoire Botanique de Mascarin. The protective inventory study presented in this article shows that the population in question is certainly wild and it is highly exceptional in the world. This study highlights biological and ecological characteristics of the population, the many threats to it, and proposes urgent conservation actions to safeguard both ex situ and in situ phenotypic and genetic components of this exceptional natural heritage. An ecological restoration operation shared by different actors mentioned above will have to be quickly implemented

Redécouverte de Lobelia parva Badré & Cadet, espèce endémique de l'île de La Réunion (Asterales : Campanulaceae)

Lobelia parva Bradé & Cadet, une campanule endémique de l'île de la Réunion, est de nouveau observé à l'endroit même du prélèvement des spécimens types, quarante-cinq ans après sa découverte et unique rencontre

Merremia pterygocaulos (Choisy) Hallier f. : une espèce indigène méconnue et non revue à La Réunion depuis le 19ème siècle… (Convolvulaceae)

La présence de <i>Merremia pterygocaulos</i> à la Réunion est attestée et si on se réfère aux flores existantes et à sa répartition mondiale, nous postulons qu’il s’agit d’une espèce indigène très rare pour La Réunion

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