Thierry Tatoni

Is the yellow-legged gull a superabundantbird species in the Mediterranean? Impacton fauna and flora, conservation measuresand research priorities

In the Mediterranean basin, the yellow-legged gull Larus cachinnans has undergone a widespread demographic increase for the past 30 years. Owing to its high ecological adaptability, its aggressive behaviour and its abundance, this gull is often considered to be a pest. The authors review and analyse the impacts of the expansion of the yellow-legged gull on fauna and flora in the Mediterranean area. Despite the relatively limited number of both intensive and general studies, it clearly appears that the population explosion has had a very diverse and severe effect on the ecosystem as a whole (flora, vertebrates, interspecific competition, extinction–colonization processes). The most serious damage has occurred around the largest breeding colonies to the detriment of fragile, rare or very restricted plant and animal species. Thus, from the point of view of fauna and flora conservation, the yellow-legged gull can, for the moment, be considered to be locally superabun dant. Control measures are often very onerous and necessitate heavy manpower and material resources. Additional extensive investigations will be necessary to assess the future development of yellow-legged gull populations and their impact on natural environments.

BASECO: a floristic and ecological database of Mediterranean French flora

The French Mediterranean zone is one of the richest of the country, with 3200 species and many endemics. Because of its interest as a synthetic tool to store and manage data, an ecological Mediterranean flora database was created. Built around five tables, BASECO allows several queries about the botanical and ecological characteristics of about 1800 plants. The database was implemented in Access, which is a relational database management system. Each species is identified by a code and is characterised by several qualitative traits relating to morphology, reproduction, life forms and biogeographical distribution, including several modalities. Each trait is informed from one or two pre-defined reference botanical handbooks as much as possible. There are many different possible uses of this database, even at a huge scale, allowing to reveal patterns hard to detect with the taxonomic approach alone.

Impact of gull colonies on the flora of the Riou Archipelago (Mediterranean Islands of south-east France)

Abstract The effects of an increasingly large yellow-legged gull Larus cachinnans colony on the flora of a Mediterranean limestone archipelago (south-east France) were studied through the analysis of floristical changes which have occurred in the past 36 years. Island plant lists can be distinguished first according to the island area, but all the islands show a common pattern of historical changes in flora. This floristical change appears to be correlated with the gull density and the percentage of ruderal plant species. Disturbance by gulls favours the massive establishment of non-native plant species which has led to the extinction of some endangered taxa through this plant species ‘enrichment’. Small islets appear to be more affected than large islands. Some preliminary conservation measures are presented.

Functional groups in phytoecology: an application to the study of isolated plant communities in Mediterranean France

The main objective of this study is to compare functional patterns versus plant composition in holm-oak forest isolates from two sites of Provence (Mediterranean France), on siliceous (Maures) or calcareous substrates (Luberon). In order to define plant functional groups, 9 traits out of a total of 71 attributes, were used. Twenty functional groups were defined with predominantly vegetative traits. Within each site, edges and forested core areas refer to different functional groups, in relation to the isolate structure and disturbance effects. In siliceous Provence, a higher structural and functional diversity occurs inside isolates, whereas on calcareous substrate, the diversity of plant functional groups which characterizes edges, is as important as in internal parts of isolates. Functional diversity does not necessarily follow the same patterns as the specific diversity, which is always greater in edges. Thus, the use of some sets of attributes, resulting from evolutionary trade-off between plants and their environment, can provide a better understanding of ecological consequences of disturbances.

Fine-scale response to landscape structure in Primula vulgaris Huds.: does hedgerow network connectedness ensure connectivity through gene flow?

Variation in pollen flow, mating performances, and seed dispersal were examined using direct and indirect approaches in contrasted hedgerow networks (i.e., dense vs. sparse) of the distylous Primula vulgaris. Seed dispersal reached negligible distances, and no difference was observed between the two hedgerow networks. On the contrary, pollen flow through Bombylius sp. activity was impeded in the dense hedgerow network. Furthermore, P. vulgaris was found to be partially self-compatible in our study site. The lower pollen flow in the dense hedgerow network, and especially in small populations, is likely to have unusually favoured self-compatibility and hence selfing in P. vulgaris short-style morph. In addition, the inbreeding depression values recorded were higher in the dense hedgerow network. Our results suggested that a dense hedgerow network does not necessarily ensure connectivity in Primula vulgaris in terms of gene flow. This study provides evidence for considering landscape structure in the microevolutionary processes.

Screening biological traits and fluoride contents of native vegetations in arid environments to select efficiently fluoride-tolerant native plant species for in-situ phytoremediation

High fluoride pollution has been detected in the surrounding soils of the coastal superphosphate industries in the Gulf of Gabes (Southeast of Tunisia). A study was conducted in vicinity of factories analysing plant functional traits combined with plant fluoride accumulation and soil metal concentrations aiming to screen more efficiently native plant species tolerant to this pollution. Aerial parts of 18 plant species out of the 10 most abundant species per site were harvested on two polluted sites of Gabes and Skhira at the vicinity of the factories and on the less polluted site of Smara. Native plant species accumulated fluoride following the gradient of soil pollution. Fluoride contents of plant aerial parts ranged from 37 mg kg(-1) to 360 mg kg(-1) and five plant species were only found in the most polluted site. However these latter had low biomass and soil cover. Crossing biological traits and fluoride contents, a selection grid for potentially restorative plant species enabled the selection of three native perennials i.e. Rhanterium suaveolens, Atractylis serratuloides and, Erodium glaucophyllum as potential candidates for an in-situ phytoremediation program on arid fluoride-polluted sites. This approach may be used in other fluoride-polluted Mediterranean environments.

Recurrent fires and environment shape the vegetation in Quercus suber L. woodlands and maquis.

The effects of fire recurrence on vegetation patterns in Quercus suber L. and Erica-Cistus communities in Mediterranean fire-prone ecosystems of south-eastern France were examined on stands belonging to 5 fire classes, corresponding to different numbers of fires (from 0 to 4) and time intervals between fires since 1959. A common pool of species was identified among the plots, which was typical of both open and closed maquis. Fire recurrence reduced the abundance of trees and herbs, whereas it increased the abundance of small shrubs. Richness differed significantly between the most contrasting classes of fire recurrence, with maximal values found in control plots and minimal values in plots that had burned recurrently and recently. Equitability indices did not vary significantly, in contrast to Shannons diversity index which mostly correlated with richness. Forest ecosystems that have burnt once or twice in the last 50 years were resilient; that is to say they recovered a biomass and composition similar to that of the pre-fire state. However, after more than 3-4 fires, shrubland communities displayed lower species richness and diversity indices than unburned plots. The time since the last fire and the number of fires were the most explanatory fire variables, governing the structure of post-fire plant communities. However, environmental factors, such as slope or exposure, also made a significant contribution. Higher rates of fire recurrence can affect the persistence or expansion of shrublands in the future, as observed in other Mediterranean areas.

Relative importance of Habitat and landscape scales on butterfly communities of urbanizing areas

Agricultural decline and urbanization entail rapid alterations of the patterns of organization of rural landscapes in Europe. The spread of the urban footprint to the adjacent countryside contributes to the development of new anthropogenic ecosystems in formerly rural hinterlands. In this study, butterflies are considered as biological indicators of these rapid environmental changes. Our purpose is to better understand changes in biodiversity related to the evolution of available habitats in a mutating landscape. In this study, we investigate butterfly communities of four land-use types (fallow lands, gardens, vineyards, woodlands) within different landscape contexts. Our results reveal that variations in structure and functional composition of these communities are related to different levels of human disturbance at both landscape scale and habitat scale.

Factors Underlying the Narrow Distribution of the Mediterranean Annual Plant Arenaria provincialis (Caryophyllaceae)

The factors responsible for the patterns of niche differentiation and narrow endemism have rarely been investigated in annual Mediterranean plants. This topic was addressed here by performing comparative studies on realized niches, regional occupancy, global biogeographical distribution and seed traits of a set of Arenaria (Caryophyllaceae) species inhabiting southern Provence (SE France), focusing in particular on Arenaria provincialis, a narrow endemic restricted to the hills and modest calcareous mountains around the city of Marseille. Field studies were carried out from 2008 to 2009 at 624 sites in the limestone mountains where Arenaria species are likely to occur. The Arenaria species occurring in southern Provence vary greatly in their patterns of regional occupancy and their biogeographical distribution. Multivariate analysis of the realized niche showed that they have some similar limiting environmental factors in common, but they do not all occupy the same habitats. Studies on the fruits and seeds showed that the endemic A. provincialis has a larger seed than its congeners and a capsule that remains closed and falls from the plant at maturity. This well-differentiated diaspore specific to A. provincialis may be responsible for the limited dispersal capacity of this species. Phylogenetic analyses showed that A. provincialis is not closely related to the other taxa inhabiting southern Provence, but rather to Arenaria occurring in highland areas in the south of France. The restricted pattern of distribution of A. provincialis is probably due to the past isolation event from which it originated and to its limited dispersal capacity, rather than resulting from its ecological niche range.

A new bioclimatic model calibrated with vegetation for Mediterranean forest areas

Abstract• Water availability is one of the main factors explaining flora composition and growth in Mediterranean regions, where it may decline with climate change.• Our goal was to develop a model for forest site assessment in Mediterranean environments, focusing on water availability to assess potential vegetation composition and productivity in any places, whatever their level of disturbance.• We designed a statistical model, using global climatic and geographic variables, as well as detailed local topographic and edaphic variables, to compute a bioclimatic index for Mediterranean forest environments. This model was calibrated in France with a flora index from 325 old forests. The model explained 80.3% of the flora index variance. The method fills a gap in existing models, bridging scales from the region to forest sites.• Beyond its theoretical aspect, it was designed to allow practical tools to be derived from it for decision-making and management, such as the assessment of climate change impact on vegetation, and of forest productivity. Its development and adaptation is possible in other Mediterranean regions, and in any region where water is one of the main limiting factors.Résumé• La disponibilité en eau est un des principaux facteurs contrôlant la composition et la croissance de la flore en région méditerranéenne. Elle devrait décroître avec le changement climatique.• Notre objectif était de développer un modèle pour l’analyse stationnelle des milieux forestiers méditerranéens. Basé sur la disponibilité de l’eau, il devait permettre l’évaluation de leur flore potentielle et de leur productivité, quel que soit leur état de perturbation.• Nous avons conçu un modèle statistique, utilisant conjointement des variables globales, climatiques et géographiques, et des variables locales topographiques et édaphiques pour calculer un indice bioclimatique adapté aux milieux forestiers méditerranéens. Ce modèle a été calibré en France sur 325 placettes de forêts âgées à l’aide d’un indice floristique dont il explique 80.3 % de la variance. Avec des échelles de travail allant en continu de la région à la station forestière, la méthode comble un vide dans la gamme des modèles existants.• Ce modèle ouvre des perspectives pour l’évaluation de l’impact du changement climatique sur la flore et de la productivité forestière. La méthode peut être adaptée à d’autres régions méditerranéennes et à toute région où le bilan hydrique est un des principaux facteurs limitants.