Species of the genus Carpobrotus, or iceplant, are succulent mat-forming perennial herbs often introduced for soil stabilization. They are common in coastal environments and may thus threaten island biodiversity. While their effects are well known on soils, plant communities and associated fauna, the effects of Carpobrotus control on vegetation recovery is poorly documented. The aim of the paper is to describe plant community trajectories after Carpobrotus removal. Location Bagaud: a 58-ha Mediterranean island, southern France. Methods Carpobrotus and its litter were removed in 2011-2012. Follow-up controls of germinations and resprouts were carried out from then on. Plant communities were surveyed every year two years before and seven years after Carpobrotus removal: on two ca. 0.5-ha sites (one coastal and one inland) and in three native plant communities used as potential references. Differences in resprouts, vegetation parameters, Bray-Curtis similarity indices between years were tested. Plant community dynamics was studied through a NMDS and two recovery indices. Results The removal of Carpobrotus and its litter led to the recovery of diverse native plant communities. To prevent Carpobrotus return and ensure success, follow-up controls were necessary for a period of at least seven years, but the amount of work decreased with time. The plant community recovering on the coastal site quickly reached a composition and structure similar to that of noninvaded coastal vegetation, although some slow-growing native species remain under-represented (e.g. Crithmum maritimum and Limonium pseudominutum). The plant community recovering on the inland site was still very different from the surrounding matorral vegetation because of its slow colonization dynamics, particularly in the presence of competitive herbaceous species. Conclusion Both sites now provide diverse native plant communities with a more diversified composition and structure (plant heights, litter, bare ground patches) than the plant communities which used to be associated with Carpobrotus mats.

Biological invasions have reached an unprecedented level and the number of introduced species is still increasing worldwide. Despite major advances in invasion science, the determinants of success of introduced species, the magnitude and dimensions of their impact, and the mechanisms sustaining successful invasions are still debated. Empirical studies show divergent impacts of non-native populations on ecosystems and contrasting effects of biotic and abiotic factors on the dynamics of non-native populations; this is hindering the emergence of a unified theory of biological invasions. We propose a synthesis that merges perspectives from population, community, and ecosystem levels. Along a timeline of ecosystem transformation driven by non-native species, from historical to human-modified ecosystems, we order invasion concepts and theories to clarify their chaining and relevance during each step of the invasion process. This temporal sorting of invasion concepts shows that each concept is relevant at a specific stage of the invasion. Concepts and empirical findings on non-native species may appear contradictory. However, we suggest that, when mapped onto an invasion timeline, they may be combined in a complementary way. An overall scheme is proposed to summarise the theoretical dynamics of ecosystems subjected to invasions. For any given case study, this framework provides a guide through the maze of theories and should help choose the appropriate concepts according to the stage of invasion.

No abstract

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Invasive plant species, such as Carpobrotus species, threaten the biodiversity of Mediterranean islands. Ecological restoration can include the control of invasive plants, but the effect of Carpobrotus removal on arthropods is understudied. Here, we evaluated the influence of Carpobrotus removal on beetle assemblages, on a Mediterranean island. Between November 2011 and February 2012, we manually removed Carpobrotus and its litter. A site composed of native shrubland vegetation located in the vicinity was studied to estimate the beetle assemblage natural variations. Two years before removal (2010)(2011), and every 2 years following removal (2013, 2015, 2017, 2019), we sampled beetles with pitfall traps. Vegetation did not change at the shrubland site and beetle assemblages stayed relatively stable. After the removal of Carpobrotus at the Carpobrotus site, a diverse halophilic grassland vegetation colonized as well as some chamaephytes. The taxonomic and functional richness of beetle species increased significantly following removal. Assemblage composition changed significantly between preand post-removal years with a high taxonomic turnover rate. Predators (e.g. Staphylinidae, Carabidae) and detritivores (Tenebrionidae) most likely benefited from the vegetation opening, while the diversification of microhabitats led to the availability of a wider variety of prey. Large floricolous beetles (Scarabaeidae) were the most reduced by Carpobrotus removal along with small non-flying beetles. This rapid change in beetle assemblages occurred within 7 years. Future studies should be carried out in areas where reference ecosystems are available to meet the requirements of a Before-After-Control-Impact approach.

Simultaneous eradications of Black Rat (Rattus rattus) and Ice plants (Carpobrotus spp.) on Bagaud Island (Port-Cros National Park, Provence, France) : preliminary results on their impacts on Athropods communities. — Biological invasions are recognized as one of the major threats to island biodiversity conservation, and numerous studies have been conducted around the world to restore the biodiversity of islands submitted to invasive species impacts. However, few scientific post-eradication studies were piloted notably for the biodiversity assessment of Arthropod communities. Bagaud Island is an integral reserve of the Port-Cros National Park (PNPC), located in the îles d’Hyères Archipelago (Var, France). In the last centuries, it has undergone two major anthropogenic disturbances : the invasion of the Black Rat (Rattus rattus) and the Ice plants (Carpobrotus spp.), two alien taxa known for their particularly negative effects on the flora and fauna of the Mediterranean island ecosystems, including Arthropods. PNPC has launched a ten-year program of ecological restoration that involves the eradication of these two invasive taxa. The Arthropod communities of the island have been analysed in their initial state in spring 2011, eradications were conducted between September 2011 and January 2013, and the first post-eradication campaign began in spring 2013. The ground fauna was sampled using four transects of Barber traps distributed in different ecological contexts of the island. This first post-eradication study reveals an increase in the abundance of arthropods trapped between 2011 (4868 individuals in 74 traps) and 2013 (6892, n = 60). The average number of trapped Arthropods was significantly higher in areas where Carpobrotus spp. have been eradicated, but declined in the bush area that housed a high density of R. rattus. The communities of decomposers explode, in contrast to predator populations. However, the global specific richness remains stable (220 morphospecies in 2011, 216 in 2013). Scientific monitoring by the PNC must be continued to better determine the direct and indirect long-term impacts of these eradications upon the structure and the functioning of the Arthropods communities of the Bagaud Island.