Laurence Affre

Eradications as scientific experiments: progress in simultaneous eradications of two major invasive taxa from a Mediterranean island

BACKGROUND Black rats, Rattus rattus, and mat-forming iceplants, Carpobrotus aff. acinaciformis and Carpobrotus edulis, are pervasive pests on Mediterranean islands. Their cumulative impacts on native biotas alter the functioning of island ecosystems and threaten biodiversity. A report is given here of the first attempt to eradicate both taxa from a protected nature reserve in south-eastern France (Bagaud Island). In order to minimise unwanted hazardous outcomes and produce scientific knowledge, the operations were embedded in a four-step strategy including initial site assessment, planning, restoration and monitoring. RESULTS Trapping, which resulted in the removal of 1923 rats in 21 045 trap-nights, made it possible to eliminate a substantial proportion of the resident rat population and to reduce the amount of rodenticide delivered in the second stage of the operation. Forty tons of Carpobrotus spp. were manually uprooted from a total area of 18 000 m(2) ; yet careful monitoring over a decade is still required to prevent germinations from the seed bank. CONCLUSION Two years after the beginning of the interventions, both eradication operations are still ongoing. Biosecurity measures have been implemented to reduce reinvasion risks of both taxa. With the long-term monitoring of various native plants and animals, Bagaud Island will become a reference study site for scientific purposes.

Geographical isolation caused the diversification of the Mediterranean thorny cushion-like Astragalus L. sect. Tragacantha DC. (Fabaceae).

Understanding the origin and evolution of Mediterranean vascular flora within the long-term context of climate change requires a continuous study of historical biogeography supported by molecular phylogenetic approaches. Here we provide new insights into the fascinating but often overlooked diversification of Mediterranean xerophytic plants. Growing in some of the most stressing Mediterranean environments, i.e. coastal and mountainous opened habitats, the circum-Mediterranean Astragalus L. sect. Tragacantha DC. (Fabaceae) gathers several thorny cushion-like taxa. These have been the subjects of recent taxonomical studies, but they have not yet been investigated within a comprehensive molecular framework. Bayesian phylogenetics applied to rDNA ITS sequences reveal that the diversification of A. sect. Tragacantha has roots dating back to the Pliocene, and the same data also indicate an eastern-western split giving rise to the five main lineages that exist today. In addition, AFLP fingerprinting supports an old east-west pattern of vicariance that completely rules out the possibility of a recent eastern origin for western taxa. The observed network of genetic relationships implies that contrary to what is widely claimed in the taxonomic literature, it is range fragmentation, as opposed to a coastal-to-mountain ecological shift, that is likely the main driver of diversification.

Consequences of iceplant (Carpobrotus) invasion on the vegetation and seed bank structure on a Mediterranean island: response elements for their local eradication

Abstract Biological invasions are one of the world’s leading causes of biodiversity loss. Islands are particularly good models for studying the impact of invasive species. Bagaud island (58 ha), which is part of Port-Cros National Park (southeastern France), is currently suffering an invasion of Carpobrotus. A restoration project has been established with the aim of eradicating these species to protect native ecosystems. The objective of the present study was to examine the plant composition of the local vegetation and seed bank (in litter and soil) focusing on (i) Carpobrotus patches and (ii) native plant communities, with the ultimate goal of determining whether Carpobrotus removal is followed by native plant community colonization. A further objective of this study was to help identify the most effective protocol for adequate ecological restoration. Native plant communities found around Carpobrotus patches can vary depending on whether the patch is located on the coast or inland; we can therefore expect a variety of plant communities to form following Carpobrotus removal. Even though Carpobrotus litter can frequently contain seeds of native species, such Atriplex prostrata, Frankenia sp. and Sonchus asper, it also contained many more Carpobrotus seeds (77.6%). Therefore, it is important to remove Carpobrotus litter to prevent large numbers of Carpobrotus seeds from recolonizing after eradication. We conclude that the most effective ecological restoration protocol consists of the following: (i) the removal of living Carpobrotus plants and (ii) the removal of Carpobrotus litter. This protocol can be made even more effective by following it up in the near and mid-term by periodic and thorough checks for Carpobrotus reinvasion.

Genomic DNA isolation and amplification from callus culture in succulent plants, Carpobrotus species (Aizoaceae)

Genomic DNA of high quality and quantity is needed to analyze genetic diversity with AFLP.Carpobrotus plant species, like most succulents, contain high amounts of polysaccharides and polyphenols, making PCR amplification difficult. Our protocol eliminates contaminants before DNA isolation by using leaf callus as plant material. This simple and inexpensive technique gives an average DNA yield of 1800 ng/g of callus and high reproducible profiles in AFLP. Our results indicate that no genetic variability is associated with callus culture conditions. This technique is suitable for studying genomic polymorphism in succulents and other plants when classic DNA extraction procedures fail.

Monographs of invasive plants in Europe: Carpobrotus

ABSTRACT This report synthesizes all aspects of the taxonomy, distribution, history of introduction and spread, ecological constrains (including preferred climate, substratum and habitats), responses to biotic and abiotic factors, biology (including phenology, vegetative and reproductive biology), economic importance and human uses, ecological impacts, legislation and management of Carpobrotus N.E.Br. (Aizoaceae), a prominent invasive plant in Europe. Carpobrotus species are mat-forming trailing succulent perennial herbs native from South Africa, introduced in Europe for ornamental and soil stabilization purposes since the beginning of the seventeenth century, now widely naturalized on coastal habitats of southern and western Europe. C. acinaciformis and C. edulis are the main species recognized outside South Africa, together with their hybrids and potential hybrid swarms. Identification conflicts both in the native and invaded areas raise doubts on the taxonomy of these taxa, but hybridization processes may boost adaptive changes in the invaded range. The release of Carpobrotus in natural environments and protected areas is prohibited in several European countries, but this taxon is not included in the list of invasive species of Union concern. Carpobrotus is a pioneer of disturbed sites and coastal areas including cliffs and sand dune systems, due to its tolerance to stress factors such as salinity, drought and excess of light. Carpobrotus invasion ultimately affects patterns of native species diversity. Moreover, it has been recognized as a major driver of soil conditions shifts and soil geochemical processes disruptions, representing a serious threat for coastal habitats. Management plans for Carpobrotus must consider its high plasticity for morphological and ecophysiological traits, which may probably explain its tolerance to a wide range of ecological conditions. Its flexible mating systems, which represent an optimal strategy to facilitate local adaptation and habitat colonization, include ability to produce apomictic seeds, self- and cross-pollination, and an intense vegetative clonality. In addition, Carpobrotus produces a large seed bank with a moderate short-term persistence, and fruits are effectively dispersed by mammals. The most efficient control methods are physical removal and herbicide application on leaves, whereas integration of biological control with other conventional management methods are likely to be most effective. A long-term monitoring of control actions and restoration of soil conditions are needed to prevent recovering from clonal parts, seed bank or mammal faeces as well as potential new invasions by other opportunistic species.