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Papeete, French Polynesia

Kueffer C.,University of Hawaii at Manoa | Kueffer C.,ETH Zurich | Daehler C.C.,University of Hawaii at Manoa | Torres-Santana C.W.,University of Hawaii at Manoa | And 4 more authors.
Perspectives in Plant Ecology, Evolution and Systematics | Year: 2010

Oceanic islands have long been considered to be particularly vulnerable to biotic invasions, and much research has focused on invasive plants on oceanic islands. However, findings from individual islands have rarely been compared between islands within or between biogeographic regions. We present in this study the most comprehensive, standardized dataset to date on the global distribution of invasive plant species in natural areas of oceanic islands. We compiled lists of moderate (5-25% cover) and dominant (>25% cover) invasive plant species for 30 island groups from four oceanic regions (Atlantic, Caribbean, Pacific, and Western Indian Ocean). To assess consistency of plant behaviour across island groups, we also recorded present but not invasive species in each island group. We tested the importance of different factors discussed in the literature in predicting the number of invasive plant species per island group, including island area and isolation, habitat diversity, native species diversity, and human development. Further we investigated whether particular invasive species are consistently and predictably invasive across island archipelagos or whether island-specific factors are more important than species traits in explaining the invasion success of particular species. We found in total 383 non-native spermatophyte plants that were invasive in natural areas on at least one of the 30 studied island groups, with between 3 and 74 invaders per island group. Of these invaders about 50% (181 species) were dominants or co-dominants of a habitat in at least one island group. An extrapolation from species accumulation curves across the 30 island groups indicates that the total current flora of invasive plants on oceanic islands at latitudes between c. 35°N and 35°S may eventually consist of 500-800 spermatophyte species, with 250-350 of these being dominant invaders in at least one island group. The number of invaders per island group was well predicted by a combination of human development (measured by the gross domestic product (GDP) per capita), habitat diversity (number of habitat types), island age, and oceanic region (87% of variation explained). Island area, latitude, isolation from continents, number of present, non-native species with a known invasion history, and native species richness were not retained as significant factors in the multivariate models. Among 259 invaders present in at least five island groups, only 9 species were dominant invaders in at least 50% of island groups where they were present. Most species were invasive only in one to a few island groups although they were typically present in many more island groups. Consequently, similarity between island groups was low for invader floras but considerably higher for introduced (but not necessarily invasive) species - especially in pairs of island groups that are spatially close or similar in latitude. Hence, for invasive plants of natural areas, biotic homogenization among oceanic islands may be driven by the recurrent deliberate human introduction of the same species to different islands, while post-introduction processes during establishment and spread in natural areas tend to reduce similarity in invader composition between oceanic islands. We discuss a number of possible mechanisms, including time lags, propagule pressure, local biotic and abiotic factors, invader community assembly history, and genotypic differences that may explain the inconsistent performance of particular invasive species in different island groups. © 2009 Rübel Foundation, ETH Zürich.

Spotswood E.N.,University of California at Berkeley | Meyer J.-Y.,Delegation a la Recherche | Bartolome J.W.,University of California at Berkeley
Biological Invasions | Year: 2013

Introduced plants with fleshy fruit can alter the dietary decisions of frugivorous birds in their novel ranges by producing fruit of higher quality or by producing fruit in greater abundance. We used fruit choice experiments with wild-caught captive Red-vented Bulbuls (Pycnonotus cafer) on the tropical Pacific island of Moorea, French Polynesia, to determine whether this bird prefers the fruit of a highly invasive tree (Miconia calvescens) over three other fruit (one alien, two native) and to determine whether birds would eat less preferred fruit when it was more abundant than preferred fruit. Birds showed consistent preferences, and chose M. calvescens more than any other species. Birds selected more abundant fruit first when a single species was presented. However, when both fruit species and abundance were modified simultaneously, patterns of preference for particular species remained intact while the response to abundance disappeared. Results imply that dietary preferences are more important than small-scale variations in abundance for fruit selection. The strong preference for M. calvescens suggests that Bulbuls will select the fruit even in habitats where it is rare. © 2013 Springer Science+Business Media Dordrecht.

Muller S.,French National Center for Scientific Research | Meyer J.-Y.,Delegation a la Recherche
Revue d'Ecologie (La Terre et la Vie) | Year: 2012

The French overseas territories represent a broad range of climatic and biogeographical conditions, from sub-arctic to equatorial, resulting in a richness, diversity and uniqueness of their floras that mirrors that of the global flora. These territories range widely in area (from small oceanic islands to large continental regions) and human population densities, leading to more or less pronounced anthropogenic impacts on natural ecosystems. Threats to the French overseas flora arc generally the same (habitat destruction, biological invasions, species overexploitation, climate change) but with varying importance depending on the territory. Conservation measures, including the establishment of lists of protected species or habitats and new protected areas, as well as habitat restoration, species reintroduction or population reinforcement of threatened species, also vary depending on the territory, in relation with their legal status, and the concern of local populations and authorities toward the conservation of their natural heritage. We underline the necessity and urgency to better know and conserve this flora (more than 10 000 vascular plants, including 3480 endemics, and with 685 protected species) of not only national but also regional and global importance.

Identifying the causes of extinction and their intensity is a prerequisite to define the status of species conservation and to set up efficient and effective conservation plans. Apetahia raiateensis H. Bâillon (Campanulaceae), an endemic shrub on three trachytic plateaus of the island of Raiatea (Society Islands), is a legendary plant in Polynesian culture and a legally protected species in French Polynesia. Systematic inventories were conducted on the plateaus Te mehani 'ute'ute (94 ha), Te mehani rahi (202 ha) and Te vaihue (12 ha) to assess populations (882 plants in 2009), to map the species, and to compare with previous inventories performed in 1995. 81 accessible plants and 820 of their stems were monitored on Te mehani rahi between 2009 and 2011, in order to quantify and understand the reasons of the species rapid extinction. The inventories revealed a rate of disappearance to be respectively of 74 % on Te mehani 'ute'ute (1995-2006) and of 76 % on Te mehani rahi (1995-2009). The plants are currently found in subpopulations restricted on the borders of the plateaus and on cliffs. After 18 months of follow-up, 41 out of 57 reproductive plants (72 %) and 219 stems were attacked by rats (Rattus spp.) and 9 reproductive plants and 133 stems were found dead. In addition, 31 % of these reproductive plants had 29 stems broken by people. Among the wilted stems with unknown causes, half (55 stems on 15 plants) might be related to the cyclone that hit Raiatea in 2010. The species habitat is also threatened by feral pigs and by the invasion of twelve naturalized alien plants. Our results support the classification of Apetahia raiateensis in the «critically endangered» category (CR) of IUCN. Rat control trials using baits around plants are currently conducted on Te mehani rahi, together with in situ propagation from seeds, for the recovery of this species of scientific and cultural heritage values.

Spotswood E.N.,University of California at Berkeley | Meyer J.-Y.,Delegation a la Recherche | Bartolome J.W.,University of California at Berkeley
Journal of Biogeography | Year: 2012

Aim We studied how the abundance of the highly invasive fruit-bearing tree Miconia calvescens DC. influences seed dispersal networks and the foraging patterns of three avian frugivores. Location Tahiti and Moorea, French Polynesia. Methods Our study was conducted at six sites which vary in the abundance of M. calvescens. We used dietary data from three frugivores (two introduced, one endemic) to determine whether patterns of fruit consumption are related to invasive tree abundance. We constructed seed dispersal networks for each island to evaluate how patterns of interaction between frugivores and plants shift at highly invaded sites. Results Two frugivores increased consumption of M. calvescens fruit at highly invaded sites and decreased consumption of other dietary items. The endemic fruit dove, Ptilinopus purpuratus, consumed more native fruit than either of the two introduced frugivores (the red-vented bulbul, Pycnonotus cafer, and the silvereye, Zosterops lateralis), and introduced frugivores showed a low potential to act as dispersers of native plants. Network patterns on the highly invaded island of Tahiti were dominated by introduced plants and birds, which were responsible for the majority of plant-frugivore interactions. Main conclusions Shifts in the diet of introduced birds, coupled with reduced populations of endemic frugivores, caused differences in properties of the seed dispersal network on the island of Tahiti compared to the less invaded island of Moorea. These results demonstrate that the presence of invasive fruit-bearing plants and introduced frugivores can alter seed dispersal networks, and that the patterns of alteration depend both on the frugivore community and on the relative abundance of available fruit. © 2012 Blackwell Publishing Ltd.

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