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Ballari S.A.,CONICET | Cuevas M.F.,CONICET | Cirignoli S.,The Conservation Land Trust Argentina | Valenzuela A.E.J.,Southern Patagonia Coordination Office | Valenzuela A.E.J.,National University of Tierra del Fuego
Biological Invasions

The wild boar is an invasive ecosystem engineer in Argentina that has lacked sufficient basic information to determine applied actions. The current distribution, impacts and management of this species were analyzed using the expert opinion surveys of protected area managers. The boar is widely distributed and occupies most of Argentina’s terrestrial ecoregions. Moreover, its populations are common, and its abundance is growing in most of the protected areas. Boars were recorded mostly in wetlands, forest and shrublands. Managers also reported a wide range of negative impacts, which included soil disturbance, vegetation damage and animal predation. Several control method types are used and in most protected areas, more than one are applied, but hunting was the most used technique. However, the effectiveness of control methods was low, suggesting the need of an urgent plan to define coordinated management actions to minimize the negative impacts of this species and also to prevent its expansion into new areas. © 2014, Springer International Publishing Switzerland. Source

Valenzuela A.E.J.,Southern Patagonia Coordination Office | Anderson C.B.,National University of Tierra del Fuego | Anderson C.B.,OSARA Omora Sub Antarctic Research Alliance | Anderson C.B.,CONICET | And 2 more authors.
Acta Oecologica

Understanding processes and impacts of biological invasions is fundamental for ecology and management. Recent reviews summarized the mechanisms by which invasive species alter entire ecosystems, but quantitative assessments of these mechanisms are lacking for actual assemblages to determine their relative importance, frequency and patterns. We updated information on introduced vertebrates in the Tierra del Fuego Archipelago (TDF) via an exhaustive literature review and new data to evaluate ecosystem impact mechanisms and provide management recommendations. To date, 24 exotic vertebrates have naturalized in TDF, outnumbering natives nearly 2:1, with the North American beaver (Castor canadensis) and muskrat (Ondatra zibethica) being the most widely distributed species and also impacting the ecosystem through the greatest number of mechanisms. Introduced vertebrates occupied most parts of the archipelago with human-inhabited islands having greater taxa richness. All exotics potentially altered ecosystems by one or more mechanisms: 100% food webs, 92% invasional meltdown, 42% habitat modification, 38% disease or parasite transmission, 21% soil property and disturbance regime changes. Impact to habitat structure was the main clustering criterion for this assemblage. Within the species that physically alter habitats, we found two sub-groups: 1) large herbivores and 2) "others" including beavers and muskrats. Species that did not alter habitat were divided further into those with predatory trophic effects (carnivorous mammals and trout, sub-group 4) and the rest with assorted impacts (sub-group 3). By establishing high quality information on archipelago-wide assemblage, distribution, impacts and mechanisms for exotic vertebrates, we recommend, based on ecological criteria, prioritizing the management of sub-group 2. A secondary priority might be given to the carnivores in sub-group 4, while species in sub-groups 1 and 3 are less urgent. As the first systematic survey of introduced fauna on an archipelago-scale, we identified knowledge gaps, such as population abundance and dynamics for specific species, which are needed to orient future work, but the notable progress made to date is highlighted. © 2013 Elsevier Masson SAS. Source

Anderson C.B.,National University of Tierra del Fuego | Anderson C.B.,CONICET | Anderson C.B.,Omora Sub Antarctic Research Alliance | Vanessa Lencinas M.,CONICET | And 4 more authors.
Diversity and Distributions

Aim: Ecological theory predicts that invasive ecosystem engineers like the American beaver (Castor canadensis) in Tierra del Fuego (TDF) affect landscape-level biodiversity and ecosystem function (BEF) when engineered habitats are novel or extensive. We tested these hypotheses on freshwater BEF, sampling benthic habitat and macroinvertebrates in natural lotic (forest and grassland streams) and natural lentic habitats (bogs, lakes) and beaver-modified lentic ecosystems (active and abandoned ponds). Location: Tierra del Fuego Archipelago (Chile and Argentina). Methods: To determine effects on patch-scale BEF, we assessed two drivers: substrate diversity (H′) and benthic organic matter standing crop (BOM, g m-2). Extent of impact was estimated as relative stream length (%) for each patch type in four 1000 ha images. Results: The freshwater landscape was 56% free-flowing streams (natural lotic), 13% bogs and lakes (natural lentic) and 31% active and abandoned beaver ponds (beaver lentic). While engineering significantly modified lotic habitats (converting them to ponds), the beaver ponds were largely similar to natural lentic systems, but engineered lentic patches retained more BOM. While benthic biodiversity in beaver ponds was less than streams, the assemblage contained no habitat-specific taxa and was a subset of the natural lentic community. Main conclusions: Invasive beavers engineer habitats whose biodiversity is similar to the landscape's natural lentic habitats, but by increasing the surface area and unit area retention of BOM via its impoundments, this invasion augments carbon standing stock approximately 72% in watersheds. While this invasion is considered the largest alteration to TDF's forested biome in the Holocene, here we discover that its impact is to ecosystem function, rather than biodiversity in the aquatic landscape. © 2013 John Wiley & Sons Ltd. Source

Liljesthrom M.,CONICET | Fasola L.,CONICET | Valenzuela A.,Southern Patagonia Coordination Office | Rey A.R.,CONICET | Schiavini A.,CONICET

A combination of infrared cameras and plasticine eggs were used to identify potential nest predators of Flightless Steamer-Ducks (Tachyeres pteneres) and Flying Steamer-Ducks (T. patachonicus) and to evaluate the relative efficacy of these methods for identifying predators. Cameras were set up at 31 artificial nests with plasticine eggs and at four Flightless and two Flying steamer-duck nests. Two avian predators, Chimango Caracara (Milvago chimango) and Southern Crested Caracara (Caracara plancus), and two mammalian predators, Fuegian Culpeo fox (Pseudalopex culpaeus lycoides) and American mink (Neovison vison), were identified as depredating artificial nests from photos. Active Flightless and Flying steamer-duck nests were found only on islets, and from the photos the Chimango and Southern Crested caracaras were identified as nest predators. Mammalian predators were not photographed on islets (neither on artificial nor natural nests). Though the potential predator community at Lapataia Bay was small, there were considerable similarities in physical evidence and marks left at nests, especially within avian predators. Also, depredated nests were sometimes revisited by other predators and these multi-predator visits sometimes caused changes to the appearance of the depredated nest following departure of the initial predator. The cameras provided an objective method for definitive identification of nest predators. Source

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