Alejandro Valenzuela | Universidad Nacional de Tierra del Fuego (original) (raw)

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Papers by Alejandro Valenzuela

Since their introduction to southern Patagonia in 1946, North American beavers (Castor canadensis... more Since their introduction to southern Patagonia in 1946, North American beavers (Castor canadensis) have become a major impact to streams and forests. Scientists and managers now call for their eradication, requiring research to orient actions. John et al. (2010) showed that predicting beaver presence, which is crucial to plan eradication efforts, varies throughout colonization time (initial = unpredictable occupation of random sites; intermediate = predictable occupation of optimal sites; long-term = unpredictable occupation of sub-optimal loca- tions). Beaver presence/absence and habitat variables (geomorphology, soil, and vegetation) were measured in the field and from satellite images in sites colonized at intermediate (Brunswick Peninsula ~1994) and long-term (Navarino Island ~1960) periods to predict this species' habitat use. Habitat suitability models were constructed using generalized linear models with those variables significantly different between sites with and witho...

Caldasia, 2021

La introducción de especies exóticas puede afectar negativamente a las especies nativas; por ejem... more La introducción de especies exóticas puede afectar negativamente a las especies nativas; por ejemplo, el perro doméstico (Canis lupus familiaris) puede aumentar su riesgo de depredación. Evaluamos el efecto de la presencia de perros y humanos sobre el comportamiento de forrajeo y uso de hábitat del fara, Didelphis pernigra, en un área exurbana en los Andes colombianos. Usamos la técnica de densidades de abandono (DDA), la cantidad de alimento dejada por un forrajeador después de explotar un parche en el que experimenta ganancias decrecientes, y que informa sobre los costos de forrajeo experimentados por un individuo, incluyendo el riesgo percibido de depredación. Medimos las DDA en experimentos en presencia de perro o humano en un área de regeneración natural de bosque andino y en una plantación exótica de Eucaliptus globulus cerca al río Bogotá en Cajicá, Colombia. Los faras utilizaron más el área de regeneración que la plantación; la plantación fue muy poco utilizada. La presencia...

Anales del Instituto de la Patagonia, 2017

Mammal Review, 2016

Invasive introduced mammals (IIMs) have ecological and social dimensions that require holistic re... more Invasive introduced mammals (IIMs) have ecological and social dimensions that require holistic research to integrate academic disciplines with basic and applied sciences. We assessed current knowledge of IIMs to determine trends in their study and management in southern South America. A keyword search was used to select indexed papers in the Web of Science. These were reviewed to assess each study's objective, methodology, country, publication year, and taxa. Unpublished ‘grey’ literature was added to evaluate further each species’ native range, year of introduction, the reason for its introduction, its distribution, dispersal pathways, impacts, and management. Most of the 190 peer-reviewed publications were focused on autecology and impacts of IIMs; less than 4% addressed management or social topics. Twenty-three IIMs have been documented in the study area. The southern Magellanic subpolar forest was the most invaded ecoregion (17 spp.), and the most studied orders, from 440 records in 190 papers, were Artiodactyla (35%) and Rodentia (28%). Together, livestock and commensals brought during early European colonisation constituted 44% of this assemblage, but hunting was the major reason behind the introduction of IIMs (30%). To enhance policies and institutional frameworks pertaining to biological invasions, we highlight the importance of: 1) recognising the presence and spread of IIMs in ‘pristine’ or protected areas; 2) improving controls to prevent new introductions and escapes; 3) including social and cultural aspects of biological invasions in research and management plans; 4) reinforcing hunting regulations; 5) establishing long-term programmes to monitor distribution and dispersion; 6) creating mechanisms for scientists and managers to co-produce research and policy programmes oriented towards applied issues; 7) developing pilot management projects in critical areas; 8) achieving societal involvement in management programmes to ensure public acceptance; and 9) developing prioritisation tools, as resources needed to manage IIMs are often limited.

Ecologia Austral

Editorial Invitada Sección Especial Ecología Austral "Invasiones Biológicas en Patagonia&quo... more Editorial Invitada Sección Especial Ecología Austral "Invasiones Biológicas en Patagonia": Las especies exóticas invasoras (EEI) son una de las causas del cambio ecológico global, afectando los ecosistemas nativos y la biodiversidad regional, produciendo pérdidas económicas y riesgos sanitarios. Si bien existen posiciones contrapuestas sobre la importancia de la biología de invasiones, poniéndose en duda los logros teóricos y prácticos de este campo científico, se propone que es una sub-disciplina tan predictiva como la ecología misma y que las invasiones biológicas representan modelos importantes para poner a prueba hipótesis asociadas a la ecología de comunidades y ecosistemas. Por otra parte, para generar estrategias de manejo de las EEI es esencial no solo entender su biología y sus interacciones con el ecosistema invadido, sino también realizar investigación aplicada. Pese al notable aumento de investigaciones sobre invasiones biológicas en Latinoamérica en las última...

Diversity and Distributions, 2013

ABSTRACT AimEcological theory predicts that invasive ecosystem engineers like the American beaver... more ABSTRACT AimEcological 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). LocationTierra 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, gm(-2)). Extent of impact was estimated as relative stream length (%) for each patch type in four 1000ha images. ResultsThe 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 conclusionsInvasive 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.

Annales Zoologici Fennici, 2012

Revista de la Sociedad Entomológica Argentina, 2015

Vespula germanica is an invasive worldwide species that has been detected in continental Patagoni... more Vespula germanica is an invasive worldwide species that has been detected in continental Patagonia of Argentina and Chile. In this work, we extend the range of this invasive wasp in Patagonia to include the Tierra del Fuego Archi- pelago. We indicate the location, year and habitat of each sighting and/or collection. The expansion pattern of this species indicates that it is well established in natural and anthropogenic areas and that it has most probably depended on human trans- port to arrive from the continent. This short communication also provides information to take practical measures for its mitigation and control, including basic information for the citizens of the island to become aware of its presence and help it not arrive to new areas. Finally, more research is recommended for management and control of this new invasive species in Tierra del Fuego.

The American mink (Neovison vison) is a semi-aquatic mustelid that was released on Tierra del Fue... more The American mink (Neovison vison) is a semi-aquatic mustelid that was released on Tierra del Fuego Island in the 1940's, subsequently spreading throughout the whole archipelago. Its introduction to other insular systems around the world has caused the reduction and ...