Until now, nonnative plant species were rarely found at high elevations and latitudes. However, partly because of climate warming, biological invasions are now on the rise in these extremely cold environments. These plant invasions make it timely to undertake a thorough experimental assessment of what has previously been holding them back. This knowledge is key to developing efficient management of the increasing risks of cold-climate invasions. Here, we integrate human interventions (i.e., disturbance, nutrient addition, and propagule input) and climatic factors (i.e., temperature) into one seed-addition experiment across two continents: the subantarctic Andes and subarctic Scandinavian mountains (Scandes), to disentangle their roles in limiting or favoring plant invasions. Disturbance was found as the main determinant of plant invader success (i.e., establishment, growth, and flowering) along the entire cold-climate gradient, explaining 40-60% of the total variance in our models, with no indication of any facilitative effect from the native vegetation. Higher nutrient levels additionally stimulated biomass production and flowering. Establishment and flowering displayed a hump-shaped response with increasing elevation, suggesting that competition is the main limit on invader success at low elevations, as opposed to low-growing-season temperatures at high elevations. Our experiment showed, however, that nonnative plants can establish, grow, and flower well above their current elevational limits in high-latitude mountains. We thus argue that cold-climate ecosystems are likely to see rapid increases in plant invasions in the near future as a result of a synergistic interaction between increasing human-mediated disturbances and climate warming.

According to the global latitudinal diversity gradient, a decrease in animal and plant species richness exists from the tropics towards higher latitudes. The aim of this study was to describe the latitudinal distribution patterns of Chilean continental flora and delineate biogeographic regions along a 4270-km north-south gradient. We reviewed plant lists for each of the 39 parallels of continental Chile to build a database of the geographical distribution of vascular plant species comprising 184 families, 957 genera and 3787 species, which corresponded to 100%, 94.9% and 74.2% of the richness previously defined for Chile, respectively. Using this latitudinal presence-absence species matrix, we identified areas with high plant richness and endemism and performed a Cluster analysis using Jaccard index to delineate biogeographic regions. This study found that richness at family, genus and species levels follow a unimodal 4270-km latitudinal distribution curve, with a concentration of richness in central Chile (31-42°S). The 37th parallel south (central Chile) presented the highest richness for all taxonomic levels and in specific zones the endemism (22-37°S) was especially high.This unimodal pattern contrasts the global latitudinal diversity gradient shown by other studies in the Northern hemisphere. Seven floristic regions were identified in this latitudinal gradient: tropical (18-22°S), north Mediterranean (23-28°S), central Mediterranean (29-32°S), south Mediterranean (33-37°S), north temperate (38-42°S), south temperate (43-52°S) and Austral (53-56°S). This regionalization coincides with previous bioclimatic classifications and illustrates the high heterogeneity of the biodiversity in Chile and the need for a reconsideration of governmental conservation strategies to protect this diversity throughout Chile.

Se reportan los resultados de las excursiones botánicas realizadas durante los años 2006-07 a las cuencas de los ríos Baker y Pascua en la Región de Aisén, Patagonia chilena. Se encontraron 342 taxa de plantas vasculares, 302 en la cuenca del río Baker y 124 en río Pascua. Las familias mejor representadas son Poaceae (52), Asteraceae (50) y Cyperaceae (15). Cuatro especies endémicas de Chile fueron encontradas en la cuenca del río Baker. PALABRAS CLAVES: Flora de Chile, Patagonia chilena, conservación, plantas invasoras.

RESUMENUno de los principales objetivos de la biogeografía es determinar si las especies se distribuyen en el espacio en forma aleatoria o si existen grupos de especies con patrones de distribución comunes. En el presente estudio determinamos a través de técnicas cuantitativas si existen corotipos, es decir, grupos de especies con patrones de distribución común entre los árboles y arbustos en la zona de transición climática mediterráneo-templada de Chile, Octava Región de Chile. Adicionalmente, evaluamos la relación entre el clima y la distribución de los diferentes grupos de árboles y arbustos de la Octava Región. El análisis de agrupamiento de especies permitió definir 24 corotipos significativos, de los cuales 18 responden significativamente con alguna variable ambiental analizada. La temperatura media anual, la temperatura media invernal y la temperatura media de verano resultaron ser las variables que mejor explican el patrón de distribución de la mayoría de los corotipos. Las tendencias geográficas de los corotipos y su relación con las variables ambientales fueron evaluadas mediante un análisis de ordenación. Los resultados señalan que los corotipos con distribución en la cordillera de los Andes se correlacionan con la temperatura de invierno en tanto que los corotipos con distribución costera se correlacionan con la mediterraneidad. Se discute respecto de la utilización de una nueva aproximación para el análisis fitogeográfico y de su utilidad en el estudio de la relación entre la vegetación y los factores ambientales que determinan su distribución.Palabras clave: corología, corotipo, variables ambientales, fitogeografía, transición climática. ABSTRACTOne main aim of biogeography is to determine if species are randomly distributed or if there exist groups of species with common distributional patterns known as chorotypes. In this study, we determined through quantitative techniques if there exists such chorotypes for trees and shrubs in the transitional Mediterraneantemperate climatic zone of Chile, Eigth Administrative Region of Chile. Additionally, we evaluated the relationship between climate and distribution of the different chorotypes. The analyses allowed defining 24 significant chorotypes, 18 of which were significantly associated with some used environmental variable. Mean annual temperature, mean summer temperature and mean winter temperature were the variables that explained the distribution of most of the chorotypes. The geographic tendencies of chorotypes and their relationship with environmental variables were evaluated with canonical correspondence analysis. The results indicated that chorotypes distributed in the Andes Range were correlated with the mean winter temperature, whereas chorotypes with coastal distribution were correlated with mediterreanity. We discusses the use of new approaches for phytogeographic analysis and its utility in the study of the relationship between vegetation and environmental factors that determine its distribution.

Aim To analyse quantitatively the biogeographical distribution pattern of species of the Cytiseae Bercht. & J. Presl (¼ Genisteae Benth.) tribe in the Iberian Peninsula and the Balearic Islands, and to identify environmental variables related to the distributional patterns.Location Iberian Peninsula and Balearic Islands, using the 61 administrative provinces as operational geographical units.Methods In order to identify chorotypes (groups of species with similar geographical distribution), we performed a upgma classification based on the similarity index of Baroni-Urbani & Buser. The method of McCoy et al. [Ecology 67 (1986), 749] enabled us to detect the significant groups and to differentiate them from those groupings that could be generated at random. Logistic regression analyses and environmental gradient analyses (DCA and CCA) were performed in order to find the relationships between the environmental variables and the observed distributional patterns.Results Sixteen chorotypes were obtained between the Cytiseae species of the Iberian Peninsula and the Balearic Islands. The thermal variables showed the greatest influence in species distribution. Specifically, temperatures (maximum, minimum and mean) of the coldest months were associated with the majority of the chorotypes. Main conclusionsThe species of the Cytiseae tribe were not randomly distributed in space, and can be classified in groups of species with common distributional patterns. The importance of cold tolerance in the distribution of these species, as well as their preference for acidic soils, was demonstrated. Certain general tendencies seem to exist with respect to the distribution of the biota in the Iberian Peninsula, and these seem to be independent of the taxonomic groups involved and to be determined by convergent macroclimatic factors.