The geographical extent of exotic plant species is a major component of invasiveness, which has been explained by intrinsic attributes of the plants, such as growth rate, reproductive type, life form, and biogeographical origin. We assessed quantitatively life cycle and biogeographical origin as determinants of the geographical distribution of naturalized plants in continental Chile, using minimum residence time (MRT) as an estimator of introduction date. We assembled a database with information on 428 plants (principally herbs) in continental Chile, corresponding to 61% of the exotic naturalized flora. For each species we recorded: (1) minimum residence time (introduction date or first recorded date in the country); (2) biogeographical origin (American, Eurasian, others); (3) life cycle (annual, perennial, others); (4) number of Chilean regions occupied by the plant. We found that 82 species (19%) have been recorded in only one region of Chile, while only three species have been found in all 13 regions of the country. About 89% of the species (381) have been found only in central Chile (Regions IV to VIII), while the remaining 11% (47) are found only in the northern (Regions I to III) or southern parts of the country (Regions IX to XII). We detected significant differences in regional spread of naturalized plants according to minimum residence time: those species with shorter MRT had more limited spread ranges than those with longer MRT. Biogeographical origin and life cycle did not explain geographical extent in Chile. This study shows that historical factors are more important than biological ones in determining the geographical extent of naturalized plants in continental Chile. Thus, caution should be exercised when assigning value to biological attributes that may confer invasiveness to naturalized plants.

Summary• In a comparative study of 26 Chilean temperate woody species, the following questions were addressed. Are germination requirements correlated with seedling light requirements? Can germination requirements be used to delimit pioneer and nonpioneer guilds?• To assess dependence of germination on canopy gaps, germination percentages were compared experimentally in gap and understorey environments. Seedling light requirements were quantified by determining the mean light environment naturally occupied by juveniles of each species.• Germination was significantly higher in the gap than in the understorey in > 30% of the species, although only one germinated exclusively in the gap. In the understorey, germination was higher in 19% of species, whereas 50% were indifferent to germination environment. Several light-demanding species germinated abundantly in the understorey. Both cross-species analysis and phylogenetically independent contrasts showed that seedling light requirements were not correlated with responsiveness of germination to the gap environment.• Results suggest that germination requirements and seedling light requirements are not coupled, and that requirement of canopy gaps for germination cannot be used to delimit pioneer and nonpioneer guilds in a Chilean temperate rain forest.

We review the literature on patterns, causes, processes and impacts of exotic plants, primarily in the mediterranean region of Chile, considering three major non-independent drivers of the invasion process: (a) Availability of exotic species propagules, (b) attributes of the local communities in which exotic species establish and through which they will eventually spread out, and (c) attributes of exotic species that either facilitate or constraint their spread into new sites. Regarding availability of propagules, central Chile matorral presents the communities with the greatest incidence of naturalized herbs, followed by the sclerophyllous forest and the espinal scrubland in the coastal range. In contrast, north-central communities have lower numbers and proportions of naturalized species of herbs in their seed banks. Availability and persistence of naturalized herbs do not differ between aboveground vegetation and seed bank. Regarding attributes of local communities associated with the establishment and the spread of exotics, grazing regime and land use emerge as the most prominent causes that render them more prone to invasion by exotics. Evidence on the effect of the fire regime is contradictory and native species richness does not seem to be an important factor. Regarding attributes of exotic species seeds, results suggest that naturalized annuals germinate within a wide temperature range, are highly resistant to cold and dry conditions, and show some degree of physiological dormancy. Additionally, naturalized annuals are highly tolerant to poor soils, but are generally intolerant to shade. These general attributes have largely determined the invasion process in the mediterranean region of Chile. Historical data indicate that an important number of exotic species were intentionally introduced, and that the spread of exotic is uncontrolled. It has been demonstrated that arrival time of exotics is of great relevance to understand present day spread of exotics in Chile, independent of their biogeographic origin. Exotic species may cause strong disruptions of ecosystem processes and functions in Chile, as exemplified by exotic tree plantations, which have altered soil chemistry, nutrient cycling, water cycle, hydrology, microclimate, and fire frequency and intensity.

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Delayed seed germination (‘dispersal in time’), as a component of a plant’s germination strategy, was studied in dicotyledoneous species of a temperate rainforest flora in Chiloé Island (42°30′S), southern Chile. The objective of this investigation was to assess, for this temperate rainforest flora, what proportion of interspecific variation in the time of seed germination—measured in days since the onset of seed dispersal in space—could be attributed to the plants’ historical and phylogenetic background and what proportion was associated with life history and ecological attributes such as seed mass, life form, dispersal syndromes and dispersal periods. To characterise germination times for 44 species from Chiloé forests (n = 150 seeds sowed per species in laboratory assays), we computed the mean germination time (GT), in days since sowing, for all seeds germinated of each species. Seeds were taken from the plants at the onset of dispersal and germinated in Petri dishes at 10/20°C. Considering all species, GTs varied between 3 and 385 days and presented an L-shaped frequency distribution. One-way ANOVAs measured the effects of each factor across all other variables. Two-way ANOVAs were used to assess significant interactions between factors. Multifactorial ANOVAs were used to evaluate the independent effects of each of six historical, phylogenetic and ecological factors on GT and to detect associations between factors. In one-way ANOVAs, phylogenetic grouping (at or above order) explained 12% of the variance in GT; dispersal period (summer v. mainly autumn dissemination of ripe seeds), biogeographic element (endemic, austral, neotropical or cosmopolitan) and dispersal syndrome (fleshy v. dry propagules) explained 7, 6 and 5% of the variance in GT, respectively. The factors life form (trees, shrub and woody vines combined, herbs and non-woody epiphytes) and seed mass (light v. heavy) explained the 4 and 2% of the variance in GT, respectively. Taxa related to Ranunculales presented the longest mean GT (148 days). Endozoochorous species had a more delayed germination than species with other dispersal syndromes. Herbs and non-woody epiphyte species showed mean GT (41 days) significantly shorter than trees and shrubs plus woody vines combined (86 and 85 days, respectively). All interactions in two-way ANOVAs were significant. Multifactorial ANOVAs revealed that the three major factors contributing to differences in GT in this temperate rainforest flora were phylogenetic relatedness, dispersal syndromes and life form (7, 6 and 6% of the interspecific variation, respectively). In this analysis, biogeographic element, dispersal period and seed mass were not significantly related to GT. For the factors examined, failure-time analysis, which takes into account all viable seeds not germinating in laboratory assays, confirmed results from multifactorial ANOVAs.

Seedlings of nine southern Chilean trees were grown at three nutrient supply rates, to examine the roles of growth rate, biomass distribution and nutrient use traits in determining species natural distributions on resource gradients. Relative growth rate (RGR) showed no overall relationship with species site requirements, although RGR of fertile-site species tended to be more responsive to nutrient supply. In the low-nutrient treatment, infertility-tolerant Fitzroya cupressoides showed a higher RGR rank than a fertility-demanding species (Laurelia philippiana) which outgrew it substantially at the highest supply rate. This reversal of RGR ranks was associated with divergent nutrient use responses: at high nutrient supply both spp. had similar plant nitrogen concentrations (PNC), whereas at the low supply rate Fitzroya's production of biomass per unit of assimilated N was twice that of Laurelia's. However, this pattern does not appear to serve as a general explanation of the respective distributions of the study species, as RGR ranks of most species were unaltered by nutrient supply. At low nutrient availability, no clear differences in shoot:root ratio (SRR) were apparent between poor-site and fertile-site species. However, at high nutrient availability, SRR was markedly higher in the latter, resulting from differences in biomass allocation to stems (not leaves). Leaf area ratios (LAR) were higher in fertile-site species than in those tolerant of low fertility, because of differences in specific leaf area rather than leaf weight ratio. Very high LAR at high nutrient supply was characteristic of most shade-tolerant angiosperms, but not of shade-tolerant conifers. Although PNC showed no overall differences between poor- and fertile-site species, sensitivity of PNC to external supply rate was greatest in two infertility-tolerant conifers. In contrast, the angiosperm Weinmannia trichosperma, although tolerant of low fertility, responded to increased nutrient supply with greatly increased RGR and little change in PNC. Results show little trait convergence between conifers and angiosperms in adaptation both to shade and to infertile soils; i.e. fitness of different taxa in a given environment may hinge on different trait combinations.

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