Diversity patterns and composition of native and exotic floras in central Chile

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(1)Acta Oecologica 37 (2011) 103e109. Contents lists available at ScienceDirect. Acta Oecologica journal homepage: www.elsevier.com/locate/actoec. Original article. Diversity patterns and composition of native and exotic floras in central Chile Javier A. Figueroa a, b, e, *, Sebastián Teillier b, Sergio A. Castro c, d, e a. Laboratorio de Ecología Vegetal, Instituto de Biología, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 330, Curauma, Placilla, Valparaíso, Chile Escuela de Arquitectura del Paisaje, Facultad de Arquitectura y Urbanismo, Universidad Central de Chile, Chile c Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Chile d Centro de Desarrollo de la Nanociencia y Nanotecnología (Cedenna), 917-0124 Santiago, Chile e Center for Advanced Studies in Ecology and Biodiversity (CASEB), Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago CP 6513677, Chile b. a r t i c l e i n f o. a b s t r a c t. Article history: Received 19 May 2010 Received in revised form 17 December 2010 Accepted 3 January 2011 Available online 3 February 2011. Floristic changes in the Mediterranean region of central Chile brought about by human impact appear to be shared with other climatic regions, although there is a notable absence of empirical studies and available quantitative evidence for the central Chile region. This study examines the cover, richness and composition of native and exotic plant species in a representative area of central Chile. Through floristic characterization of 33 sites sampled using 40 40 m plots distributed along transect on which the two farthest sites were separated by 50 km, the floristic richness and cover patterns, as well as the general land use characteristics were evaluated (native matorral, espinal, abandoned farming field, forest plantations, periurban sites, road sites, river bank, and burnt site). We recorded 327 species of plants; 213 species were native and 114 were exotic. The average number of species was heterogeneous in all sites, showing a greater relative native frequency in those sites with a lower level of anthropic intervention. Except for the matorral, the cover of exotic species was greater than that of native species. No relation was found between richness and cover in relation to the different types of land use. The relationship between cover of native and exotic was negative, although for richness did not show relationship. Results show that the exotic species are limited by resources, although they have not completely displaced the native species. The native and exotic floras respond to different spatial distribution patterns, so their presence makes it possible to establish two facts rarely quantified in central Chile: first, that the exotic flora replaces (but does not necessarily displace) the native flora, and second, that at the same time, because of its greater geographic ubiquity and the abundance levels that it achieves, it contributes to the taxonomic and physiognomic homogenization of central Chile. Ó 2011 Elsevier Masson SAS. All rights reserved.. Keywords: Floristic similarity Introduced species Species richness Species turnover. 1. Introduction The world’s Mediterranean-type ecosystems are characterized by presenting high levels of floristic richness (Davis et al., 1994). It is estimated that nearly 20% of the world’s flora is found in the five Mediterranean-type regions, which together cover less than 5% of Earth’s surface area (Cowling et al., 1996). Various ecological and evolutionary factors have been suggested to explain this diversity (di Castri, 1981; Arroyo et al., 2000), which is important not only because of its richness, but also because of its high level of endemism (Myers et al., 2000). In spite of this importance, Mediterranean-type ecosystems have undergone substantial changes in their structure and ecosystemic. * Corresponding author. Instituto de Biología, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile. Tel.: þ56 32 2274843. E-mail address: javier.fi[email protected] (J.A. Figueroa). 1146-609X/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.actao.2011.01.002. functions as a consequence of human impact (Rundel, 1998). At present these regions support a large and increasing proportion of the world’s human population, with equally increasing demands for space and natural resources (Rundel, 1998; Sala et al., 2000). As a consequence of this the biota in these ecosystems is seriously threatened; hence they are considered hotspot regions on the global scale (Myers et al., 2000). The modification of diversity in the Mediterranean-type ecosystems is manifested in all biological groups and under various temporal and spatial scales (Mooney et al., 1989). Of particular importance are the changes in floristic composition because this involves conspicuous modifications in the physiognomy, structure and function of the ecosystems (Randall et al., 1998). Modifications of the flora comprise two mechanisms (McKinney and Lockwood, 1999): extinction or extirpation of species, and the concomitant increase of the number of species introduced by humans (Groves and di Castri, 1991; Gaertner et al., 2009). Therefore, the balance between both processes is one of the main agents that determine.

(2) 104. J.A. Figueroa et al. / Acta Oecologica 37 (2011) 103e109. the floristic future of these ecosystems, whose magnitude and trends have yet to be established empirically. The Mediterranean-type area of central Chile (31e38 S) corresponds to one of the world’s five Mediterranean ecosystem regions (Cody and Mooney, 1978). This region contains a floristic richness of 2395 native species, of which 50% are endemic (Arroyo et al., 1995; Arroyo and Cavieres, 1997). Moreover, there are 507 exotic species that represent 18% of total flora (Arroyo et al., 2000). This proportion is relatively low compared to California, its closest climatic analogue, even standardizing that number per unit area (Arroyo et al., 2000; Jiménez et al., 2008). However, regardless of this regional scenario, the processes and mechanisms that determine the diversity of native and exotic species and the patterns that characterize their distribution are aspects that are little understood in central Chile (Figueroa et al., 2004). In this line, only three comparative studies with California have made some progress. Firstly, Arroyo et al. (2000) analyzed the patterns of richness of weed species from a political-administrative standpoint. They found that the number of weed species was significantly associated with the type of land use, particularly with urban areas and roads. Later, Sax (2002), in a comparative study of xerophytic bushy communities in the arid portion of Mediterranean Chile, reported that the diversity of exotic species correlated positively with that of native species. Finally, Jiménez et al. (2008) compared the taxonomic composition of the exotic flora of Chile and California, finding that in spite of the compositional differences between the two regions, in the presence of human perturbation both floras tended to increase in similarity. The latter authors suggested that due to the process of globalization and the increase of anthropic perturbations, the regional floras may tend to become homogenized. Although many of the floristic changes in the Mediterranean region of central Chile appear to be shared with other climatic regions (i.e. Randall et al., 1998; Loreau et al., 2001; Western, 2001; Gritti et al., 2006; Manor et al., 2008), there is a notable absence of empirical studies and quantitative evidence in this region. In the present study we characterize the diversity, richness and compositional patterns of the vascular flora in a representative area of the Mediterranean region of central Chile. Distinguishing between native and exotic floristic components, we evaluated at the landscape level, their spatial distribution, richness, and coverage patterns in relation to sites that differ in type of use and intensity of the anthropogenic perturbations. The questions that we will attempt to answer are (1) what is the relation between species richness and cover of native and exotic species? (2) what local scale factors can be associated with the richness and composition of exotic and native species? and (3) what sizes and trends in floristic change can be established for the Mediterranean region of central Chile? 2. Materials and methods 2.1. Study area The study was conducted in the western sector of the Coastal Range in central Chile, over a distance of 50 km (around 33 S, see Fig. 1). In general terms, this area has regional importance due to its character as a floristic refuge during the last glaciations (Villagrán and Armesto, 2005). This geographic strip, below 1300 masl, has a Mediterranean-type climate characterized by an average annual precipitation of 435 mm and mean temperatures that reach 18.5 C in the warmest month and 10.2 C in the coldest month of the year (Luebert and Pliscoff, 2006). In terms of vegetation, the formations originally recognized for our study area correspond to sclerophyllous coastal forest, characterized by the presence and dominance of woody species with sclerophyllous leaves (Gajardo, 1994). At present, the. Fig. 1. Geographic location of the 33 sites sampled among Olmué, Concón and Casablanca, Valparaíso Province, Chile.. vegetation physiognomy of this area shows various structures and effects as a consequence of human intervention, among which we can recognize the so-called matorral, which corresponds to a successional remnant of the original native sclerophyllous forest; the espinal formations where most of the tree cover has been removed and replaced by the presence of espino (Acacia caven, a native Fabaceae) in the bushy-arboreal stratum and by exotic grasses in the herbaceous stratum; farming sites where intensive cultivation is associated with the presence of exotic weeds and native annuals; and forest plantations consisting mainly of the exotic species Pinus radiata, Eucalyptus globulus, and Eucalyptus camaldulensis (Teillier et al., 2010). 2.2. Sampling Over a distance of 50 km we selected 33 sampling sites according to their accessibility (Fig. 1). In each of them a 40 40 m plot was made available, except in the sites located on the edge of roads (N ¼ 7 sites), where plots of 2 m 400 m were used. At the center of each plot the geographic coordinates were determined by GPS (Garmin GPSmap 60CSx). Within each plot the vascular flora composition and cover of both the native and exotic components were established. The cover was established by means of the abundance-frequency scale of Braun-Blanquet (1979), and the values were then converted into percentages in accordance with the following equivalence: 5 ¼ 87.5%; 4 ¼ 62.5%; 3 ¼ 37.5%; 2 ¼ 17.5%; 1 ¼ 5%; þ ¼ 0.1% (Braun-Blanquet, 1979). The geographic distance was also determined for all the pairs of sample sites, as well as the current use of the soil in each plot. The geographic distance was set as the linear distance (km) between the plots using GPS, while the vegetation condition of land use of each site was inferred according to the following classification: matorral sites (MAT ¼ 4 sites), espinal sites (ESP ¼ 7 sites), abandoned crop sites (AGR ¼ 6 sites), and forest plantations (FOR ¼ 5 sites). Other sites were classified with respect to their location, periurban sites (URB ¼ 2 sites), road edge sites (ROA ¼ 7 sites), river bank (RIV ¼ 1 site), and recent fire condition (BUR ¼ 1 site burnt <3 years). Since fires are intentional in central Chile, the vegetation types had been burnt at some stages by human cause (Rundel, 1998). Nevertheless, in our study only 1 of the 33 sites showed evidence of having been affected by fires recently. The matorral corresponded to successional native forests with low trees and canopy cover above 70%. The espinal site was dominated by the woody Fabaceae A. caven, which presents a cover of <40.0%. The soil of the crops had been abandoned for at least three years and occasionally they presented shoots of woody plants. Forest.

(3) J.A. Figueroa et al. / Acta Oecologica 37 (2011) 103e109. plantations corresponded to fast-growing exotic trees (Pinus radiate and Eucalyptus globules mainly) that were poorly managed, and so presented abundant herbaceous in the understory. 2.3. Data analysis From a floristic standpoint we compared the distribution of richness (S) and cover of native and exotic species. Similar to Guo and Symstad (2008), we used the proportion of species richness and cover to reduce the effects of factors such as area and resource availability. To recognize differences in the exotic and native proportion of richness and cover in each and across the 8 land types we used paired t-tests and the ManneWhitney Rank Sum test when a normality test failed (Sokal and Rohlf, 1995). To investigate the strength of various relationships among native and exotic richness, native and exotic covers and proportion of species richness and cover across the 8 land types we used linear regression. Then we studied the floristic composition patterns by determining the floristic similarity between the sites. Here we used the Jaccard index (Jaccard, 1900) applied separately for the set of native and exotic species. The Jaccard index is determined by the following algorithm: J ¼ c (a þ b c)1, where c represents the number of species shared by two sites, a is the number of species in a site, and b is the number of species present in the other site. The values of this index vary between zero and one to indicate null or total similarity, respectively, and they can be presented as percentages from 0 to 100%. In this way we obtained two similarity matrices between sites, which were represented as cladograms using the UPGMA procedure (McGarigal et al., 2000). Finally, we evaluated the effect of the geographic distance on the similarity patterns of both native and exotic species. For this purpose we applied the Mantel test (Webster and Oliver, 2001) for the different floristic similarity matrices (i.e., native and exotic) versus the matrix of geographic distance between sites. 3. Results 3.1. Patterns of richness and cover We recorded 327 species of vascular plants in the 33 sites sampled. Of them, 213 species were native and 114 were exotic. Analysis of the sites according to the type of land use showed that species richness was distributed heterogeneously among them (Table 1). The largest number of species was recorded in sites disturbed with espinal (N ¼ 176), road edge (N ¼ 152) and abandoned farming field (N ¼ 150), while the lowest richness occurred in the burnt site, (N ¼ 41; see Table 1). When we analyzed the proportion of richness of native and exotic species according to the land use, the results showed that matorral, abandoned field and espinal were strongly dominated by native flora (Table 1). Although in the 3 sites (matorral, road edge and abandoned farming field) the proportion of native species was significantly greater than of exotic species (Table 1), for all the sites combined the proportion of native and exotic species did not present differences. When we analyzed proportion of cover of native and exotic species by site, the results were heterogeneous. The matorral was strongly dominated by native cover, whereas road edge and abandoned field were strongly dominated by exotic cover (Table 1). However, the proportion of cover of exotic species was significantly greater than that of native species across the 8 sites combined (Table 1). In the other 5 sites (espinal, river bank, forest plantation, periurban and burnt), the proportion of cover did not show significant differences between native and exotic species (Table 1).. 105. Table 1 Native and exotic proportion of richness, and native and exotic proportion of cover in 8 types of land use in central Chile. MAT: matorral; ROA: road edge; AGR: abandoned farming field; ESP: espinal; RIV: river bank; FOR: forest plantation; URB: periurban site; and BUR: burnt site. The total number of species (N) recorded for each site and the number of plots used in the sampling (NPlots) are also shown. Paired t-tests were used for statistical analysis. ns ¼ P > 0.05. Proportion of richness. Proportion of cover. Native. Exotic. P. Native. Exotic. P. Total N. MAT ROA AGR ESP RIV FOR URB BUR. 83.6 49.5 23.8 63.2 48.6 64.2 13.5 55.8. 16.4 50.5 76.2 36.8 51.4 35.9 86.5 44.2. 0.029 ns <0.001 0.017 ns ns ns ns. 86.9 30.6 6.2 35.5 44.5 30.7 1.8 33.4. 13.1 69.4 93.8 64.5 55.5 69.3 98.2 66.6. <0.001 0.05 <0.001 ns ns ns ns ns. 133 152 150 176 70 134 78 41. 4 7 6 7 1 5 2 1. Total. 50.3. 50.0. ns. 31.3. 68.7. <0.001. 327. 33. NPlots. The relationship between covers of native and exotic species was negative (Fig.2A) although richness did not show a significant relationship (Fig. 2B). When we analyzed the relationship between richness and cover of exotic species, the tendency was positive but weak, although significant (r2 ¼ 0.12) (Fig. 2C). However, the relationship between richness and cover of native species was more strongly positive, accounting of 27% of the variation (P ¼ 0.002) (Fig. 2D). We also found a positive regression between exotic proportion of richness and cover (r2 ¼ 0.43; P < 0.001), as we did when considering the native proportion (r2 ¼ 0.43; P < 0.001) (Fig. 2E and F). 3.2. Patterns of floristic similarity The floristic similarity between sites calculated using the whole set of native species had an average value of 11.6%, with a range of 0.0e39.0%. Interestingly, grouping the sites according to their level of floristic similarity (Fig. 3A) did not show a consistent conglomeration of sites with similar soil use. In fact, the greatest similarity levels were recorded between abandoned farming sites (AGR5), forest plantations (FOR3), and periurban sites (URB2). On the other hand, the similarity calculated for the exotic flora showed an average value of 22.1%, with a range of 0.0e58.6%. Again, cladogram grouping (Fig. 3B) did not show consistent groupings between the use condition and the composition of the soil. Here the clade of greatest floristic similarity grouped an abandoned farming site (AGR5) and a periurban site (URB2). Comparing the similarity levels recorded for native and exotic floras, it was seen that the similarity calculated using native species was significantly less than that obtained for the exotic flora (U ¼ 19.8; P < 0.05), implying that the sites sampled share a larger number of exotic than native species. The floristic similarity values of native as well as exotic species were associated negatively with geographic distance (Fig. 4A and B). Their parameters and correlation levels were: J ¼ 9E05 DIST þ 13.5 (r ¼ e0.182), and J ¼ 9E05 DIST þ 24.2 (r ¼ 0.120), respectively. Of these, only the case of the native flora showed a statistically significant relation (P < 0.05) (Fig. 4A). 4. Discussion In terms of the number of species of exotic plants present in the area, central Chile has been considered a region that is less invaded or is in an earlier stage of invasion than other regions of the world, including other Mediterranean-type ecosystems (Arroyo et al., 2000; Figueroa et al., 2004; Jiménez et al., 2008). However, our.

(4) 106. J.A. Figueroa et al. / Acta Oecologica 37 (2011) 103e109. 140. 45. A. r² = 0.428 P < 0.001. B. 40 Number of Exotic Species. Cover of Exotic Species (%). 120 100 80 60 40 20. r² = 0.08 P = 0.1. 35 30 25 20 15 10 5. 0. 0 0. 20. 40. 60. 80. 100. 120. 0. 10. Cover of Native Species (%) 140. 120. C. r² = 0.124 P = 0.044. 100 80 60 40. 40. 50. 60. D. r² = 0.2685 P = 0.002. 80. 60. 40. 20. 20 0. 0 0. 10. 20. 30. 40. 50. 0. 10. Number of Exotic Species 120. E. 20. 30. 40. 50. 60. Number of Native Species. 120. r² = 0.4331 P < 0.001. Native Proportion of Cover. 100 Exotic Proportion of Cover. 30. 100 Cover of Native Species (%). Cover of Exotic Species (%). 120. 20. Number of Native Species. 80. 60. 40. F. r² = 0.4322 P < 0.001. 100 80 60 40 20. 20. 0. 0 0. 20. 40. 60. 80. 100. Exotic Proportion of Richness. 0. 20. 40. 60. 80. 100. Native Proportion of Richness. Fig. 2. Relationship between cover of exotic and native species (A), number of native and exotic species (B), number of exotic species and cover of exotic species (C), number of native species and cover of native species (D), exotic proportion of richness and exotic proportion of cover (E) and native proportion of richness and native proportion of cover (F).. results indicate that the richness and abundance of exotic species on a local scale constitute a problem of concern for the conservation of the native flora in the region. In fact, as shown by our study, at the local level the exotic flora cover can be three times the native species cover. Clearly, the exotic flora tends to be more abundant and physiognomically more important than the native flora, a fact that until now has lacked a quantitative magnitude indicator at the local scale in central Chile. Recent research indicates that the presence of exotic species can effectively exclude native plant species in Mediterranean-type. ecosystems (Gaertner et al., 2009). Studies conducted on small scales reveal the stronger impact of exotic invasion on native species richness. Evidence of this kind for central Chile is particularly scarce (Sax, 2002; Figueroa et al., 2004; Castro et al., 2005; Pauchard et al., 2008). However, it is improbable that this mechanism is responsible for the lower representation of native flora on a local level (Mooney et al., 1989; Bustamante and Simonetti, 2005; Arroyo et al., 2000). Rather, the high rate of anthropogenic perturbation in the soils that were studied seems to facilitate the expansion of exotic species and the reduction of native species.

(5) J.A. Figueroa et al. / Acta Oecologica 37 (2011) 103e109. 107. Fig. 3. Floristic similarity dendrograms of the 33 sites sampled. (A) Floristic similarity calculated using only native species. Average floristic similarity ¼ 11.6. (B) Floristic similarity calculated using only exotic species. Average floristic similarity ¼ 22.1..

(6) 108. J.A. Figueroa et al. / Acta Oecologica 37 (2011) 103e109. Fig. 4. Relation of floristic similarity for the 33 sites sampled and geographic distance. (A) Native species; (B) exotic species.. representation (Williamson, 1996; Arroyo et al., 2000). As there might be pre-existing differences prior to invasion, it is difficult to attribute reduction of native species exclusively to exotic plants (Gaertner et al., 2009). Two key questions here are (1) what specific anthropic activities promote the invasion and spread for the naturalized species? and (2) in what way is native species diversity reduced in response to these perturbations? To date only a few studies suggest possible explanations in response to these questions. For example, Sax (2002) has shown that native and exotic plant richness are positively correlated, even in sites exposed to fire a year or more ago. This author’s work took place in semi-arid environments, whose land use pattern differs from that of our area. However, in our study the native and exotic covers are negatively correlated (Fig. 2A) suggesting that exotic cover may be limited by space or resources (Guo and Symstad, 2008). This is consistent with that found in the xeric-sloped matorral in central Chile; then, it appears that competition between herbaceous native and naturalized species may be affecting their abundance in post 1-year burn sites (Sax, 2002). When considering native and exotic richness, although the relation was negative we found no significant association (Fig. 2B). For example, in matorral and road edge sites there is higher cover of exotic species than expected from the richness due to the presence of strongly invasive species (e.g. Trifolium tomentosum, Vulpia myuros, Lolium multiflorum and Avena barbata) (Table 1) and to the response of the native plants to a different perturbation regimen. These results indicate that a few invasive exotics can account for. a great amount of abundance even when they are only a minor fraction of the richness (Guo and Symstad, 2008). When the invisibility is measured in terms of exotic richness of a community, abandoned farming field sites are the most invaded of the 8 sites studied. Similarly, when the degree of invasion is expressed as exotic cover, the abandoned field is physiognomically dominated by the exotic flora. Agricultural fields are the source of various exotic plants that remain for several years after the fields are abandoned, and the fields remain in a degraded state that prevents the establishment of native plants (Cramer et al., 2008). Consistently, we find that the native matorral composed of low trees and canopy cover above 70% presented the lowest degree of invisibility, which is supported by results from other forest habitats (Knight et al., 2008; Manson et al., 2009; Gaertner et al., 2009). According to Arroyo et al. (2000), in a study conducted on a larger spatial scale than ours, both road and urban area densities were related positively with agricultural weed richness. Along this line, our results were disconcerting because the distribution of floristic richness as well as compositional similarity did not show any association between sites subjected to similar use conditions. For example, matorral sites with low levels of anthropogenization showed degrees of richness and exotic composition similar to sites with greater anthropogenization, such as those of espinal, abandoned farming fields, or exotic forest plantations. This situation most likely reflects the complex interaction existing between the patches of original vegetation and those with different patterns of land use in recent history. Perhaps studies on a regional scale would not be sensitive to the spatial heterogeneity that is found on a landscape scale. Clearly, this field of research requires greater depth as most of this evidence relies on the examination of distributional patterns. The floristic composition of the studied sites showed, in general terms, low levels of compositional similarity, with an average floristic similarity of 16.8%. The results of the separate analysis of the native and exotic floras showed that the native species describe distributional patterns of greater spatial replacement than the exotic species. This was determined, on the one hand, by the fact that the sites were more similar to one another (i.e., higher Jaccard values) for the composition of exotic (lower beta diversity) than native species (higher beta diversity), while, on the other hand, the native flora showed a low but significant effect of geographic distance on floristic similarity, though this relation was not significant in the case of the exotic flora. These results show without any doubt that the native and exotic floras present different patterns of spatial distribution. The greater ubiquity of the exotic flora in relation to the native flora supports the hypothesis of floristic homogenization at the species level for central Chile on a landscape scale. The homogenization can be defined as an increase in the compositional similarity between sites that originally showed greater differences (Olden, 2006). Considering the floras present in Chile’s administrative regions, Castro and Jaksic (2008) reported that the similarity values have not changed significantly throughout the country’s central regions. However, Jiménez et al. (2008) reported an increase in floristic similarity in the administrative regions of central Chile (which correspond to the Mediterranean-type region) and California, due to the presence of the species shared by both regions. It is difficult to establish an increase in floristic similarity in our study area because we do not know the original floristic composition and similarity. It is possible that some native species have disappeared locally in our study sites, and therefore an attempt to calculate the original similarity based on the native flora would be highly speculative. However, the ubiquity of the exotic flora in the sample sites and the high levels of coverage that they have achieved make it reasonable to suggest the hypothesis that our study area has.

(7) J.A. Figueroa et al. / Acta Oecologica 37 (2011) 103e109. lost taxonomic and physiognomic heterogeneity (sensu Olden and Rooney, 2006) due to the geographic expansion and local abundance of exotic species (Olden and Poff, 2003). It is important to point out that both taxonomic and physiognomic homogenization processes in central Chile would be the result of the introduction of a restricted stock of species on a regional scale, but that locally they achieve dominance in richness and especially in coverage. In summary, the Mediterranean-type region of central Chile is going through a process of biotic change imposed by human presence and land use patterns. This process will undoubtedly continue over time and it is irreversible (Arroyo et al., 2000; Figueroa et al., 2004; Castro et al., 2005). Our data show quantitatively and for the first time that these changes are severe on a local scale, because in spite of the smaller number of exotic species than native species, their importance with respect to coverage and physiognomy is greater. Since it is impossible to establish the original vegetation and floristic state of our study area, we suggest that the communities of central Chile are going through a process of floristic homogenization. Further studies are required to understand the mechanisms that promote this change (according to Fig. 2A could be the competition for resources), because at our scale of analysis we find a complex relationship between richness and composition and land use patterns. Acknowledgements This study was funded by DII-VIEA PUCV (Project DI No 122.709/ 2008), and intern project of the Universidad Central de Chile. S.A. Castro was partially supported by Fondecyt No. 11085013, CEDENNA, and CASEB. References Arroyo, M.T.K., Cavieres, L.A., 1997. 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