Sergio Antonio Castro

Cities host a heterogeneous composition of native and exotic plants, yet the spatial distribution of plant richness and its drivers remain poorly understood. We evaluated the influence of the center-edge gradient, along the environmental gradient from the historic city center to the urban edge, and habitat type, reflecting local conditions, on plant richness in Santiago, Chile. Sidewalks, parks, and vacant lots (n = 234 per habitat type) were randomly sampled across varying distances from the historic center and urban edge, recording neighborhood socioeconomic level and municipality. Four richness metrics were analyzed using generalized linear mixed models (GLMMs): total richness, richness by origin (native or exotic), and richness by life form (trees, shrubs, or herbs), considering habitat type, socioeconomic level, and distances as fixed effects and municipality as a random effect. We recorded 699 species (13% native and 87% exotic; 23% trees, 20% shrubs, and 56% herbs). Distances to the city center and urban edge had no significant effect, whereas habitat type emerged as the primary determinant: sidewalks exhibited higher total, native, and exotic richness with more trees and shrubs, whereas vacant lots were dominated by herbs. These patterns indicate that floristic richness is distributed in a mosaic, independent of urban gradients. Given the importance of Santiago’s Mediterranean region as a biodiversity hotspot, the low representation of native species is concerning. Increasing their presence and associated ecosystem services requires tailored interventions for each habitat type.

The composition of the vascular flora in Punta Arenas city, found in the city’s public spaces, was studied. The species were identified and recorded in a database, which was supplemented with information on taxonomic classification, growth habit, Raunkiaer’s life form, origin status (native or exotic), and original continent-level distribution. These data were compared with studies conducted in five other cities in central Chile, together with an analysis of compositional similarity with these cities, by using the additive complement of Simpson’s index (1– β_sim). In Punta Arenas, 119 species were identified, showing a higher proportion of Gymnosperms compared to central Chilean cities. The most represented families were Asteraceae (16 species), Fabaceae (14), Rosaceae (14), Poaceae (12), and Pinaceae (10), which together accounted for 55% of the floristic richness. The compositional similarity between Punta Arenas and the other central Chilean cities ranged from 0.187 to 0.315, showing lower similarity than expected by chance (Montecarlo randomization test; P < 0.05). The primary origin distribution of Punta Arenas’ vascular flora was European, unlike central Chilean cities where it was Asian. Finally, the proportion of exotic species (91.6%) and the number of exotic species per native species (16 exotics/native) were the highest documented for cities in Chile and higher than in other 114 cities worldwide. These results indicate that Punta Arenas’ urban flora differs from the flora in central Chilean cities, not only in taxonomic composition but also in growth habit, biogeographical origin, and high level of exoticism. These differences are likely due to the city’s territorial isolation and extreme southern location (53°S), leading to a unique urban flora configuration.

The biodiversity of assemblages that experience the introduction and extinction of species may lead to responses in two important facets: The taxonomic and functional diversity. The way in which these facets are associated may reveal important implications and consequences for the conservation of those assemblages. Considering the critical situation of freshwater fishes in continental Chile (30° – 56° S), we analyzed how the taxonomic (TD_β) and functional (FD_β) facets of β-diversity, and their components of turnover and nestedness, are associated. We evaluated changes in β-diversity (ΔTD_β and ΔFD_β), turnover (ΔTD_tur and ΔFD_tur), and nestedness (ΔTD_nes and ΔFD_nes) in 20 fish assemblages from their historical (pre-European) to current composition. We also simulated future trends of these changes, assuming that native species with conservation issues would become extinct. Our results show that the fish assemblages studied are in a process of loss of β-diversity, both in taxonomic and functional facets (ΔTD_β = -3.9%; ΔFD_β = -30.4%); also, that these facets are positively correlated in the assemblages studied (r = 0.617; P < 0.05). Both components showed by loss in nestedness (ΔTD_nes = -36.9%; ΔFD_nes = -60.9%) but gain in turnover (ΔTD_tur = 9.2%; ΔFD_tur = 12.3%). The functional β-diversity decreased more than the taxonomic (ΔFD_β > ΔTD_β), which was caused chiefly by six exotic species of Salmonidae, whose geographical spread was wider and that at the same time shared several morpho-functional traits. Our forecasts, assuming an intensification in the extinction of Endangered and Vulnerable native species, indicate that the process of homogenization will continue, though at a lower rate. Our study shows that the freshwater ichthyofauna of continental Chile is undergoing biotic homogenization, and that this process involves the facets of taxonomic and functional β-diversity, which are show high correlation between historical and current compositions. Both facets show that process is influenced by nestedness, and while turnover contributes to differentiation (both taxonomic and functional), its importance is overshadowed by nestedness.

<![CDATA[ABSTRACT The germinative dynamics of Gaultheria mucronata (L.f.) Hook. & Arn. seeds from fruits of different colors were compared. Seeds from white, pink and dark-pink fruits were subjected to germination trials, evaluating the final germination percentage, accumulated germination percentage and the mean germination period (T50). The results did not show statistically significant differences between the treatments, implying that the fruit color polymorphism does not show differences in the germinative behavior analyzed here.]]>

Las especies del género Platanus se encuentran ampliamente distribuidas en el globo, por su uso ornamental. Aunque existen 10 especies válidas, de ellas se ha generado un número no determinado de híbridos. Por ello, en distintas ciudades donde estos taxa se han plantado la riqueza y representación taxonómica de Platanus es confusa y controversial. A través de un procedimiento basado en PCR sobre el gen LFY-i2, un gen informativo para identificar especies de Platanus, analizamos la diversidad del género en Santiago, midiendo además, su representación. Para ello, muestreamos 269 árboles de Platanus distribuidos en calles y avenidas de Santiago, evidenciando que existen al menos, siete taxa, entre las que se hallan las especies P. occidentalis y P. orientalis, además de cinco taxa híbridas; uno de estos híbridos es P. × hispanica, en tanto que los otros cuatro no tienen nominación ni origen discernible a partir del gen LFY-i2. En términos de la representación, el conjunto de taxa híbridos acumuló 84,7% de los árboles muestreados; mientras que P. orientalis y P. occidentalis juntos acumularon el 15,3% de los árboles. De las dos especies, P. orientalis fue la más frecuente (14,9%), mientras que entre los híbridos, el más frecuente fue Platanus A (40,8%); en contraste, P. × hispanica representó una baja proporción de la muestra (1,9%). Estos resultados confirman la presencia P. occidentalis, P. orientalis y P. × hispanica en Santiago, no obstante, la representación acumulada de estos tres taxa (17,2%) es menor a la de híbridos no determinados (82,8%). El reconocimiento taxonómico y representación de especímenes de Platanus en Santiago es una importante herramienta para proyectar futuros esfuerzos de arborización urbana, especialmente en atención a los servicios ecosistémicos que de ellas devienen.

Urban forests are conformed by a variable representation of native and exotic species. Because these species differ in the morpho-functional traits that possess, they may have a differential participation in the provision of ecosystem services in cities. Here, we compare ecosystem services inferred from morpho-functional traits of native and exotic tree species present in Santiago, Chile. Five traits associated with ecosystem services valuation (V_i) were scored (1 versus 0), and compared between native and exotic tree species, weighting those ecosystem services according to multi-criteria decision analysis procedure (MCDA). We found that native and exotic species did not have significant differences in the ecosystem services provided to urban dwellers (F = 1.2; P > 0.05); but these results were obtained when ecosystem services were not weighted according to their demand in Santiago. When weights were pondered, native species provided more ecosystem services than did exotic trees (F = 7.1; P < 0.008). Complementarily, we also found that the ecosystem services ranked for native and exotic species did not correlate with their spatial distribution (occupancy, O_i). These results highlight the need to use criteria based on ecosystem services to tree planting in Santiago, prioritizing native species because, in comparison to exotic ones, they provide more ecosystem services demanded city dwellers.