ANTONIO AGRI Y SU CONJUNTO VINYL REPLICA ANTONIO AGRI

[Mina Delahoussaye]

The accordion links three major ethnic musical strains in Texas: the Bohemian-German brass bands; the Mexican conjunto groups; and the Cajun-black bands that play zydeco. Cantinas, Catholic parish halls, supper clubs, and agricultural society buildings (like the oldest in Texas at Cat Spring) all house this joyous music.

FOREWARD Exotic plant invasions to the mediterranean region of Chile: causes, history and impacts Invasión de plantas exóticas en la región mediterránea de Chile: causas, historia e impactos JAVIER A. FIGUEROA*, SERGIO A. CASTRO, PABLO A. MARQUET & FABIAN M. JAKSIC Centro de Estudios Avanzados en Ecología & Biodiversidad, Pontificia Universidad Católica de Chile, Santiago CP 6513677, Chile Dirección para correspondencia ABSTRACT 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, 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. Key words: exotic species, plant invasions, naturalized plants, invasion history, ecosystem disruption. RESUMEN Revisamos la literatura sobre patrones, causas, procesos e impactos de las plantas exóticas, principalmente en la región mediterránea de Chile, considerando tres factores determinantes del proceso de invasión: (a) Disponibilidad de propágulos de las especies exóticas, (b) atributos de las comunidades locales en las cuales las especies exóticas se establecen y a partir de las cuales eventualmente se expanden, y (c) atributos de las especies exóticas que facilitan o restringen su expansión a nuevos sitios. Con relación a la disponibilidad de propágulos, el matorral de Chile central presenta las comunidades con la mayor incidencia de hierbas naturalizadas, seguido por el bosque esclerófilo y el espinal de la Cordillera de la Costa. En contraste, las comunidades al norte de Chile central tienen menores números y proporciones de hierbas naturalizadas en sus bancos de semilla. La disponibilidad y persistencia de hierbas naturalizadas no difiere entre la vegetación emergida y el banco de semillas. En cuanto a los atributos de las comunidades locales, asociadas al establecimiento y expansión de las especies exóticas, tanto el régimen de pastoreo como el uso de la tierra emergen como los factores más prominentes en hacerlas susceptibles a la invasión por exóticas. La evidencia sobre el efecto del régimen de incendios es contradictoria y la riqueza de especies nativas tampoco aparece como un factor importante. Con relación a la atributos de las especies exóticas, los resultados sugieren que las anuales naturalizadas germinan dentro de un amplio rango de temperaturas, que son altamente resistentes a las condiciones frías y secas, y que muestran un cierto grado de dormancia fisiológica. Además, las anuales naturalizadas son altamente tolerantes a los suelos pobres, y generalmente intolerantes a la sombra. Estos atributos generales han sido determinantes en el proceso de invasión de la región mediterránea de Chile. Los datos históricos indican que un número importante de especies exóticas fueron introducidas intencionalmente, y que su expansión es incontrolada. Se ha demostrado que la fecha de arribo de las especies exóticas es de gran relevancia para entender su actual dispersión en Chile, independientemente de su origen biogeográfico. Las especies exóticas pueden causar grandes perturbaciones de procesos y funciones ecosistémicas en Chile, tal como lo ejemplifican las plantaciones de árboles exóticos, que han alterado la química del suelo, el ciclaje de nutrientes, el ciclo del agua, la hidrología, el microclima, y la frecuencia e intensidad de incendios. Palabras clave: especies exóticas, invasiones de plantas, plantas naturalizadas, historia de invasión, perturbaciones ecosistémicas INTRODUCTION In the past five centuries, the rate of interchange of fauna and flora among distant regions of the planet has increased considerably (DAntonio & Vitousek 1992, Lodge 1993, Williamson 1996). Either intentionally or inadvertently species of a wide spectrum of taxonomic and geographic origins have been relocated by man, by facilitating their dispersal through previously insurmountable biogeographic barriers (Mack et al. 2000, Sakai et al. 2001). Once in their new habitat, introduced species may establish viable populations (Lodge 1993, Kolar & Lodge 2001) and in some cases, surpass the abundance and geographic distribution of comparable native species (Lodge 1993). Although the existence of biological invasions had been noted for some time (Darwin 1872, Elton 1958), it has only been in the last two decades that a profound interest has developed, owing to the important ecological, economic and human health impacts of exotic species (Bright 1996, Sakai et al. 2001, Mooney & Hobbs 2000, Pimentel et al. 2000, Mooney et al 2001). At the ecological level, invasive species are capable of modifying the patterns of abundance and distribution of native species in the community (Williamson 1996), to the point of causing the local extinction of native populations (Vitousek et al. 1996). This fact becomes more worrying if we consider that present day rates of species introductions are unprecedented in history, and they are far from being under control (Williamson 1996). The existing evidence suggests that greater changes in global diversity can be expected if species introductions are not controlled, especially in the species-rich mediterranean-type regions of the planet (Sala et al. 2000). Vascular plants are among the most ubiquitous invaders of the biosphere (Elton 1958, DAntonio & Vitousek 1992, van Auken 2000). The majority of these plants have been introduced for agricultural, sylvicultural, ornamental, or medicinal purposes (Williamson 1996), but many have been introduced accidentally (Newsome & Noble 1986). In Chile, close to 700 exotic vascular plant species are considered weeds in agro-ecosystems (Matthei 1995), and many of them have also established in natural and semi-natural environments (Montenegro et al. 1991, Arroyo et al. 2000). The majority of these are concentrated in the central region of Chile (Matthei 1995), which below 2,000 m elevation corresponds to the mediterranean-type climate area of the country (di Castri & Hajek 1976). Mediterranean ecosystems here and elsewhere are eco-regions with high floristic richness and endemism on a global level (Cowling et al. 1996, Arroyo et al.1999, Myers et al. 2000). Despite the importance of invasions in Chilean mediterranean-type ecosystems, little is known about the underlying causes of these invasions, historical processes, and their consequences for native species and ecosystem functions. Here, we provide an exhaustive review of the relevant literature, with the purpose of assessing what we know and what are the major gaps in our knowledge of the invasion processes in Chilean mediterranean-type ecosystems. For methodological and analytical purposes we concentrate on the causes of invasions and naturalizations in central Chile by focusing on three major non-independent drivers associated to the spread of exotic species (Fig. 1). We identify propagule availability, attributes of local communities, and attributes of exotic species as the three major interacting components of the invasion processes in central Chile. The establishment and spread of exotic species depends on an initial availability of propagules that will initiate the process of invasion within a local community. For this initial colonization to be successful a match between the attributes of the local community, which define its invasibility (e.g., disturbance regime, abiotic and biotic characteristics) and the ecological and physiological requirements and tolerances of the exotic species, which define their invasiveness, is required. Depending on this, a given species will either establish and reproduce in a local community or become locally extinct. Each result will affect the availability of propagules, thus recursively affecting the process of invasion through time. In the following paragraphs we elaborate on what we know about these interacting components of the invasion process and explore the effects of invasive plants on different ecosystem functions in Chilean mediterranean ecosystems. Finally, we identify areas of knowledge where research is scarce and/or urgent for a better understanding of the ecological consequences of plant invasions in mediterranean-type ecosystems of Chile.
Fig. 1: Representation of interactions among three general causes of exotic plant invasions. The exotic species pool is determined by exotic plant availability established above the ground and in the seed bank of the soil. The native community attributes are represented by plant richness and disturbance regime. Finally, species attributes determine exotic plant traits associated with their successful naturalization and further spread. Representación de las interacciones entre tres causas generales de la invasión de plantas exóticas. El conjunto de especies exóticas es definido por la disponibilidad de plantas exóticas en la vegetación y en el banco de semillas del suelo. Los atributos de la comunidad nativa están representados por la riqueza de plantas y el régimen de perturbaciones. Finalmente, los atributos de las especies quedan definidos por los rasgos de las plantas exóticas asociados con su naturalización exitosa y posterior expansión. AVAILABILITY OF EXOTIC PLANT PROPAGULES Established plant pool Naturalized species in central Chile amount to 18 % of the total flora and to 27 % in the case of herbs (Arroyo et al. 2000). However, this percentage varies at the scale of local communities in central Chile (Table 1). For instance, the frequency of naturalized herbs (e.g., Erodium spp., Medicagopolymorpha, Malva nicaensis) was close to 45 % of the established vegetation in a managed "matorral" (Las Cardas, 30 S), from where domestic herbivores were excluded for five years (Lailhacar & Aylwin 1988, Lailhacar & Torres 2002, Torres 1999). Further, in a pre-montane sclerophyllous matorral (San Carlos de Apoquindo, 33 S), naturalized herbaceous species (e.g., E. cicutarium, Vulpiabromoides, Anthriscuscaucalis, Geraniumrobertianum), represented approximately 50 % of the taxa established aboveground (Figueroa et al. in press). Instead, in a protected semiarid thorn-scrub of northcentral Chile (Aucó, 31 S), only 20 % of ephemeral species recorded (e.g., E. botrys, E. malacoides, Galium aparine) corresponded to naturalized species (Gutiérrez et al. 2000). In sum, the available evidence suggests that the central Chilean matorral is one of the communities with the greatest incidence of naturalized herbaceous flora. Other authors have suggested the same for the sclerophyllous forest and the espinal of the Coastal Mountain Range, with frequencies of naturalized species above 50 % (Montenegro et al. 1991). Propagules stored in the soil Assessing the availability of naturalized plants for an area requires not only knowing where the flora came from in an established community, but also information on the propagule reserve in the soil (Thompson & Grime 1979, Holmes & Cowling 1997). For instance, the percentage of naturalized herbs in the seed bank of the pre-montane sclerophyllous matorral at San Carlos de Apoquindo (33 S) represents approximately 55 % of the total number of herbaceous taxa (Figueroa et al. in press). Still, a number of naturalized species present in the seed bank were not recorded among the established plants at the site during the same season (e.g., Aphanusarvensis, Nasturtiumofficinale, Polygonumaviculare, Portulacagrandiflora). Close to 60 % of the total density of buried seeds, including native and naturalized herbs in exposed successional areas belonged to the exotic grass Vulpiabromoides (Figueroa et al. in press). On the other hand, a managed grassland of central Chile (Rinconada de Maipú, 32 S) (Olivares et al. 1994), had almost twice the concentration of buried seeds and greater dominance of naturalized herbs in the seed bank than the pre-montane matorral of San Carlos de Apoquindo. Olivares et al. (1994) identified nine taxa in the seed bank, of which eight were naturalized herbs (E. botrys, E. cicutarium, E. malacoides, Avenabarbata, Hordium murinum, Vulpia sp., Trifoliumglomeratum and Medicago polymorpha). In a deciduous matorral of semiarid central Chile (Fray Jorge, 30 S), naturalized annuals (e.g., E. cicutarium, M. nicaensis) represented about 20 % of the total number of seeds (Gutiérrez & Meserve 2003). A minor representation of naturalized species was found in the seed bank of a thorn-scrub matorral in north-central Chile with high presence of ephemeral native species (Table 1), where the most abundant exotics belonged to Erodium spp. (Gutiérrez et al. 2000). Finally, available information shows that north-central Chilean communities have smaller richness and proportion of naturalized herbs in the seed bank than do central Chilean communities. Nevertheless, there is not enough evidence to suggest that the naturalized herb availability and persistence differs strongly between the established vegetation aboveground and the seed bank, perhaps with the exception of the steppe matorral of north-central Chile (see Table 1).
TABLE 1 Percent of exotic herb species recorded in communities of central Chile with regard to the total number of herbs established on the ground and stored in the seed bank. Nd = no data. Percentages were obtained from lists of species (flora) published by the authors cited, with exception of Sax (2002a) who reported the mean number of plants. All authors presented data at a medium- and small-size scale, with exception of Arroyo et al. (2002) who recorded at a regional scale Porcentaje de hierbas exóticas establecidas en el suelo y almacenadas en el banco de semillas, considerando el número total de hierbas registradas en comunidades de Chile central. Nd = no hay datos. Los porcentajes fueron obtenidos desde las listas de especies que los autores publicaron, a excepción de Sax que informó el número promedio de plantas. Todos los autores presentan datos a una escala de tamaño mediano y pequeño, a excepción de Arroyo que informó a una escala regional Community Location Exotics on the ground Exotics in the seed bank References Deciduous matorral 30 S 21 19 Gutiérrez & Meserve (2003) Atriplex matorral 30 S 45 Nd Lailhacar & Torres (2002) Steppe matorral 31 S 20 12 Gutiérrez et al. (2000) Managed grassland 32 S Nd 88 Olivares et al. (1994) Evergreen matorral 33 S 50 55 Figueroa et al. (2004) Xeric matorral 33 S 47 Nd Sax (2002a) Acacia espinal Coastal range > 50 Nd Montenegro et al. (1991) Central Chile 33-37 S 27 Nd Arroyo et al. (2000) ATTRIBUTES OF THE LOCAL COMMUNITY Diverse factors in the native community may facilitate the establishment of exotic plants (Hobbs 2000). For instance, the burning of native vegetation (Richardson et al. 1990, DAntonio 2000, DAntonio et al. 2001), grazing pressure (Whisenant & Uresk 1990, Stohlgren et al. 1999a, Holmgren 2002), changes in land use (Rudnicky & McDonnell 1989, Kowarik 1990, Rapoport 1993, 2000, Drayton & Primack 1996) and low diversity of the native community (Elton 1958) may increase the susceptibility to invasion by exotic plants. Each of these factors is considered in more detail below, with regard to information available from central Chile. Fire regime The intentional burning of vegetation is a widely used agricultural technique that has been applied since the Spanish conquest (Aronson et al. 1998). The natural present-day vegetation did not evolve in response to natural fires occurring during dry summers, as it did in other mediterranean-type climate regions (Muñoz & Fuentes 1989). It is widely recognized that fires in the matorral are either directly or indirectly caused by humans (CONAF 1998, Montenegro et al. 2002). At the same time, the first reports of naturalized plants in this region are contemporary with the quick spread of European culture in Chile. Notwithstanding, the introduction of plants and the use of fire are not clearly related (Holmgren 2002) but few experimental studies exist on the effects of fire on the composition and abundance of naturalized plants in Chile (Keeley & Johnson 1977, Avila et al. 1981, Holmgren 2000a,b). Exotic invasive grasses have replaced vast regions of evergreen matorral in central Chile (Holmgren 2002), which is the likely underlying factor of high frequency of fires (Kunst et al. 2003). There are suggestions that invasive annual populations rebound quickly after fires whereas native perennials recover slowly, but there is no agreement among authors on the importance of fires in the invasibility of communities in central Chile. On one hand, in burned woodlands of Acacia caven, one year after a wildfire, 44,200 seedlings per m2 were recorded of the naturalized annuals Vulpia, Koeleria and Bromus (Trabaud 1991). Further, Avila et al. (1981) reported that fire increased the abundance of naturalized herbs such as Erodium cicutarium, E. botrys, Stellariacuspidata, Discurainiacumingiana,Matricaria chamonilla and Avenabarbata in a matorral on the Coastal Mountain Range (Cuesta Barriga, 33 S). Recently, Sax (2002a) also showed that fire favored exotic species richness and cover over native species in a xeric matorral. The conclusions of these authors are concordant with observations made in southern France and western North America, where naturalized species that also occur in Chile, enhance the frequency of fires (e.g., Arundodonax, Bromus madritensis, B. tectorum, Carduuspycnocephalus, E. cicutarium, Geraniumrobertianum, Schismusbarbatus, and Sonchusasper) (Trabaud 1991, Dukes & Mooney in this special issue). Nevertheless, there are contradictory data as well. For instance, Keeley & Johnson (1977) and Holmgren et al. (2000a,b) showed that fire in the Chilean matorral does not have differential effects on the relative abundance and composition of exotic (e.g., Lophocloacristata, E.cicutarium, Medicago polymorpha) and native herbs (e.g., Bromusberterianus, Amsinkiahispida). Likely, the opposed views on the effects of fire are due to confounding factors that affect community invasibility (e.g., grazing, land use, species richness) and whose interaction determine the establishment of exotic and native plant species. All these effects are difficult to sort out with traditional methods of vegetation sampling (Stohlgren et al. 1999b). Thus, this is a subject that needs to be studied further by using experiments that control for multiple confounding factors. Grazing regime Rabbits, together with cattle, goats, and horses, introduced from Europe, are widely distributed in the country and represent the principal herbivores in the matorral (Jaksic 1998). Particularly, European rabbits have been shown to arrest the process of succession in the native matorral (Fuentes et al. 1983). Although there is no conclusive evidence demonstrating that rabbits reduce the richness of native plants, their relative abundance is surely reduced with respect to that of naturalized species (Sáiz & Ojeda 1988, Holmgren et al. 2000a). Specifically, when matorral plots were subjected to rabbit grazing, the native grass Bromusberterianus proved to be the most affected species, losing 30 % more biomass than the introduced grass Lophocloa cristata (Holmgren et al. 2000a). In contrast to rabbits, native small mammals have more limited effects on matorral vegetation (Fuentes et al. 1983). Rabbits prefer to graze on exposed sites lacking shrub cover (Jaksic 1998). As the diet of rabbits consists mostly of native herbs, this herbivore may be facilitating the growth of naturalized annual herbs in open spaces and outside shrubs (Jaksic & Fuentes 1980). This may have resulted in the presently observed spatial segregation, with perennial native herbs restricted to protected sites under the shrub canopy, and with naturalized annual herbs common on exposed sites outside shrubs (Jaksic & Fuentes 1980). Nevertheless, this spatial segregation of invasive versus native annual plants does not always occur (Table 2), and could be the result of differences in nutrient availability and light.. For example, in a study of a semi-arid grassland (Las Cabras, 30 S), from where livestock had been excluded but that was exposed to grazing by rabbits, the naturalized annual species Medicagopolymorpha and Erodium moschatum were concentrated below the canopy or in the periphery of Cassiacoquimbensis and of Acacia caven, respectively (Lailhacar & Aylwin 1988). In these abandoned grasslands, the spatial distribution of annual herbs was associated rather to organic matter contents of soils, Nitrogen availability, and soil pH (Lailhacar & Aylwin 1988), as well as to water availability, and shrub species cover and identity (Lailhacar et al. 1999, Torres 1999, Lailhacar & Torres 2002).
TABLE 2 Main establishment site for exotic annual plants in matorral communities of central Chile Principal sitio de establecimiento de plantas anuales exóticas en comunidades de matorral de Chile central Community Exotic species Establishment site Authorities Evergreen matorral Evergreen matorral Cassia matorral Acacia matorral Atriplex matorral Atriplex matorral Atriplex pruned matorral Anthriscus caucalis Geranium robertianum Medicago polymorpha Erodium moschatum Erodium moschatum Malva nicaensis Erodium moschatum Under the canopy Under the canopy Under the canopy Canopys edge Canopys edge Indifferent Under the canopy Figueroa et al. (2004) Figueroa et al. (2004) Lailhacar & Aylwin (1988) Lailhacar & Aylwin (1988) Torres (1999) Torres (1999) Torres (1999) With respect to exotic livestock, there is consensus that its presence has enhanced naturalized spread to the detriment of native perennials and annuals (Lailhacar et al. 19991, Holmgren et al. 2000a,). Further, the introduction and management of livestock may have provoked the replacement of native hemicryptophytes by both native and naturalized annuals, which have the advantage of resisting the most stressful periods of the year as seeds (Lailhacar 1986). Most authors concur that naturalized plants of Eurasian origin are better adapted and have greater tolerance to grazing by livestock because they evolved under the pressure of indigenous Eurasian livestock (Holmgren 2002). In sum, it is evident that grazing by livestock and rabbits has facilitated the spread of naturalized plants in central Chile (Jaksic & Fuentes 1980, Lailhacar 1986, Lailhacar & Aylwin 1988, Sáiz & Ojeda 1988, Holmgren et al. 2000a, Holmgren 2002) increasing species invasiveness and decreasing community invasibility in central Chile. However, the putative effect of rabbits in promoting the spatial segregation of native perennial herbs and introduced annuals is not conclusive. Land use In Chile, the richness of exotic flora is directly related to the density of roads (e.g., Cotula australis, Hypochaeris radicata), and of urban (e.g., Lactuca serriola) and cultivated soils (e.g., Raphanus sativus) (Arroyo et al. 2000). Results of a comparative analysis between central Chile and California, and comparisons among regions of Chile, suggest that plant naturalization is more frequent in areas of greater urban population growth, and contrary to expectations, the amount of agricultural land does not have a significant effect (Matthei 1995, Arroyo et al. 2000). This pattern could emerge because roads facilitate the spread of exotic plants, and urban centers represent storage sites for seeds that come from external and internal markets. Likewise, at the landscape scale, the distribution of exotic plants was studied on rural roads in two national parks in the Andean Cordillera (39 S) by Pauchard & Alaback (2004). This study showed that rural roads are functional corridors and serve as sources of exotic propagules that facilitate the spread of exotic species (e.g., Hypochaerisradicata, Agrostiscapillaris, Rumexacetosella, Lotusuliginosus) into protected native communities. Therefore, it is important to consider that changes in land use may alter and modify the processes of invasion and availability of exotic plants (Hobbs 2000, Pauchard & Alaback 2004). Notwithstanding the above, studies in central Chile have not yet evaluated the mechanisms underlying the spread of exotic species on converted soils. Changes in land use are directly correlated with disturbance and erosion increments (Hough 1995), soil and air temperature (McDonnell et al. 1993), CO2 and O3 concentration (Sukopp 1998), precipitation likelihood (Botkin & Beveridge 1997), as well as nutrient, pollutant, pesticide, and herbicide retention and storage (Pouyat & McDonnell 1991). Future experimental research in this area should control for multiple factors associated with changes in soil and land use. Native species richness Elton (1958) suggested that species-rich communities should be the most resistant to biological invasions. Nevertheless, the study by Arroyo et al. (2000) in central Chile did not provide support for Eltons original hypothesis. This region harbors a lower number of exotic species as compared to California, despite having a lower species richness of native plants per surface area. However, Arroyo et al.s results may be considered more indicative than robust, given that in drawing comparisons at such large biogeographical scales, it is difficult to have an adequate number of replicates (Stohlgren et al. 1999a), and the difference between the number of exotic species in both regions could also be strongly influenced by propagule pressure (Kolar & Lodge 2001), that presumably is higher in California than in Chile. In contrast, at the small scale of 1-m2 to 400-m2 plots, Sax (2002a) concluded that, at least in the dry matorral on the coast of central Chile, the richness of exotic species was positively correlated with the diversity of native plants. This author suggested that both native and exotic species are responding similarly to environmental conditions and thus competition may not be operating, or not controlling local species richness (but see Byers & Noonburg 2003). Several studies have suggested that the causes that explain the increase in exotic species richness should be similar to those factors involved in the increase of native species richness within the same communities (Pickard 1984, Rejmánek 1996, Wiser et al. 1998, Smith & Knapp 1999). Specifically, disturbances and fluctuating resources in plant communities may facilitate the coexistence of native and exotic species (Davis et al. 2000, Sax et al. 2002). Finally, Eltons original hypothesis has not been subjected to test at a regional scale in central Chile. The great variety of native and anthropogenic communities in the region could be an appropriate scenario for determining the effect of plant nat