From Spain to Chile: environmental filters and success of herbaceous species in Mediterranean-climate regions

Abstract

In central Chile, many exotic species associated with cereal culture and livestock activities were introduced during Spanish colonization. Nowadays, Chilean semi-natural grasslands are a mixture of native species and exotics that mainly originated in the Mediterranean Basin. The establishment and persistence of exotics (i.e. naturalization) can be due to abiotic (climate and soil properties) and biotic (interaction between plants) factors. We assess the importance of these environmental factors as filters that have promoted/ limited the successful naturalization of Spanish species in Chile. Fifteen sites distributed throughout a wide range of Mediterranean climatic conditions, with similar geomorphology and land-use, were selected in both Chile and Spain. At each site we recorded a broad set of soil and climate variables as well as plant species richness during two consecutive years. In Chile, species were classified as natives or exotics whereas in Spain species were classified as colonizers (species that have been naturalized in Chile) or exclusives (only present in Spain). Species richness was higher in Spain (229 species) than in Chile (152), the latter with a high proportion (almost 50 %) of exotics. Different environmental factors affected species richness in each Mediterranean region. In Spain, species classified as colonizers were weakly related to a combination of soil and climate properties, while in Chile the number of exotic species was highly related with climate conditions (especially water availability). Lack of association between native and exotic species richness indicated that biotic filters (i.e. species competition) are less important than abiotic ones in transcontinental naturalization in Chile.

Exotic Plant Species in the Mediterranean Biome: A Reflection of Cultural and Historical Relationships

“…In central Chile, positive relationships were found in both shrublands [135] and grasslands [107,122]. Similar relationships were also documented in the Californian shrublands [123] and for post-fire vegetation communities in the Californian chaparral [124,136] and grasslands [137].…”

“…Regarding abiotic filters (climate-and edaphic-related) acting at a regional scale, previous reports suggested a filtering process in both the source and the recipient areas but acting with different intensity in each of them [107]. Existing literature stated that the influence of abiotic factors was stronger in the recipient area, where especially the climate determined the successful naturalisation of exotic species [107], agreeing with previous reports about invasibility [108][109][110]. For example, in the Mediterranean region of central Chile, the increase in species richness with precipitation, and with the shortening of summer drought, was greater for exotic than for native species [107].…”

“…Existing literature stated that the influence of abiotic factors was stronger in the recipient area, where especially the climate determined the successful naturalisation of exotic species [107], agreeing with previous reports about invasibility [108][109][110]. For example, in the Mediterranean region of central Chile, the increase in species richness with precipitation, and with the shortening of summer drought, was greater for exotic than for native species [107]. Therefore, exotic species naturalisation appeared enhanced by an improvement in the main limiting resource (water) (supported by the 'resource availability hypothesis') [103,111,112].…”

Ecotypic differentiation and phenotypic plasticity combine to enhance the invasiveness of the most widespread daisy in Chile, Leontodon saxatilis

“…However, since its arrival, it has become widely distributed (from 32°S to 42°S) and is present in several administrative regions far beyond the Mediterranean area 46 , indicating an unexpectedly high invasiveness. L eontodon saxatilis is the most frequent alien species in Chile 47 , which provides further evidence of its success in colonizing new areas and overcoming a diversity of novel conditions 48 . Anthropogenic activities seem to determine the spatial distribution of L .…”

Non-random co-occurrence of native and exotic plant species in Mediterranean grasslands

“…The above explained interpretation is coherent with the progressive loss of richness of exotics species from the Mediterranean Basin as climatic adversity in Chile increases (higher temperature, less precipitation and a higher number of months with water deficit). Other physical factors not addressed in the present study, such as, for instance, soil characteristics or those associated with the history of the introduction of land-uses and species into Chile's Mediterranean region (Ovalle et al, 1996;Lonsdale, 1999;Figueroa et al, 2004;Castro et al, 2005;Martín-For es et al, 2015) might also be contributing to reducing the richness of the exotics species in Chile at the sites with higher levels of water stress. Whatever the case may be, the different degrees of spatial co-occurrence observed between the native and colonizer species in Chile is coherent with a different response by both groups to environmental variations.…”