173 Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile Abstract Wild lettuces (Lactuca L.) provide valuable genetic resources for crop breeding, but are also significant invasive weeds. We explored the distributions, habitats, and ecological characteristics of populations of wild Lactuca species in central Chile. We documented two species – Lactuca serriola L. (prickly lettuce) and Lactuca virosa L. (opium/bitter lettuce) in 204 localities. These observations indicate that: i) both allochthonous (Euroasian) Lactuca species occur and are able to regenerate in central Chile; ii) L. serriola forms dense populations in urbanized areas; iii) both species can expand along transport corridors to high elevations; iv) the spread of L. virosa and persistence of dense populations in elevations above 2,000 m a.s.l. prove the invasiveness of this species in extreme climates; v) both species may contain novel traits of interest for germplasm conservation. Izvleček Divje vrste ločik rodu Lactuca L. predstavljajo pomemben rezervoar genskih virov z uporabno vrednostjo za žlahtnitelje, lahko pa predstavljajo tudi nezaželen invazivni plevel. Preučili smo razširjenost, rastišča in ekološke značilnosti populacij divjih vrst rodu Lactuca v osrednjem Čilu. Na 204 lokacijah smo dokumentirali dve vrsti divje solate in sicer pripotno ločiko (Lactuca serriola L.) ter strupeno ločiko (Lactuca virosa L.). Rezultati kažejo da se obe alohtoni (evroazijski) vrsti pojavljata in uspešno obnavljata v osrednjem Čilu. L. serriola se pojavlja v gostih populacijah v urbanih območjih, obe vrsti se širita ob transportnih poteh do najvišjih nadmorskih višin. Širjenje in pojavljanje vrste L. virosa v gostih populacijah na nadmorskih višinah nad 2000 m n. v. nakazujejo invazivnost te vrste v ekstremnih klimatskih razmerah, obe vrsti pa imata nove značilnosti, ki so pomembne za ohranjanje dednine. Key words: allochthonous species, elevational limits, germplasm conservation, opium lettuce, plant invasion, prickly lettuce. Ključne besede: alohtone vrste, višinske omejitve, ohranjanje dednine, strupena ločika, rastlinska invazija, pripotna ločika. Corresponding author: Aleš Lebeda E-mail: ales.lebeda@upol.cz Received: 16. 10. 2020 Accepted: 10. 7. 2021 Aleš Lebeda1, Eva Křístková1, Colin K. Khoury2,3,4, Daniel Carver3,5 & Chrystian C. Sosa2,6,7 DOI: 10.2478/hacq-2021-001921/1 • 2022, 173–186 1 Palacký University in Olomouc, Faculty of Science, Department of Botany, Olomouc, Czech Republic. 2 International Center for Tropical Agriculture (CIAT), Cali, Colombia. 3 United States Department of Agriculture, Agricultural Research Service, National Laboratory for Genetic Resources Preservation, Fort Collins, CO, USA. 4 Saint Louis University, Department of Biology, St. Louis, MO, USA. 5 Colorado State University, Geospatial Centroid, Fort Collins, CO, USA. 6 Pontificia Universidad Javeriana Cali, Departamento de Ciencias naturales y Matemáticas, Cali, Colombia. 7 Grupo de investigación en Evolución, Ecología y Conservación EECO, Programa de Biología, Facultad de Ciencias Básicas y Tecnologías, Universidad del Quindío, Armenia, Colombia. 21/1 • 2022, 173–186 174 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile Introduction The genus Lactuca L. (Asteraceae) is represented by about 100 species, including one domesticated taxon – lettuce (Lactuca sativa L.) (Lebeda et al., 2007a; Lebeda et al., 2004). Two species – Lactuca serriola L. (prickly lettuce) and Lactuca virosa L. (opium/bitter lettuce) – both native to the Mediterranean region (Feráková, 1977), occur as non-native populations (sensu Pyšek et al., 2004) in co- rollary climates in central Chile. While the taxa are close relatives to the domesticate and have contributed as ge- netic resources to its improvement (Lebeda et al., 2002, 2008, 2014, 2019b), they exhibit the potential to become significant invasive species in the country (Alexander et al., 2009a, b; Alexander, 2010, 2013, 2016; Fuentes et al., 2014). Background on target taxa and region L. serriola L. is an annual to biennial therophyte, grow- ing preferably on fertile, carbonate-rich soil, but its eco- logical amplitude is rather wide. The species is considered native to North (Mediterranean) and East Africa; West, Central, and South Asia; and to Europe, and is natural- ized in Southern Africa, Australasia, North America, and South America (Lebeda et al., 2004). This is a pioneer plant of open habitats including screes, quarries, ruins, and agricultural fields. It grows in areas with disturbed soil surfaces and has become a typical weedy plant of sub- urbs and expanding cities (Feráková, 1977). L. serriola is spreading in Europe along transport corridors (railway tracks and roads), and is considered a weedy species with high invasiveness potential (Lebeda et al., 2001, 2004, 2007a, b; Alexander, 2010), including the capacity to establish at high elevations (Alexander et al., 2009a). In Europe it is frequently recorded at elevations of 200 – 600 m.a.s.l. Above this altitude it is rather rare, but has been recorded in Switzerland at 1,500 m.a.s.l., in Turkey at 1,750 m.a.s.l., in Afghanistan at 3,100 m.a.s.l., and in the northern Himalayas up to 3,600 m.a.s.l. (Lebeda et al., 2004). L. serriola is a morphologically highly variable species, and according to the shape (division) of its leaves, two varieties have been identified: L. serriola L. var. serriola with divided cauline leaves, and var. integrifolia with en- tire cauline leaves (Feráková, 1977). Both varieties, also recognized as forms (Lebeda et al., 2001) have glabrous inflorescences. A third variety, L. serriola var. coriacea has a densely prickly upper stem and inflorescence (Feráková, 1977). Large variation in morphological traits and devel- opmental stages, at least to some extent related to envi- ronmental conditions, has been observed (Lebeda et al., 2007a, b). L. virosa L. is an annual to biennial thermophilous species, considered native to Europe and North Africa from lowland to submontaneous regions, mostly in the Mediterranean basin, up to 1,000 m.a.s.l. in central France, 1,560 m.a.s.l. in Switzerland, and 2,300 m.a.s.l. in Morocco (Lebeda et al., 2004). Usually it grows in ruderal (disturbed and waste) places, including road- sides, embankments, and grassy margins. As for natu- ral habitats, sand dunes near the seashore, rocks, screes, and forest clearings are optimal (Feráková, 1977). Leb- eda et al. (2004) summarized recent data on its distri- bution and documented that L. virosa is rare in central Europe, its historical synanthropic area is receding, and it is considered as an endangered species in some areas in Germany and Austria. Recent records on this species are missing from some European countries, e.g. from Czech Republic (Grulich, 2019). The species was introduced as a medicinal plant into several other countries in Europe and also into Northern America (Feráková, 1977; Leb- eda et al., 2019a), and is naturalized in Australasia (Leb- eda et al., 2004). Within L. virosa, there is a considerable variation with regard to leaf form, spination and anthocyanin pigmenta- tion. The following intraspecific taxa are recognized: var. virosa with non-lobed, entire leaves, and var. cruenta with divided leaves (Feráková, 1977). Both L. serriola and L. virosa are now essentially glob- ally distributed (Lebeda et al., 2004, 2007b). L. serriola is considered a weedy species in many countries (Lebeda et al., 2004, 2007b), and an invasive species in North Amer- ica (Lebeda et al., 2012a, 2019a) and in Chile (Fuentes et al., 2014). L. virosa is considered to have similar invasive- ness potential (Macaya et al., 1999). Central Chile is one of five major regions in the world having a mediterranean-type climate, with winter-wet and summer-dry conditions, and irregular timing of rain- fall events in autumn (di Castri, 1991; Guillerm, 1991). The Chilean mediterranean-climate zone can be divided physiographically into four regions: the Cordillera de los Andes in the east with numerous peaks over 5,000 m.a.s.l.; the Cordillera de la Costa to the west with peaks that seldom rise over 1,000 m.a.s.l.; the “Depresion In- termedia“ of the Central Valley between these ranges; and the littoral fringe bordering the Pacific Ocean (Montene- gro et al., 1991). These eco-geographic conditions, combined with dense human population settlements and extensive agricul- tural practices favor the spread of non-native (Pyšek et al., 2004) and exotic (Figueroa et al., 2004) plant species introduced from the Old World Mediterranean basin, Southern Africa, and other areas with mediterranean cli- mates (Fox, 1990; Myers, 1990; di Castri, 1991; Figuer- 21/1 • 2022, 173–186 175 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile oa, et al. 2004). Entry of many non-native plants into Chile has been connected to settlement of Europeans in and after the 16th century, however exact dates are rarely known (Aschmann, 1991). Marticorena & Quezada (1985) reported 13 percent of the Chilean flora as intro- duced plants, while more recently, Fuentes et al. (2013) recorded 743 naturalized taxa from 361 genera, over half of which may be considered invasive. Some 113 species of introduced or naturalized herbs were recorded in the mediterranean-climate zone by Montenegro et al. (1991). To our knowledge, no native (autochthonous) Lactuca species occur in Chile (Lebeda et al., 2004). Data on first records of non-native (allochthonous) Lactuca in the country are limited and differ by source. Cultivated let- tuce (L. sativa) is documented from the first half of 19th century by Gay (1847), who gave a short description of the genus and examples of three cultivated types, clas- sified as annual species Lactuca crispa, Lactuca capitata and Lactuca sativa; the author also mentioned a fourth cultivated species Lactuca laciniata Roth, described as a biennial with higher leaves pinnatifid and lower leaves runcinate. The name L. laciniata Roth. has been recog- nized as a synonym for L. serriola L. (Feráková, 1977), thus this description could be the first of L. serriola in Chile. Further, L. laciniata in Gay (1847) may repre- sent primitive oilseed lettuce, which is characterized by a high percentage (35%) of oil in the seeds, which has been used for cooking (Boukema et al., 1990). Boukema et al. (1990) mentioned that oilseed lettuce may be either L. serriola or L. sativa, or intermediate types between these species. The first verified record of L. serriola in Chile dates from 1901 (Fuentes et al., 2014). Occurrences of Lactuca scarriola L. (synonym for L. serriola L.) in Quinta Normal and other sites around Santiago de Chile was reported by Reiche (1910). In a check list of alien flora in Chile, four Lactuca species are mentioned – L. serriola (first re- cord in 1905) and L. virosa (1933), as well as cultivated L. sativa (1955), and another non-native wild species, Lactuca saligna L. (1960) (Ugarte et al., 2011). L. sativa, L. serriola and L. virosa are the only species reported in a previous (Marticorena & Quezada, 1985) and the most recent checklist of vascular plants in Chile (Rodriguez et al., 2018). Introduced L. serriola as a naturalized herb of the med- iterranean-climate zone was recorded in sclerophyllous matorral and montane matorral communities in Chile (Montenegro et al., 1991). However this species was not mentioned by Montenegro et al. (1991) among the non-native species whose invasion is closely related to dis- turbance, and which are abundant along railway tracks, roadsides, paths, and cultivated fields. By the end of the 20th century L. serriola as a weedy species was reported in central Chile from the region 4 (administrative units in Chile) – Coquimbo in the North to region 9 – Araucania in the South (Matthei, 1995). Re- cently the northern frontier of known distribution was ex- panded, reaching region 2 – Antofagasta (Novoa Quezada & Matus Ardile, 2013). L. serriola was mentioned as a spe- cies with high invasion potential by Fuentes et al. (2014). L. virosa was not mentioned in previous lists of vas- cular plants in Chile until it was identified within her- barium specimens by Macaya et al. (1999). The original described area of distribution between the region M – Metropolitana and the province Ňuble (region 8 – Bio- bio) as reported by Macaya et al. (1999) was enlarged to the Northwest (region 5 – Valparaiso) and South (region 9 – Araucania) by Novoa Quezada & Matus Ardiles (2013). Macaya et al. (1999) summarized the following observations on L. virosa: i) this ruderal species is distrib- uted along roads and disturbed soil, and in areas of alti- tudes of 700–1,500 m.a.s.l. co-exists alongside L. serriola. In mountains regions, it reaches higher altitudes than L. serriola and forms pure stand populations; and ii) this spe- cies was not likely introduced to Chile recently, given its large range. L. virosa is occasionally misidentified as L. serriola, and, because it is an non-native species, has not been given much attention by botanists. In this study we contribute to knowledge on L. serriola and L. virosa populations in Chile. We build on assess- ments focused on Europe (Doležalová et al., 2001; Leb- eda et al., 2001, 2007a, b, 2009), the Near East (Lebeda et al., 2012b), and North America (Lebeda et al., 2012a, 2019a, b) to record the distributions, habitats, and eco- logical characteristics of the species in the central region of Chile, based on field surveys conducted in 2016 and 2017. We discuss these findings in light both of their util- ity as genetic resources as well as the risks they represent as invasive species. Materials and methods Field work occurred in March 2016 and from Febru- ary – March 2017, covering central Chile between 31° 54,818´S (Los Villos) and 35°59,550´S (plateau over river Maule in the Andes), and from 72°03,410´W near the Pacific coast (Lora) to 70°07´44,12´´W (Portillo) in the Andes. The total length of routes was 3,975 km. The trips included the southern part of the administrative re- gion 4 – Coquimbo, then  regions 5 – Valparaíso, M – Metropolitana, 6 – Libertador O’Higgins, and 7 – Maule. Detailed routes are displayed in Figure 1. The lowest el- evation site was situated 16 m.a.s.l. (by Lora), and the 21/1 • 2022, 173–186 176 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile highest at 2,707 m.a.s.l. (near Portillo). A wide diversity of habitats were visited, including urban areas (towns and cities), transport corridors, places with disturbed soil for house construction, abandoned areas, agricultural field margins, farmlands, and industrial areas. Over a total of 204 sites, detailed observation and monitoring was performed at 175 locations (Figure 1), with an additional 29 road-side locations observed from the vehicle (places where it was not possible to stop). Information on the characteristics of plant populations (including number and density of plants, developmental stage, and presence of diseases and pests), habitats, and geographic locations were recorded. Determination of Lactuca species and infraspecific classification were per- formed according to Feráková (1977). In some sites the seed samples from individual plants of L. serriola (180 sites) and L. virosa (24 sites) were col- lected in both years. Passport data were recorded follow- Figure 1: Routes of field observations of L. serriola and L. virosa in central Chile in 2016 and 2017. Slika 1: Pot terenskih opazovanj vrst L. serriola in L. virosa v osrednjem Čilu v letih 2016 in 2017. 21/1 • 2022, 173–186 177 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile ing Lebeda et al. (2007b). The collected seed material is part of the Lactuca Working Collection at the Depart- ment of Botany of Palacký University in Olomouc (Czech Republic) and will be used for detailed characterization and evaluation purposes in follow-up studies. To further characterize ecology of the sites, ecogeo- graphic information at a resolution of 30 arc-seconds (ca. 1 km2 at the equator) for 23 bioclimatic and topographic variables from WorldClim 2 (Fick & Hijmans, 2017) and a CGIAR-Consortium for Spatial Information dataset based on the NASA Shuttle Radar Topography Mission (STRM) data (Jarvis et al., 2008), were extracted for all localities (Data are by authors). These data were used to further characterize the two species with regard to their climatic and topographic niches in the field sites in cen- tral Chile, both with regard to individual eco-geographic variables as well as through multi-factorial analyses and visualizations, including principal component analysis, Mahalanobis distances, PERMANOVA, and non-metric multidimensional scaling (Oksanen et al. 2020). Results L. serriola alone was recorded at 166 sites, L. virosa alone at 21 sites, and both species at 17 sites. The positions of the 175 sites where detailed field observations were re- corded and localities precisely documented by GPS are presented in Figure 1. Individual plants of L. serriola L. f. serriola with divided cauline leaves were observed at 155 sites, L. serriola L. f. integrifolia with entire cauline leaves only at one site, and plants representing both forms at two sites. L. virosa L. var. cruenta with divided leaves was observed at four sites and L. virosa L. var. virosa with entire cauline leaves at 12 sites, while the presence of both varieties at the same site was not observed. The cauline leaf status for L. virosa was not adequately developed at 14 sites, hindering infraspe- cific classification. The divided cauline leaves of L. serriola f. serriola predominated within this species across sites, while entire leaves were more common for L. virosa (i.e., var. virosa). Characteristics of populations and presence of diseases and pests While the estimated number of individual plants ob- served varied from a few individuals to dozens and excep- tionally hundreds of plants for L. serriola, the number of individuals of L. virosa per site was generally lower – from a few individual plants to a dozen. The number of plants was observed to be connected not only with climatic and topographic conditions, but also with the character of habitats and the intensity and type of human impact. For example, along roads and highways, in municipal parks, by bus stops, and around petrol stations the use of pesti- cides for weed control reduced the growth of the species, leaving only individuals that were missed or otherwise escaped from control. In areas with houses under con- struction and in ruderal (disturbed and waste) places not subject to weed control, the species‘ populations thrived. L. serriola plants in most sites were at the stage of fruit maturity. However, in some sites, young plants were also observed. These developed from the bases of plants mowed earlier in the summer, or grew from cypselas (achenes) produced earlier the same year. We recorded two types of composed inflorescence – corymbose and pyramidal panicles of heads. In sites where L. virosa plants were at a stage of fruit maturity, there were usually also leaf rosettes of young plants observed. These plants will produce seeds the fol- lowing year. Generally, there were few visible symptoms of diseases on plants recorded. Powdery mildew infection caused by Golovinomyces bolayi S. Takam., A. Lebeda & M. Götz (Braun et al., 2019) was recorded only on one L. serriola plant growing by a house in the center of Santiago de Chi- le, and on a number of L. serriola plants growing along a local road in El Sotillo. Symptoms of lettuce downy mil- dew (Bremia lactucae Regel.), as a most important disease of lettuce (L. sativa), were not observed. In some locati- ons (Hualaňé, Lora, Laguna Colbún, Cajón de Maipó), aphids were seen on the inflorescence of L. serriola plants. L. virosa populations in central Chile appeared to be una- ffected by pests and diseases. Habitats The distribution of L. serriola and L. virosa across differ- ent habitats is summarized in Table 1 and in Figure 2. L. serriola was more or less equally distributed in urban habitats and in the rural areas (Figures 2, 3). Inside the cities, it was recorded in ruderal or neglected areas along local roads, in places with house construction, in cracks in pavement, and near houses. Outside of cities, the dis- tribution of L. serriola in ditches and in grassy areas along transport corridors predominated. L. serriola also oc- curred by bus stops, petrol stations, and in parking places near roads and highways. Its occurrence in agricultural and industrial areas was less frequently observed. It was not recorded in sandy dunes along the Pacific coast. Its distribution in urban and commercial areas between Viňa del Mar and Valparaiso by the Pacific ocean was associ- ated with human activities (transport, houses, industry) in urban areas. 21/1 • 2022, 173–186 178 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile Category of habitat Number of sites with Lactuca species L. serriola L. serriola and L. virosa L. virosa Urban (city intravilan) 1.1 in pavement, along street, by house 16 0 0 1.2 grassy area, along water corridor 6 0 0 1.3 municipal park, grassy area 14 1 4 1.4 municipal park, along road 3 0 1 1.5 local inhabitation (suburb, condominio, village), along road 23 0 0 1.6 area with house construction 3 0 0 1.7 ruderal area in intravilan 6 0 0 Total 71 1 5 Countryside (outside of city, town) 2.1 along road, by petrol station, bus stop, parking place 20 1 0 2.2 along road in grassy area, in ditch 42 7 6 2.3 along road in gravel 9 5 10 2.4 along railway track 1 0 0 2.5 ruderal area by road 4 1 0 Total 76 14 16 Agricultural areas (fields, farms) 3.1 along road 9 0 0 3.2 along field 5 2 0 Total 14 2 0 Industrial areas 4.1 by industrial objects 5 0 0 Total number of sites 166 17 21 Figure 2: Frequency of occurrence of L. serriola and L. virosa in various habitat types in central Chile observed in 2016 and 2017 (Lser – presence of L. serriola, Lvir – presence of L. virosa, LserLvir – presence of L. serriola and L. virosa on monitoring site. Habitat category 1 denotes urban areas (1.1 in pavement, along street, by house; 1.2 grassy area, along water corridor; 1.3 municipal park, grassy area; 1.4 municipal park, along road; 1.5 local dwelling (suburb, condominium, village), along road; 1.6 area with house construction; 1.7 ruderal area in intravilan). Habitat category 2 denotes countryside (2.1 along road, by petrol station, bus stop, parking place; 2.2 along road in grassy area, in ditch; 2.3 along road in gravel; 2.4 along railway track; 2.5 ruderal area by road. Habitat category 3 denotes agricultural areas (fields, farms) (3.1 along road; 3.2 along field). Habitat category 4 denotes industrial areas (4.1 by industrial objects). Slika 2: Frekvenca pojavljanj vrst L. serriola in L. virosa v različnih habitatnih tipih v osrednjem Čilu v letih 2016 in 2017 (Lser – prisotnost vrste L. serriola, Lvir – prisotnost vrste L. virosa, LserLvir – prisotnost vrst L. serriola in L. virosa na preučevanih rastiščih. Oznaka habitata 1 predstavlja urbana območja (1.1 na pločniku, ob cesti, ob hiši; 1.2 travnata območja, ob vodotoku; 1.3 mestni park, travnato območje; 1.4 mestni park, ob cesti; 1.5 stanovanjska območja (predmestje, stanovanjski bloki, vas), ob cesti; 1.6 območje stanovanjske gradnje; 1.7 ruderalna območja v urbanem prostoru). Oznaka habitata 2 predstavlja ruralna območja (2.1 ob cesti, pri bencinski črpalki, avtobusna postaja, parkirišče; 2.2 travnate površine ob cesti, v jarku; 2.3 gramoz ob cesti; 2.4 ob železniških tirih; 2.5 rudealne površine ob cesti. Oznaka habitata 3 predstavlja kmetijske površine (polja, kmetije) (3.1 ob cesti; 3.2 ob poljih). Oznaka habitata 3 predstavlja industrijske površine(4.1 ob industrijskih objektih). Table 1: Habitats with occurrence of L. serriola and L. virosa in central Chile observed in 2016 and 2017. Tabela 1: Habitati, v katerih sta se pojavljali vrsti L. serriola in L. virosa v osrednjem Čilu v letih 2016 in 2017. 21/1 • 2022, 173–186 179 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile Figure 3: Habitats of L. serriola in Central Chile: a – Santiago, Tunel San Christobal; b – Santiago, Parque Metropolitano; c – along ruta 5 (Santiago – Las Vegas); d - Talanga; e – El Colorado; f – over Rio Blanco. Slika 3: Habitati vrste L. serriola v osrednjem Čilu: a – Santiago, Tunel San Christobal; b – Santiago, Parque Metropolitano; c – ob cesti 5 (Santiago – Las Vegas); d - Talanga; e – El Colorado; f – nad reko Rio Blanco. c a e f b d 21/1 • 2022, 173–186 180 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile ca e b d Figure 4: Habitats of L. virosa in Central Chile: a, b, c – road over Canjón Maipú (Figure 4b: red oval – L. serriola, white oval – L. virosa); d, e – gravel plateau over river Maule. Slika 4: Rastišča vrste L. virosa v srednjem Čilu: a, b, c – cesta nad kanjonom Maipú (Slika 4b: rdeča elipsa – L. serriola, bela elipsa – L. virosa); d, e – gramozni plato nad reko Maule. 21/1 • 2022, 173–186 181 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile Lactuca virosa predominated along transport corridors, either alone or together with L. serriola (Figures 2, 4). In urban areas it was observed only in a Municipal park of the capital. It was not observed in agricultural or indus- trial areas. Distributions and elevational limits L. serriola was observed at altitudes from 18 m.a.s.l. (Li- canté) to 2,235 m.a.s.l., with eleven sites located above 1,000 m.a.s.l. The lowest altitude where L. virosa was observed was 16 m.a.s.l. (by Lora), while nine sites were above 1,000 m.a.s.l., with the highest at 2,707 m.a.s.l. (Figure 1). Species distributions along roads in elevational gradi- ents were observed in detail along three routes: i) Los An- des – Portillo; ii) Pirque – Cajón Maipu; iii) Lago Colbún – plateau over Rio Maule: i) Los Andes – Portillo Along the R 60 from nearby Los Andes (824 m), L. ser- riola plants were observed. Dense populations were also observed in gravel over the Rio Colorado, and dispersed populations were seen at higher elevations in gravel and stones along the mountain road up to 2,235 m, and again at 2,365 m a.s.l. Above this elevation, L. serriola was re- placed by L. virosa plants, which were dispersed along the road up to 2,707 m.a.s.l. (Figure 1). We did not have the opportunity to verify the presence of leaf rosettes along the mountain road and thus to confirm whether plants can reproduce in these sites. ii) Pirque – Cajón Maipú Near Pirque, L. serriola plants were observed along road G-27, then both species (L. serriola and L. virosa) were present as the road began to rise in elevation (Figure 1). Both species were recognized above 1,315 m.a.s.l. in the direction of Volcan San José, including well developed leaf rosettes of L. virosa (Figure 4a, b, c). iii) Lago Colbún – plateau over Rio Maule Along road 115 by Lago Colbún (about 300 m) L. serriola and L. virosa were observed either separately or together in sites. L. serriola was then recorded at 1,057 m.a.s.l., and both species documented on slopes along the road above 1,139 m.a.s.l. At 1,361 m.a.s.l. (by Baňo de Camanario), only L. virosa was recorded (Figure 1). The habit of plants growing along the road in altitudes around 1,500 m.a.s.l. was influenced by windy conditions. Dense populations of L. virosa were observed continuously in higher elevations up to 2,148 m.a.s.l. in a gravel plateau over the Rio Maule, where a relatively dense and seem- ingly stable population of a dozen well developed plants persisted (Figure 4d, e). We suspect that achenes are transported to higher elevations by air turbulences caused by seasonal heating and by vehicles (Cousens et al. 2008, Křístková et al. 2014, Novotná et al. 2011). Beyond this plateau, the relief changed and the soil was more rocky, so the conditions for plants were no longer favourable. Eco-geographic niches Some variation with regard to climatic and topographic niches was found between the two species within their occurrences in central Chile (Figure 5, Supplementary material Figure 1). In general, L. serriola occurrences were acclimatized to warmer temperatures, especially for excep- tional environmental outlier populations, while L. virosa occurrences demonstrated greater acclimatization to cold- er temperatures, particularly at higher elevations in the Andes. While differences between the species with regard to precipitation variables were more mixed, L. serriola oc- curs overall in drier areas and L. virosa in wetter environ- ments (again related to higher elevations). Also notable for both species, for certain variables, was the relatively large spread of populations across ranges, especially with regard to precipitation (Figure 5). Multi-factorial analy- ses of the measured variables were unable to differentiate significant climatic and topographic differences between Figure 5: Climatic characterization of sites where L. serriola, L. virosa, and both species were found, for A) annual mean temperature, and B) annu- al precipitation. The thick vertical line represents median values across occurrences, the boxplots between 25 and 75% of variation, and circles the outliers within 90% of total variation. Please see Supplementary material Figure 1 for characterizations for all eco-geographic variables. Slika 5: Klimatske značilnosti rastišč, kjer se posamezno pojavljata vrsti L. serriola, L. virosa ali skupaj. A) letna povprečna temperatura in B) letna količina padavin . Debela navpična črta predstavlja mediano vseh vrednosti, škatle predstavljajo variabilnost med 25 in 75%, krožci pa predstavlja- jo osamelce znotraj 90% celotne variabilnosti. Za značilnosti vseh eko-geografskih spremenljivk glej Sliko 1 v dodatnem materialu. 5 10 15 200 400 600 800 A B 21/1 • 2022, 173–186 182 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile the two species populations in central Chile regarding the sites where they do not overlap, but do highlight wind speed and altitude as important contributing factors, especially for environmental outlier populations (Supple- mentary material Figure 2A, 2B and 2C)) suggesting that even if the species have similar environmental conditions they are not exactly equal (p<0.01). Discussion This novel information on the distributions, habitats, and ecological characteristics of L. serriola and L. virosa popu- lations in central Chile adds considerably to the available information for the species in the region. We add 183 new occurrences for L. serriola and 38 for L. virosa; the Global Biodiversity Information Facility lists only 49 and 62 occurrences for the species in the country, respectively (GBIF 2020). Introduced allochthonous Lactuca species can develop novel traits through acclimitization to newly colonized habitats, including adaptation to extreme environmental conditions and resistance to important diseases which im- pact the crop, as seen in L. serriola populations in the USA (Lebeda et al., 2014, 2019a, b). The elevational limit of 2,235 m.a.s.l. recorded for L. serriola during our recent observations in central Chile is significantly higher than existing records from the Mediterranean and Central Eu- rope (Lebeda et al., 2004). The species is known from North America at elevations above 2,000 m.a.s.l. (Lebeda et al., 2012a), and from Afghanistan and the northern Himalayas at above 3,000 m.a.s.l (Lebeda et al., 2004). The occurrence of L. virosa at the high elevation of 2,707 m.a.s.l. in central Chile is of interest, and supports earlier observations by Macaya et al. (1999) of acclimitization to mountainous areas. The species has not been observed in Europe or North America at this altitude (Lebeda et al., 2004, 2012a, 2019a). In 2016 we observed L. virosa at a high of 848 m.a.s.l. (near Pontrémolli) in Italy (Europe). In the Flora of North America, L. virosa is reported from Alabama, California and Washington, DC (Strother, 2006). Our surveys confirmed its continued but very rare presence in California and Washington State (Lebeda et al., 2012a). Powdery mildew was observed on L. serriola in only two sites in Chile. In comparison, this disease is very common at the end of its growing season in central Europe, ob- served in Slovenia (Doležalová et al., 2001) and relatively frequently in Austria (Lebeda et al., 2001), Czech Repub- lic, Germany, and the Netherlands (Lebeda et al., 2007a), in the USA and Canada (Lebeda et al., 2012a), and more recently in France, Italy, Slovakia, Poland, Hungary, and Croatia (Lebeda & Mieslerová, 2011; Mieslerová et al., 2020). We did not observe powdery mildew on L. virosa in Chile. In other countries L. virosa is infected by pow- dery mildew sporadically (Lebeda & Mieslerová, 2011; Mieslerová et al., 2020). We were able to locate only one unique accession of Lactuca from Chile within major genebank and botanic garden databases, including the Genesys plant genetic resources portal (Global Crop Diversity Trust 2019), the United Nations Food and Agriculture Organization World Information and Early Warning System on Plant Genetic Resources for Food and Agriculture (WIEWS) (2019), the Global Biodiversity Information Facility (2019), and the USDA National Plant Germplasm Sys- tem (2019). The accession (CGN 18677) is of L. virosa, donated to the Centre for Genetic Resources (Nether- lands) in 1996 by a Dutch seed company, with no further provenance information other than that it comes from the Andes region in Chile (Global Crop Diversity Trust 2019). Given that the surveyed Lactuca species in central Chile occur at higher elevations and present noticeably less impacts from disease than in other regions, among other traits of interest, and that populations from the area are poorly represented in ex situ repositories, further col- lecting of these species for germplasm conservation may be warranted. Further, our review of the overlap of the study sites with conservation areas listed in the World Database of Protected Areas (IUCN 2019) indicated that none of the occurrences we visited are in a conservation area. While these non-native species would certainly not be applicable for targeted conservation in protected areas, further surveying of protected areas for the species, and collection of found populations for germplasm conserva- tion prior to eradication, may be considered. The occurrence of L. serriola in urban areas corresponds with the results of Figueroa et al. (2020) who recorded this species in soil seed banks in urban vacant lots of San- tiago de Chile (Pauchard et al., 2004, 2006). Gärtner et al. (2015) focused their study on characterising the di- versity, composition and distribution of native and non- native ruderal species present in different suburbs of San- tiago de Chile; L. serriola was recorded on 2 sites and L. virosa on 5 sites out of 41 surveyed. The presence of non-native ruderal plant species was monitored by Hauck et al. (2016) in La Campana Na- tional Park, central Chile, however they do not mention the presence of L. serriola. Teillier et al. (2010) moni- tored the presence of alien species in the western slope of the Coastal Range (Valparaiso province), and L. serriola was observed on 15 sites from 33 sites investigated. As stressed by Figueroa et al. (2004), future experimental 21/1 • 2022, 173–186 183 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile research should be aimed at study of mechanisms under- lying the spread of non-native species on converted soils, and factors directly associated with changes in soil and land use. Our recent observations support the conclusions of Lembrechts et al. (2016, 2017) that roads may play a more important role as drivers of species range changes than previously assumed. From data on the Lactuca spe- cies presented in this paper it is evident that Chilean roadsides serve as corridors for species movements and as such trigger range change dynamics of species (whether native or non-native) into new climatic zones (Paiaro et al., 2011), such as with L. virosa in high altitudes in the Andes. Our observations also support the assertion by Lembrechts et al. (2016) and McDougall et al. (2018) that roadsides can serve as important early detection tools, where shifts in species ranges will become visible first. Roadside monitoring systems might however be sensitive to short-term population fluctuations (Lem- brechts et al., 2016). In the Chilean mountains, there has been minimal management of non-native species (Pauchard & Alaback, 2004), probably because their direct economic impacts are not yet significant, or at least not well enough docu- mented. In general the focus of management of non-na- tive species is limited to agricultural systems, where con- trol of borders, early detection, and rapid response are key strategies (McDougall et al., 2011). Awareness of threats from non-native species in natural systems is growing, as evidenced by new laws proposed for safeguarding the Chilean Protected Area Systems (Pauchard et al., 2012) and the creation of the Laboratory of Biological Invasions (Fuentes et al., 2014, 2015). The climate in central Chile appears to facilitate the distribution of weedy Lactuca species from the Old World Mediterranean region. Alongside L. serriola and L. virosa, such species in the genus also include Lactuca saligna L. and Lactuca viminea (L.) J. et C. Presl. L. sa- ligna grows from lowlands to low montane elevations in Europe, mostly in open sunny exposures, on waste places, borders of woodlands, arable fields, river banks, and also along railways and roads as a weed (Feráková, 1977). It is currently reported from only a few locations in the USA (Lebeda et al., 2012a), namely from Salinas, California which also has a mediterranean climate (di Castri, 1991). We see no reason why this species could not find suitable conditions for its entry and settlement in the equivalent mediterranean-climate zone in Chile. L. viminea is an apophyte growing in vineyards, around ruins, on walls, screes, and in quarries (Feráková, 1977). It was observed in France and Italy (Lebeda et al., 2001), and is very fre- quent in the coastal rocky parts of Croatia and in the Cro- atian islands in the Adriatic sea (namely Brač and Mljet) (E. Křístková, pers. communication), however it has not yet been observed in the New World. Conclusions Novel information on the distributions, habitats, and ecological characteristics of populations of non-native Lactuca species in central Chile were generated. These observations indicate that: i) both allochthonous (Eu- roasian) Lactuca species occur and are able to regenerate in central Chile; ii) L. serriola forms dense populations in urbanized areas; iii) both species can expand along transport corridors to high elevations; iv) the spread of L. virosa and persistence of dense populations in eleva- tions above 2,000 m a.s.l. prove the invasiveness of this species in extreme climates; v) both species may contain novel traits of interest for germplasm conservation; and vi) both species should be monitored (and treated) in ur- banized and agricultural areas, as well as in mountainous areas. Supplementary material on-line Figure S1 – Climatic and topographic characterization of sites where L. serriola, L. virosa, and both species were found. Figure S2 – A. Non-metric multidimensional scaling, B. principal component analysis, and C. Biplot of prin- cipal component analysis. Acknowledgements Help of Dr. Marko Maras with translation of abstract to Slovenian language is greatly acknowledged. This research was supported by the following grants: Min- istry of Education, Youths and Sports, Czech Republic (MSM 6198959215), Internal grant agency of Palacký University in Olomouc (IGA_PrF_2019_004; IGA_ PrF_2020_003; IGA_PrF_2021_001), and the USDA National Institute of Food and Agriculture (grant no. 2019-67012-29733/ project accession no. 1019405). Aleš Lebeda  https://orcid.org/0000-0003-3601-583X Eva Křístková  https://orcid.org/0000-0003-1816-5500 Colin Kahlil Khoury https://orcid.org/0000-0001-7893-5744 Daniel Carver  https://orcid.org/0000-0002-1344-6357 Chrystian Camilo Sosa  https://orcid.org/0000-0002- 3734-3248 21/1 • 2022, 173–186 184 Lebeda et al. Distribution and ecology of wild lettuces Lactuca serriola L. and Lactuca virosa L. in central Chile References Alexander, J. M. (2010). 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