First record of Crataegus monogyna Jacq. (Rosales: Rosaceae) in Buenos Aires province, Argentina

species of tree native to Europe, northwest Africa and western Asia, but which has been introduced in many other parts of the world where it can be an invasive weed (Potter et al. 2007). It is a small tree 5–8 m tall with a dense crown, the bark is dull brown with vertical cracks (Potter et al. 2007). The younger stems bear sharp thorns 1–1.5 cm long. The leaves are 2–4 cm long, obovate and deeply lobed, usually with obvious spicules. The flowers are produced in late spring in corymbs of 5–25 together. Each flower is about 1 cm diameter, with five white petals and red stamens. The fruit is oval and dark red about 1 cm long, with a single seed (Potter et al. 2007). In Argentina, C. monogyna has been cited previously as an introduced species to Rio Negro and Neuquén provinces (Figure 1) (Zuloaga et al. 2008). C. monogyna is characterized by sexually diploid, highly The genus Crataegus (commonly known as “hawthorns”) includes more than 140 species of shrubs and trees within the family Rosaceae. Most of the species of the genus are native to temperate regions of the Northern Hemisphere in Europe, Asia and North America (Phipps et al. 2003; Potter et al. 2007). Crataegus spp. usually grows up to 5–9 m, has a type of bark smoothy grey, small pome fruits and thorny branches. The leaves are somewhat variable in shape, with lobed or serrate margins, grow spirally arranged on long shoots, and in clusters on spur shoots on the end of twigs (Phipps et al. 2003; Potter et al. 2007). Patterns of phenotipic variation between genus Crataegus are commonly associated with the occurrence of gametophytic apomixis (Camp and Gilly 1943; Harlan and De Wet 1975; Dickinson 1983; Dickinson and Phipps 1985). Crataegus monogyna Jacq. (Rosales, Rosaceae) is a Abstract: Crataegus monogyna Jacq. (Rosales: Rosaceae) is cited and collected for the first time for Buenos Aires province, Argentina. Its distribution is extended within Argentina and southern South America, since it was only known from Río Negro and Neuquén provinces in southern Argentina until now. Universidad Nacional de La Plata, Museo de La Plata, División Zoología Vertebrados, Sección Ornitología, Paseo del Bosque S/N, La Plata (B1904CCA), Argentina. * Corresponding author. E-mail: lsegura79@yahoo.com.ar Luciano N. Segura *, Adrián Jauregui and Diego Montalti First record of Crataegus monogyna Jacq. (Rosales: Rosaceae) in Buenos Aires province, Argentina

species of tree native to Europe, northwest Africa and western Asia, but which has been introduced in many other parts of the world where it can be an invasive weed (Potter et al. 2007). It is a small tree 5-8 m tall with a dense crown, the bark is dull brown with vertical cracks (Potter et al. 2007). The younger stems bear sharp thorns 1-1.5 cm long. The leaves are 2-4 cm long, obovate and deeply lobed, usually with obvious spicules. The flowers are produced in late spring in corymbs of 5-25 together. Each flower is about 1 cm diameter, with five white petals and red stamens. The fruit is oval and dark red about 1 cm long, with a single seed (Potter et al. 2007). In Argentina, C. monogyna has been cited previously as an introduced species to Rio Negro and Neuquén provinces ( Figure 1) (Zuloaga et al. 2008).
C. monogyna is characterized by sexually diploid, highly The genus Crataegus (commonly known as "hawthorns") includes more than 140 species of shrubs and trees within the family Rosaceae. Most of the species of the genus are native to temperate regions of the Northern Hemisphere in Europe, Asia and North America (Phipps et al. 2003;Potter et al. 2007). Crataegus spp. usually grows up to 5-9 m, has a type of bark smoothy grey, small pome fruits and thorny branches. The leaves are somewhat variable in shape, with lobed or serrate margins, grow spirally arranged on long shoots, and in clusters on spur shoots on the end of twigs (Phipps et al. 2003;Potter et al. 2007). Patterns of phenotipic variation between genus Crataegus are commonly associated with the occurrence of gametophytic apomixis (Camp and Gilly 1943;Harlan and De Wet 1975;Dickinson 1983;Dickinson and Phipps 1985). promiscuous and can easily generate hybrids with other individuals including other taxonomic series, as many species of America (Núñez-Collin and Hernández-Martínez 2011). Although this species is apomictic in North America (Dickinson and Phipps 1986), other authors reported that apomixis is not common in Europe (Yeboah Gyan and Woodell 1987;Guitán and Fuentes 1992;Chacoff et al. 2008).
As part of a research program on the reproductive biology of a south temperate bird: the Red-crested Cardinal Paroaria coronata (Passeriformes: Thraupidae) in natural forests of central-eastern Argentina during 2005-2014, we detected the presence of the exotic tree C. monogyna distributed among other native trees. After an extensive literature review, we conclude that this is a new record for the Buenos Aires province in Argentina and that this species has few records in southern South America (Zuloaga et al. 2008).
The specimens collected (February 2014) were determined with the help of specific literature (Phipps et al. 2003) and subsequently deposited in the Herbarium of Museo de La Plata (LP). Individual tree measurements were obtained by a tape measure (4 m long) and values presented are means ± standard errors.
At the study area we found 10 specimens of C. monogyna distributed among native trees in the forest ( Figure 2). They were 4.5 ± 0.3 m in high (range = 3-6.2 m), their tree-canopy was 4.2 ± 0.4 m in width (range = 2.1-6.2 m), and their trunk diameter at 20 cm above the ground was 18.7 ± 1.4 cm (range = 12-26 cm). We observed C. monogyna flowering during the austral spring (October-November) and with fruits during the austral summer (February-March). Despite looking for young specimens, we could not detect the presence of seedlings growing in the study area.
The present study reports the first record of C. monogyna to Buenos Aires province in central-eastern Argentina, and extends its distribution within southern South America. From the number of specimens found, their sizes, and their specific location within the forest (Figure 2), a possible hypothesis on the origin of these trees could be natural reproduction, although we did not find any seedlings growing in the study area. However, Valek (1980) suggested that the way in which favorable conditions for seedling establishment by Crataegus individuals tend to be very localized both in time and space (erosion surfaces, abandoned agricultural land), and this could be the reason for the localized presence of these alien trees in the study area.
Most of the studied specimens reached four meters high and five meters wide, size that effectively serve as nesting-tree for birds as the Red-crested Cardinal (Segura and Arturi 2009;Segura and Reboreda 2012;Segura and Berkunsky 2012). However, during nine consecutive years monitoring the breeding performance of this bird (where more than 850 different nest-trees were identified), we never observed C. monogyna used as a nesting-tree (LNS, pers. obs.). By contrast, in this site Cardinals have nested exclusively on native trees (Segura and Arturi 2009).
Specimens of C. monogyna were dispersed intermingled between the native trees at the study area probably as a result of frequent seed dispersal by birds and small mammals (see also Courtney and Manzur 1985;Guitián 1998) combined with successful establishment (Lo et al. 2009). Birds have been long considered as the main seed dispersers (Van der Pijl 1982). During our observations, we recorded one bird species consuming fruits of C. monogyna: the Rufous-bellied Thrush (Turdus rufiventris). This bird species has been described as an effective seed disperser (Rodríguez 2001;Gasperin and Pizo 2009) and could be the responsible for the presence of C. monogyna in the area.
Some studies have documented positive effects of hybridization on invisibility, such as faster growth, greater size and increased aggression (Ellstrand and Schierenbeck 2000;Perry et al. 2001). In addition, the potential apomictic behavior (Dickinson and Phipps 1986) and highly promiscuity (Núñez-Collin and Hernández-Martínez 2011) of C. monogyna could further increase its invasive potential. Our results, other than increase the distributional range of this invasive species, highlight about the presence of an aggressive alien tree species in a natural south temperate forest of South America.

Acknowledgments:
We thank Emiliano Torres y Luis Del Sotto for allowing us to collect and enter on their property; Mariana Grossi and Gustavo Delucchi (Herbarium of Museo de La Plata) for their suggestions and invaluable help with species identification; and Angelo Manzatto and one anonymous review for helpful comments on a previous version of this manuscript. The Universidad Nacional de La Plata covered our field expenses (Proyecto de Incentivos 11/N708).