Pilosella Hill – Mouse-ear-hawkweed
The genus Pilosella belongs to the most diverse and taxonomically difficult taxa of vascular plants. This is due to an interplay of frequent hybridization events, polyploidy, and the coexistence of sexual, agamospermic (= apomixis sensu Nogler 1984) and vegetative propagation (cf. Krahulcová et al. 2000, Fehrer et al. 2007). Different reproduction modes and ploidy levels occur not only between, but also within species and populations.
In more than half of the Pilosella species, different ploidy levels have been detected, with diploid to octoploid cytotypes being found in natural populations (cf. Fehrer et al. 2007). Diploid cytotypes (at least the naturally occurring ones) are usually sexual, tetraploids are apomictic or sexual, hexa- and octoploids are apomictic, odd-numbered polyploids are apomictic. However, triploids are often sterile and restricted to vegetative reproduction. Sexual reproduction is therefore also possible in polyploid cytotypes, and even the formation of sexual and apomictic seeds in a single flower head is not unusual in Pilosella (cf. Krahulcová & Krahulec 2000, Krahulcová et al. 2000, Fehrer et al. 2007).
The type of apomixis in Pilosella is autonomous apospory (Rosenberg 1906, 1907 Koltunow et al. 1998). The agamospermic seed formation takes place through the development of the female gametophyte (embryo sac) from a vegetative cell of the nucellus, the so-called aposporic initial cell, whereby the actual spore-forming tissue (archespore) remains unaffected and a sexual embryo sac can be developed additionally. This enables parallel sexual fertilization, which is why apospory can be regarded as a facultative apomixis. No fertilization is necessary for the development of the endosperm (autonomous endosperm development).
Like most apomictic plant groups, agamospermic Pilosella forms fertile pollen and can act as pollen parent in hybridizations. In contrast to obligatory apomicts (e.g. apomictic species of Hieracium s. str.), facultative apomictic Pilosella may also be the seed parent (Krahulec et al. 2004, Fehrer et al. 2005). Both female and male gametes may be reduced or unreduced, which explains the high number of different ploidy levels. In addition, albeit more rarely, polyhaploid progeny may form through the parthenogenetic development of reduced egg cells of polyploid cytotypes (Krahulcová & Krahulec 2000, Krahulec et al. 2004, Krahulcová et al. 2012).
The combination of these complex processes described above results in an enormous diversity of forms within the genus with fluent transitions between the different taxa, which makes species differentiation extremely difficult (Krahulcová et al. 2000, Fehrer et al. 2005, 2007, Fehrer 2012). The concept of principal and intermediate species, developed by Nägeli & Peter (1885), offers a pragmatic approach to deal with this problem. Principal species are characterized by wide distribution areas and/or ± distinct morphologically differentiated characters, while intermediate species represent morphological links between two or more principal species and therefore show a combination of the morphological character states of principal species. The morphological position of the intermediate species is expressed by a formula (e.g. P. arida: officinarum - piloselloides, P. visianii: officinarum < piloselloides). However, the terms, principal and intermediate species, should not be understood as evaluations in the sense of "better" and "worse" species. As Schuhwerk & Fischer (2003) emphasize, principal species do not always have a larger area and are not always more clearly defined or easier to identify than intermediate species.
According to this taxonomic concept, principal species are referred as parental taxa in the evolution of the genus, while intermediate species represent hybridogenic descendants of principal species. Within most principal species diploid cytotypes exist but intermediate species usually contain only polyploids (Fehrer et al. 2007).
Besides principal and intermediate species, a very large number of infra-specific taxa (subspecies, varieties, subvarieties, forms, subforms) have been described for Hieracium s.l. (incl. Pilosella). These can only be distinguished by subtle morphological traits. Some of these groups might represent fixed local populations, others only local modifications, which is why Gottschlich (1996) requires a "clean-up of this subtle taxonomy, leading to the peeling out of morphologically, geographically and locally tangible groups". It should be noted that in Pilosella, unlike in Hieracium s. str., recent and ongoing hybridizations play an important role and that morphologically solid groups are only partially formed (Gottschlich & Heinrichs 2001). Numerous intermediate species (probably) occur only as spontaneous primary hybrids, for others, this is the case at least in parts of their distribution area (cf. Schuhwerk & Fischer 2003, Gottschlich 2009, remarks in the species profiles). As Gottschlich & Heinrichs (2001) point out, there is currently "no viable alternative to the pragmatic principal and intermediate species concept" for Pilosella. For the preferred concept of micro-species outside of Central Europe, see Schuhwerk (1996; 2002).
As already advocated by Schultz & Schultz (1862), today Pilosella is mostly separated from Hieracium as an independent genus. Traditionally, eight sections were distinguished within Pilosella (Zahn 1923, 1930), six of which are represented in Germany.
The genus Pilosella is autochthonous in Eurasia and Northeast Africa (N-Algeria, N-Morocco) (see Fehrer et al. 2007, Map 1), but has a clear distribution focus in Europe. In the Asian part of the area, the number of species declines rapidly to the east, and only a few species are widespread, as far as Mongolia (Gottschlich 1996). Synanthropic occurrences of some species can be found in East Asia, North America, southern South America, SE-Australia, and New Zealand (Bräutigam 1992, Fehrer et al. 2007). As neophytes, they are partly to be regarded as invasive species in these regions (e.g. Duncan et al. 1997, Krahulec & Krahulcová 2011, Moffat et al. 2015, Wilson et al. 2006).
Pilosellaspecies mainly colonize open, oligotrophic habitats (Bräutigam 1992). Diploid cytotypes are found mainly in near-natural habitats, polyploids frequently in anthropogenically, disturbed, and low-competitive habitats (Křišťálová et al. 2010).
Pilosella species are perennial, herbaceous plants with horizontal to vertical rhizomes. A basal rosette of leaves (basal leaves) is usually present; in very few species, this rosette is missing. The peduncle is leafless (only in single-headed taxa), or bears few to rarely several, leaves. The leaves have entire or slightly dentate margins and are gradually narrowed into the base without a distinct petiole (Hieracium species: leaves often clearly dentate and petiolate). In multi-headed taxa a forked or a paniculate to umbellate inflorescence is developed. The flower heads have a well-developed, imbricate to multi-seriate involucrum and bear either pure yellow or abaxially red-striped or completely red to orange-colored flowers which are enrolled at the bottom and mostly ligulate at the top. More rarely are plants whose flowers remain completely enrolled. The teeth of the ligulate flowers are not ciliate. The receptaculum bears neither scales nor bristles. The margins of the cavities of the receptaculum from which flowers or fruits emerge are often very shortly dentate. The dark colored fruits (achenes) are 1.0-2.5 mm long, and each of their longitudinal ribs ends in a short, tooth-like projection (in Hieracium s.str. larger fruits with imperforated ribs). The simple, dirty-white pappus hairs are arranged in a single row (uniseriate) and are easily breakable (brittle). In contrast to Hieracium, Pilosella species often have stolons, which give raise to leaf rosettes of daughter plants and thus serve for vegetative propagation. In addition, runner-like, flowering side shoots (flagella) can be developed.
(see Bräutigam 2011, Gottschlich 1996, 2009, Schuhwerk & Lippert 1991, Schuhwerk & Fischer 2003)
In general, species should be collected at their main flowering time, as individuals flowering in late autumn often show atypical characters. Hence, the most optimal collection time is usually between the end of May and the end of June.
Before collection, the population should be carefully analyzed to determine whether it actually consists of only one taxon and to gain an impression of the intraspecific (and in the presence of several taxa, interspecific) variation. As long as the population size permits, at least 2, but preferably 3-5, well-developed individuals should be collected per taxon, which should reflect the observed variation in characters as representatively as possible. However, plants whose main shoot is dead, mown or grazed should not be (initially) considered. The individuals should be collected completely, i.e. including rhizome, basal leaf rosette, and, if necessary, runners and flagella.
Characters which may not be visible after drying (e.g. leaf, flower and style colors) should be noted in the field or before pressing.
A strong magnifying glass (magnifying 15 to 20 times) or a stereomicroscope is necessary to determine the characteristics of the different hair types. All individuals collected should be used for the determination process. In addition, all characters described in the keys must be taken into account because individual traits can deviate from the typical (described as “most”) characters state due to the often pronounced variability. It is therefore necessary to ascertain the combination of character states which suits best to the plant to be determined.
Explanation of some important characters and terms relevant for determination:
- forked branching − the branching extends at least over a quarter of the upper peduncle and the main branches are unbranched or are branched once at most
- high-forked − all forked branches start above the middle of the peduncle (the lowest branch approximately in the middle of the peduncle at most)
- deep-forked − at least one forked branch starts below the middle of the peduncle
- secondary peduncles − additional peduncles growing relatively steeply and straight upwards next to the main peduncle
- flagella − basal lateral shoots, initially growing like runners, then ascending and terminating in one or several heads
Hair types:
- Hair (top hair)) − simple, multicellular, unbranched and glandless hair
- Glands (glandular hairs) − consisting of stem and ± clearly spherical glandular head (very small, maximum 0.3 mm long, glands are also referred to as microglands)
- Stellate hair − shortly stalked or unstalked and apically radially branched, causing − when accumulated − grey to white tomentose pubescence
The portal contains all the taxa treated by Bräutigam (2021). However, the broadly defined species Pilosella guthnikiana s. l. and P. rubra s. l. were further subdivided according to narrower species concepts. In addition, in contrast to Bräutigam (2021), two subspecies of P. caespitosa and three somewhat more narrowly defined subspecies of P. piloselloides (Vill.) Soják s .l. as well as P. duerkhemiensis as an independent species were distinguished. In addition, P. cochlearis, which has also been recorded in Germany, has been included. So far it has not been possible to find reliably determined specimens of all the taxa considered.
For the species profiles, the studies of Nägeli & Peter (1885), Zahn (1906, 1923, 1929), Gottschlich (1996), Schuhwerk & Fischer (2003) and Bräutigam (2011) were mainly used. The publications of Vollmann (1905), Touton (1921-1922), Merxmüller (1982), Gottschlich & Meierott (2007), Meierott & Gottschlich (2008) were also taken into consideration.
We would like to thank the Botanical State Collection of Munich (M) and the Herbarium of the Ludwig-Maximilians-University of Munich (MSB) for providing suitable specimens.
Bräutigam, S. 1992. Hieracium L. In: Meusel, H. & Jäger, E. J. (Hrsg.). Vergleichende Chorologie der zentraleuropäischen Flora. Band 3. Text. Gustav Fischer Verlag, Jena: 325-333.
Bräutigam, S. 2011. Pilosella Vaill. In: Jäger, E. J. (Hrsg.). Rothmaler, Exkursionsflora von Deutschland. Gefäßpflanzen: Grundband. 20. Auflage. Spektrum Akademischer Verlag Heidelberg: 817-829.
Bräutigam, S. 2016. Pilosella Hill. In: Jäger, E. J. (Hrsg.). Rothmaler, Exkursionsflora von Deutschland. Gefäßpflanzen: Grundband. 21. durchgesehene Auflage. Springer Spektrum: 817-829.
Bräutigam, S. 2021. Pilosella Hill. In: Müller, F., Ritz, C., Welk, E. & Wesche, K. (Hrsg.). Rothmaler, Exkursionsflora von Deutschland. Gefäßpflanzen: Grundband. 22. Auflage. Springer Spektrum: 834-845.
Bräutigam, S. & Greuter, W. 2007. A new treatment of Pilosella for the Euro-Mediterranean flora. Willdenowia 37: 123-137. (Volltext)
Bräutigam, S. & Schuhwerk, F.. 2005. Hieracium L. In: Jäger, E. J. & Wener, K.(Hrsg.). Rothmaler, Exkursionsflora von Deutschland. Gefäßpflanzen: Kritischer Band. 10. bearbeitete Auflage. Spektrum Akademischer Verlag Heidelberg: 741-746. (Auszug)
Buttler, K. P., Thieme, M. & Mitarbeiter 2016. Florenliste von Deutschland - Gefäßpflanzen. Version 8. Frankfurt am Main. [online] (Aktuelle Version)
Buttler, K. P., May, R. & Menzing, D. 2018. Liste der Gefäßpflanzen Deutschlands. Florensynopse und Synonyme. BfN Skripten 519. Bundesamt für Naturschutz. (Download bei FloraWeb)
Duncan, R. P., Colhoun, K. M. & Foran, B. D. 1997. The distribution and abundance of Hieracium species (hawkweeds) in the dry grasslands of Canterbury and Otago. New Zealand Journal of Ecology 21: 51-62. (Volltext)
Dunkel, F. G., Hildel, W. & Rességuier, P. 2007. Hieracium fallax Willd. und weitere Hieracium echioides-Zwischenarten im nordwestlichen Bayern. Forum Geobotanicum 3: 1-10. (Volltext)
Fehrer, J. 2012. Das Abenteuer Habichtskräuter: Molekularbiologische Untersuchungen in der Oberlausitz und den angrenzenden Gebieten. Berichte der Naturforschenden Gesellschaft der Oberlausitz 20: 43-50. (Volltext)
Fehrer, J., Šimek, R., Krahulcová, A., Krahulec, F., Chrtek. J., Bräutigam, E. & Bräutigam, S. 2005. Evolution, hybridisation, and clonal distribution of apo- and amphimictic species of Hieracium subgen. Pilosella (Asteraceae: Lactuceae) in a Central European mountain range. In: Bakker, F. T., Chatrou, L. W., Gravendeel, B. & Pelser, P. B. (Hrsg.). Plant Species-Level Systematics: New Perspectives on Pattern & Process. Regnum Vegetabile 143. Gantner Verlag, Ruggell, Liechtenstein: 175-201. (Volltext)
Fehrer, J., Krahulcová, A., Krahulec, F., Chrtek, J. Jr., Rosenbaumová, R. & Bräutigam, S. 2007. Evolutionary aspects in Hieracium subgenus Pilosella. In: Hörandl, E., Grossniklaus, U., van Dijk, P. J. & Sharbel ,T. F. (Hrsg.). Apomixis: Evolution, Mechanisms and Perspectives. Regnum Vegetabile 147. Gantner Verlag, Ruggell, Liechtenstein: 359-390. (Volltext)
Ferrer-Gallego, O. P. & Mateo, G. 2015. Typification of Hieracium pilosella L. (Asteraceae). Annales Botanici Fennici 52: 202-204.
Gadella, T. W. J. 1987. Sexual tetraploid and apomictic pentaploid populations of Hieracium pilosella (Compositae). Plant Systematics and Evolution 157: 219–245.(Volltext)
Gottschlich, G. 1996. Hieracium L. 1753. In: Sebald, O., Seybold, S., Philippi, G. & Wörz, A. (Hrsg.). Die Farn- und Blütenpflanzen Baden-Württembergs. Bd. 6: Spezieller Teil (Spermatophyta, Unterklasse Asteridae) Valerianaceae bis Asteraceae. Eugen Ulmer Verlag Stuttgart: 393-535.
Gottschlich, G. 2009. Die Gattung Hieracium L. (Compositae) in der Region Abruzzen (Italien). Stapfia 89: 1-328. (Volltext)
Gottschlich, G. 2010. Pilosella sciadophora. In: Greuter, W. & Raus, Thomas (Hrsg.). Med-Checklist Notulae, 29. Willdenowia 40: 195.
Gottschlich, G. 2017. Typusmaterial und andere bedeutsame Belege der Gattung Hieracium im Herbarium der Universität Heidelberg (HEID). Berichte der Botanischen Arbeitsgemeinschaft Südwestdeutschland 8: 7-27. (Volltext des Zeitschriftenheftes)
Gottschlich, G. 2020a. Synopse der für Deutschland nachgewiesenen Arten und Unterarten der Gattung Hieracium s. l. (Hieracium s. str. und Pilosella), aufgeschlüsselt nach Vorkommen in den einzelnen Bundesländern. Forum geobotanicum 9: 1-59. (Volltext)
Gottschlich, G. 2020b. Anmerkungen zur Nomenklatur von Hieracium kalksburgense Wiesb. und Wiedereinsetzung des Namens Hieracium canum Peter. Kochia 13: 17-21.(Volltext)
Gottschlich, G. 2020c. Ergebnisse von Herbar-, Feld- und Literaturstudien zur Gattung Hieracium s. l. (Hieracium s. str. und Pilosella) als Vorarbeiten für die „Neue Flora von Bayern“. Berichte der Bayrischen Botanischen Gesellschaft 90: 129-146. (Volltext Zeitschriftenband)
Gottschlich, G. 2021a. Nomenklatorische Notiz zu Pilosella cana. Berichte der Bayrischen Botanischen Gesellschaft 91: 256-257. (Volltext Zeitschriftenband)
Gottschlich, G. 2021b. Hieracium mirabile – ein taxonomisches Mirakel. Kochia 14: 25-35. (Volltext)
Gottschlich, G. & Bräutigam, S. 2021. Validierung des Namens von Pilosella aequimontis. Berichte der Bayrischen Botanischen Gesellschaft 91: 258. (Volltext Zeitschriftenband)
Gottschlich, G. & Meierott, L. 2007. Hieracium aequimontis Gottschl. & Meierott, eine bisher übersehene Art aus dem thüringisch-fränkischen Grenzgebiet. Berichte der Bayrischen Botanischen Gesellschaft 77: 141-144. (Volltext Zeitschriftenband)
Gottschlich, G. & Schuhwerk, F. 2014. Pilosella In Lippert, W.. & Meierott, L. Kommentierte Artenliste der Farn- und Blütenpflanzen Bayerns. Selbstverlag der Bayerischen Botanischen Gesellschaft: 239-249.
Gutermann, W. 2019. Notulae nomenclaturales 46–59. Neilreichia 10: 135-154. (Volltext)
Hand, R., Thieme M. & Mitarbeiter 2020ff. Florenliste von Deutschland (Gefäßpflanzen), begründet von Karl Peter Buttler, Version 11ff. [online]. (Aktuelle Version)
Heinrichs, J, & Gottschlich, G. 2001. Bemerkenswerte Sippen aus der Hieracium calodon-Verwandtschaft im Rheinland. Decheniana 154: 7-14.
Koltunow, A. M., Johnson, S. D. & Bicknell, R. A. 1998. Sexual and apomictic development in Hieracium. Sexual Plant Reproduction 11: 213-230. (Volltext)
Krahulec, F. & Krahulcová, A. 2011. Ploidy levels and reproductive behaviour in invasive Hieracium pilosella in Patagonia. NeoBiota 11: 25-31. (Volltext)
Krahulec, F., Krahulcová, A., Fehrer, J., Bräutigam, S., Plačková, I, & Chrtek, J. Jr. 2004. The Sudetic group of Hieracium subgen. Pilosella from the Krkonoše Mts: a synthetic view. Preslia 76: 223–243. (Volltext)
Krahulcová, A. & Krahulec, F. 2000. Offspring diversity in Hieracium subgen. Pilosella (Asteraceae): new cytotypes from hybridization experiments and from open pollination. Fragmenta Floristica et Geobotanica 45: 239-255. (Volltext)
Krahulcová, A., Krahulec, F. & Chapman, H. M. 2000. Variation in Hieracium subgen. Pilosella (Asteraceae): What do we know about its sources? Folia Geobotanica 35: 319-338.
Krahulcová, A., Raabe, U. & Krahulec, F. 2012. Prozesse innerhalb hybridisierender Pilosella-Populationen: P. aurantiaca und P. officinarum in Hagen (Nordrhein-Westfalen). Kochia 6: 123-141. (Volltext)
Křišťálová, V. Chtrek, J., Krahulcová, A. Bräutigam, S. & Krahulec, F. 2010. Populations of species of Pilosella in ruderal habitats in the city of Prague: frequency, chromosome numbers and mode of reproduction. Preslia 82: 437-464. (Volltext)
Meierott, L. & Gottschlich, G. 2008. Hieracium L. In: Meierott, L. & Mitarbeiter. Flora der Haßberge und des Grabfelds. Neue Flora von Schweinfurt. Bd. 2. IHW-Verlag, Eching: 1031-1073.
Merxmüller, H. 1982. Hieracium schneidii - ein unbekannter bayrischer Endemit. Berichte der Bayrischen Botanischen Gesellschaft 53: 91-95. (Volltext Zeitschriftenband)
Moffat, C. E., Ensing, D. J., Gaskin, J. F., de Clerck-Floate, R. A. & Pither, J. 2015. Morphology delimits more species than molecular genetic clusters of invasive Pilosella. American Journal of Botany 102: 1145-1159.
Nägeli, C. & Peter, A. 1885. Die Hieracien Mittel-Europas, monographische Bearbeitung der Piloselloiden mit besonderer Berücksichtigung der mitteleuropäischen Sippen. Oldenbourg, München. (Volltext)
Netzwerk Phytodiversität Deutschland & Bundesamt für Naturschutz (Hrsg.) 2013. Verbreitungsatlas der Farn- und Blütenpflanzen Deutschlands. Landwirtschaftsverlag, Münster.
Nogler, G. A. 1984. Gametophytic apomixis. In: Johri, B. M. (Hrsg.). Embryology of Angiosperms. Springer-Verlag, Berlin, Heidelberg: 475-818.
Ostenfeld, C. H. 1910. Further studies on the apogamy and hybridization of the Hieracia. Zeitschrift für induktive Abstammungs- und Vererbungslehre 3: 241-285. (Volltext)
Rosenberg, O. 1906. Über die Embryobildung in der Gattung Hieracium. Berichte der Deutschen Botanischen Gesellschaft 24: 157-161. (Volltext)
Rosenberg, O. 1907. Cytological studies on the apogamy in Hieracium. Botanisk Tidsskrift 28: 143-170. (Volltext)
Schack, H. W. 1934. Nova Hieracia Bavarica. Berichte der Bayerischen Botanischen Gesellschaft 21: 58-60. (Volltext)
Schuhwerk, F. 1996. Kommentierte Liste der bayrischen Hieracium-Arten. Teil I. Taxonomisches Konzept, Arten des Subgenus Pilosella a-f. Berichte der Bayerischen Botanischen Gesellschaft 66/67: 193-198. (Volltext Zeitschriftenband)
Schuhwerk, F. 2002. Some thoughts on the taxonomy of Hieracium. Berichte der Bayerischen Botanischen Gesellschaft 72: 137-152. (Volltext)
Schuhwerk, F. & Fischer M. 2003. Bestimmungsschlüssel der Untergattung Hieracium subg. Pilosella in Österreich und Südtirol. Neilreichia 2-3: 13-58. (Volltext)
Schuhwerk, F. & Lippert, W. 1991. Vorläufiger Bestimmungsschlüssel für die Hieracien des Bayrisch-Böhmischen Waldes. Hoppea 50: 343-407.
Schultz, F. W. & Schultz, C. H. 1862. Pilosella als eigene Gattung aufgestellt. Flora 45: 417-441. (Volltext)
Touton, K. 1921-1922. Die rheinischen Hieracien. Vorstudien zur neuen Flora der Rheinlande. I. Teil. Die Pilosellliden. Jahrbücher des Nassauischen Vereins für Naturkunde 73: 41-73, 74: 2-50. (Volltext 73), (Volltext 74)
Turesson, B. 1972. Experimental studies in Hieracium pilosella L. II. Taxonomy and differentiation. Botaniska Notiser 125: 223-240. (Volltext)
Vollmann, F. 1905. Die Hieracienflora der Umgebung von Regensburg. Denkschriften der Königlich-Bayerischen Botanischen Gesellschaft in Regensburg IX. Bd. Neue Folge III. Bd.: 61-100. (Volltext)
Wilson, L. M., Fehrer, J. Bräutigam, S. & Grosskopf, G. 2006. A new invasive hawkweed, Hieracium glomeratum (Lactuceae, Asteraceae), in the Pacific Northwest. Canadian Journal of Botany 84: 133-142.
Zahn, K. H. 1906. Die Hieracien der Schweiz. Neue Denkschriften der allgemeinen schweizerischen Gesellschaft für die gesammten Naturwissenschaften 40: 163–728. (Volltext)
Zahn, K. H. 1923. Compositae-Hieracium. Abteilung II. Sect. XL. Pilosellina - Sect. XLVII. Praealtina. In: Engler, A. (Hrsg.) Das Pflanzenreich IV.280. Heft 82: 1147-1705. (Volltext)
Zahn, K. H. 1929. Hieracium L. In: Hegi, G. (Hrsg.) Illustrierte Flora von Mitteleuropa. Bd. IV, Teil 4. Compositae II: 1182-1351 (Nachdruck 1987, Verlag Paul Parey, Berlin-Hamburg.).
Zahn, K. H. 1930. Hieracium, Untergattung Pilosella. In: Ascherson, P. & Graebner,P. Synopsis der Mitteleuropäischen Flora, 12. Band, 1. Abteilung: 1–492. Gebrüder Borntraeger, Leipzig. (Volltext)
Wesenberg, J. & Bräutigam S. 2017 (aktualisiert 2024). Pilosella Hill. In: Dressler, S., Gregor, T., Hellwig, F.H., Korsch, H., Wesche, K., Wesenberg, J. & Ritz, C.M. Bestimmungskritische Taxa zur Flora von Deutschland. Herbarium Senckenbergianum Frankfurt/Main, Görlitz & Herbarium Haussknecht Jena. [online] https://bestikri.senckenberg.de
