102 ACTA BOT. CROAT. 77 (1), 2018 Acta Bot. Croat. 77 (1), 102–104, 2018 CODEN: ABCRA 25 DOI: 10.1515/botcro-2017-0020 ISSN 0365-0588 eISSN 1847-8476 Short communication Erigeron acris L. subsp. angulosus (Gaudin) Vacc. (Asteraceae), a new taxon in the flora of Poland Artur Pliszko* Department of Taxonomy, Phytogeography and Paleobotany, Institute of Botany, Jagiellonian University, Kopernika 31, 31-501 Kraków, Poland Abstract – The paper reports for the first time the occurrence of Erigeron acris subsp. angulosus in Poland. This rare European temperate plant was found in August 2014 in a former sand and gravel quarry, close to the Sobolewo reservoir in the town of Suwałki, north-eastern Poland. Species composition of the habitat is charac- terized by a phytosociological relevé based on the Braun-Blanquet method, diagnostic characters in comparison to the morphologically similar E. acris subsp. droebachiensis are presented using scanning electron microscopy imaging, and an identification key for E. acris s. l. in Poland is given. Keywords: distribution, Erigeron, indumentum, Poland, scanning electron microscopy * Corresponding author, e-mail: artur.pliszko@uj.edu.pl Introduction Erigeron acris L. subsp. angulosus (Gaudin) Vacc. (As- teraceae), a European temperate representative of E. acris L. s. l. (Greuter 2003, 2006–2016), is confined mainly to the alpine zone of the Alps (Šída 1998, 2000, 2004). It has been reported from France, Italy, Switzerland, Liechtenstein, Aus- tria, Slovenia, Germany, the Czech Republic, Slovakia, Hun- gary, Romania and Estonia (Greuter 2006–2016). This bien- nial or perennial herb usually occurs in scree and gravel river bank plant communities of the class Thlaspietea rotundifolii (Mucina 1997). One of the most reliable diagnostic charac- ters that allows E. acris subsp. angulosus to be distinguished from most of the other subspecies of E. acris is the absence of villous indumentum on stems, leaves, and involucral bracts, with the exception of the short-stipitate glandular trichomes on involucral bracts (Šída 1998). In Poland, a recent study based on herbarium materi- als of E. acris s. l. deposited in the Polish herbaria (Pliszko 2015) revealed the occurrence of three subspecies, namely E. acris subsp. acris, E. acris subsp. droebachiensis (O. F. Müll.) Arcang., and E. acris subsp. serotinus (Weihe) Greuter. The present paper provides the first record of E. acris subsp. an- gulosus in Poland and is aimed at showing the morphologi- cal characteristics of the taxon as well as its distribution and habitat. Materials and methods Erigeron acris subsp. angulosus was identified based on morphological features given by Šída (1998, 2000, 2004) and its voucher specimens are deposited in the Herbari- um of the Institute of Botany of the Jagiellonian University in Kraków (KRA). A phytosociological relevé followed the Braun-Blanquet method (Braun-Blanquet 1964). Names of syntaxa and diagnostic species followed Mucina (1997). As- sociated plants were identified after Wójciak (2003) and Rut- kowski (2004). Names of taxa followed Mirek et al. (2002) and Ochyra et al. (2003). In morphometric and SEM stud- ies E. acris subsp. angulosus was compared to the morpho- logically similar E. acris subsp. droebachiensis. Measure- ments were taken on herbarium specimens. Indumentum terminology followed Werker (2000). Specimens of E. acris subsp. droebachiensis used in the morphometric study were collected in Brzozowiec (south-eastern Poland) in July 2013 and 2014 (GPS coordinates: 49°25'54,36"N/22°11'57,36"E), whereas those used in the SEM study were collected in Toruń (north-central Poland) in July 2013 (GPS coordinates: 53°1'21,06"N/18°33'22,68"E). Samples of dry cauline leaves, peduncles, and capitula were mounted on aluminum stubs coated with double-sided conductive carbon tabs. Next, the samples were coated with gold in a sputter-coater and exam- ined with a Hitachi S-4700 scanning electron microscope at ERIGERON ACRIS SUBSP. ANGULOSUS IN POLAND ACTA BOT. CROAT. 77 (1), 2018 103 an accelerating voltage of 10 kV, part of the standard proce- dure for viewing biological specimens in the SEM method (Bozzola and Russell 1999). Results and discussion Erigeron acris subsp. angulosus was discovered in Au- gust 2014 on the south-eastern outskirts of the town of Suwałki, north-eastern Poland (GPS coordinates: 54°4'18,06"N/22°57'48,84"E; altitude: 157 m.a.s.l.). Accord- ing to Zając (1978), the locality is situated within the FB18 square unit of the ATPOL cartogram grid. A small popula- tion consisting of 25 individuals was found in a former sand and gravel quarry, close to the Sobolewo reservoir (Fig. 1). Vegetation in this anthropogenic habitat is represented by populations of grassland and ruderal plant species. The spe- cies composition in the site occupied by E. acris subsp. an- gulosus is characterized by the following phytosociological relevé: size of relevé: 25 m²; cover of herb layer: 20%; cover of moss layer: 40%; Ch.Cl. Artemisietea vulgaris: Poa com- pressa 2, Melilotus albus +; Ch.Cl. Koelerio-Corynephoretea: Helichrysum arenarium 1, Arenaria serpyllifolia +, Herni- aria glabra +, Ceratodon purpureus (d) 3; Ch.Cl. Festuco- Brometea: Artemisia campestris 1, Centaurea stoebe +; oth- ers: Erigeron acris subsp. angulosus 1, Hieracium pilosella 1, Oenothera sp. 1, Echium vulgare +, Erigeron acris subsp. ac- ris +, Pinus sylvestris +. Taking into consideration the se- lected quantitative features (Tab. 1), E. acris subsp. angulo- sus clearly shows shorter stems and synflorescences, and a lower number of capitula than E. acris subsp. droebachiensis. The number of cauline leaves is similar in both subspecies; however, the lower cauline leaves of E. acris subsp. angulosus are much narrower than those of E. acris subsp. droebachien- sis. Regarding the SEM micrographs (On-line Suppl. Figs. 1–3), in contrast to E. acris subsp. droebachiensis, E. acris subsp. angulosus has no unbranched multicellular uniseri- ate non-glandular trichomes on involucral bracts, pedun- cles, and cauline leaves. On the other hand, the unbranched short-stipitate multicellular biseriate glandular trichomes are densely distributed on involucral bracts and sparsely on pe- duncles in both subspecies. Moreover, involucral bracts in E. acris subsp. angulosus are serrated relatively more deeply at the apex than those in E. acris subsp. droebachiensis (On- line Suppl. Fig. 2). The occurrence of E. acris subsp. angulosus in north-east- ern Poland suggests that there may be a continuity of its geo- graphical distribution between Central Europe and the Baltic states, since the taxon is present in Estonia (Greuter 2006– 2016). Furthermore, it is worth mentioning that most of the specimens collected in Suwałki have relatively more cauline leaves than those characterized by Šída (1998, 2000, 2004). This can be explained by the fact that they were found flow- ering in late summer. Erigeron acris subsp. angulosus typi- cally flowers in June, and at higher altitudes in July (Šída 2000, 2004). For example, summer specimens of E. acris sub- sp. acris often produce more cauline leaves than typical late spring specimens, especially after mowing or grazing (Plisz- ko 2015). In this connection, it should also be mentioned that similar specimens with numerous glabrous cauline leaves and a low number of capitula were collected between Miedzierza and Sielpia Wielka (south-central Poland) by Walas in September 1929 (KRA 0124518). These specimens were mistakenly identified as E. acris subsp. droebachiensis (Pliszko 2015). However, it is hard to decide if they belong to E. acris subsp. angulosus because their atypical features seem to be a result of mowing or grazing. The locality between Miedzierza and Sielpia Wielka needs to be re-examined and the identity of the plant should be confirmed in the flower- ing stage in June or July. E. acris subsp. angulosus is the rarest subspecies of E. ac- ris in Poland. Although the habitat in which the plant was discovered shows an anthropogenic character, it should be viewed as a native taxon. Its presence was confirmed in July 2016 with one flowering specimen. The expansion of trees and shrubs during secondary succession and recreational use of motorcycles are the main factors that can pose a threat to the E. acris subsp. angulosus population in Suwałki. Fig. 1. Erigeron acris subsp. angulosus in Suwałki, north-eastern Po- land: A – upper part of the plant; B – habitat (photos by A. Pliszko). Tab. 1. Morphological comparison of the selected quantitative characters of Erigeron acris subsp. angulosus and E. acris subsp. droebachien N – number of examined individuals. Numbers indicate mean value (out of brackets), minimum and maximum values (in brackets). Character Erigeron acris subsp. angulosus (N=15) Erigeron acris subsp. droebachiensis (N=15) height of stem (cm) 31.9 (22.0–45.0) 46.6 (28.5–62) number of cauline leaves 17.4 (12–24) 19.2 (10–25) size of lower cauline leaf (cm) 3.8 × 0.4 (2.5–6.5 × 0.3–0.6) 7.6 × 1.0 (4.5–12.0 × 0.7–1.4) number of capitula 6.2 (3–9) 21.3 (6–46) lenght of synflorescence (cm) 6.6 (4.5–10.0) 14.1 (7–24) PLISZKO A. 104 ACTA BOT. CROAT. 77 (1), 2018 Acknowledgements I would like to thank M.Sc. Eng. Anna Łatkiewicz (De- partment of Mineralogy, Petrology and Geochemistry of the Institute of Geological Sciences of the Jagiellonian University in Kraków) for her help in taking SEM images. I also thank Identification key for Erigeron acris s. l. in Poland 1. Stems and leaves densely villous, involucral bracts abaxially densely villous and sparsely short-stipitate glandular ..............................................................................2 Stems and leaves glabrous or sparsely villous at the base, involucral bracts abaxially densely short-stipitate glandular, glabrous or sparsely villous ............................3 2. Cauline leaves 4–16, flat, usually erect; internodes 1.0–8.0 cm; capitula in paniculiform synflorescence ..........................Erigeron acris subsp. acris the anonymous reviewers for their suggestions and comments. This work was financially supported by the Jagiellonian Uni- versity in Kraków (grants for research projects DS/MND/ WBiNoZ/IB/4/2013 and DS/MND/WBiNoZ/IB/2/2014). References Bozzola, J. J., Russell, L.D., 1999: Electron Microscopy. Principles and Techniques for Biologists. 2nd ed. Jones and Bartlett Pu- blishers, Boston, Toronto, London, Singapoure. Braun-Blanquet, J., 1964: Pflanzensoziologiae, Grundzüge der Vegetationskunde. 3rd ed. Springer-Verlag, Wien-New York. Greuter, W., 2003: The Euro+Med treatment of Astereae (Com- positae) – generic concepts and required new names. Will- denowia 33, 45–47. Greuter, W., 2006–2016: Compositae (pro parte majore). In: Greuter, W., Raab-Straube, E. von (eds.), Compositae. Euro+Med Plantbase – the information resource for Euro- Mediterranean plant diversity. Retrieved January 27, 2016 from http://ww2.bgbm.org Mirek, Z., Piękoś-Mirkowa, H., Zając, A., Zając, M., 2002: Flow- ering plants and pteridophytes of Poland, a checklist. W. Szaf- er Institute of Botany, Polish Academy of Sciences, Kraków. Mucina, L., 1997: Conspectus of classes of European vegetation. Folia Geobotanica et Phytotaxonomica 32, 117–172. Ochyra, R., Żarnowiec, J., Bednarek-Ochyra, H., 2003: Census catalogue of Polish Moses. W. Szafer Institute of Botany, Pol- ish Academy of Sciences, Kraków. Pliszko, A., 2015: Taxonomic revision and distribution of Eriger- on acris s. l. (Asteraceae) in Poland. Phytotaxa 208, 021–033. Rutkowski, L., 2004: A key for identification of vascular plants of lowland Poland (in Polish). Wydawnictwo Naukowe PWN, Warszawa. Šída, O., 1998: Taxonomic problems in Erigeron sect. Trimorpha (Compositae) in Eurasia. Preslia 70, 259–269. Šída, O., 2000: Erigeron acris agg. in the Czech Republic and Slova- kia. Zprávy České botanické společnosti 35, 1–33 (in Czech). Šída, O., 2004: Erigeron L. In: Slavík, B., Štěpánková, J. (eds.), Flo- ra of the Czech Republic vol. 7, 140–153. Academia, Praha (in Czech). Werker, E., 2000: Trichome diversity and development. In: Hal- lahan, D. L., Gray, J. C. (eds.), Advances in botanical research. Incorporating advances in plant pathology. Plant trichomes, vol. 31, 1–35. Academic Press, London. Wójciak, H., 2003: Lichens, bryophytes, pteridophytes. Flora of Poland. Multico Oficyna Wydawnicza, Warszawa (in Polish). Zając, A., 1978: Atlas of distribution of vascular plants in Poland (ATPOL). Taxon 27, 481–484. Cauline leaves 12–36, broadly undulate, recurved; internodes 0.2–3.8 cm; capitula in racemiform or paniculi- form synflorescence ............... Erigeron acris subsp. serotinus 3. Basal leaves with acute apex; cauline leaves narrowly lanceolate to linear; peduncles sparsely short-stipitate glandular or glabrous; capitula in racemiform synflorescence .................Erigeron acris subsp. angulosus Basal leaves with obtuse apex; cauline leaves lanceolate; peduncles densely to sparsely villous and short-stipitate glandular; capitula in paniculiform synflorescence .........Erigeron acris subsp. droebachiensis