Blackwell Science, LtdOxford, UKBOJBotanical Journal of the Linnean Society0024-4074The Linnean Society of London, 2005? 2005 1473 333347 Original Article PLOIDAL LEVELS IN ARCTIC-ALPINE DRABA H. H. GRUNDT ET AL. Botanical Journal of the Linnean Society, 2005, 147, 333–347. With 1 figure Ploidal levels in the arctic-alpine polyploid Draba lactea (Brassicaceae) and its low-ploid relatives HANNE HEGRE GRUNDT1, RENATE OBERMAYER2 and LIV BORGEN1* Downloaded from https://academic.oup.com/botlinnean/article/147/3/333/2420553 by guest on 28 September 2021 1National Centre for Biosystematics, Natural History Museums and Botanical Garden, University of Oslo, PO Box 1172 Blindern, NO-0318 OSLO, Norway 2Institute of Botany, University of Vienna, Rennweg 14, AU-1030 Vienna, Austria Received June 2004; accepted for publication September 2004 Ploidal level information is of particular importance in intricate polyploid complexes such as in arctic-alpine Draba. Relative DNA content is reported for the tetra- and hexaploid D. lactea and seven of its low-ploid relatives. Flow cytometry was used to study 200 plants from 93 populations, the screening based on relative fluorescence. Absolute DNA content was determined by Feulgen densitometry for 13 plants from seven species, and reference chromosome numbers were determined in 12 plants (1–3 per species) representing six species. The plants grouped into diploids (2n = 16), tetraploids (2n = 32), hexaploids (2n = 48), and two triploids. Each ploidal level showed a linear increase in relative DNA content, pointing to a relatively recent polyploid origin. The diploid level was confirmed in D. nivalis, D. subcapitata, D. fladnizensis, and D. lonchocarpa. Draba palanderiana, reported previously as di-, tetra- and octo- ploid, was diploid in all investigated accessions. Hexa- and tetraploids were observed in D. lactea, in approximately the same ratio (8 : 1) as reported previously. The ploidal levels of the Central Asian D. altaica and D. turczaninovii are reported here for the first time as diploid and tetraploid, respectively. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 333–347. ADDITIONAL KEYWORDS: chromosome numbers – cytotypes – Feulgen densitometry – flow cytometry – nuclear DNA content. INTRODUCTION gen densitometry. Flow cytometry is also used for rapid screening of ploidal levels (e.g. Bräutigam & Chromosome numbers and ploidal level information Bräutigam, 1996; Husband & Schemske, 1998; Suda have long played important roles in many fields, & Lysák, 2001; Suda, 2002, 2003; Greilhuber, Såstad including plant taxonomy, evolutionary biology and & Flatberg, 2003), for instance for use in systematics reproductive biology (Stebbins, 1950; Grant, 1981; (e.g. Kiehn, 1995; Ohri, Fritsch & Hanelt, 1998). Sev- Stace, 1989). Many species are uniform with respect to eral studies in species groups and genera have showed ploidal level, but the occurrence of different cytotypes a convincing correspondence between C-values and within a taxonomic species is not unusual, especially taxonomic treatments (e.g. Bos¸ caiu, Vicente & Ehren- in autoploids (e.g. Ness, Soltis & Soltis, 1989; Suda & dorfer, 1999; Cerbah et al., 1999; Zonneveld, 2001), Lysák, 2001). As chromosome number determination suggesting that C-value information can be used as is laborious, exact counts exist for only a small number an important taxonomic marker (Ohri, 1998). Ploidal of plants. level determination using flow cytometry facilitates More recently, information about nuclear DNA con- the screening of a large number of plants rapidly and tent has been used in a variety of disciplines (cf. Ben- relatively inexpensively, but it does not provide exact nett, Bhandol & Leitch, 2000 and references therein). chromosome numbers. Standard techniques for determination of absolute Ploidal level information is of particular value in DNA contents (C-values) are flow cytometry and Feul- complex polyploid groups where reticulate evolution may have played an important role, as for instance *Corresponding author. E-mail: [email protected] in groups of Draba (Brochmann, 1992; Koch & Al- © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147, 333–347 333 334 H. H. GRUNDT ET AL. Shehbaz, 2002). Most Draba species have the base chmann, Soltis & Soltis, 1992b, c; Widmer & Bal- chromosome number x = 8 (e.g. Löve & Löve, 1961, tisberger, 1999). Three diploids, D. fladnizensis and 1975), and the ploidal levels range from diploids D. nivalis (Böcher, 1966) and later also D. subcapitata (2n = 16) to 18-ploids (2n = 144). Many Draba species (Brochmann et al., 1992c; Scheen, Elven & Bro- are reported with only one ploidal level, but several chmann, 2002), have been suggested as possible con- are known with additional levels. tributors to the genome of D. lactea. Recent molecular All species investigated here except two from Cen- analyses suggest, however, that D. palanderiana rep- tral-Asia belong to the group that Mulligan (1974) resents a more plausible parental lineage (Grundt termed ‘Draba nivalis and close allies’. This contains et al., 2004). closely related species at both diploid and low poly- The aim of this study was to investigate ploidal lev- ploid levels and is therefore well-suited for studies of els in D. lactea and its low-ploid relatives in order to Downloaded from https://academic.oup.com/botlinnean/article/147/3/333/2420553 by guest on 28 September 2021 polyploid evolution (see Grundt et al., 2004). These obtain a better basis for evolutionary and taxonomical Draba species are perennial, arctic-alpine rosette studies in this arctic-alpine species complex. In par- plants (Tolmachev, 1939; Cody, 2000) and comprise the ticular we wanted to ascertain the possible occurrence mainly hexaploid (2n = 48) and partly tetraploid of intraspecific variation in ploidal levels and to deter- (2n = 32) D. lactea Adams (including D. pseudopilosa mine the hitherto unknown ploidal levels for the two Pohle, see Berkutenko, 1979; R. Elven, H. H. Grundt Central Asian species D. altaica and D. turczaninovii. & V. V. Petrovsky, unpubl. data), the diploids (2n = 16) Since no data on C-values in Draba can be found in the D. nivalis Lilj., D. lonchocarpa Rydb., D. fladnizensis literature, an additional aim was to investigate abso- Wulfen, and D. subcapitata Simmons and the di-, lute nuclear DNA content in these Draba species. tetra- and octoploid D. palanderiana Kjellm. (Table 1). Draba lactea, D. subcapitata, D. nivalis, and D. fladnizensis have circumpolar distributions MATERIAL AND METHODS (Hultén, 1968; Hultén & Fries, 1986). Draba palande- riana and D. lonchocarpa are restricted to western MATERIAL North America and eastern Asia (Hultén, 1968). Included in the flow cytometric analyses are 200 The two Central-Asian species, D. altaica (C. A. plants from 93 populations of D. altaica, Mey.) Bunge and D. turczaninovii Pohle & N. Busch, of D. fladnizensis, D. lactea, D. lonchocarpa, D. nivalis, hitherto unknown ploidal levels, seem closely related D. palanderiana, D. subcapitata, D. turczaninovii, and to the above group. Draba altaica, a name formerly one unnamed taxon (Table 2). Populations were applied to what is now known as D. subcapitata, is selected to cover a wide range of the distribution area considered to be closely related to D. fladnizensis (A. of the species, i.e. mainly the circumpolar region, but Ebel, unpubl. data). Tolmachev (1939) regarded also more southern latitudes (Table 2). In 50 popula- D. turczaninovii as a member of the same series as tions, two plants were selected for flow cytometric D. nivalis and Ebel (2000 and unpubl. data) considers analyses of ploidal level. In 27 populations, only one it to be closely related to both D. nivalis and plant was used, either because only one plant was D. lonchocarpa. However, molecular analyses have available or because of a close geographical proximity shown that it seems to be more closely related to to other analysed populations. In 16 populations more D. fladnizensis (Grundt et al., 2004). Thus, ploidal than two plants were used, for instance if some popu- level information for these two taxa is of importance in lations contained morphologically deviating plants assessing their possible contribution to the evolution or if preliminary flow cytometric results showed in D. lactea and its low-ploid relatives. deviating ploidal levels (see Table 2). As references, Different chromosome counts have been reported for chromosome numbers were determined in 12 plants a few of these species (Table 1), some of which have representing six different species in addition to esti- proven to be erroneous. One diploid count was mates of C-values using Feulgen densitometry in 13 reported for D. lactea (Dawe & Murray, 1981b; plants covering seven different species (Tables 2, 3). Table 1), but the voucher (ALA) agrees with D. nivalis The Draba plants were cultivated in the Phytotrone, (R. Elven, H. H. Grundt & V. V. Petrovsky, unpubl. University of Oslo. Vouchers are deposited in O. Spe- data), a conclusion also supported by molecular data cies identifications were straightforward for most of for a specimen collected from the same locality in the plants and are supported by molecular analyses Alaska (Grundt et al., 2004). The vouchers of two tet- (Grundt et al., 2004), which have been our guideline in raploid plants named as D. fladnizensis (Table 1) have a few morphologically doubtful cases (cf. Table 2): pop- been identified later as D. lactea (R. Elven, H.