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FNA | Family List | FNA Vol. 20 | Asteraceae

193. Eurybia (Cassini) Cassini in F. Cuvier, Dict. Sci. Nat. ed. 2. 16: 46. 1820.

Aster [Greek eurys, wide, and baios, few, perhaps alluding to the few, wide-spreading ray florets]

Luc Brouillet

Aster Linnaeus subg. Eurybia Cassini, Bull. Sci. Soc. Philom. Paris 1818: 166. 1818

Perennials, 10–120 cm (rhizomes long and slender to short and thick, sometimes cormoid, often becoming woody). Stems ascending to erect, usually simple, rarely branched proximally, glabrous or ± densely hairy, usually eglandular, sometimes stipitate-glandular. Leaves basal and cauline; alternate; sessile or petiolate; blades cordate, ovate, obovate, elliptic, or oblong to spatulate, oblanceolate, or lanceolate, usually gradually reduced distally, margins entire or serrate, sometimes spinulose-serrate, faces glabrate to hairy, usually eglandular, sometimes stipitate-glandular. Heads radiate, usually in corymbiform arrays, rarely borne singly. Involucres cylindro-campanulate to broadly campanulate, (4–14(–16) ×) 4–25+ mm. Phyllaries 20–140 in 3–7 series, 1-nerved (usually rounded adaxially, sometimes low-keeled), broadly ovate or oblong to oblanceolate, lanceolate, or linear, unequal, bases indurate (rarely wholly foliaceous), margins narrowly scarious (seldom herbaceous), often ciliolate (green zones ± basally truncate, in distal 1 / 3 – 3 / 4 of phyllary (outer) to less than 1 / 6 and only along midnerves (inner), apices obtuse to acute, faces glabrous, ± strigillose, puberulent, scabrellous, strigoso-villous, or villous, sometimes ± stipitate-glandular. Receptacles flat to slightly convex, pitted, epaleate. Ray florets 5–60, pistillate, fertile; corollas white to purple (coiling at maturity). Disc florets 8–260, bisexual, fertile; corollas yellow, becoming purple at maturity, barely to abruptly ampliate, tubes shorter to longer than funnelform to campanulate throats, lobes 5, usually erect to spreading, sometimes ± reflexed, deltate, triangular, or lanceolate; style-branch appendages lanceolate. Cypselae cylindro-obconic to fusiform, ± compressed, 7–12(–18)-nerved, faces glabrous or sparsely to densely strigillose, eglandular; pappi persistent, of 35–70+, reddish, orange, cinnamon, tawny, tan, yellowish, or pinkish, unequal, soft to stiff, barbellate or barbellulate, often apically ± clavate bristles in 2–4 series. x = 9.

Species 23 (23, including 1 hybrid, in the flora): North America, n Eurasia.

Eurybia traditionally has been treated within Aster in a broad sense. G. L. Nesom (1994b), in his review of North American asters, showed that Aster in a broad sense does not form a natural group and proposed splitting it into several genera, among which Eurybia is one. In his treatment, Nesom included Herrickia within Eurybia, as sect. Herrickia in subg. Eurybia. Such views were generally supported in molecular phylogenetic studies (J. C. Semple et al. 2002). L. Brouillet et al. (2004) showed, however, that Oreostemma, Herrickia, Eurybia, and Triniteurybia form a grade at the base of the Machaerantherinae and that Herrickia and Eurybia are distinct.

The subgenera and sections proposed by G. L. Nesom (1994b), based on anterior taxonomy, could not be confirmed in the molecular studies cited above. I chose not to use subgeneric limits as proposed by Nesom because they may not reflect actual relationships. For instance, there is a clear gradation between members of sect. Calliastrum (Torrey & A. Gray) G. L. Nesom (subg. Eurybia) and sect. Heleastrum (de Candolle) G. L. Nesom. Also, I do not recognize sect. Eryngiifoliae (Alexander) G. L. Nesom distinct from sect. Heleastrum, as there is no clear demarcation between the two as currently defined. Finally, sect. Radulini (Rydberg) G. L. Nesom appears artificial to me, but currently there is no good way to reassign its species. The Eurybia radulina complex of western North America clearly constitute a group, but it is unclear whether the western E. conspicua or the eastern E. radula and E. saxicastelli are close to them. Members of other sections may have played a role in the reticulate evolution of sect. Eurybia, even though it is well marked by its cordate leaves and disc florets with long tubes and short, campanulate corollas. Therefore, species are described below in a rough taxonomic order, with diploids listed before polyploids of the same group.

1 Basal and/or proximal cauline leaves (at least some) cordate; e North America   (2)
+ Basal and/or proximal cauline leaf blades not cordate   (10)
2 (1) Peduncles and involucres ± stipitate-glandular   (3)
+ Peduncles and involucres usually eglandular   (5)
3 (2) Rays white; phyllaries sparsely stipitate-glandular; adaxial leaf faces villous, eglandular   13 Eurybia schreberi (in part)
+ Rays deep to pale purple; phyllaries sparsely to densely stipitate-glandular; adaxial leaf faces sparsely strigose or sparsely puberulent, stipitate-glandular   (4)
4 (3) Proximal cauline leaf blades broadly ovate to ovate, bases cordate; innermost phyllaries appressed, usually to 7 mm   14 Eurybia macrophylla
+ Proximal cauline leaf blades ovate to elliptic-ovate, bases rounded to cordate; innermost phyllaries longer than 7 mm, at least some apically reflexed, ± squarrose, or twisted   15 Eurybia ×herveyi (in part)
5 (2) Phyllaries (at least some) squarrose   (6)
+ Phyllaries not squarrose   (7)
6 (5) Phyllaries usually 46–75(–90), oblong-lanceolate; ray florets (7–)16–20(–30), white or lavender; disc florets 20–40   9 Eurybia mirabilis
+ Phyllaries 36–50, ovate, elliptic, or lanceolate; rays 7–15, blue or violet; disc florets 20–25   10 Eurybia jonesiae
7 (5) Leaf faces abaxially scabrous, adaxially hirsute, veins prominent; rosettes absent in spring   8 Eurybia furcata
+ Leaf faces abaxially sparsely strigose to villous or glabrous, adaxially glabrescent to sparsely strigose or villous, veins not prominent; rosettes present in spring, persistent or withering by flowering   (8)
8 (7) Clones with sterile rosettes (on short rhizomes); proximal cauline leaf blades broadly ovate to ovate, bases cordate, sinuses broad, margins usually with 15–30 teeth per side; peduncles sparsely to moderately villous   13 Eurybia schreberi (in part)
+ Clones lacking sterile rosettes; proximal cauline leaf blades ovate, bases cordate, sinuses narrow or none, margins usually with 6–15 teeth per side; peduncles ± densely villous   (9)
9 (8) Peduncles to 1.5 cm; involucres (3.5–)4.2–6(–7.5) mm; ray florets 5–10(–12), laminae (5–)10–15 mm; disc florets 12–19(–25)   11 Eurybia divaricata
+ Peduncles usually more than 1.5 cm; involucres 6.5–9(–10) mm; ray florets (8–)12–16(–20), laminae (10–)17–18(–20) mm; disc florets (12–)17–26   12 Eurybia chlorolepis
10 (1) Leaf blades linear, ± grasslike, often coriaceous, often parallel-nerved or obscurely nerved, margins entire or ± spinose-serrate (se United States)   (11)
+ Leaf blades lanceolate or elliptic- or lanceolate-ovate to ovate, oblong to narrowly elliptic, oblanceolate to obovate or spatulate, not coriaceous or if ± coriaceous, not linear with margins entire, serrate or spinulose-serrate   (15)
11 (10) Stems villous; phyllaries 70–140; ray florets 25–60, white to pinkish; disc florets 115–260   22 Eurybia eryngiifolia
+ Stems glabrous or glabrescent proximally, ± villous or strigillose distally; phyllaries 20–80+; ray florets 8–35, pale to dark purple; disc florets 18–60   (12)
12 (11) Distal stems villous to glabrescent; phyllaries 20–40, ± loose, not spreading; ray florets 8–17   23 Eurybia spinulosa
+ Distal stems strigillose, villoso-hirsute or hirtello-puberulent; phyllaries 30–65+, ± spreading or reflexed; ray florets 8–35   (13)
13 (12) Distal stems hirtello-puberulent; heads usually in corymbiform arrays, some-times borne singly; involucres 7–9 mm; rays 8–25; pappus bristles fine   19 Eurybia avita
+ Distal stems strigillose to villoso-hirsute; heads usually in spiciform or corymbiform arrays, rarely borne singly; involucres 8–12 mm; rays 15–35; pappus bristles coarse   (14)
14 (13) Distal stems strigillose; heads borne in spiciform arrays, sometimes corymbiform terminally; outer phyllaries sometimes coriaceous, margins scabrous or scabroso-ciliate   20 Eurybia hemispherica
+ Distal stems strigillose to ± villoso-hirsute; heads borne in corymbiform arrays; outer phyllaries not coriaceous, margins densely ciliate proxi-mally (indurate part), distally scabrous (foliaceous part)   21 Eurybia paludosa
15 (10) Peduncles and phyllaries stipitate-glandular   (16)
+ Peduncles and phyllaries eglandular (or only peduncles sparsely stipitate-glandular)   (19)
16 (15) Leaves cauline (w North America)   2 Eurybia conspicua
+ Leaves basal and cauline   (17)
17 (16) Stems hispido-villous distally; leaf margins entire; mid cauline leaf bases auriculate-clasping; heads in elongate, racemo-corymbiform arrays, branches ascending; w United States   1 Eurybia integrifolia
+ Stems sparsely strigose, hispido-villous, or villous distally; leaf margins entire to ± serrate; mid cauline leaf bases attenuate to slightly clasping; heads in open, corymbiform arrays; e United States   (18)
18 (17) Basal leaf blades ovate, bases broadly rounded (to cordate); mid and distal cauline leaf margins serrate; involucres (6–)7–11 mm   15 Eurybia ×herveyi (in part)
+ Basal leaf blades lanceolate or elliptic to ovate- or obovate-elliptic or spatulate, bases attenuate; mid and distal cauline leaf margins usually entire, sometimes crenulate-serrulate; involucres 7.5–14(–16) mm   18 Eurybia spectabilis
19 (15) Leaves basal and cauline, only midnerves conspicuous; cauline leaf margins entire or slightly serrate, teeth and apices indurate (e United States)   (20)
+ Leaves cauline, ± markedly veined; cauline leaf margins usually ± serrate, sometimes entire, teeth sometimes ± indurate, apices not indurate   (21)
20 (19) Rootstocks: thick, woody, ovoid to spheric caudices; stems usually ± densely villous distally; involucres 6.5–9 mm; phyllaries 24–35; ray florets (5–)8–14; disc florets 10–20, tubes longer than throats   16 Eurybia compacta
+ Rootstocks: rhizomes herbaceous becoming woody, slender, scaly; stems strigose or villoso-strigose or hirsuto-strigose distally; involucres 7–11(–13) mm; phyllaries 35–65; ray florets 13–30; disc florets 25–40, tubes shorter than throats   17 Eurybia surculosa
21 (19) Plants in clones; distal stems ± villosulous; leaf margins ± recurved; e North America   (22)
+ Plants clumped; distal stems villous or villosulous to lanate; leaf margins not recurved; w North America.   (23)
22 (21) Plants 10–100 cm, distally glabrescent to ± villosulous; mid cauline leaf blades lanceolate, oblanceolate, narrowly obovate, or narrowly elliptic, 10–42 × 3–8 mm, ± remotely, ± deeply serrate; rays purple   6 Eurybia radula
+ Plants 40–120 cm, distally villosulous; mid cauline leaf blades broadly elliptic to oblanceolate, (70–)90–140 × 40–50(–60) mm, coarsely serrate; rays white to pale purple   7 Eurybia saxicastelli
23 (21) Plants 10–70 cm; stems ascending to erect, ± densely villous distally; leaves coarsely serrate (teeth mucronate), cauline bases often ± clasping; phyllaries not purplish, margins not purple; rays white (sometimes purplish) (w coast United States)   3 Eurybia radulina
+ Plants 1–50 cm; stems decumbent to ascending, villosulous or villous to ± lanate distally; leaves ± serrate to serrulate or entire, cauline bases subauriculate or slightly clasping; phyllaries ± purplish or margins purple; rays purple (sometimes pale)   (24)
24 (23) Distal stems villosulous; leaf margins entire or serrulate; phyllaries unequal, margins purple, not squarrose or reflexed; mountains, s British Columbia, w United States   4 Eurybia merita
+ Distal stems villous to densely lanate; leaf margins serrate or entire; phyllaries subequal or barely unequal, purplish at least distally (but not only on margins), squarrose; w Canada, Alaska, Idaho, Montana   5 Eurybia sibirica

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