4.
Symphyotrichum subulatum
(Michaux) G. L. Nesom, Phytologia. 77: 293. 1995.
Annual saltmarsh or eastern annual saltmarsh aster, aster subulé
Aster subulatus
Michaux, Fl. Bor.-Amer. 2: 111. 1803
Annuals
, (10—)30—150 cm; tap-rooted.
Stems
1, erect (often with purple or purplish brown areas), glabrous or glabrate, sometimes strigillose in leaf axils.
Leaves
thin (green to dark green), margins often strigilloso-ciliolate, faces glabrous; basal withering by flowering, long-petiolate (petiole bases sheathing), sparsely ciliate, blades ovate to oblanceolate, 10—90 × 6—14 mm, bases attenuate to cuneate, rounded, margins entire or serrulate or crenulate, apices rounded, obtuse, or acute; proximal cauline withering by flowering, petiolate, subpetiolate, or sessile, blades narrowly lanceolate or subulate, 20—100(—200) × 1.5—10(—20) mm, bases attenuate, margins subentire, entire, or serrulate, apices acute to acuminate; distal sessile, blades narrowly lanceolate to subulate, 5—113 × 0.5—5.5 mm, apices acuminate.
Heads
(10—) 30—100(—150), in open, diffuse, paniculiform arrays.
Peduncles
(0.2—)0.5—4 cm, bracts 4—8(—17).
Involucres
cylindric to turbinate, 5—7(—8.2) mm.
Phyllaries
in 3—5 series, broadly or narrowly lanceolate to subulate, unequal, bases indurate, margins hyaline, often purple-tinged, entire, green zones lanceolate (usually narrow, sometimes broad and covering most of distal portion), apices acute, faces glabrous.
Ray florets
16—30(—54) in 1—3 series; corollas white, pink, or lavender, laminae 1.3—7 × 0.2—1.3 mm.
Disc florets
4—10(—13); corollas yel-low, sometimes tinged with purple, 3.4—5.2 mm, throats narrowly funnelform, lobes ± spreading to erect, nar-rowly triangular, 0.3—0.7 mm, glabrous.
Cypselae
light brown to purple, narrowly obovoid to fusiform, some-times ± compressed, (1.2—)1.5—2.7(—3) mm, 5-nerved, faces sparsely strigillose;
pappi
white, (3—)3.5—5.5 mm.
Varieties 5 (5 in the flora): North America, Mexico, West Indies, Bermuda, Central America, South America; widely introduced worldwide.
Five varieties of
Symphyotrichum subulatum
are recognized for North America based on differences in chromosome number, ray lamina color and size, array shapes, number of series of ray florets, number of disc and ray florets, and other, more cryptic characters (S. D. Sundberg 2004). These varieties were treated as species by G. L. Nesom (1994b, 2005d). Variety
ligulatum
is apparently an obligate outcrosser and is the least variable variety (Sundberg). Other varieties are self-compatible, which could facilitate the fixation of mutations in populations.
The five varieties are nearly entirely allopatric, and intermediates between pairs of varieties are not uncommon where they approach one another. Populations that are intermediate in ray lamina size between vars.
ligulatum
and
parviflorum
are widespread in southern Texas, New Mexico, Arizona, and northern Mexico. Intermediates between vars.
elongatum
and
parviflorum
and between vars.
elongatum
and
subulatum
occur in Florida. Despite these observations, hybridization experiments and chromosome number differences suggest that the varieties are mostly reproductively isolated (S. D. Sundberg 1986, 2004).
In older floras the name
Aster exilis
Elliott has been applied to
Symphyotrichum subulatum
vars.
ligulatum
and
parviflorum
. The status of this name is uncertain; the type specimen has been lost and the description of the plant is inadequate for determining the taxon to which the name should be applied (G. L. Nesom 1994b; S. D. Sundberg 2004).
