keys to the vascular plants of east texas - Botanical Research ...

890 POACEAE/DICHANTHELIUM
(pers. comm.) also reports that some East TX specimens have the contracted panicles typical of
the taxon recognized by Freckmann and Lelong (2003a) as D. aciculare subsp. neuranthum
(Griseb.) Freckmann & Lelong. Even though this taxon has not been formally reported for TX
(e.g., Hatch 2002), it is possible that it is a member of the East TX flora. The following key is
modified from Lelong (1986) and Freckmann and Lelong (2003a):
1. Spikelets 1.7–2.3 mm long, blunt; leaf blades 3.5–6(–8) cm long and to 4 mm wide ____________ var. aciculare
1. Spikelets 2.4–2.8(–3) mm long, often pointed or beaked; leaf blades (5–)6–16 cm long and to 7
(–8) mm wide ______________________________________________________________ var. angustifolium
var. aciculare. Culms usually 35 cm or less tall. An Angelina Co. (BRIT) specimen is the only one
for East TX we have seen that is var. aciculare; L. Brown (pers. comm.) notes that a Hardin Co.
collection is also of this variety. [Panicum aciculare Desv. ex Poir., Panicum ovinum Scribn. & J.S.
Sm.] While not officially designated as such (e.g., TOES 1993; Carr 2002d; Poole et al. 2002),
given its limited distribution in the state, we consider this variety to be of conservation concern
in TX. �
var. angustifolium (Elliott) S.L. Hatch, (narrow-leaved). Culms usually 35–75 cm tall. Widespread
in e 1/3 of TX, with a few locations scattered to the w; almost all East TX specimens of
this species that we have seen are of var. angustifolium. [D. angustifolium (Elliott) Gould, Panicum
aciculare Desv. ex Poir. var. angustifolium (Elliott) Wipff & S.D. Jones, Panicum aciculare
var. arenicoloides (Ashe) Beetle, Panicum angustifolium Elliott, Panicum arenicoloides Ashe]
The fruits are reportedly dispersed by ants, which are apparently attracted to a substance (possibly
an oil) found under the first glume (Gaddy 1986).
Dichanthelium acuminatum (Sw.) Gould & C.A. Clark (long-pointed, tapering to tip). Plant 10–
70(–90) cm tall, ranging from densely villous to ± glabrous; hairs of ligule and adjacent hairs (=
pseudoligule) usually 1.5–6 mm long, at least some usually 2 mm or more long (ligule length is
often critical in distinguishing this from other species); leaf blades usually 3–12 mm wide;
spikelets 1.1–2.1 mm long. Apr–Jun, again late summer–fall. According to Lelong (1986), D.
acuminatum is “probably the most polymorphic and troublesome species in the genus.” After
examining numerous specimens of D. acuminatum, it is not clear what the best approach is for
describing the variation seen in it and its relatives—different authors have taken radically different
approaches. This is an excellent example of evolutionary processes resulting in a pattern
of variation not easily divided into distinct taxa. Some authorities (e.g., Freckmann 1981a) recognized
as distinct species some taxa that are here recognized as varieties (e.g., D.
longiligulatum). Yatskievych (1999), on the other hand, submerged a number of taxa (including
D. ovale var. villosissimum) into Panicum acuminatum var. acuminatum. Hatch (2002) treated
D. consanguineum as D. acuminatum var. consanguineum. Freckmann and Lelong (2003a) took
a still different approach and treated D. acuminatum as being composed of 10 subspecies. This
species exhibits extensive geographic variation and has numerous local “microspecies” associated
with autogamous reproduction (Freckmann 1981a). As a result, until a detailed study of
the group throughout its range is carried out (hopefully using molecular techniques), it is
highly likely that various state and regional floras will differ in the number of species and/or
varieties recognized. We have attempted to give formal recognition to taxa that can be reasonably
and consistently separated—having said this, we warn that intermediates are definitely to
be expected. Several taxa sometimes treated as belonging to D. acuminatum are excluded from
that species here. Because of its consistently small spikelet size (a critical character in
Dichanthelium taxonomy), we are recognizing D. wrightianum as a distinct species. Also,
based on recent work by Freckmann and Lelong (2003), we are treating the taxon that had previously
been recognized as D. acuminatum var. villosum as D. ovale subsp. villosissimum—
spikelet size supports this view. On the other hand, we are synonymizing several varieties
(fasciculatum, implicatum, thurowii) with D. acuminatum var. acuminatum. Because of the
intergrading patterns of variation, it seems most reasonable to recognize the following infraspe-