Botrychium simplex E. Hitchcock (little grapefern) - Colorado Natural ...

Botrychium simplex is challenging to identify
with confidence since it is highly variable, small, and
cryptic. Farrar (2001) notes that “B. simplex is by far
the most variable of diploid moonworts,” and Wagner
and Wagner (1983) wrote that “Only a few botrychiums
have such astonishing variability as B. simplex.” They
also noted that “no species approaches B. simplex in the
extent of its variability. Var. compositum stands in vivid
contrast to var. tenebrosum.”
Within Region 2, both the eastern and western
forms described by Wagner and Wagner (1993) are
present, and it appears that all three of the varieties
recognized by Wagner and Wagner (1993) occur here.
Wagner and Wagner (1993) provide a summary of the
diagnostic characters of Botrychium simplex; these are
summarized in Table 6. A comparison of the varieties
recognized by Farrar (2005) is included in Table 3.
Botrychium simplex is a small perennial fern,
seldom exceeding 8 cm tall (Lorain 1990). It has
small roots (0.5 to 1 mm in diameter) and a highly
variable trophophore, which is 1 to 7 cm long, oblong
to long-elliptic, 0.3 to 2 cm wide, truncate to round
at the base, round at the apex, pinnate or sometimes
nearly simple, entire, round pinna apices, and entire
or crenulate margins (Lellinger 1985, Farrar 2005).
Useful field marks for B. simplex include its diminutive
size, succulent stem, single compound leaf that is often
clasping the sporophore, its unbranched fertile frond,
and the tendency for the trophophore and sporophore
to connect at ground level (Figure 2; Farrar 2005). It
is highly variable and only distinguished absolutely
from other grapeferns by its larger spores, which
are unusually large for a diploid species, ranging in
diameter from 0.035 to 0.050 mm (Rook 2002, Farrar
2005). Occasional plants are found that have sporangia
dotting the margins of the trophophore (Figure 3).
These are called supernumerary sporangia and are seen
infrequently in all moonwort species (Farrar 2005).
Botrychium simplex is diploid with 45 chromosomes
(2n = 90) (Wagner 1993, Wagner and Wagner 1993).
Detailed descriptions for both “eastern” and
“western” Botrychium simplex appear in Wagner and
Wagner 1993. Several field characteristics are useful for
distinguishing these two types of B. simplex. Western B.
simplex has a sporophore that is longer relative to the
trophophore, lacks a common stalk, and has fan-shaped
pinnae. See Table 6 for a comparison of diagnostic
characteristics between these types, and Figure 3,
Figure 4, and Figure 5 for specimens representing
these types.
14
Botrychium simplex var. compositum is roughly
equivalent to the “western” B. simplex of Wagner and
Wagner 1993 (Figure 3). It is usually has a three-parted
leaf as shown in Gray (1908), Hitchcock and Cronquist
(1969), and Cronquist et al. (1972). The shape of
the trophophore is distinctive in having three main
branches (Lorain 1990). The sporophore diverges at or
just above ground level (Welsh et al. 1993, Farrar 2005)
or sometimes below ground level (as noted on some
specimens collected by Peter Root).
Botrychium simplex var. tenebrosum occurs in
eastern North America (Wagner and Wagner 1993) and
elsewhere, including Wyoming (Figure 4; Hartman and
Nelson 2001). It was thought by Wagner and Wagner
(1993) and others to be a persistent juvenile, but current
genetic evidence suggests otherwise. Var. tenebrosum is
distinguished from var. simplex (Figure 5) by its smaller
size, slender stature, and its simple and rudimentary
trophophore attached near the top of an exaggerated
common stalk. Wagner and Wagner (1993) describe
a western equivalent to B. simplex var. tenebrosum,
with a lower attachment of the trophophore, which is
longer and more herbaceous in texture. The spores of
var. tenebrosum are larger than those of var. simplex
(Eaton 1899). Clausen (1938) includes photographs
of specimens of B. simplex var. tenebrosum. Var.
tenebrosum has been mistaken for B. simplex var.
simplex and B. matricariifolium.
Botrychium simplex is frequently confused with
other species of Botrychium in Region 2 and elsewhere.
Within Region 2, B. simplex specimens have been
misidentified as B. lunaria and B. hesperium. In several
cases, one plant on an herbarium sheet containing
several plants has been annotated as B. lunaria or in one
case B. paradoxum. Many medium or large specimens
of B. simplex have flabellate pinnae that strongly
resemble B. lunaria (Wagner and Wagner 1981). In
Oregon, well-formed plants can be mistaken for B.
pumicola, and immature plants are easily confused
with B. minganense and B. lunaria (Zika et al. 1995).
A key point in separating B. simplex from simplex-like
minganense (B. “colorado”) is that in B. simplex, the
sporophore separates from the stipe at or just below the
soil surface (Figure 2; Root personal communication
2003). Before its circumscription, B. montanum was
known as B. simplex in Montana (Vanderhorst 1997).
Botrychium simplex also looks like B. mormo (Wagner
1998). In Iowa, Michigan, and Nebraska, B. simplex has
been found associated with B. campestre, with which
it is the putative parent species of B. gallicomontanum
(Farrar and Johnson-Groh 1991, Farrar personal
communication 2003).