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

(Read et al. 2000). The subterranean, achlorophyllous
gametophyte of B. lunaria (subgenus Botrychium)
may live under ground for up to five years (Winther
personal communication 2002) using carbohydrates
and minerals gained from the mycorrhizal interaction
(Schmid and Oberwinkler 1994). Daigobo (1979)
observed infection of the gametophyte of B. multifidum
(subgenus Sceptridium) with an endophytic (arbuscular
mycorrhizal) fungus in all gametophytes examined at all
developmental stages. Dormancy in Botrychium species
appears to be related to the health of mycorrhizae
(Johnson-Groh 1998).
It is unknown how or if the mycorrhizal
interaction changes when the gametophyte develops
into a sporophyte, but it certainly shifts from a parasitic
relationship to a more mutualistic relationship since the
sporophyte is chlorophyllous and not wholly dependent
on a mycobiont for carbohydrates. Botrychium
sporophytes have reduced, non-proliferous roots that
lack hairs (Wagner and Wagner 1993), and they depend
upon mycorrhizae (Bower 1926, Foster and Gifford
1989). Observations of root samples of B. multifidum
and B. virginianum showed 100 percent infection, with
all roots having the same degree of infection (Kempema
et al. 2003).
Arbuscular (also referred to in the literature as
vesicular-arbuscular) mycorrhizae are a known fungal
symbiont with Botrychium species (Berch and Kendrick
1982, Schmid and Oberwinkler 1994). Johnson-Groh
(1999) hypothesizes that the most important factor
in the establishment and persistence of Botrychium
occurrences is the presence of mycorrhizae. Little
is known about the nature of this interaction. Farrar
(1998) noted that mycorrhizal fungi are low in species
diversity, ubiquitous in disturbed and undisturbed
sites, and generalists in what plant species they infect
(Smith and Read 1997). Recent studies have measured
high species diversity of arbuscular mycorrhizal (AM)
fungi in a single hectare (Bever et al. 2001). A single
plant root was observed to host up to 49 species of
AM fungi (Vandenkoornhuyse et al. 2002). These
observations, coupled with the ubiquity and low host
specificity of AM fungi, suggest that mycorrhizae may
not be a limiting factor in the distribution of B. simplex.
Future studies will be able to identify fungal symbionts
of Botrychium species through experimentation with
gametophytes in axenic culture (Read et al. 2000).
Mycorrhizae can affect the composition of a plant
community by shifting the intensity of competitive
interactions (Read 1998, Van Der Heijden et al. 1998).
Marler et al. (1999) found that the exotic spotted
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knapweed (Centaurea maculosa) had more intense
competitive effects on Festuca idahoensis (Idaho
fescue) when grown together in the presence of
mycorrhizal fungi. With their tight association with
mycorrhizae, similar work with Botrychium species is
needed to understand the potential for mycorrhizaemediated
interspecific competition.
Hybridization
Hybrids between Botrychium species are rare
(Wagner and Wagner 1993, Wagner 1998). At least
10 records of sterile hybrid combinations have been
documented (Wagner 1980, Wagner et al. 1984, Wagner
et al. 1985, Wagner and Wagner 1988, Wagner 1991,
Wagner 1993, Ahlenslager and Lesica 1996). There
are no records of hybrids in Region 2, but it is possible
that hybrids may exist where B. simplex occurs with B.
lunaria in several locations in Region 2. Two sterile
hybrids have been documented between B. simplex
and other Botrychium species. Botrychium lunaria
(Wagner and Wagner 1988) and B. matricariifolium
(Wagner 1980, Wagner 1991) are both capable of
hybridizing with B. simplex. The resulting offspring
have intermediate characteristics and sterile, abortive
spores (Wagner 1993).
Evidence from cytological and molecular
research on many moonwort species strongly suggests
an allopolyploid origin through historic hybridization
events (Wagner 1993, Hauk and Haufler 1999,
Wagner and Grant 2002). Three polyploid moonworts,
Botrychium hesperium, B. pseudopinnatum, and B.
gallicomontanum, are believed to have arisen through
ancient hybridization events involving B. simplex. As
such, these species are referred to as “nothospecies.”
Table 5 describes the purported parentage of these
nothospecies. Other moonworts also have a suspected
hybrid parentage, including the recently described B.
alaskense, which is an allotetraploid of B. lunaria and
B. lanceolatum (Wagner and Grant 2002).
The anatomy of the gametophyte (Bower 1926)
and the difficulty that gametes encounter when traveling
through dry soil (McCauley et al. 1985, Soltis and Soltis
1986) serve to limit outcrossing and hybridization.
Morphological and genetic analyses of genus
communities have demonstrated that hybridization
rarely occurs, and most hybrids have abortive spores
(Wagner and Wagner 1983, Wagner et al. 1984, Wagner
and Wagner 1986). This demonstrates the presence of
multiple species in these genus communities rather than
intraspecific variants.