Is Gametophyte Sexuality in the Laboratory a Good Predictor of Sexuality in Nature?

1 Pages·2002·0.62 MB·English

by  Tom A Ranker

American
Fern Journal 92(2):112-118
(2002)
Gametophyte
Good
Is Sexuality Laboratory
in the a
Predictor
of Sexuality Nature?
in
Tom
Ranker and
a. Heather Houston
A.
Museum
University and Department
of Environmental,
Population,
and Organismic
Biology, 218 UCB, CO USA
University of Colorado, Boulder, 80309-0350
A
Abstract.—
previous study examined
the sexual expression of cultured gametophytes
of the
Hawaiian
endemics Sadleha
cyatheoides and grown
pallida on
S. mineral-enriched
agar. In the
we
present work, conducted
field studies on the sexual expression
of natural populations
of
Sadleria spp. gametophytes. Our
primary was
goal compare
to
field-collected data
to the labora-
tory-based data of the study
earlier to assess if the laboratory data were an accurate
reflection of
what
occurring Our
is in nature.
results suggested
that for generally inferring mating systems
m
operatmg
nature, agar-based
laboratory studies of gametophytes lead to the same conclusions
would
as observations
of field-collected gametophytes. For
detailed studies of gametophyte
sex-
and
uality development,
however, an medium
agar-based produces
significantly
different results
true
study
regardless of growth medium. we
Thus,
suggest caution
in the use of agar growth
as a
medium,
and
the use of laboratory
conditions
in general, for studies of fern gametophyte sexual
development. -^
The
gametophytes
homosporous
of
ferns possess the
ability be
to either
unisexual
[antheridiate
or archegoniate]
or bisexual. In may
addition, they
undergo
developmental
sequences
involving
changes
in sexuality over time
due
to genetic and/or environmental
factors (Klekowski,
&
1969a; Greer
McCarthy.
Because
1999). gametophytes
most
of
species are easy grow
to in
many
culture,
studies have been conducted
on
cultured
gametophytes
to
assess such
factors as sexual expression/ontogeny
Klekowski,
[e.g., 1969b),
antheridiogen
production and
response
Stevens & Werth
(e.g., and
1999)
populational
genetic
load/isolate
potential
[Peck
1990)' Numerous
et
al.,
studies have employed
data from
lab-cultured
gametophytes make
to inferen-
ces about mating
systems
operating
in nature &
[e.g., Soltis 1990 and
Soltis,
references Chiou
therein;
&
et al, 1998;
Li
Haulier, many
Although
1999).
studies have examined
gametophytes
were
that
cultured on
mineral-enriched
agar, several have employed
various
natural
substrates (Rubin &
Paolillo 1983-
Greer. Pangua
1993;
et 1994; Lindsay &
al.,
Dyer, &
1996; Greer
McCarthy!
1999; see also Dyer, and
1979, A
references
therein). few
have
studies
combined
genetic data from
natural
populations
of sporophytes
with
labora-
tory data from
cultured
gametophytes
to assess
the
relationship between
gametophytic
and
attributes
and
levels
patterns
of
populational
aenetic
employ
hat
data from
lab-cultured
gametophytes
have
at least one assump-
"'"""^^^^
°^^--d - thTLborZy
P^°^^^^^^
rindicTrofwh
are indicative whatr*''
of
occurrmg
is in nature. At
one
least study however
has
demonstrated
significant
differences
in the sexual
expression
gametophytes
o'f'