The Occurrence of Trichomanes godmanii (Hymenophyllaceae) on Welfia georgii (Arecaceae) at the La Selva Biological Station, Costa Rica

2004·3.9 MB·English

by  Robbin C Moran

—
American
Fern
Journal 94(2):70-76
(2004)
The
Occurrence Trichomanes godmanii
of
(Hymenophyllaceae) on
Welfia georgii (Arecaceae)
La
the Selva
at Biological Costa Rica
Station,
MORAN
ROBBIN
C.
New
The New
York USA
Botanical Garden, Bronx, York
10458-5126,
RoMiNA
ViDAL Russell
Department
of Plant Biology, Southern
Illinois University Carbondale, Carbondale,
at
USA
62901-6509,
Illinois
Abstract.—
Field observations suggested
that the epiphytic fern Trichomanes godmanii occurred
more
frequently and abundantly on the trunks palm
of the Welfia georgii than on the trunks of
We
dicotyledonous
trees. tested this observation by randomly
statistically selecting 25 individuals
of W. georgii and the nearest dicotyledonous
tree of similar dbh, for a total of 50 trunks. For each
trunk up we
to a height of three meters, recorded the presence or absence of godmanii and,
T.
if
we
present, visually estimated percent cover using a ranked We found
scale. that the fern occurred
more
frequently and abundantly on palm
the than on dicotylendonous No was
relationship
trees.
found between
the diameter of the trunks and
vegetative cover. This one of the few
is host-specific
preferences recorded among We
epiphytic why
cannot
ferns. fully explain the fern occurs more
and
frequently abundantly on
the trunks
of Welfia georgii instead of dicot trees, but the fern^s
adhesive hairs on rhizomes and
its petioles probably help attachment smooth
to the trunk of
the palm.
The
epiphytic habit prominent
Of
is in pteridophytes.
the approximately
9,000 species of pteridophytes considered by
Kress
worldwide,
(1986, 1990]
Mesoamerica
Moran
Mo
Station, epiphytic species compose 49% and 42%
of the
pteridoflora,
(Grayum
respectively and
Churchill,
1987; Nadkarni and
Wheelwright!
2000). Despite the prominence
epiphytism
of
in pteridophytes, work
little
has been done on documenting
species-specific host Most
associations.
reports
of associations
consist of casual
observations, such
as those reported
for fern
epiphytes
largely or
entirely
restricted to the root mantles ferns-
of tree
epiphytes such
as Tmesipteris
in Australasia (Brownsey and
Smith-
Dodsworth, and Blechnum
1989],
fragile (Liebm.] Morton &
C. V.
Lellinger,
Costaricia werckleana H.
Christ, Terpsichore lehmanniana
(Hieron.) A. Sm.,
R.
semihirsuta
T, (Klotzsch] A. R. Sm., and Trichomanes
capillaceum
In
L.
Mesoamerica (Moran and
Thp
Riba, 1995. n. 3991. nnlv a^.
Qtnti'ofiVai .+
Moran
trunk
They
occurred enough
frequently
in their samples be
to tested
statistically, 11 (35%)
occurred more
frequently on
tree fern root mantles.
MORAN
& RUSSELL: TRICHOMANES GODMANII ON
WELFIA GEORGII
71
The present study was prompted by an observation made by Grayum and
Churchill La
(1989} at the Salva Biological Station in Costa Rica about the
frequency of occurrence of Trichomanes godmanii Hook, on the trunks of the
palm
WeljiageorgiiH. A. Wendl. exBurret. They observed godmanii was
that T.
—
frequently found a low-trunk epiphyte on palm palm
as the a ubiquitous
the
at
La
Selva
^piphyt
was
observation subsequently confirmed by
the senior author the La Selva
at
We
decided to test these observations by sampling and analyzing the
results
We
Welfi^
dicotyledonous second, no
trees; that there difference in the abundance,
is
expressed percent godmanii on
as vegetative cover, of T. Welfia georgii versus
dicotyledonous
trees.
we
Besides these two hypotheses about host preference, examined
the
possible influence of the palm's dbh on the percent cover Trichomanes
of
We
godmanii. expected no influence because the age of the palm not
is
correlated with the diameter of trunk (Rich, 1986). Therefore, larger diameter
its
would
trunks not necessarily be available for a longer time for the fern
to
colonize and form a greater percent cover. The null hypothesis we tested was
that of no correlation between percent vegetative cover of the fern and the trunk
diameter of the palm.
Methods
The La Selva Biological Station located in Heredia Province, the
is at
confluence of the Puerto Viejo and Sarapiqui rivers, near Puerto Viejo de
Sarapiqui, on the Caribbean side of Costa Rica, 10^26'N, 83°59'W. The elevation
about 50 m, and the vegetation relatively aseasonal, tropical wet
is is forest,
mm
with an average annual rainfall of 4,000 (McDade and Hartshorn, 1994).
We
Camino
sampled along an established called the Experimental Sur
trail
beginning a point where meets the Sendero Tres Ribs in front of the clearing
at
it
We
sampled
that harbors the laboratory buildings. 25 pairs of trees, each pair
We
consisting of one georgii and one angiosperm. sampled a palm
Welfia first
We
and then selected the nearest dicotyledonous tree of similar (± 10 cm] dbh.
we
sampled and sampled
microclimatic trunks
pairs to control for effects, of
similar dbh to control for differences in presence or percent cover that might be
associated with trunk width. Only the lower three meters of the trunks were
When
sampled. the fern was present, percent vegetative cover on each trunk
=
was visually estimated and then scored using a ranked scale where absent,
= = = - -
1-10% 11-25%, 26-50%, 51-75%, 76-100%.
1 cover, 2 3 4 5
To
frequency occurrence
the hypothesis (no difference in the of of
test
first
we
Trichomanes godmanii on georgii versus dicot trunks], used Fisher's
Welfia
X
Exact Test (Langley, 1971). This test is a 2 2 contingency table that should be
N
when
used contingency between and 50
instead of a chi-square table is 8
N
=
(we had 50; the 25 pairs). The probabilities were calculated for a
i.e.,
72 JOURNAL
Fig. A. Welfia georgii without Tricbomanes
1. godnmnii, showing smooth
surface of trunk B
Trunk
of Welfia georgii covered with T. godmanii. C. Close up of T. godnmnii colony. D
Fertile
cm
frond godmanii
of T. (about 1 long]. All photographs taken at the La Selva Biological
Station.
Costa Rica.
MORAN
& RUSSELL: THICHOMANES GODMANII ON WELFIA GEORGII
73
Table Contingency table showing the occurrence of Trichomanes godmanli on the trunks of
1.
Weljia georgii and dicotyledonous trees at the La Selva Biological Field Station, Costa Rica.
According to a Fisher's exact test, T. godmanii occurred more frequently on the trunks of W, georgii
=
[P 0.0014).
Dicot W. georgii Total
Absent
20 8 28
Present 5 17 22
Total 25 25 50
we
two-tailed because were interested in whether godmanii occurred
test T.
more on angiosperms To
frequently either Welfia georgii or trunks. the
test
second hypothesis [no difference in the percent vegetative cover of
T.
we
godmanii on used Wilcoxon/
Welfia georgii versus dicot trunks), a
sum
Kruskal-Wallis rank Included in were only those trunks
test. this test
where was
the fern present (17 palms, 5 dicots). For the third hypothesis (no
correlation between percent vegetative cover of godmanii with the dbh of
T.
we
palm where was
the trunks), included only those 17 trunks the fern present.
We
between dbh palm and
then tested for a correlation of the percent cover of
The
the fern using Spearman*s rank coefficient. significance level for three
all
<
P
was The
hypotheses described paragraph
set at 0.05. statistical tests in this
were performed using JMP package, version and
the statistical 3.3.2 (Sail
Lehman,
1996).
cm
Several species of Trichomanes with leaves less than 3 long occur at the
La Selva Biological Station^ and these can be easily confused with T. godmanii
we
examined
(Grayum, During sampling suspected individuals of
1989). T.
godmanii the presence of cross-connections between the false veins. This
for
characteristic distinguishes T. godmanii from all other similar small species of
Trichomanes (Wessels Boer, 1962). Other characteristics helpful in identifying
the species were glabrous lamina margins without black paired or stellate
(i.e.,
hairs) and green-margined involucres (not black margined; Fig. ID). At the La
Selva Biological Station, none of the other small species of Trichomanes form
godmanii on
large extensive mat-like colonies that does the trunks of Welfia
T,
georgii
Results
Trichomanes godmanii was present on 17 palms
In the 25 paired samples,
cm
and 5 dicot The mean dbh of the palms sampled in this study was 17
trees.
mean
with a range of 13-25 cm. The for the nearest dicot trees of
(s.d. 2.2),
cm
cm 9-26
dbh was with range of dbh.
similar 17.7
(s.d. 5.5),
Trichomanes
Hypothesis .—no difference in the frequency of occurrence of
1
The was
godmanii on versus dicot trunks. null hypothesis
Welfia georgii
(P= The occurs more frequently on the palm.
rejected 0.0014; Table fern
1).
—
godmanii
Hypothesis no difference in the percent vegetative cover of T.
2.
was
on The hypothesis rejected
Welfia georgii versus dicot trunks. null
74 AMERICAN FERN JOURNAL: VOLUME NUMBER
94
2 (2004)
25
20
w
Welfia georgii
15 Dicot
trees
o
°
10
5
1-10
11-25 26-50 51-75 76-100
Percent Cover
Comparison
Fig. 2. of percent vegetative cover of Thchomanes godmanii on
25 trunks of Welfia
georgu and
25 trunks of dicotyledonous
La
trees at the Selva Biological Station Costa Rica
According
to a Wilcoxon/Kruskal-Wallis rank sum
godmanii had
test, T. greater percent cover on
=
Welfia georgu than on
dicotyledonous
trees (P 0.0186).
(P=
The
0.0186; more
Fig. fern abundant
2]. is (higher percent on
cover) the
palm.
Hypothesis 5.—no
correlation between
percent T
vegetative cover
of
godmanii
with dbh
the of the palm The
trunks.
null hypothesis was
retained
F=
-
0.37; There was no
(rs 0.149). correlation between abundance
the
of fern
and dbh
the of the palm.
Discussion
Grayu
Welfi
than on
dicot
trees (hypothesis
This one
1). is of the few
host-specific
relationships that have been documented
statistically in ferns (for others see
Moran
et 2003).
al.
Trichomanes
godmanii
seems
be one
to of the few
ferns capable of
colonizmg
the trunks of Grayum
Welfia
georgii. and
Churchill noted
(1989)
unnamed
an
that
species of Elapboglossum
also occurred
on
rarely the trunks
w
gustifi
MORAN
75
The showed Trichomanes godmanii was more
results also that not only
frequent on the palm, but also more abundant (hypothesis The colonies
2).
When
could be dense was
so that the surface of the trunk obscured. present,
they always occurred around the base of the trunk IB) and diminished
(Fig.
upward, some
but in cases dense colonies extended five meters above the
ground (at La Selva the palm can attain a height up to 23 meters; Rich, 1986].
The
large extensive colonies of the fern (Fig. IB) are formed by the plants' long-
creeping rhizomes that occasionally branch and run horizontally or upward
around
the trunk.
was
There no correlation, however, between percent cover of the fern and
dbh palm many
of the (hypothesis Like palms, Welfia georg// begins vertical
3).
maximum
growth with stem support and
a girth that sufficient to height,
is its
maintains same same width grows Thus
it the or nearly as taller (Rich, 1986).
it
wider trunks do not necessarily represent older individuals that have been
available for colonization for a longer time by epiphytes. Given this, one would
amount
expect an equal of the fern in terms of percent cover on both narrow
and wide and what we
diameter trunks, this found.
is
Why
Trichomanes godmanii most and abundant on
frequent
Welfia
is
palm
georgiif Perhaps allelopathy plays a with the trunk presenting
role,
a chemical that inhibits epiphytes other than the fern. This idea, however,
cannot be assessed because allelopathy has never been investigated in the
trunks of W. georgii nor any other palm (Andrew Henderson, pers. com.). More
promoting growth smooth palm
likely in of the fern the texture of the trunk.
is
This might favor the fern two ways. First, could hinder other epiphytes from
it
establishing and attaching the trunk. This might be because of the smooth
surface itself or because such surfaces retain less water or nutrients than
would
rougher surfaces. In either case, fewer epiphytes free the fern from
competition, allowing more space, and nutrients. Second, unlike other
light,
it
epiphytes, the smooth surface of the palm might be an easy substrate
for T.
godmanii members Trichomanes Didymoglossum,
Like of
to grasp. all sect. T.
godmanii and sometimes
rootless, but rhizomes, petioles, basal portions
is its
of the midrib, bear abundant specialized hairs called ^'adhesive hairs"
(Schneider, 2000). These usually form a dense mat surrounding the rhizome
and are dark, and several-celled. They have a cuticle (as do the rhizomes)
stiff,
and apparently do not absorb water or mineral nutrients, but they might hold
w^ater by capillary action and gradually release this water to the lamina as
it
Many
and
Trichomanes absorb water mineral nutrients
dries. species of
which one between
directly through their leaves, are only cell layer thick the
The main
veins and lack a cuticle or nearly so (Haertel, 1940). function of the
The numerous
however, appears be attachment. presence of these
hairs, to for
some
hairs greatly increases the surface area for clinging to the substrate. In
species of Trichomanes sect. Didymoglossum, the adhesive hairs branch or
when
enlarge the they touch the substrate (Duckett et 1996),
at tip al.,
Trichomanes godmanii has such branched
increasing adhesive or
ability.
would smooth
swollen hairs (pers. obs.) that facilitate its colonizing surfaces.
we
Trichomanes angustifrons, the only other fern found on the trunks, also
is
,
AMERICAN FERN VOLUME NUMBER
76 JOURNAL:
94
2
(2004J
member
a of sect. Didymoglossum and has the adhesive hairs, suggesting the
importance
of this type of indument growing on smooth
for
surfaces.
why
Nevertheless, adhesive hairs cannot be the only reason godmanii
T.
flourishes on palm. Four other species of Trichomanes Didymoglossum
sect.
occur at the La Selva Biological Station (Grayum and and
Churchill,
1989),
although they have adhesive hairs, only one of them was
[T. angustifrons]
found on the palm. All of the other four grow primarily on Thus,
dicots.
although adhesive
hairs probably play an important
role, they are not the entire
why
reason godmanii
7. prefers the trunks of
Welfia georgii.
Acknowledgments
This study was done while the junior author was a student in Sistemdtica de Plantas
Tropicales,
a course sponsored by the Organization
for Tropical Studies (OTS). This course was coordinated by
the senior author, and funding came
for the course primarily from the Andrew Mellon
G.
who we
Foundation, thank We
for their outstanding generosity. thank OTS Academic Advisor
Barbara Lewis
her help with
for administering the course, and students Eduardo Mendoza and
Alvaro We
Idarraga for their help with sampling. also thank Andrew Henderson
generously
for
sharing knowledge
his extensive of palms, and Harald Schneider for his comments on adhesive
hairs in Trichomanes.
Literature Cited
BRcnvNSEY, and New
p. C. Smtth-Dodsworth. 1989. Zealand Ferns and
J., J. Allied Plants. David
Bateman
Auckland.
Ltd.,
;fcett
M. Camus, M. Gibby and
In:
R. Johns, eds. Pteridology
J. in Perspective. Royal Botanic
J.
Gardens, Kew, UK.
W.
Kress, The
1986. systematic
J. distribution of vascular epiphytes; an update. Selbyana 9:2-22.
—
_,„„.
,. ^^wi.^vxLi^ai vac5i.uiai GpipiiyiBs. rp. zj^-ZDi.
iji In: U. Luttge, ed.
Vascular
Plants as Epiphyses. Evolution and
Ecopbysiology.
Ecological Studies 76. Springer-
New
New
Verlag, York, York.
Grayum, M. H. and H. W. An
Churchill.
1987. introduction
to the pteridophvte Finca La
flora of
Selva. Anier. Fern 77:73-89.
J.
Grayum, M. and W.
H. H. Churchill. The
1989. vascular flora of the La Selva Biological Station,
Costa
Rica. Polypodiophyta. Selbyana
11:66-118.
Haertel,
O. 1940. Physiologische
studien an Hymenophyllaceae.
Wasserhaushalt und
II. resistenz.
Protoplasma
4:489-514.
Langley,
R. 1971. Practical Simply
Statistics Explained. Dover New
Publications, York
McDade,
a. and
L. G. S. Hartshorn. 1994. La Selva
Biological
Station. Pp. 6-18. McDade,
A.
In: L.
K. S. Bawa, H. A. Hcspenheide and
G. S. Hartshorn, eds. La Selva Ecology and
Natural
History
of a Neotropical Rain The
Forest. University USA
of Chicago,
Illinois
MORAN, C,
R. Klimas and M.
S. Carlsen.
2003. Low-trunk
epiphytic on
ferns tree ferns versus
angiosperms
in Costa Rica. Biotropica 35:48-56.
M
Rich, P. 1986, Mechanical
architechire
of arborescent
rain
forest palms. Principes 30:117-131.
and
Sall, A. Lehman. JMP A
1996.
J Start Statistics, Guide and
to Statistical Data Analysis using
IMP and JMP IN SAS
Software. USA
Institute, Gary, North
Carolina
ScHNEmER, U. Morphology
2000. and anatomy
of roots in the filmy
fern Trichomaneae
tribe H.
Schneider
(Hymenophyllaceae,
and
Filicatae) the evolution
of
rootless taxa. Bot. Linn. Soc.
J.
Wessels Boer, The New
G. 1962. World
species of Tnchomanes
J. Didymoglossum
and
sect.
Mwrogonium.
Acta
Bot. Neerl. 11:277-330.