The Relictual Fern Genus Loxsomopsis

12 Pages·2001·6.4 MB·English

by  Marcus Lehnert

American Fern Journal 91(l):13-24 (2001)
The Fern Genus Loxsomopsis
Relictual
Marcus Maren Monnich, Thekla
Lehnert,
Pleines,
Alexander Schmidt-Lebuhn, and Michael Kessler
Albrecht-von-Haller-Institut Pflanzenwissenschaften, Abteilung Systematische Botanik,
fiir
Germany
Untere Karspiile D-37073 Gottingen,
2,
—
We
Abstract. conducted a systematic revision of the genus Loxsomopsis H. Clirist (Loxomata-
^
Many
ceae] based on 99 herbarium sheets representing about 52 separate gatherings. morpholog-
much
ical characters varied considerably, but as of this variation was found within individual
collections was of taxonomic relevance. Characters that varied between specimens but
little
it
remained roughly constant within individual gatherings included the pubescence of lamina, pet-
and sorus, hair size and coloration, presence or absence of glaucous layers on the lamina
iole,
we
surface, and spore surface structure. However, found no correlation in the occurrence of two
or more of these characters and were unable to morphologically define discrete species within the
we Maxon.
genus. Thus, consider Loxsomopsis to include one variable species, L. pearcei (Baker)
The morphological variation probably the result of the distribution of the species in small,
is
isolated populations in ephemeral early successional habitats, leading to continuous population
extinction and establishment of new population based on few propagules. Notes on ecology and
distribution, full taxonomy, and specimen citations are provided.
and
Loxsomopsis Christ the Neotropical representative of the relictual
is
Loxoma,
taxonomically family Loxomataceae, vvhose other genus,
Isolated fern
New
Loxsomopsis
North Zealand. distinguished
restricted to the Island of is
is
from Loxoma principally by sporangia in which about two-thirds of the
its
and which
annulus thickened only the apical thickened]
cells are [vs. cells
tax
family
now along with Cyatheaceae,
believed to be related to the tree fern alliance,
is
Dicksoniaceae, Lophosoriaceae, and Metaxyaceae on the basis of anatomical,
morphological, and molecular characters (Markham and Given, 1979; Steven-
comm.).
son and Loconte, 1996; A.R. Smith, pers.
on
The genus Loxsomopsis was described by Christ (1904) based L. costar-
icensis from Costa Rica, but the first species was actually described in 1891
by Baker Dicksonia pearcei from Ecuador and was transferred to Loxso-
as
Maxon Two have been
mopsis by in 1933. further species described, L. leh-
and from
mannii from Ecuador by Hieronymus in 1904, L. notahilis Bolivia
been
by Slosson in 1912. Because of the distinctness of the genus, there has
debate about the generic delimitation and the placement of individual
little
The however, clearcut and has
species. delimitation of the species, is less it
and
been suggested only one species should be recognized (Tryon Tryon,
that
Loxsomopsis appears be and/
1982; Tryon and Stolze, 1989). Overall, to rare
A
modern
and poorly represented in herbaria. treat-
or localized in the field is
ment genus The present study an outcome of a course on
for the is lacking. is
taxonomy and systematics and based on a morphological anal-
pteridophyte
is
AMERICAN FERN VOLUME NUMBER
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1
ysis of 99 herbarium sheets of Loxsomopsis representing about 52 separate
gatherings from 15
herbaria.
Morphological Characters
—
Stems. Stems dichtomously
are long-creeping, branched, dark
terrestrial,
mm
cm
brown,
1.5-5 in diameter, and with internodes 1-7
long. Scattered,
A
dark, fibrous roots are produced from all sides. physical relationship of the
was
roots to the leaf bases not noticed. Stems are densely pubescent with
stiff
bristles (defined as in Lellinger, 1985, by having pluriseriate bases and an
mm
uniseriate apex] that are dark brown, 0.8-2.4
long, basally pluriseriate
with about 8-16 and with an apex 3-25
cells, uniseriate consisting of
cells
The
(Fig. lA). entire variation of length and number can be found
bristle cell
on
individual stems. Presumably depending on growth
the location, bristles
can be
erect or appressed, with both conditions well
as as intermediates pre-
on same The
sent the stem. stems are solenostelic (Ogura, 1972). Root cortex
anatomy
corresponds Osmunda-type
to the (Schneider, with hypo-
1996), a
dermis and
of sclereids inner formed by
cortical layers relatively thin-walled
cells.
and
Petioles, rhachises cosfae.— convex
Petioles are adaxially
to flattened-
mm
and
sulcate 0.6-4
in diameter. Coloration varies from dark blackish
or
brown
reddish
to pale olivaceous brown, with the proximal portion generally
being darker. The proximal 1-2 cm
of the petioles are generally densely cov-
are
further
have been
abraded, leaving raised multicellular scars. Petiole length comprises
length
ramer
Rhachises
are similar
Rhachis
coloration generally paler than and
is that of the petiole markedly darker
is
on on
the adaxial than The when
the abaxial rounded
side. costae,
dry, are to
brown
slightly sulcate with a base and
pale yellowish medial and
distal por-
Scattered
tions. hairs (defined
as in Lellinger, 1985, being
as uniseriate
amma
Laminae.—
Leaves monomorphic,
are catadromous,
subcoriaceous,
circin-
with
m
of reported by Tryon and Tryon and
5 (1982) Tryon and were
Stolze (1989)
herbarium
not evident
in material available to us nor observed
in the (M.
field
Leaf
small
are
with proximal pinnae
the generally being the longest, reaching about 50%
of
lamina
mae
and segments
are obliquely
margins, and with
the ultimate
LEHNERT ET LOXSOMOPSIS
15
AL.:
E
E
B
A
mm
1
c
o
m
3
3
E
E
Stem showing
Morphological details of Loxsomopsis pearcei. A] bristles, variability in
Fig.
1,
Moran
Moran lamina surface hairs, 3057; C) Hairs
and number, 3057; B] Variability of
size cell
and
from indusium, Moran 3057; Dj Young sorns with short receptacle sporangial stalks: left side
indusium removed. Ollgaard 74387; E) Ripe sorus with lengthened receptacle and spo-
of hairy
Sporangium, showuig
indusium removed, Lent 738; F) the
rangial stalks; left side of glabrous
% show-
annulus with about of the cells indurated. Ollgaard 74387; G) Detail of pinna,
subvertical
and
ing forked-subpinnate venation, sorus location on vein ending at lamina margin, pubes-
free,
cence on adaxial side, Goldgewicht 86369.
AMERICAN FERN VOLUME NUMBER
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Fig. Variability of lamina and
2. size, dissection, shape. A] shown
Distal portion of a large leaf,
without the three proximal pinna Grayum
pairs, 7212; B) Fully-developed,
mid-sized
fertile, leaf,
Prieto 259; C) Fully developed, sterile, very small leaf, Qllgaard 90634B; Dj Mid-sized with
leaf
notably segment Lehmann
differing shape, 5715; E-G) Proximal pinnae showing
differences in
degree of dissection, segment orientation, and shape, Lehmann
5059, Goldgewicbt 86369, Gold-
gewicht
863.
LEHNERT ET LOXSOMOPSIS
AL.: 17
acroscopic and second-order segments than
fertile leaves, first- are larger their
basiscopic counterparts, whereas on leaves they can occasionally be of
sterile
similar Degree of lamina dissection, shape of pinnae and pinnules, and
size.
orientation of the pinnae vary considerably between leaves and individuals
(Fig. Smaller leaves tend to have longer, narrower, ascending pinnae,
2).
whereas larger leaves tend to have broader, more spreading pinnae. During
lamina development, segments tend be more rounded than on mature
to
Veins forked-subpinnate and catadromously branched
leaves. are free, (Fig.
1).
Laminae of Loxsoinopsis can be glabrous to densely pubescent abaxially
mm
up brown,
with uniseriate, to 2 long, light to tortuous, septate hairs (Fig.
The frequency and coloration of this vestiture varies geographically, with
1).
Costa Rican specimens characterized by long, pale hairs whereas specimens
from some Ecuadorean locations have dark brown Bolivian specimens
hairs,
which among and
tend to have a glaucous abaxial lamina surface varies within
shown
and have
collections (Tryon Stolze, 1989). Field observations that older
laminae are more glaucous than younger ones (M. Lehnert, pers. obs.). Adax-
the laminae are always glabrous.
ially
—
on and
Sori of Loxsoinopsis are located marginally veins are directed
Sori,
downward on
from the lamina surface. Generally, a single sorus located the
is
acroscopic side of each terminal pinnule or ultimate segment, although ocas-
sionally a second sorus found basiscopically. Sori are narrowly cyathiform
is
to urceolate and have a laterally free and protruding indusium with an entire
rim. Superficially, they resemble sori of the Hymenophyllaceae. Indusia are
glabrous sparsely pubescent with hairs ID) resembling those of the
to (Fig.
laminae
(Fig. IC).
Sporangia and paraphyses are borne on a columnar receptacle whose basal
much
measuring
portion elongates during sorus maturation, eventually as as
50% As young have
indusium
of the entire length (Fig. ID, E). a result, sori
which most whereas mature
narrow indusia conceal of the sporangia, in
fairly
beyond more open indusium. Ripe
the majority of sporangia protrude the
sori
mm
mm
about wide and 1.75-2.75 long. Paraphyses are uniseriate,
sori are 1
mm
5-
and
unbranched, and without thickened 0.5-0.8 long, consist of
cells,
10 which about 2-3 times longer than wide.
are
cells
—
Sporangia. The number of sporangia per sorus varies from (10)15 to 30(50),
much found on Sporangia are borne on
with of this variation single leaves.
6-rowed that lengthen somewhat during sorus maturation.
short, ca. stalks
Sporangia are more or less pyriform (Fig. IF), about 350 (xm wide and 450 |xm
among and between The
long, with very variation in size collections.
little
and
annulus complete, almost bypasses the stalk, consists of 30 to
vertical,
is
group
55 Annular cells are indurated, except for a of laterobasal cells
cells.
make
These
which and have thinner walls. thin-walled cells
are smaller cell
up annulus
about 1/4 of the (Fig. IF).
—
with promi-
Loxsomopsis tetrahedal-globose
Spores, Spores of are trilete,
and
nent angles, with the laesure 1/2 to nearly equal the spore radius, lack
much
Spores 41-62 in diameter, with of this variation
chlorophyll. are
iJtm
=
= mean
found in single sori, e.g., 41-60 jxm [n 20, 54 jjim) measured in
AMERICAN FERN JOURNAL: VOLUME NUMBER
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1
Fig. 3. Spores of Loxsomopsis pearcei. A) Verrucate spore with irregular granular deposit, Gold-
gewicbt 86369; B) Slightly pitted spore, Moran 3051; C) VariabiUty of surface structuring in ver-
rucate spores, 011gaard 9479,
Goldgewicht 86369, In three cases [Bues 2119, Hading 24597, Lent 738] the
number
of spores per sporangium was determined be Spore
to 128. surface
is
slightly pitted (Fig. 3B] to strongly verrucose (nomenclature Lellinger and
after
humps
with
Taylor, 1997] distinct or longish, coalescent ridges 3A; see
(Fig.
also Tryon and Lugardon, 1991:213). These formed by
structures are two-
a
layered perispore (Tryon and Lugardon, 1991). Spores derived from a single
specimen
are generally but some
similar, there is variation in the degree of
coalescence The
of the tubercules
(Fig. 3C). spores are often, but not always,
covered with an
irregular granular deposit
(Fig. 3 A).
tophyt Gametophyt
and
Atkinson They
(1956). are epigeal, chlorophyllous, obcordate somewhat
to
elongate, centrally thickened, with and
thin margins, bear long, multicellular
hairs. Archegonia are borne on the lower surface of the thickened portion,
especially with
apically, the several- many-celled on
to antheridia located the
lower surface, and less often on the upper
surface.
Chromosome
number.—Loxsomopsis =
has been reported as 46 from Cerro
21
Vueltas, Costa by Wagner
Rica,
(1980).
Taxonomic
Considerations
Many
within
taxonomic
stem and
petiole diameters,
relative petiole length, degree and shape lamina
of
dissection, size of the stem and petiole bristles, the number of annulus
cells,
number
the of sporangia per sorus, and spore
size.
Characters that varied between specimens but remained
roughly
constant
lamina
sorus
surface
LEHNERT ET LOXSOMOPSIS
AL.: 19
A B C D E
=
A/ 8
^OOO
=
8
A/
OOOO
=
2
A/
OOO
O
=
3
A/
m^(30<^
A/=4
=
2
/V
OOO
=
/v
i
^
0<S
=
6
A/
0(J
A/-4
O
0(J
=
3
A/
0003
= 2
/v
/V=
1
OOO
N
= 2
N
=
^
=
3
A/
=
2
/V
among
Fig. 4.
number
ings of Loxsomopsis pearcei from 21 localities, indicating the of gatherings per site (AO.
Lamina
shown
(petiole pubescence followed the same pattern and is thus not as an independent charac-
B) Lamina hair coloration: white: pale, black: brown. C] Indusium puhesence: white: glabrous,
ter).
black: hairy. D] Glaucous lamina surface: white: absent, black: present. E) Spore surface: white:
smooth black: verrucose. Due to sterile or incomplete material, not every gath-
to slightly pitted,
ering has been considered for each character. The open circle shows the locality of a specimen
not studied by us [Palacios and Clark 12463 {MO]).
There were some
among independent characters. noticeable
a correlation these
were found For example, Costa
geographic trends, but exceptions also (Fig. 4).
and
Rican specimens characterized by rather long, pale frequently abun-
are
was
one specimen [Evans 2 660A] completely glabrous.
dant lamina but
hairs,
eruvian
AMERICAN FERN JOURNAL: VOLUME NUMBER
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sembled that of the Costa Rican specimens. Dark brown hairs were restricted
60%
to Ecuadorian populations, but occurred in only about of the specimens
examined. Bolivian specimens were characterized by a glaucous abaxial
all
among
lamina Pubescent indusia were found only Ecuador, but not
surface. in
all specimens from the region. The conspicuous differences in spore surface
were and
structure specimen-specific not related to the developmental stage
among
of the spores, as has been reported, Polypodiaceae (van Uffelen,
e.g.,
None
1997). of these geographical trends were correlated with variation in
other independent characters. Overall, the apparent independence of character
A
variation precludes the delimitation of multiple taxa within Loxsomopsis.
comparable which
situation of a variable species cannot convincingly be
di-
vided into discrete species presented by Plagiogyria semicordata (Zhang and
is
Nooteboom,
1998).
While we
cytological or molecular analyses found no evidence
are lacking,
to suggest that different ploidy levels are represented within Loxsomopsis.
much
Spore size varied as within as between individuals and we found no
individuals with malformed would
consistently or abortive spores that indi-
between
cate hybridization plants of different ploidy
levels.
We
among
interpret the considerable morphological
variation pop-
different
Loxsomopsis
ulations of to be a result of the localized and ephemeral nature
of the growth sites of the species and overall Since Loxsomopsis
its rarity.
occurs mostly on disturbed such and new
sites as landslides roadsides, pop-
ulations are presumably regularly formed and then quickly conditions
lost as
are altered during vegetation succession. The dynamic metapopu-
result a
is
new
which
lation structure in populations are frequently formed by one
or
few
spores (Eriksson, 1996). Such a population structure would favor genetic
and would
drift explain the independent variation of morphological charac-
ters.
we
summary,
In have been
unable any
to detect character combinations
that
would
permit the delimitation of different taxa within Loxsomopsis. While we
cannot
rule out the Loxsomopsis we
possibility that includes
cryptospecies,
have found no
evidence
support assumption and
to this consider genus
the
to
include
a single variable Loxsomopsis
species,
pearcei.
Geographic
DisTRmuTioN
known
Loxsomopsis
from
is Costa Rica, Colombia, Ecuador, Peru, and Bo-
livia (Fig. 4). In Costa Rica, Loxsomopsis is confined to three separate popu-
corresponding
lations, to the volcanoes Poas and and
Barva, to the Cordillera
de Talamanca. In Colombia, specimens have been
obtained from
the eastern
Veneznel
Whil
— ~ ^
mf i
may
species well occur
there. In Ecuador, there one specimen Loxsomop-
is of
from Andean
the northwestern
sis slope, but most collection come from
the
and
central southern portion of the eastern Andean where been
slope, has
it
collected along major roads
all traversing the region, and nresumablv occurs
LEHNERT ET LOXSOMOPSIS
AL.: 21
The
as one fairly large, nearly continuous population. species appears to be
from well-known
absent the botanically rather northern portion of the eastern
versant. In Peru, Loxsomopsis has been collected three scattered
at localities
in the central portion the country. absence from northern Peru, including
Its
Amazonas
several well-collected localities in the departments and San Martin
may
well represent a real distributional gap. In contrast, the lack of collections
may
from southern Peru be a result of the low collecting activity in the region.
known
In Bolivia, there are three localities for Loxsomopsis, two of which, the
La Paz-Coroico and the Cochabamba-Villa Tunari roads, correspond the
to
We
most intensively studied areas in the country. suspect that Loxsomopsis
occurs in intermediate areas as well.
Ecology
m m
Loxsomopsis has been collected between about 1950 and 2700 in Costa
m m
and between 1800 and 3600 Andes. The
Rica, in the majority of speci-
mens
have been gathered from roadside and edge but numerous
forest habitats,
specimens from Volcan Poas in Costa Rica have been found along the margin
of the volcanic Tryon and Tryon open
crater lake. (1982) cite habitats in ra-
vines, on brushy slopes and open woodland as growth sites for Loxsomopsis.
Andes, Loxsomopsis on by and
In the occurs slopes disturbed landslides along
roadsides, growing syntopically with aggressive colonizing ferns of the genera
Sticlierus (Gleicheniaceae) and Hypolepis (Dennstaedtiaceae) with which
it
forms dense tangles [Leon and Young, 1996, M. Kessler and M. Lehnert, pers.
Leaves of Loxsomopsis are sometimes long with a pendent apical portion
obs.).
and lean on adjacent shrubby plants [Tryon and Tryon, 1982). Loxsomopsis
has been collected on a wide variety of geological substrates, ranging from
volcanic soils in Costa Rica to sandy soils and lutites in the Andes.
Generally, Loxsomopsis appears to be rather rare. In Bolivia, has been
it
which
recorded only four times in a total of about 300 vegetation plots (of
approximately 90 covered suitable early- to mid-successional vegetation) lo-
cated in the right elevational belt within the distributional area oi Loxsomopsis
Loxsomopsis
{M, unpubl. In southeastern Ecuador, locally
Kessler, data). is
common
on comm.).
roadsides 011gaard, pers.
(B.
Taxonomic Treatment
—
Loxsomop-
Loxsomopsis H. Christ, Bull. Herb. Boiss. 4:399. 1904. Type:
II,
H.
costaricensis Christ.
sis
A
monotypic genus, with the characteristics of single species.
its
Maxon, Wash.
Loxsomopsis pearcei (Baker) Proc. Biol. Soc. 46:105. 1933. Dick-
sonia pearcei Bakery Ann. Bot. (Oxford) 197. 1891. Dennstaedtia pearcei
5:
1905.—
(Baker) H. Christ, Index 218. Type: Ecuador, "Eastern Andes,
fil.
8000-9000ft." Pearce 251 (Holotype, K!; Photo, US).
AMERICAN FERN JOURNAL: VOLUME NUMBER
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[2001J
—
Loxsomopsis
costaricensis H. Christ, Bull. Herb. Boiss. 4:399. 1904. Type:
II,
Costa Rica, Werckle 279 (Holotype,
P!).
—
Loxsomopsis lehmannii Hieron., Bot. Jahrb. Syst. 34:435. 1904. Type: Ecua-
montium
dor, [Morona-Santiago,] prope Chinguinda, declivibus Cordillera
Lehmann
Oriental de 1800-2500m, 5061 Ac-
Sigsig, (Isotype, K!, US!).
cording to Tryon and Stolze (1989) holotype destroyed in LZ.
—
Loxsomopsis
notabilis Slosson, Bull. Torr. Bot, CI. 39:285. 1912. Type: Boliv-
[La Paz, Franz Tamayo,] near Apolo, 6000 Williams 1303 (Holotype,
ia,
ft.,
US!; Isotypes, US!).
P!,
with
Terrestrial fern long-creeping, slender to rather stout, branched, sole-
nostelic stem bearing dark brown,
stiff, multicellular, basally pluriseriate bris-
m
tles. Leaves remote, non-articulate, 0.3-1.5 long. Petiole as long as to some-
what
longer than lamina, with
a single, gutter-shaped vascular bundle, adax-
convex
ially to flattened-sulcate, with the base and sometimes
bristles at fur-
Lamina
ther along the petiole. narrowly to broadly deltate, 1-pinnate-
pinnatij&d to bipinnate-pinnatifid, firm, catadromous, hypostomatic; pinnae
(sub)sessile, subopposite, asymmetric, the basiscopic segments reduced,
sec-
ondary pinnae and segments
obliquely ascending, decurrent, ultimate
seg-
ments
margin
deltoid-lanceolate, crenate Stomata Veins
to entire. paracryptic.
free, forked-subpinnate, catadromously branched. Sori terminal on a vein, pro-
truding beyond the margin, directed downwards from plane of lamina, pro-
fusely paraphysate; sorus cyathiform
to urceolate, laterally free; receptacle co-
lumnar. Sporangia on
annulus
short, pluriseriate stalks; almost con-
vertical,
and
tinuous 3/4 indurated. Spores trilete, 41-62 |xm in diameter, slightly pitted
to verrucate. mostlv granulate.
Specimens Examined
CosTA
Rica. Alajuela: Shore of lake on Poas Volcano, 2500 m, Lent 512 Near edge
of lake,
[¥);
Poas Volcano, 2500 m, Lent 738 (F); Along shore of old crater lake of Volcan Poas, 2500 m, Mickel
3654 (NY); Poas 8500 sandy by
lake, ft., in soil lake shore, Stork 2522 (US); Edge of small lake
NW
km
inside of an extinct sub-crater of Volcan Poas, about 11 of Heredia, 2700 m, Taylor 4496
(NY); Shore of lake, crater summit, Volcan Poas, 2600 m, Weston 4624 (UC). Heredia: Volcan
Barba, 6700 Evans 2660A (MO, U, Z); Headwaters of Rio Santo Domingo, km NE San
ft., ca. 3 of
N
Rafael de Vara Blanca, slope of Volcan Barba, 10° 11.5' N, 84° 07' W, 2060 m, Grayum 7212
(MO, US); Bordes del Rio Grande, afluente del Rio Patria, en el Paso del GaUito, macizo del Volcan
Barba, 2045 m, Jimenez 2272 NY, UC,
(F, US); Southeast shoulder, near end of Route 113, 6 miles
NNE
of San Rafael de Heredia, Lloyd (MO, San km N
s.n. UC); Jose, 10 of San Rafael de Heredia
on Volcan Barba, 1950 m, Mickel 3001 (UC, US); Rio de las Vueltas, 2100 m, Goldgewicht 863
En
(US); el Rio de las Vueltas, 2000 m, Goldgewicht 86369 (CR); End of 113, where road crosses
rt.
m
Rio Patria about 100-200 upstream, 2000 m, Moran 3051 (AAU). Limon: N
flank of Cerro Casma,
along Ujarras—San Jose Cabecar trail, Cordillera de Talamanca, 09° 20' 30" N, 83° 13' 30" W,
2250-2270 m, Grayum 10329 (CR. F, MO); RI. La Amistad Valle de Silencio, 09° 07' 15" N, 82°
57' 55" W, 2450 m, Moroga 339 unknown:
(CR, UC). Prov. Werckle 225
(P).
Colombia. Municipio de San
Nariiio: Francisco, carretera Pasto-Mocoa, entre El Mirador San
y
Francisco, 1500-2200 m. Mora 4449 (COL). Norte de Santander: Municipio
de Toledo, de Toledo