Isoetes maxima, a New Species from Brazil

2009·2.9 MB·English

by  R James Hickey

New
maxima,
from
Isoetes a Species Brazil
R. James Hickey
USA
Miami
Botany Department, Ohio 45056
University, Oxford.
Macluf
C. Cecilia
Paseo del Bosque s/n, 1900 La Plata, Argentina
MeLANIE
LiNK-PfiREZ
from other fully aquatic species in South America by a combination of overall size, leaf
its
Key Words.— maxima, new
/soefes Brazil, species
While examining Isoetes from eastern we encountered specimen
Brazil, a
whose known
and
large size dark coloration are unlike any species from that
The
have numerous, and
region. plants very narrow, densely packed,
finely
and
tapering leaves, its megaspores are rugulate to tuberculate. In contrast,
other large Isoetes in this region of South America have broader leaves that are
densely packed, and megaspores Macluf
less reticulate (Fuchs-Eckert, 1986; et
al, 2008).
The specimens in question were collected by Aloysio Sehnem in 1970.
Sehnem new
determined his collection to be a species and designated so on
it
maxima. The
the intended
label as Isoetes label indicates the collection as the
Sehnem new
holotype; however, never described or validly published the
We
have name Sehnem had on
species. elected to use the that inscribed the
specimen and
label since the overall stature robust appearance of the taxon
merit the appellation.
maxima TYPE.—
Macluf and BRAZIL.
Isoetes Hickey, Link-Perez, nov.
sp.
Cambara, Fortaleza, Aparados, in aqua rivi in campo, 1200 m, 2/5/70, A.
Sehnem (PACA PACA;
10960
74904). (holotype: isotypes: FHS). Figs, 1-14.
Cormus cm
erectus, bilobatus, 2.5-3.0 radices succulentae, dichot-
latus;
mm
cm
omae. Foliae 30-50, ad 45 longae, strictae, erectae, 1.5-2.0 latae ad
mm mm
medium, 8-10
ca latae basi; alae atrovirentes vel fuliginosae, 2.0 latae
cm
ad sporangium, 10-25 longae (20-50% per longitudinem ascen-
foliae
dentes), apice attenuate; subula atrovirens, erecta, semi-teres, apice long-
neque neque
iattenuato, nitido corneo; fasiculi fibrosi peripherici praesentes;
squamellulis Labium 850-875 475-500
carentibus. triangule, fim altum, [im
latum. Ligula magna, auriculata manifeste; pulvinus residuus triangularis,
mm
cm
30-50%
persistens, ca 2 longum et 1.5 latum. Velum incompletum,

HICKEY ET NEW
ISOETES MAXIMA, A FROM
AL.:
SPECIES BRAZIL
VOLUME NUMBER
AMERICAN FERN JOURNAL: 99 3 (2009)
Sporangium
sporangium longitudinem descendens. basale, ellipticum,
per
mm mm
2-4 non maculatum. Megasporae
hyalinum, 5-6 longum, latum,
pagina
525-(583.8)-650 |im diametro, globosae, distalis
cretaceae,
triletae,
cingulum
pagina proximalis
verrucata vel tuberculata (vel laevis), laevis,
27-33
Microsporae brunneae atrobrunneae, monoletae, |im longae,
vel
leave.
^m
20-23
echinatae.
latae,
cm
numerous,
corms bilobed, 2.5-3.0 across. Roots
Plants large, erect,
cm
succulent, dichotomously branched. Leaves 30-50, to 45 long, straight,
mm
mm
1.5-2.0 wide mid-length, ca 8-10 wide at the base; alae dark
erect, at
mm
cm
10-25 up
wide sporangium, extending the
green to brown, 2.0 at the
leaf (20-50% of total leaf length), apex attenuate; subula dark green, erect,
appearing apex long attenuate, neither glossy nor corneous, fibrous
half-terete,
475-
Labium 850-875 ^im high,
bundles present; scales absent. triangular,
^m cushion
500 wide. Ligule massive, distinctly auriculate; dark,
large,
mm mm
down
Velum and
wide. extending
persistent, triangular, ca 2 long, 1.5
5-
30-50% sporangium; lower velum also present and covering
covering of the
mm
2-
10% sporangium. Sporangium hyaline, 5-6 long,
of basal, elliptic,
mm
4 wide, concolorous. Megaspores dull white, trilete, 525-(583.8)-650 |im
in equatorial diameter, distal surface rugulate to tuberculate (to laevigate),
comprised an open reticulum of proximal surfaces laevigate,
of fibrils,
subtriangular globose in polar view and globose in equatorial view, laesurae
to
^m smoother than the
44.5 high, equatorial ridge 30 jim wide, girdle typically
brown
brown en masse, monolete,
ornamentation. Microspores dark
to
distal
convex
proximal
27-33 ^im long, 20-23 ^im wide, elliptic in polar view, face
and broadly rounded, perispore surface echinate with longer
distal face
echinae
distally.
Paratypes.—BRAZIL. Itaimbezinho, Sao Francisco do Paulo, in stagno ad
(PACA
Sehnem 17148
flumen Perdizes, 900 m, Dec. 1980, A. 74905).
24,
alt.
Cambara, Fortaleza, in rivulo submersum in lectu, ah. 1000m, Jan 10, 1973. A.
Sehnem (PACA
12362
74906).
known
maxima an endemic only from three collections out
Isoetes aquatic
is
grows submerged
of the Cambara region of Rio Grande do Sul in Brazil. It in
900 1200 m.
streams elevations of to
at
Species of Isoetes from Rio Grande do Sul have either reticulate or
The
megaspores. reticulate-spored species of
tuberculate-rugulate to rugulate
Those and
South America are in desperate need of revision. species of eastern
southern South America (from Minas Gerais to Buenos Aires) constitute an
them
had paid than
exceptionally difficult assemblage, having less attention to
Andes. Fuchs-Eckert
northern (1986)
the reticulate-spored species of the
on
focusing primarily the
treated the reticulate-spored species of this region,
non-Andean were
State of Santa Catarina. Although most reticulate species
covered, these taxa are imperfectly differentiated.
still
The only two non-reticulate species in southeastern Brazil are Isoetes weberi
Weber and maxima. Megaspore ornamentation in both species varies
Isoetes
megaspore
dramatically
from tuberculate to rugulate, but the species differ in
HICKEY
ET ISOETES MAXIMA, A NEW
AL.: FROM
SPECIES BRAZIL
Size: Isoetes weberi spores have mean
a 356 and
of
a range of 220
to
450 ^m; maxima
those
of /. range from 525 to 650 jim with a mean of 583
)im.
At
high
magnifications, the megaspore
surfaces of both
species
consist of a
coarse open
reticulum
of
structural elements. This type
of surface not seen
is
any
in of the
reticulate spored
species. Microspores
in both species
are
fundamentally
echinate, but
in weberi
the echinae
are broader, more
/.
columnar and
distally muricate
(Hickey, Both
1985). species have moderately
well developed
vela extending 50% down
about
the sporangium. The
species
also markedly
differ and
in the size shape of the labium. maxima
In
the
/.
labium
narrowly
is triangular, with length width
a
to ratio of about and
1.8 to 1
mm
reaching
lengths
of 0.85-0.88 The
in height. labium
of weberi ranges
mm /.
hom
1.0-1.8
in height, narrowly oblong and
is has a length width
to
ratio
The
of 2.3-3.3. labium
of weberi
typically
/. is bifid distally, a condition
known
othe^rwise only
in tennesseensis Luebke and Budke
I. (Budke
et al,
Isoetes weberi lowland m
is a species growing
at elevations of 10-20
whereas maxima
found
about 1200 m. The
/. is at presence of scale leaves
around
the corms
in weberi
suggests
that frequents
/. drier habitats with only
it
seasonal inundation, and
so from more
differs the aquatic maxima.
Isoetes
The
rather large megaspores seen maxima
in Isoetes suggest an
origin
through
polyploidy. Within maxima
the vicinity oil. only weberi stands
as a
/.
likely parent. In fact, the similar morphology and
habit in conjunction with
the
common,
open
reticulum
of the megaspores
suggest an between
affinity these
two. Candidates
for a second parent more
are problematic and
perhaps must
be
sought
further north
in the
states of Bahia, Espirito Santo and Rio de
Janeiro,
perhaps
to the poorly understood organensis Weber
or Weber.
/. ulei
/.