A NEW SPECIES OF DIOSCOREA (DIOSCOREACEAE) FROM THE ANDES OF VENEZUELA

7 Pages·2003·3.9 MB·English

by  L J Dorr

NEW
A
OF DIOSCOREA (DIOSCOREACEAE)
SPECIES
EROM
THE ANDES OE VENEZUELA
Dorr
Stergios
Basil
L.J.
MRC~166
Dept. Biology (Botany),
RESUMEN
especie de Dioscorea,
a
Palabras Claves: Dioscoreaceae, Dioscorea, Venezuela, Andes
Four species of Dioscorea (Dioscoreaceae) have been collected in Guaramacal
L.
National which an 200 km^ montane
Park, protects area of of cloud
ca. forest,
m
and paramo
forest, near the northern end of the Cordillera de Merida
Portuguesa and Trujillo states, Venezuela (Dorr et al. 2000). Two of the species,
khmannii Ulme and
D. D. meridensis Kunth, are well-circumscribed although
m
infrequently collected and with wide ranges the Andes, extending south
to
When
Ecuador and we
Peru. published a catalogue of the vascular plants of
Guaramacal, we had two and we
not yet identified of the four species, listed
A
them as Dioscorea and Dioscorea B (Dorr 2000). The ap-
sp. sp. et latter
al,
&
Humb. num-
pears to be D. coriacea Bonpl. ex Willd., a variable species with a
ber of synonyms and an extensive range in the Andes (Colombia and Venezu-
known
ela to Bolivia).The former, however, cannot be associated with any species
and
described here new.
as
is
&
nov
Dorr Venezuela,
Stergios, sp. (Figs. 1-2). Type: trujillo: Mpio.
:
N
rque Nacional Guaramacal. road from Bocono to Guaramacal, SE of Bocono, slope
&
in, 09-13'N, 07012'W, 2000 m, 13 Jul 1995 9 Dorr Barnett 8057 (holo-
c? f Is),
(
, ,
MEXU,
; ISOTYPES; US).
Dioscorea lisae Dorr & Stergios. A. Habit (of a plant with mixed inflorescences, either mail
Fig. 1
.
inflorescences arising from the axils of infructescences). B. Staminate flower. C. Pistillate flower. (A, Dorr etal. 892
1,
Dorr &Barnett 8057, PORT; Dorr &Barnett 8057, MEXU).
B, C,
Herbaceous twining vines; dioecious (or monoecious, with staminate inflores-
cences found on pistillate plants in fruit). Stems delicate, terete, twisting to the
right (dextrorse), glabrous. Leaves alternate, entire. Leaf blades ovate-lanceolate,
7-11 X 3.2-5 cm, 5-7-nerved, the base cordate to truncate, the apex acuminate
cm
membranous;
long-acuminate, glabrous, petioles 1.5-3.5 long, glabrous,
to
glandular-dotted below. Staminate inflorescences paniculate, pendent,
faintly
cm
8-13 with 1-4 racemose branches, flowers the rachis minutely-
long, solitary,
papillate, delicate; each flower subtended by a pair of unequal, acicular
mm mm
5-8
bracteoles, 1-1.25 long; pedicels long, minutely-papillate to
ca.
&
smooth. Staminate flowers greenish-red (Licata Cuello 217) to purple {van
der Werjf& Ortega 6066), rotate at anthesis, the tepals equal, distinct, 1.25-1.5 x
mm,
stamens borne on annular
0.75 lanceolate, glabrous; a flattened, disc,
3,
mm
filaments very short, ca. 0.25 tall, thickened, anther cells ovoid, free (or con-
staminodia
nivent), introrsely dehiscent; absent. Pistillate inflorescences spi-
cm
cate, pendent, to 14 long, solitary; each flower subtended by a pair of un-
mm
equal, acicular bracteoles ca. 1.5-1.75 long. Pistillate flowers with tepals
mm,
equal, distinct, ca. 1-1.25 x 0.5 lanceolate, glabrous; styles fused at the
3,
base and free towards the apical stigmatic surfaces; staminodia absent. Cap-
2-3 cm, apex and
sules X 1.2-1.4 elliptic, the base rounded, flattened, green (dry-
ing light blown) with dark, elliptic maculations, glabrous seeds 2 per locule,
05 05 cm
winged
ca X irregularly lenticular ovate-lcnticulai compiessed,
to
Cudlo 2433 (PORT) Parque Nacio
and abo\e paik headquarteis
just
PORT
ital 7981 (N\ US) Paique
t
Ui&(udlo2l ZlPORTumcate)
m
uuimaL
loC 2000 2750
il
m
K,l 2100 23 00 4 Sep 1966
N
IlC uiiamac 09^ 14 070^
il
IMO
PORT)
known
Distribution and ecology —Dioscorea lisae presently only from the
is
m
km
Ramal de Guaramacal Trujillo Venezuela This ridge 40 long
state, a
is
km
offshoot of the more extensive Cordillera de Meiida which extends 325
from Tachira to Lara. All but one of the collections we examined aie from the noi th
slope (mostly Qda. Segovia) of the Cerro de Guaramacal; the exception
sole a
is
collection from the south slope (Qda. Jirajara) of the same mountain. Dioscorea
has been montane and upper-montane 1790-2750
lisae collected in forest;
(-3100) m. Flowermgjune, September, and November; February
fruiting
July,
&
The US sheet of Steyermark Rahe 97309 mislabeled with a locality in
is
Tachira and the date 27 August 1966. Bono (1996: 526) also reported this collec-
from which may
tion (as Dioscorea coriacea) Tachira, suggests other duplicates
unambiguous
be mislabeled. Steyermark's field notes are about the fact that he
and Marvin Rabe collected a Dioscorea in Guaramacal on 4 September 1966
and was numbered
that the collection 97309. Since all of the data on the labels
number
used by Steyermark are printed save for the collection and determina-
tion, which are typed, it is easy to imagine a typist grabbing one or more labels
when
from wrong
the stack preparing the distribution of duplicate sheets.
Etymology— The
epithet honors Lisa Ceryle Barnett, botanist, science ad-
many
and
ministrator, wife of LJD. She has participated in collecting trips to
Guaramacal as well as numerous other expeditions by foot, mule, horse, or jeep
to remote forests and paramos in the Venezuelan Andes.
DISCUSSION
Knuth
Following the classification of (1924), Dioscorea lisae belongs in subg.
Helmia (Knuth) Benth the ovules are attached near the distal (stylar) end of
.;
the ovary and the wing developed unilaterally toward the proximal end
is
(i.e.,
toward the base of the capsule). Several characters, including the presence in
male flowers of a large glandular disc (not always readily apparent) and race-
mose male inflorescence branches with solitary flowers that have 3 anthers and
lack staminodia, suggest a placement in Cycladenium Uline of Knuth's
sect.
(1924) scheme. In Ruber's (1998) classification, D. lisae keys to sect. Trigonohasis
Uline of Mexico and Central America, which he also associates with sect.
from Cycladenium
Dioscorea lisae differs other species in sect. in that its
which
male flowers have very long pedicels, greatly exceed the bracteoles in
length, and female flowers produce relatively large capsules, which have
its
rounded (versus acute) apices and bases. As noted above, at least one of the speci-
&
mens we was
iSteyermark Rahe 97309) refer to D. lisae misidentified earlier
number
from morphologi-
as D. coriacea, but D. lisae differs that species in a of
summarized
cal characters in Table
1.
One
Dioscorea lisae apparently is not strictly dioecious. of our collections
(Dorr US) has and male inflorescences and would appear that
et al. 8921, fruit it
male
the sexes are separated temporally In this case the inflorescences evidently
arise well after the female inflorescences have produced flowers and set fruit.
Condon and Gilbert 1990) discuss what might be an analogous situation
(1988,
in the Cucurbitaceae. The genera Gurania (Schltdl.) Cogn. and Psiguria Arn.,
both neotropical vines that were long thought to be dioecious, are actually
and They documented
monoecious only temporally dioecious. that these gen-
They
era have size-related and intra-seasonal sex changes. also discovered
Our sample
strongly male-biased sex ratios. limited size (ten collections) hints
at a male-biased sex ratio in D. lisae; nine collections have male flowers and six
have female flowers and/or Nonetheless, the exact nature of sex expres-
fruit.
and same and
sion in this species factors controlling the are not at all clear will
with herbarium specimens
not be resolved alone.
While Dioscorea almost universally considered to be dioecious, there are
is
number
a of other reports, usually dismissed, that this is not true of all species.
summarized view by
Burkill (I960: 327) the prevailing stating categorically "to
date we do not have a single proved case of the two sexes being fertile on the one
what we have records imperfect male organs and imperfect
individual: of
is
may
what
female organs intruded into be fertile individuals of the other sex."
Al-Shehbaz and Schubert (1989: 67) referred to the reports of such deviation as
"abnormally-monoecious"; Huber (1998: 220) cited a "a reports of monoecy,
fev^^
most them American and Caddick
of referrnig to species et (2002: 109)
al.
...";
wrote that plants of Dioscorea are "dioecious but vestigial male/female parts
usually present." Xifreda (1982a, 1983; 1984), studying Argentinian spe-
[are] b;
cies of Dioscorea, described D.Jurcata Griseb., D. hiewnymi Uline ex R. Knuth,
Hauman
megalantha Cydadenium),
D. Griseb., D. stenopetala (all sect. D. de-
mourae UlineexR.Knuth.D.haumanii (bothsect.Monaddpha
Xifreda Uline),
Haumen
and pikomayensis Centrostemon monoecious. She
D. Griseb.) as
(sect.
also observed infraspecific variation in male flowers of several species, notably
some
D. megalantha; in collections the glandular disc not readily apparent or
is
anomaly made
this to collections being at different stages in floral develop-
Hammel
ment. (2000), relying upon his field knowledge of populations of D.
Morton
Icpida C.V. (sect. Tngonohasis), recently reported that this Central
American species monoecious and that flowers precociously with stami-
is
it
nate fkm'ers, then produces pistillate flowers toward the apex of an inflores-
cence and even some hermaphroditic flowers. Plants of D. lepida observed in a
show
later flowering or fruiting stage consequently or no evidence of the
little
Hammel
staminate inflorescences. Given the evidence presented here and by
(2000), seems clear that careful field observations need to be coupled with
it
herbarium, laboratory, and greenhouse studies to clarify what could be a wide
range of different floral sex strategies in Dioscorea.
ACKNOWLEDGMENTS
work was supported by funds from Survey and
Field the Biological Inventories
Museum
Program of the National of Natural History, and herbarium work by
We
Andrew
the W. Mellon Foundation. are indebted to the staff of Guaramacal
National Park for generous assistance in the field; the Ministerio del Ambiente
and INPARQUES MO, and VEN
for collecting permits; the curators of NY, for
Garden
the use of their collections; the staff of the Missouri Botanical Library
Hammel
for photocopies of the field books of Steyermark; and Barry (MO),
J.A.
B
.
Lauren Raz and an anonymous comments,
(NY), reviewer
for critical
were prepared by
trations Alice Tangerini.
REFERENCES
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in
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J.
BoNo,G.1996.Florayvegetaci6ndelEstadoTachira,Venezuela.MuseoRegionale
Natural! (Torino), Monografie 20:1-951.
960.The organography and the evolution of Dioscoreaceae, the
BuRKiLL, I.H.I fa
9-41
yams.J. Linn. Soc.Bot. 56:31
2.
Caddick, Wilkin, Rudall,TA.J. Hedderson, and M.W. Chase. 2002. Yams rec
L.R., P. P.J.
recircumscription of Dioscoreaceae and Dioscoreales.Taxon 51:103-1
14.
Condon, M.A. and LE.Gilbert. 988. Sex expression of Gurania and Psiguria (Cucu
1
Neotropical vines that change Amer. 75:875-884.
sex. Bot.
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Condon, M.A. and 1990. Reproductive biology and natural history of
L.E.Gilbert. r
DM.
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A new Novon
Hammel, 2000. species of Dioscorea from Costa 0:378-38
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