Endemic families of Madagascar. XII. Resurrection and taxonomic revision of the genera Mediusella (Cavaco) Hutchinson and Xerochlamys Baker (Sarcolaenaceae)
Author
Hong-Wa, Cynthia
text
Adansonia
2009
3
2009-12-31
31
2
311
339
http://www.bioone.org/doi/abs/10.5252/a2009n2a7
journal article
10.5252/a2009n2a7
1639-4798
5190688
5.
Xerochlamys diospyroidea
(Baill.) Baker
,
Journal of the Linnean Society
,
Botany
25: 296 (1889)
. —
Sarcolaena diospyroidea
Baill.
,
Bulletin de la Société linnéenne de Paris
1: 565 (1886)
. —
Leptolaena diospyroidea
(Baill.) Cavaco
,
Bulletin du Muséum national d’Histoire naturelle
, 2
e
sér., 23: 135 (1951). —
Type
:
Madagascar
, Prov.
Fianarantsoa
, Ambatomenaloha, [
20°37’S
,
46°33’E
], 1876, fl.,
Grandidier 62
(holo-, P! [P00047871]).
ADDITIONAL MATERIAL EXAMINED. —
Madagascar
.
Prov.
Fianarantsoa
,
Itremo
, [
20°32’S
,
46°33’E
],
1700 m
,
IX.1956
,
Bosser
10022
(
P
,
TAN
)
. —
1964,
Bosser
18876
(
P
,
TAN
)
. —
Idem
, along road between
Finandrahana
and
Itremo
,
27-40 km
west of
Finandrahana
,
1400- 1500 m
,
26.
I
.1975
,
Croat
29847
(
MO
,
TAN
)
. —
[
20°33’S
,
46°36’E
],
1300-1400 m
,
27.
I
.1975
,
Croat
29899
(
MO
,
TAN
)
. —
Idem
,
20°36’38”S
,
46°35’03”E
,
1570 m
,
18.VIII.2003
,
Hong-Wa et al
.
144
(
MO
,
P
,
TAN
)
. —
Idem
, massif de
l’Itremo
,
Ianasana
,
20°34’08”S
,
46°35’44”E
,
1433 m
,
23.
VI
.2005
,
Hong-Wa et al
.
350
(
MO
,
P
,
TAN
)
;
Hong-Wa et al
.
351
(MO, P, TAN). —
Hong-Wa et al
.
352
(MO, P, TAN). —
Idem
, montagnes ouest
d’Itremo
, [
20°32’S
,
46°33’E
],
1500-1700 m
,
17- 22.
I
.1955
,
Humbert
28153
(
MO
,
P
)
. —
Idem
,
20°35’09”S
,
46°35’46”E
,
1440 m
,
23.III.1999
,
Labat
et al
.
3029
(
B
,
G
,
K
,
MO
,
P
,
TAN
,
WAG
)
. —
20°35’34”S
,
46°35’37”E
,
1410 m
,
26.III.1999
,
Labat
et al
.
3038
(
B
,
G
,
K
,
MO
,
P
,
TAN
,
WAG
)
. —
Idem
,
Antsirakambiaty
,
20°35’22”S
,
46°34’01”E
,
1830 m
,
27.III.1999
,
Labat
et al
.
3052
(
B
,
G
,
K
,
MO
,
P
,
TAN
,
WAG
)
. —
Idem
,
20°58’45”S
, 46°58’73”E,
1513 m
,
23.II.2001
,
Ludovic
&
Razafitsalama
4
(
MO
,
P
,
TAN
,
TEF
)
. —
Idem
,
Ianasana
,
7 km
à l’ouest
d’Itremo
,
20°36’06”S
,
46°34’18”E
,
1630 m
,
1.II.1999
,
Messmer
&
Andriatsiferana
750
(
G
,
MO
,
P
)
. —
[
20°32’S
,
46°33’E
],
1300-1800 m
,
XI.1970
,
Morat
3659
(
P
,
TAN
)
. —
[
20°34’S
,
46°38’E
],
1500 m
,
II.1919
,
Perrier de la Bâthie
12486
(
P
)
. —
[
20°36’S
,
46°32’E
],
1500 m
,
6-8.III.1999
,
Rabenantoandro
et al
.
63
(
MO
,
P
,
TAN
)
. —
Idem
, route to
Morondava
,
42.5 km
west of
Ambatofinandrahana
, [
20°35’S
,
46°36’E
],
1500 m
,
6.VII.1992
,
A
.
Randrianasolo
234
(
MO
)
. —
Idem
, eastern margin of the
Itremo
Massif,
c.
19 km
west of
Ambatofinandrahana
,
20°34’21”S
,
46°34’54”E
,
1580- 1700 m
,
10.III.2000
,
Schatz
et al
.
3960
(
MO
,
P
)
. —
Idem
,
Anasana, PK
112, [
20°32’S
,
46°33’E
],
3.VIII.1959
,
Service Forestier
19503
(
P
,
TEF
)
. —
Idem
, rive droite
de l’Ambatorangotana
, massif
de l’Itremo
, [
20°34’S
,
46°35’E
],
1650-1700 m
,
21.II.1970
,
Service Forestier
29042
(
MO
,
P
,
TEF
)
. —
Around Ambatofinandrahana
, [
20°33’S
,
46°48’E
],
17.II.1938
,
Decary
s
.
n
. (
TAN
)
. —
Rauh
799
(
TAN
)
. —
Mt. Ambatomenaloha
(
Itremo
massif), [
20°37’S
,
46°33’E
],
1500 m
,
17.
I
.1955
,
Service Forestier
11551
(
K
,
P
,
TEF
)
.
DESCRIPTION
Shrubs to small trees; young twigs tomentose, older twigs pubescent. Leaf blades dark green above, lighter beneath, ovate to rounded, rarely elliptic, 2-4.5 ×
1.5-3.4 cm
, subcoriaceous, densely covered with erect golden trichomes, base rounded, margin revolute, apex obtuse to emarginate, midrib visible only beneath, secondary veins indistinct, 6-10 per side,
2.5-4 mm
apart, looping
1-3.5 mm
from the margin; petiole
2-5 mm
long, pubescent. Inflorescences terminal sometimes axillary, with 2-8 flowers; peduncle
1-3 mm
long, pubescent, pedicel absent to
0.5 mm
, pubescent. Involucre brown, cupulate, 3-10 ×
4-10 mm
, with dense golden trichomes, teeth 18-27, 1-
3.2 mm
long; flowers
15-25 mm
long at anthesis from apex of pedicel to apex of petals; sepals oblong, 6-10 ×
3-7 mm
, deeply emarginate, exserted
1-4 mm
beyond the involucre; petals dark pink fading to white, oblong, 12-24 ×
5-13 mm
, exceeding the involucre by
9-14 mm
; disc
2-3 mm
tall; stamens 20-44, 8-
17 mm
long; ovary ovoid,
3 mm
high, style
6-14 mm
long, pubescent, stigma
0.5-1 mm
wide. Fruits subglobose to globose, 6-10 ×
7-10 mm
, exceeding the accrescent involucre by
2-5 mm
; seeds brown, ellipsoid
2-4 mm
long, 3-12 per fruit.
PHENOLOGY
Flowering and fruiting from October to June.
VERNACULAR NAMES
Kitoto.
HABITAT
Xerochlamys diospyroidea
is one of the dominant elements of the evergreen sclerophyllous
Uapaca bojeri
(tapia) woodland in the Itremo massif, occurring on quartzite, marble, and metamorphic and igneous substrates from
1100-1800 m
in the subhumid bioclimatic zone.
DISTRIBUTION
In central
Madagascar
in the area around Itremo (
Fig. 4
).
REMARKS
Xerochlamys diospyroidea
can be easily recognized by its dense golden indumentum that covers the flattened young twigs, both surfaces of the leaves and the involucre, its leaf blades less than
5 cm
long, and its dark pink flowers fading to white at maturity.
The
type
specimen of this species (
Grandidier 62
) has relatively small (<
3 cm
long) elliptic leaf blades with an acute apex, while all other specimens collected from the same region have larger, more or less ovate to round leaf blades with an obtuse to rounded apex. However,
Humbert 28153
has lamina of both shapes: the specimen at MO and the one of duplicates at P have small elliptic and acute leaf blades corresponding to those of the
type
, whereas the other specimen at P has four fragments, three with small elliptic blades and one with larger rounded blades. Apart from differences in leaf shape and size, indumentum density varies slightly between the two forms. It is unclear whether the two entities comprising
Humbert 28153
represent different developmental stages of the same individual or were collected from separate plants; they are both in flower. The elliptic form is the less common of the two, but both come from the same area and are certainly variants of the same taxon, perhaps occurring in different habitats, or possibly one of them displaying post-fire morphology. Despite this variation, both forms can be easily distinguished from other co-occurring species such as
X
.
itremoensis
, which is glabrous,
X
.
elliptica
, which is also glabrous and moreover differs in having mostly white flowers (vs. dark pink fading to white at senescence in
X. diospyroidea
), and
X
.
bojeriana
, which is pubescent, but has white trichomes and small leaf blades (<
3 cm
long) and short petiole (<
3 mm
long). Field observations also indicate that these four species distinctly differ in growth form;
X
.
diospyroidea
is a dense, erect shrub to a small tree,
X
.
bojeriana
is a slender, erect shrub,
X
.
elliptica
is a small tree, and
X
.
itremoensis
is a prostrate shrub.
FIG. 4. — Distributions of
Xerochlamys elliptica
F.Gérard
(
Å
),
X
.
diospyroidea
(Baill.) Baker
(▲),
X
.
tampoketsensis
F.Gérard
(■) and
X
.
villosa
F.Gérard
(●) mapped on the bioclimatic zones of Madagascar (after
Cornet [1974]
, simplified by Schatz [2000]).
CONSERVATION STATUS
Xerochlamys diospyroidea
is a very abundant local endemic from the Itremo massif, and has not been recorded within a protected area. With an extent of occurrence of
468 km
2, an area of occupancy of
63 km
2, and only five known subpopulations, this species is preliminarily assigned a status of Endangered [EN B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv)].