Aeonium Mascaense, a new species of crassulaceae from the Canary Islands

              BOTÁNICA MACARONESICA 10 < 1982) 57
AEONIUM MASCAENSE. A NEW SPECIES OF CRASSULACEAE
FROM THE CANARY ISLANDS.
DAVID BRAMWELL
Jardín Botánico Canario "Viera y Clavijo" del Excmo. Cabildo Insular de Gran Canaria.
SUMMARY
A new species of Crassulaceae from the Canary Islands, Aeonium mas-caense,
is described for the first time. It is endemic to a small área of the
island of Tenerife in the Barranco de IVIasca. The characters differentiating it
from other species of Aeonium sect. Urbica are discussed as are its ecology
and distribution. A list of associated species is given.
RESUMEN
Se describe por primera vez una nueva especie de Crassulaceae de las
Islas Canarias, el Aeonium mascaense. Es planta endémica de una pequeña
área en el barranco de Masca, de la isla de Tenerife. Se trata de los caracteres
diferenciadores con respecto a otras especies de Aeonium sect. Urbica, así
como de su ecología y reparto. Se dá una lista de especies asociadas.
INTRODUCTION
Though the flora of the Canary Islands is now very well known, their rug-ged
terrain with extensive áreas of cliffs and deep ravines make exploration
difficult and a few novelties are still expected'to occur, this is the case with
the new species of Aeonium described here.
58 DAVID BRAMWELL
The genus Aeoniumis one of most interesting of the Cañarían genera be-cause
of its high concentration of species resulting fronn local adaptive ra-diation
(Lems, 1960; Voggenrelter, 1974) and its disjunct East African-
Macaronesian distribution (BramweII, 1972).
The genus was extensively monographed by Praeger (1932) and only two
local endemlc species have been described since, A. rubrolineatum Svent.
(Sventenius, 1954) and A. vestitumSvent. (Sventenius, 1960). Both these are
very rare endemic species which were overlooked by previous explorers and
the new species described below is also a species of restricted distribution
found in a very small área and with a known population of less than fifty
plants which means that it must immediately be considered as yet another se-riously
endangered Canarian endemic species. Aeonium mascaense is, howe-ver,
now included in a programme of cultivation of endangered endemics
carried out in the Jardín Botánico Canario "Viera y Clavijo" on the island of
Gran Canaria.
DESCRIPTION
AEONIUM MASCAENSE spec. nova
Haec species in Nivaria regione septentriono-occidentali rarissima ab affi-nibus
A. castello-paivae, A. haworthii et A. decorum inflorescentia glabra,
antheris productis acutis, foliorum rosulis compactis, section foliari elliptica
recedit.
Holotypus: D. BramweII n°. 1386, Nivaria Ínsula (Tenerife dicta) in
anfractuosís Mascae ubi reperta fuit die 26 martii 1969. In Herb. Hort. Bot. Ca­ñar.
"Viera y Clavijo" (JVC) servatus.
Much branched, small, glabrous subshrub up to 25 cm, forming a dense
bush. Stems with prominent, rough leaf-scars. Leaves in small dense roset-tes,
glaucous green, shiny, red-edged and streaked, spathulate-claviform up
to 3.5 cm long, very fleshy, apiculate, rounded on the lower surface, more or
less convex on the upper; the margins with long, forward-curved cilia.
Flowering stems erect, 20-30 cm, palé pink, with a few bracts; inflores-cences
lax, the buds broadly conical, white becoming palé pink on anthesis.
Flowers 6 to 8 - parted, campanulate. Calyx fleshy, glabrous to very sparsely
AEONIUMMASCAENSESP. NOV. CRASSULACEAE 59
Figure 1: Aeonium mascaense
60 DAVID BRAMWELL
A - A. decorum B - A. mascaense
C- A. castello-paivae D - A. haworthii
Figure 2: Inflorescence branches of A. mascaense and its nearest relativas.
AEONIUMMASCAENSESP. NOV. CRASSULACEAE 61^
pubescent, the teeth fleshy, deltoid, subacute. Petáis about 1 cm, lanceolate,
acute, white to palé pink. Stamens white, the anthers elongated and very
acute at the apex. Carpels erect, white to palé pink with the styles pink-tipped.
Figure 1.
TAXONOMY
This extremely rare plant is a member of the section Urbica of the genus
>4eoA7/£y/r? which contains several small, natural series of species including the
A. haworthii group in which the present species must be placed. The A. ha-worthiigroup
consists of two species endemia to the island of La Gomera, A.
decorum Webb ex Bolle and A. castello-paivae Bolle and two found only on
Tenerife A. haworthiiWehh & Berth. and A. mascaense. All are small, much-branched
shrublets with campanulate creamy-white to pink flowers and
small, dense leaf-rosettes. They are generally species of dry, rocky áreas bet-ween
sea-level and about 800 m. and except for A. mascaense are locally
common.
A. mascaense is the smallest, most delicate and rarest species of the
group and, indeed, of the section Urbica. It is distinctfrom the other members
in its small, tight rosettes of very fleshy, shiny red-streaked leaves which are
manifestly convex on the upper surface and in the rough leaf-scars which are
less prominent than those of A. decorum and somewhat resemble those of A.
ciliatum. The glabrous inflorescence of A. mascaense is like that of A. ha-worthii,
the inflorescence of both the other species being finely pubescent. A.
mascaense\s, however, easily distinguishable from A. haworthiiby leaf-shape
and colour, flower-colour and by the very elongated, pointed anthers. The dif-ferential
characters are shown in figures 2, 3, 4 & 5.
A. mascaense is probably best considered as a vicariant of the Gomera
species A. decorum and A. castello-paivae and several species otherwise con-fined
to the island of La Gomera also occur in the Masca área of Tenerife, for
example Dicheranthusplocamoides, Sideritislotsyi(W\Xh\ia\. mascaensejand
Polycarpaea carnosa var. spathulata. This gives some botanical support to
Hausen's suggestion (Hausen, 1956), based on geological evidence, that the
Masca región of Tenerife may once have been physically connected with the
nearby island of La Gomera.
62 DAVID BRAMWELL
A-A.decorum B-A. mascaense a-A.decorum b-A.mascaense
C-A.castello-paivae D-A. haworthii c-A. c.-paivae d-A. haworthii
ÜJ
A- A. decorum C-A, castello-paivae
B- A. mascaense D-A. haworthi
Figure 3: Floral and bud detalls of A. mascaense, A. decorum, A. castello-paivae and A. ha­worthii.
AEONIUMMASCAENSBSP. NOV. CRASSULACEAE 63
<cy
A- A. decorum
O
B- A.-mascaense
•cy <C7
D- A. haworíhü
C- A, castello-paivae
Figure 4: Leaf outline and transversa section of A. mascaense and its three closest relatives.
ECOLOGY AND DISTRIBUTION
A. mascaense has only been found in a very small área of the Barranco
de Masca on the western side of the island of Tenerife at about 400 m. above
sea-level Fig. 6. This make.s it probably the rarest and most narrowly distribu-ted
of all the Cañarían /leo/7/iy/77 species and it is found in associatlon with se-veral
other very restricted local endemic species such as Te/ine osyroides, Lo­tus
mascaensis, Cheirolophus canaríensis, Sonchus fauces-orci, Aeonium se-difolium
and Crambe laevigata.
The base rocks of the área are ancient basalts and phonolites with nume-rous
olivine dykes and A. mascaense is found amongst the loóse rocks and
boulders beneath the high vertical cliffs of the valley below the hamiet of Mas­ca.
The rupicolous habitat in sunny, exposed places is typical of all the species
of the group. A list of species observed in the same área as A. mascaense is
contained in fig. 7.
A. mascaense A. haworthii A. decorum A. castello-paivae
leaf-scars
leaf T.S.
leaf - shape
calyx
inflorescence
flower colour
anthers
ridged
oval
spathulate-claviform
very fleshy, glabrous
glabrous
white-pale pink
elongated, acute,
filaments glabrous
smooth
upper surface fíat
obovate
very prominently ridged
upper surface fíat
oblanceolate-spathulate
glabrous, slightly fleshy pubescent
glabrous pubescent
palé yellow, suffused pink pink
rounded, subacute, rcunded,
filaments finely pubescent filaments pubescent
in upper 1/3
smooth
flattish on both surfaces
subspathulate
glandular-pubescent
pubescent
creamy white or pinkish
rounded,
filaments
glandular pubescent
Figure 5. Differential characters for species of the A. mascaense group.
AEONIUMMASCAENSESP. NOV. CRASSULACEAE 65
PENÍNSULA DE TEÑO I^
o 1 2 3 KM.
Punta
Figure 6: Distribution of A. mascaense in the Barranco de Masca, Tenerife.
66 DAVID BRAMWELL
In the same communUy:
Polypodium macaronesiacum
Argyranthemum foeniculaceum
Lavatera acerifolia
Rubia fruticosa
Senecio herítierí
Habenaría tridactylites
Teiine osyroides
Lotus mascaensis
4
. Tricholaena teneriffae
Dicheranthus plocamoides
Sonchus fauces-orci
Lobularia intermedia
Micromeria varia
Crambe laevigata
Monanthes pallens
Aeonium urbicum
Convolvulus perraudieri
Hyparrhenia hirta
In the immediate área:
Cheirolophus canariensis
Sonchus cf. capillaris
Polycarpaea carnosa
Lavandula pinnata
Sideritis lotsyi
Euphorbia atropurpúrea
Euphorbia broussonetii
Echium aculeatum
Silene cf. lagunensis
Dorycnium broussonetii
Plantago arborescens
Paronychia canariensis
Dactylis smithii
Tricholaena teneriffae
Davallia canariensis
Aichryson parlatorei
Vieraea laevigata
Descurainia millefolia
Aeonium sedifolium
Aeonium X burchardii
Chamaecytisus proliferus
Bupleurum salicifolium
Férula linkii
Tinguarra montana
Phyllis viscosa
Salvia broussonetii
Asparagus scoparius
Figure 7: Associated species of A. mascaense in the Barranco de Masca, Tenerife.
BIBLIOGRAPHY
BRAMWELL D. 1972, Endemism in the Flora of the Canary Islands. In Valentine D.H. ed. Taxo-nomy,
Phytogeography and Evolution. pp. 141-159. Academic Press. London.
HAUSEN H. 1956, Contributions to the Geology of Tenerife. Soc. Sci. Fenn. Comm. Phys.
Math. 18: 1-271.
LEMS K. 1960, Botánica! Notes on the Canary Islands II. The evolution of plant forms in the is­lands:
Aeonium. Ecology^'\: 1-17.
PRAEGER R.L. 1932, An Account of the Sempervivum Group. Royal Hort. Soc. London 265 pp.
SVENTENIUS E.R. 1954, Specilegium Canariense W. Bol. Inst. Nac. Inv. Agron. 30: 29-42.
— 1960, Additamentum ad Floram Canariensem.. Inst. Nac. Inv. Agron. Madrid 95 pp.
VOGGENREITER V. 1974, Geobotanische Untersuchungen an der Natürlichen Vegetation der
Kanareninsel Tenerife. Dissertationes Botanicae Band 26: 1-718.