Haseltonia 22: 55–63. 2016
55
ALOE ×INOPINATA GIDEON F.SM., N.R.CROUCH & OOSTH.,
(ASPHODELACEAE) [ALOE ARBORESCENS MILL. × ALOE CHORTOLIRIOIDES
A.BERGER VAR. CHORTOLIRIOIDES]: A NOTHOSPECIES FROM THE
BARBERTON CENTRE OF ENDEMISM, EASTERN SOUTH AFRICA
GIDEON F. SMITH1, 2, 8
ESTRELA FIGUEIREDO1, 2, 9
NEIL R. CROUCH3, 4, 10
DELIA OOSTHUIZEN5, 11
RONELL R. KLOPPER6, 7, 12
1
Department of Botany
P.O. Box 77000
Nelson Mandela Metropolitan University
Port Elizabeth, 6031
South Africa
2
Centre for Functional Ecology
Departamento de Ciências da Vida
Universidade de Coimbra
3001-455 Coimbra
Portugal
3
Biodiversity Research, Assessment and
Monitoring
South African National Biodiversity Institute
P.O. Box 52099
Berea Road, 4007
South Africa
4
School of Chemistry and Physics
University of KwaZulu-Natal
Durban, 4041
South Africa
5
11 Savanna Street
Nelspruit, 1200
South Africa
6
Biosystematics Research and Biodiversity
Collections Division
South African National Biodiversity Institute
Private Bag X101
Pretoria, 0001
South Africa
7
H.G.W.J. Schweickerdt Herbarium
Department of Plant and Soil Sciences
University of Pretoria
Pretoria, 0002
South Africa
8
email: smithgideon1@gmail.com
email: epnfigueiredo@gmail.com
10
email: N.Crouch@sanbi.org.za
11
email: delia@mountainlands.co.za
12
email: R.Klopper@sanbi.org.za
9
Abstract: The natural hybrid between Aloe arborescens Mill. and A. chortolirioides A.Berger var. chortolirioides (Asphodelaceae) is here formally described as a nothospecies, A. ×inopinata Gideon F.Sm., N.R.Crouch
& Oosth. The hybrid occurs at Kamhlabane, about 37 km [22 miles] east of Barberton, as well as at Twello
373JU in the Barberton district, Mpumalanga. It has been known in horticulture for many years, following
the introduction of wild-sourced material by Gilbert W. Reynolds.
Keywords: Aloe arborescens Mill.; Aloe chortolirioides A.Berger var. chortolirioides; Aloe ×inopinata Gideon
F.Sm., N.R.Crouch & Oosth.; Asphodelaceae; Barberton Centre of Endemism; history; natural hybrid;
nothospecies; South Africa; taxonomy
INTRODUCTION
‘good’ species (see for example Figueiredo & Smith,
2012 on A. ×commutata Tod.; Smith & Figueiredo,
The ease with which species of Aloe L. (Aspho- 2015b on A. ×nobilis Haw.; and Figueiredo & Smith,
delaceae) hybridise to yield off-spring with varying 2016 on A. ×schimperi Tod., A. ×schoenlandii Baker,
levels of fertility is well-known (Smith & Figueiredo, and A. ×paxii A.Terracc., respectively). Only with
2015a). When first introduced into the climatically the more detailed exploration of the African, Arabimore severe Europe, the exclusively Old World aloes an, Madagascan, and Mascarene land masses was it
were usually grown together under glass where acci- established that many ‘species’ were in fact the proddental pollination and fertilisation led ultimately to uct of alooid promiscuity in cultivation, or in their
the description of several of the hybrid progenies as natural habitats.
56
SMITH ET AL.—ALOE ×INOPINATA
Figure 1. Aloe arborescens in the vegetative phase at Barberton
Nature Reserve (Mountainlands), where it grows in the mist
belt, among other habitats. Photograph: Neil R. Crouch.
Figure 2. The racemes of Aloe arborescens are conical and
range from sparsely- to densely-flowered. Photograph:
Gideon F. Smith.
Figure 3. The shrubby Aloe chortolirioides var. chortolirioides produces short, variously orientated, Xerophyta-like
stems that are often scorched and blackened by veld fires.
Leaves are nearly linear, except at the much broadened base,
and carry small, white teeth on the margins. Photograph:
Neil R. Crouch.
Aloe arborescens Mill. (Figures 1–2) is one of the
most common parents of both natural and artificial
hybrids encountered in Aloe, and sometimes with
representatives of close generic relatives, with Smith
et al. (2012) documenting 31 known hybrid combinations, including nine named ones. Although being
largely, but not exclusively, self-incompatible, A. arborescens nonetheless hybridises freely across many of
the infrageneric groups recognised in Aloe by Berger
(1905), resulting in what today are in some instances
considered to be intergeneric hybrids, based on a recently revised generic classification for Aloe (Grace et
al., 2013). That A. arborescens is so regularly identified as a parent in hybrid events is not surprising as
it has the third-widest distribution range of all aloes
[after A. myriacantha (Haw.) Schult. & Schult.f.,
and A. buettneri A.Berger sensu lato]. The range of
A. arborescens stretches in a near continuous coastal
arch from the Cape Peninsula through the Eastern
Highlands of Zimbabwe, and into southern Malawi
(Smith et al., 2008; 2012). It has been suggested that
the occurrence of A. arborescens on the Cape Peninsula is a result of the species having escaped from
cultivation and its subsequent colonization of natural fynbos vegetation (Moll & Scott, 1981; Kesting,
2003). Forms of A. arborescens flower at virtually any
time of the year, from mid-winter to mid-summer,
and where they occur sympatrically with other coflowering Aloe species, hybrids are frequently generated. Arguably the best known of the natural hybrid
swarms to which A. arborescens has contributed genes
is around Mossel Bay in the southern Cape, the likely area from which A. ×principis (Haw.) Stearn [=Pachidendron principis Haw. (Haworth, 1821: 37–38)]
was recorded as a ‘species’.
In South Africa, highly floriferous forms of
A. arborescens—with attractive, sickle-shaped leaves
that are carried in dense rosettes—are often used as
a parent in deliberate crosses aimed at producing
cultivars (Smith & Figueiredo, 2015a). In Europe,
A. ×spinosissima Jahand. is a widely grown hybrid,
HASELTONIA VOL. 22. 2016
57
Figure 4. The racemes of Aloe chortolirioides var. chortolirioides are capitate (head-shaped) and range from densely- to sparselyflowered. Photograph: Delia Oosthuizen.
Figure 5. Aloe ×inopinata in its natural habitat at Barberton Nature Reserve (Mountainlands) in the Barberton district, Mpumalanga, South Africa. Photograph: Delia Oosthuizen.
SMITH ET AL.—ALOE ×INOPINATA
58
Table 1. Characters on which Aloe ×inopinata can be separated from A. arborescens and A. chortolirioides var. chortolirioides.
Character
Aloe
arborescens
Aloe ×inopinata
Aloe chortolirioides var.
chortolirioides
20–30
c. 3
often with spots on leaf bases;
often longitudinally lined with a
light green central stripe
purplish
capitate
c. 5
Plant height (cm)
Leaf width (mm)
Leaf maculation
c. 100–300
c. 50
without spots;
lineation absent
Colour of leaves that
dry on the stems
Inflorescence shape
Raceme length (cm)
dull light brown
50–60
8–25
without spots; very rarely spotted;
longitudinally lined with lighter
stripes
purplish-brown
conical
20–30
conical to abruptly conical
10–15
with A. arborescens and the miniature A. humilis [var.
echinata (Willd.) Baker] being the parents (Smith,
2005: p. 85; Smith & Figueiredo, 2015a: p. xiii, Figures 1 and 2).
We here describe the natural hybrid between Aloe
arborescens and A. chortolirioides A.Berger var. chortolirioides (Figures 3–4) as Aloe ×inopinata Gideon
F.Sm., N.R.Crouch & Oosth. (Figure 5). Over the
past 50 years plants have become established in horticulture, and the hybrid was recently recorded from
two additional localities. Note that the surname
‘Oosthuizen’ of one of us (DO), has not been published before as the author of a plant name; initials
are accordingly not required. As the name has 10 letters it is abbreviated following the rule that it should
end at a consonant preceding a vowel (Brummitt &
Powel, 1992). Diagnostic characters, and information on the habitat and geographical distribution
range of this nothospecies are provided.
BACKGROUND
While conducting research towards his magna
opera (Reynolds, 1950, 1966), Dr Gilbert W. Reynolds became the most widely travelled of all the
students of the genus Aloe. During his extensive
field trips in search of aloes he covered more than
240,000 km [150,000 miles] on the African continent, Madagascar, and beyond (Reynolds, 1950;
1966; Walker, 2010; Crouch et al., 2013). This enabled him to determine the provenance of several
species that up to that time had been known in cultivation only, as well as to reflect on the parentage of
other ‘species’ that had not been recorded from the
wild. On the basis of his own field observations he
was therefore able to resolve the origin of what speculatively were hybrids. Accordingly, in his works on
the aloes of Africa and Madagascar he included lists
of all natural hybrids that he encountered.
In Reynolds (1950: 413) 15 natural hybrids are
listed as having Aloe arborescens as one parent. One
of these (Reynolds 1950: 413, natural hybrid 3) is
with A. chortolirioides [var. chortolirioides] as the
other parent, which Reynolds referred to as an
“…unexpectedly wide cross…”, and earlier in the
book, on p. 127, as “A very wide and unexpected
cross”. On p. 413 he further noted that the “…plant
transplanted readily, and grew well”. This hybrid is
illustrated under the treatment of A. chortolirioides
(Reynolds 1950: 126, Figure 95), where it was recorded as the only natural hybrid known to Reynolds involving A. chortolirioides. It should be noted
that, while two varieties are currently recognised in
A. chortolirioides—the typical one and A. chortolirioides var. woolliana (Pole-Evans) Glen & D.S.Hardy—
it was at species rank that Reynolds (1950: 128–129)
recognised A. woolliana Pole-Evans.
Reynolds was a regular visitor to the National
Herbarium of South Africa, a facility of what was
then the Division of Botany and Plant Pathology,
later the Botanical Research Institute (BRI), in Pretoria (Gunn & Codd, 1981). This amenity is currently part of the South African National Biodiversity Institute (SANBI). Although Reynolds rarely
published in the Division’s house journal, Bothalia,
he sometimes disseminated his research findings in
the Division’s other outlet, The Flowering Plants of
South Africa. However, he preferred for the most part
to describe the alooid and other plant novelties he
encountered in the then fledgling Journal of South
African Botany of the Kirstenbosch National Botanic
Garden (Klopper et al., 2013). It was likely during a
visit made by Reynolds to the National Herbarium
that he provided material of the hybrid to Mr Dave
(David Spencer) Hardy [born Pretoria, 24 September 1931; died Pretoria, 31 May 1998], at the time a
horticulturist employed in the Pretoria National Botanical Garden, which is also today part of SANBI’s
network of National Botanical Gardens (Glen, 1998).
Hardy grew material of the hybrid in a glasshouse
in the nursery area of the Garden. One of us (GFS)
had occasion to visit Hardy in the early 1980s and
was shown material of the plant, where it thrived
in comparatively low light conditions adjacent to
an artificial pond, in virtually year-round wet soil.
Hardy freely distributed material of this hybrid (and
other plants he kept in the nursery, for that matter;
see Glen, 1998: 240) to visitors, and plants became
widely available, especially among amateur collectors
of aloes, and succulent growers in general.
At the type locality of Aloe ×inopinata several
plants grow within an area of about 100m 2, together
with both parents. Additionally, A. craibii Gideon
F.Sm. and A. barbertoniae Pole-Evans occur within
this small spot of exceptional aloe richness. This cluster occurs within that area near Barberton bounded
by the topocadastral square 2531CA, which is rec-
HASELTONIA VOL. 22. 2016
Figure 6. The shrubby Aloe ×inopinata is in all respects finer
and more graceful-looking than A. arborescens, with the leaves
much narrower. Photograph: Delia Oosthuizen.
ognised currently as the most aloe-diverse hotspot in
southern Africa (see Crouch et al., 2013, Figure 2).
The Flora of Southern Africa (FSA) region is one of
three major centres of present-day species denseness
in aloes, East Tropical Africa and Madagascar comprising the other two (Carter et al., 2011). Holland
(1978) earlier demonstrated that Aloe diversification
could largely be explained by terrain diversity, which
was given as a function of local relief, degree of dissection of terrain, steepness or otherwise of slopes
and the complexity of the array of slope facets. In
the Barberton region there is great terrain diversity,
as well as heterogeneity of altitude, soil, and local climate conditions.
DIAGNOSTIC CHARACTERS OF ALOE
×INOPINATA
Although in most respects intermediate between
the two parent species, Aloe ×inopinata can be easily
separated from A. arborescens and A. chortolirioides
var. chortolirioides based on gross vegetative and reproductive morphological characters. While a shortstemmed, shrubby entity, much like A. arborescens,
A. ×inopinata is in all respects finer and more graceful-looking than A. arborescens, with the leaves much
narrower (Table 1; Figure 6). The leaves of A. ×inopinata are often adorned with faint or prominent longitudinal lines, especially on the adaxial surface, like
those of A. chortolirioides var. chortolirioides, but generally lack spots (Figure 7). The immaculate nature
of the leaf surfaces is a character shared with A. arborescens. In rare instances both surfaces of the leaves
of A. ×inopinata are sparsely white-spotted (Figure 8),
a character in turn inherited from the other parent,
A. chortolirioides var. chortolirioides, where spots are
particularly noticeable at the broad leaf base. Interestingly, leaves that dry on the stems of A. ×inopinata
persist for a time (unlike those of A. chortolirioides
var. chortolirioides that often burn off in the veld fires
to which the species is so well adapted). The leaves
themselves, as well as the exposed surface of freshly
59
Figure 7. The leaves of Aloe ×inopinata are often adorned
with lighter green longitudinal lines, especially on the adaxial
surface, and are mostly immaculate. Photograph: Delia Oosthuizen.
Figure 8. In rare instances both surfaces of the leaves of Aloe
×inopinata are sparsely white-spotted. Note the exotic Pinus
plantations in the background. Photograph: Delia Oosthuizen.
Figure 9. The dry leaves of Aloe ×inopinata that remain attached to the stems take on a purplish-brown colour. Photograph: Delia Oosthuizen.
60
SMITH ET AL.—ALOE ×INOPINATA
Limpopo Province (Figure 11; orange on map).
The distribution ranges of Aloe arborescens and
the nominate variety of A. chortolirioides overlap in
Mpumalanga, Swaziland, and Limpopo. However,
the hybrid has a narrow geographical distribution
range and is only known from three relatively close
localities, all in South Africa’s Mpumalanga Province
(Figure 11; black on map). It has been recorded from
only the Barberton district, from near the summit of
Kamhlabane, about 37 km [22 miles] east of Barberton in the Eastern Transvaal [now Mpumalanga] by
Reynolds (1950: 126), and Twello 373JU, where two
sites are known some 3 km [2 miles] apart. The two
Twello localities, within the Barberton Nature Reserve (Mountainlands) and Songimvelo Nature Reserve respectively, are each approximately 11 km [7
miles] east of Barberton. All three localities fall within the Barberton Centre of Endemism (Van Wyk &
Smith, 2001).
DESCRIPTION OF ALOE ×INOPINATA
Aloe
×inopinata
Gideon
F.Sm.,
N.R.Crouch & Oosth. Sp. nov. Type: South
Africa, Mpumalanga Province, Barberton district, Barberton Nature Reserve (Mountainlands), Twello 373JU, 1500m [4920’] above
sea level, (–CC), 01 March 2016, D. Oosthuizen 1960 (BNRH holo-).
Figure 10. The racemes of Aloe ×inopinata are shorter than
those of A. arborescens (Figure 2), and longer and more
conical than those of A. chortolirioides var. chortolirioides
(Figure 4). Photograph: Delia Oosthuizen.
broken leaves of the hybrid, dry a purplish-brown
colour (Table 1; Figure 9). Not many species of Aloe
have leaves that dry purple on the stems, Aloe succotrina Weston from the Western Cape being a notable
exception (Walker et al., 2015).
In terms of inflorescence morphology, the racemes of Aloe ×inopinata are shorter than those of
A. arborescens (Figure 10), and longer and more conical than those of A. chortolirioides var. chortolirioides.
Likewise, floral density on the racemes of Aloe ×inopinata is intermediate between the parents.
GEOGRAPHICAL DISTRIBUTION
RANGES OF ALOE ARBORESCENS, A.
CHORTOLIRIOIDES, AND A. ×INOPINATA
Aloe arborescens is a widespread species occurring
in southern Africa from the Cape Peninsula eastwards in a fairly narrow near-coastal band through
KwaZulu-Natal, and inland to the eastern Free State,
Mpumalanga, Swaziland, and South Africa’s Limpopo Province. It has also been recorded from mostly
mountainous areas in central and eastern Zimbabwe,
southern and central Mozambique, and southern
Malawi (Figure 11; red on map).
Aloe chortolirioides has a much more limited geographical distribution range that is focussed around
Barberton in Mpumalanga, and northern Swaziland,
with outlying localities recorded from South Africa’s
Diagnosis: Although having a shrubby growth
form, Aloe ×inopinata differs from the much more
robust Aloe arborescens in being a smaller plant in all
respects, with narrower leaves, the margins of which
are adorned with fine, white, firm teeth. The inflorescences of Aloe ×inopinata are shorter than those
of Aloe arborescens, but longer and more conical than
those of Aloe chortolirioides var. chortolirioides. Aloe
×inopinata further differs from Aloe chortolirioides var.
chortolirioides in lacking the short, stubby, Xerophytalike stems, and in having much broader leaves that
are arranged in larger rosettes.
Description: Much-branched shrub, 0.5–0.6 m
high. Stems up to 3.5–4.0 cm in diameter, erect,
branching at or near the base, branches spreading,
with persistent dried leaves for 5–7 cm. Rosettes
0.4–0.6 m in diameter. Leaves densely rosulate, at
branch apices, spreading, becoming recurved, light
to mid-green, without spots or rarely with scattered
white spots on both surfaces, texture smooth, lanceolate-attenuate, 20–40 cm long, 0.8–2.5 cm wide at
base; margin whitish or of similar colour to that of
leaf surface, with small, firm, white teeth, straight or
basally pointed towards stem and apically forwardpointing, 0.8–1.2 mm long, 5–9 mm apart at midleaf; fresh exudate pale creamy beige, drying purplish.
Inflorescences 1–2 simultaneously from a rosette,
± 40–60 cm high, erect, simple. Peduncle ± 30–50
cm long, ± 10 mm wide at base, green to purplish
green, stout, with few, broadly deltoid to ovate-elongated, straw-coloured, scarious, many-nerved sterile
bracts, ±12 mm long, 6 mm wide. Racemes subconical to conical or conical-cylindrical, 8–10 cm long,
HASELTONIA VOL. 22. 2016
61
Figure 11. Known geographical distribution ranges of Aloe arborescens in South Africa, Swaziland, and southern Mozambique (red on map), and A. chortolirioides var. chortolirioides (orange on map). The black dots indicate the known localities of
A. ×inopinata.
5–7 cm wide, erect, densely flowered, buds erect to
spreading; flowers covered by floral bracts in early
development, pendulous when open. Floral bracts
broadly ovate-elongated, 12–15 mm long, up to 6
mm wide at base, straw-coloured to brownish-white,
scarious, many-nerved. Pedicels 20–22 mm long,
orangey-red. Flowers: perianth orangey-red, paler
towards mouth, purplish-green-tipped in bud, ± 30
mm long, 3–5 mm across ovary, slightly narrowed
above ovary, widening slightly towards wide-open
mouth, cylindric-trigonous, outer segments free to
the base, tips flared; stamens with filiform-flattened,
yellow filaments, anthers orange-brown, included or
slightly exserted; ovary 5 mm long, 2.5 mm diameter, green; style yellow, exserted for 5–8 mm. Fruit
obovoid capsule, purplish brown. Seeds not seen.
Chromosome number unknown.
Eponymy: From the Latin inopinata (English:
‘unexpected’) in accordance with Reynolds (1950:
127) who referred to an encounter with this hybrid
as “unexpected”.
Habitat: Species that grow in association with
Aloe ×inopinata at the Barberton Nature Reserve
(Mountainlands) type locality include Hypoxis limicola B.L.Burtt [Hypoxidaceae], Ekebergia pterophylla
(C.DC.) Hofmeyr [Meliaceae], Streptocarpus dunnii Hook.f. [Gesneriaceae], Watsonia watsonioides
(Baker) Oberm. [Iridaceae], Erica woodii Bolus [Ericaceae], Justicia linifolia (Lindau) V.A.W.Graham
(=Siphonoglossa linifolia (Lindau) C.B.Clarke) [Acanthaceae], and Alepidea peduncularis A.Rich. [Apiace-
ae]. The hybrid grows in the mist belt at an altitude
of ca. 1500m [4920’] above sea level on shallow soils
amongst rocks and shrubs such as Burchellia bubalina (L.f.) Sims [Rubiaceae]. The vegetation type is
Barberton Montane Grassland (Gm 17) (Mucina
et al., 2006), a mosaic of short grassland and rocky
shrubland set in typically rugged terrain.
Flowering time: February to March. In contrast,
Aloe arborescens is known to flower at any time of
the year, with most forms of the species peaking in
mid-winter (June to August). The flowering peak of
A. chortolirioides var. chortolirioides is July to August
(Bornman & Hardy, 1971: 297). Further, Van Wyk
& Smith (2014: 302) has recorded A. chortolirioides,
without differentiating which variety, as having a
long flowering period, which can stretch from March
(autumn) to September (spring), and also note that
the species will spontaneously flower in response
to occasional fires. Evidently both parent species of
A. ×inopinata have a greater or lesser tendency towards out-of-peak-season flowering, and cross-pollination and fertilization during such a chance flowering event may well have given rise to the hybrid.
Such stochastic and erratic behaviour also explains
why A. ×inopinata has not been observed across the
full range where A. arborescens and A. chortolirioides
are sympatric. It is noteworthy that most slender
aloes (Aloe sect. Leptoaloe A.Berger), the group to
which A. chortolirioides belongs, as well as the related
grass aloes (Aloe sect. Graminialoe Reynolds) flower
in the summer months, like A. ×inopinata. As the
62
SMITH ET AL.—ALOE ×INOPINATA
parents of the nothospecies are anticipated to very
rarely flower at the same time as the hybrid, this
significantly decreases the likelihood of regression
through backcrossing (with the parents), such that
speciation through hybridisation may eventuate.
Common names: None recorded.
ADDITIONAL SPECIMENS OF
ALOE ×INOPINATA EXAMINED
SOUTH AFRICA.
MPUMALANGA PROVINCE [TRANSVAAL
pro parte].
The National Herbarium in Pretoria (PRE) holds
two black & white prints of a plant collected at
Kamhlabane with the number G.W. Reynolds 2827.
The plants figured flowered in his garden on 13
March 1939, and on 07 March 1940. However, no
specimens with this number could be traced, and it
might be that Reynolds did not make a specimen of
this plant, as there are no records of such specimens
referenced in the Botanical Database of Southern Africa (BODATSA) (see http://newposa.sanbi.org/).
CULTIVATION AND PROPAGATION OF
ALOE ×INOPINATA
This hybrid is one of the easiest aloes to cultivate
and propagate. It is surprisingly tolerant of high
soil moisture levels, growing well even when waterlogged for short periods. Propagation is through the
numerous basal and stem sprouts that can be easily
removed and rooted in gritty sand.
ACKNOWLEDGEMENTS
Anonymous referees, as well as Dr Tim Harvey,
are thanked for their comments on the manuscript.
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