Plectranthus acariformis P.I.Forst. and P. geminatus P.I.Forst. (Lamiaceae): new species from south-east Queensland

2014·7 MB·English

by  Paul I Forster

Plectranthus acariformis P.I.Forst. and P. geminatus P.I.Forst.
(Lamiaceae): new species from south-east Queensland
Paul I. Forster
Summary
Forster, P I. (2014). Plectranthus acariformis P.I.Forst. and P. geminatus P.I.Forst. (Lamiaceae): new
species from south-east Queensland. Austrobaileya 9(2): 279-291. Plectranthus acariformis and
P. geminatus are newly described and illustrated: both are endemic to south-east Queensland. The
former is currently known from a single population on trachyrhyolite in Noosa National Park near
Coolum on the Sunshine Coast whereas the latter occurs in several localities associated with basalt
and rhyolite derived from the Mt Warning caldera in the Lamington Plateau and Numinbah Valley.
Key Words: Lamiaceae, Plectranthus, Plectranthus acariformis, Plectranthus geminatus, Australia
flora, Queensland flora, Noosa National Park, Lamington Plateau, Numinbah Valley, new species,
taxonomy, conservation status
P.I.Forster, Queensland Herbarium, Department of Science, Information Technology, Innovation
and the Arts, Brisbane Botanic Gardens, Mt Coot-tha Road, Toowong, Queensland 4066, Australia.
Email: Paul. Forster@dsitia. qld.gov. au
Introduction
The genus Plectranthus L.Herit. is diverse Materials and methods
in Australia with over 40 recognised species
Fieldwork was undertaken in south-east
(Forster 2011,2014). In south-east Queensland
Queensland to procure fresh material
(equivalent to the Southeast Queensland
for specimens and cultivation enabling
bioregion, cf. Sattler & Williams 1999), 11
observation of variation in phenology. The
native species are currently recognised with
subsequent descriptions and observations
five of these (P. fragrantissimus P.I.Forst., P.
are based on these recent collections and
habrophyllus P.I.Forst., P. leiperi P.I.Forst.,
other historical collections in the Queensland
P. omissus P.I.Forst. and P. torrenticola
Herbarium (BRI).
P.I.Forst.) endemic. Hypotheses on speciation
in the genus in Australia have been previously Taxonomy
outlined (Forster 2011) and it is to be expected
Plectranthus acariformis P.I.Forst., sp.
that further taxa will be newly discovered in
nov.; With affinity to P. parviflorus Willd.
the region and elsewhere.
but differing in the thickened base to the
Two additional species are described stems (versus a distinct rounded tuber), the
in this paper. One of these (P. acariformis distinctive glandular trichomes with enlarged
P.I.Forst.) has a highly restricted distribution bases that impart crenate to crenulated
and is known from a single locality which margins to the floral bracts and the greater
may indicate that it is an example of recent number of flowers in the verticillasters (lb-
speciation. The other species (P. geminatus 24 versus up to 10). Typus: Queensland.
P.I.Forst.) is more widespread and known Moreton District: Noosa National Park, Mt
from five localities. Emu (Peregian) summit, 5 February 2014,
P.I. Forster PIF40678 & G. Leiper (holo: BRI
[2 sheets + spirit]; iso: K, MEL, NSW, US
distribuendi).
Erect herb to 50 cm high; foliage scentless
when crushed, not clammy; non-glandular
and glandular trichomes uncoloured, non-
Accepted for publication 25 August 2014
glandular trichomes with prominent raised
280 Austrobaileya 9(2): 279-291 (2014)
bases, sessile glands 8-celled, orange. Roots 2.5- 3 x c. 0.2 mm, non-glandular trichomes
thickened-tuberous to fibrous. Stems square, sparse, antrorse to divaricate, 4-8-celled
erect to straggling, fleshy, with stringy up to 0.5 mm long, glandular trichomes
fibres, the lower parts up to 7 mm diameter scattered to sparse, very short (< 0.2 mm
and noticeably thickened (although not with long), sessile glands absent. Flower calyces
a rounded tuber), pink-purple to pink-green, 2.6- 2.8 mm long, non-glandular trichomes
upper parts with persistent indumentum, non- sparse, antrorse to divaricate, 4-8-celled up
glandular trichomes sparse to dense, retrorse, to 0.5 mm long, glandular trichomes sparse
6-10-celled up to 1 mm long, glandular and very short (< 0.2 mm long), sessile glands
trichomes absent or scattered to sparse, very sparse. Corolla 9-11.5 mm long, lilac-purple;
short < 0.1 mm long, sessile glands absent. tube 4.5-5.5 mm long, weakly curved at 25-
Leaves discolorous, petiolate; petioles 5-25 x 30° 1.5-2 mm from the base, slightly inflated
1.5-3 mm, channelled on top, non-glandular upwards, non-glandular trichomes absent
trichomes dense and shaggy, retrorse, or scattered, 2-celled and very short (< 0.1
4-10-celled up to 1 mm long, glandular mm long), glandular trichomes and sessile
trichomes absent or scattered to sparse, very glands absent; upper lobes suborbicular,
short < 0.1 mm long, sessile glands absent or erect to reflexed, 1.9-2.3 x 1.8-2.3 mm,
occasional; laminae lanceolate-ovate to ovate, non-glandular trichomes sparse, divaricate,
fleshy, strongly keeled, 10-45 x 5-42 mm, 2-4-celled up to 0.3 mm long, glandular
crenate with 6-8 teeth up to 4 mm long on trichomes absent, sessile glands sparse;
each margin, of similar length along margin, lateral lobes oblong, 1.3-1.5 k 0.7-0.8 mm,
secondary teeth poorly developed; tip acute; glabrous; lower lobe oblong-ovate, 5-5.5 x
base obtuse to rounded; upper surface mid¬ 5-5.2 mm, non-glandular trichomes sparse,
green and with a hoary silver frosting from divaricate, 2-4-celled up to 0.3 mm long,
indumentum, veins impressed, non-glandular glandular trichomes absent, sessile glands
trichomes dense, antrorse to somewhat sparse; filaments filiform, 8-9 x c. 0.2 mm,
divaricate, 4-10-celled up to 1 mm long, lilac, fused for 3-4 mm from the base; anthers
glandular trichomes and sessile glands absent; c. 0.4 x 0.3 mm; style filiform, 8-9 x c. 0.2
lower surface pale green and with a hoary silver mm, lilac, bifid for c. 0.4 mm. Fruit calyces
frosting from indumentum, veins strongly 4-4.6 mm long; upper lobe broadly ovate,
raised, non-glandular trichomes dense and 2-2.2 x 2-2.2 mm; lateral lobes lanceolate,
shaggy (interlocking), divaricate, 6-10-celled 1.5-1.8 x 0.6-0.8 mm; lower lobes lanceolate-
up to 0.8 mm long, glandular trichomes falcate, 2-2.5 x c. 0.4 mm. Nutlets ± circular
generally absent or a few ‘micro’ trichomes in outline, compressed flattened globose,
on veins that are < 0.1 mm long, sessile glands 0.8-0.9 mm wide, 0.4-0.5 mm thick, brown,
scattered and deeply recessed. Inflorescence weakly verrucose. Figs. 1-5.
up to 300 mm long, usually single or with
Additional specimens examined: Queensland.
1 or 2 side branches; axis square in cross-
Moreton District: Mt Peregian, Coolum (cult. The Gap,
section, pink, non-glandular trichomes sparse Brisbane), Jan 1957, Blake 20077 (BRI); Noosa NP, Mt
to dense, divaricate, 4-10-celled up to 1 mm Emu (Peregian) (cult. Beenleigh), Jan 2014, Leiper s.n.
(BRI [AQ837023], NSW).
long, glandular trichomes absent, or sparse
and minute (< 0.3 mm long), sessile glands Distribution and habitat: Plectranthus
absent; bracts obovate-rhomboid, 2.2-2.8 x acariformis is currently known only from
1.3-1.9 mm, ecomose, margins irregularly Mt Emu (Peregian), a small volcanic plug
crenate to crenulate due to enlarged bases of overlooking the Pacific Ocean on the Sunshine
glandular trichomes, non-glandular trichomes Coast in south-east Queensland. Plants of
sparse, divaricate, 4-10-celled up to 0.9 mm this species were common at the summit of
long, glandular trichomes scattered and the mountain (small hill in reality) in low
very short (< 0.3 mm long), sessile glands heathland on fine grained trachyrhyolite
occasional to scattered; verticillasters (Willmott 2004) rock outcrops. These
16-24-flowered, 5-10 mm apart; pedicels peraluminous rhyolites are also found on Mt
Forster, Plectranthus acariformis and P geminatus 281
Fig. 1. Plectranthus acariformis. A. habit of flowering stem x0.5. B. adaxial leaf surface xl. C. abaxial leaf surface
xl. D. verticillaster with buds x4. E. floral bract xl2. F. lateral view of flower x6. G. front view of flower x6. H. lateral
view of flower pedicel and calyx x8.1. lateral view of fruiting pedicel and calyx x8. J. non-glandular hair from foliage
demonstrating enlarged basal cell x36. All from Leiper s.n. (BRI [AQ837023]). Del. W. Smith.
282 Austrobaileya 9(2): 279-291 (2014)
Fig. 3. Plectranthus acariformis. Detail of foliage from plants at Mt Emu (Forster PIF40678 & Leiper). Photo: G.
Leiper.
Forster, Plectranthus acariformis and P geminatus 283
Fig. 4. Plectranthus acariformis. Partial inflorescence with flowers from plants at Mt Emu (Forster PIF40678 &
Leiper). Photo: G. Leiper.
Fig. 5. Plectranthus acariformis. Thickened (non-tuberous) stems bases from plants at Mt Emu {Forster PIF40678 &
Leiper). Photo: G. Leiper.
284 Austrobaileya 9(2): 279-291 (2014)
Tinbeerwah in the Glasshouse Mountains and Levin (2000) whereby every species has to
are Cenozoic in origin (Cohen et al. 2007). begin somewhere in space and time.
Notes: Plectranthus acariformis was first Other Plectranthus species from
collected by either Stan Blake or one of his Queensland that appear to be ‘stuck on a
collectors prior to January 1957 with the rock’ at their putative point of origin include
material cultivated by Blake in his Brisbane P. actites PI.Forst., P. arenicola PI.Forst.,
garden. The population of plants was P. bipartitus PI.Forst., P. cyanophyllus
rediscovered by Glenn Leiper sometime PI.Forst., P. insularis PI.Forst., P. minutus
prior to January 2014 and is the only species PI.Forst., P. splendens PI.Forst. and P.
of this genus found to date on Mt Emu. Both thalassoscopicus PI.Forst. In some cases
P. graveolens R.Br. and P. parviflorus have (P. bipartitus, P. splendens) the ‘rock’
been collected from the nearby Mt Coolum in question is an inselberg and there are
that has similar rock outcrops; however, these definitely multiple subpopulations (‘islands
are dominated by comendite (peralkaline on islands’ cf. Porembski et al. 2000); in
rhyolite) (Willmott 2004; Cohen et al. others on inselbergs this is still unknown
2007). The two hills are separated by 6 km (P. actites, P. cyanophyllus, P. minutus).
of dissimilar habitat of lowland heathlands For the remaining species (P. arenicola, P.
and swamps. Plectranthus acariformis is insularis, P. thalassoscopicus) the available
quite dissimilar to primary hybrids of these habitat (rock platforms or small outcrops)
two species; however, the possibility that is much smaller and can be measured in a
it is a result of hybridisation followed by handful of hectares or a few hundred square
polyploidy requires investigation. This mode metres. Further targeted field collections may
of speciation is now known to be increasingly well negate these observations; however, in
common in many plant groups (Soltis et al. most instances suitable habitat is lacking or
2003; Hegarty & Hiscock 2004; Mallett 2007) geographically well removed.
and would support the hypothesized patterns
Plectranthus acariformis differs from
of diversification in the Australian taxa of this
P. parviflorus in a number of characters,
genus (Forster 2011).
most notably the thickened but non-tuberous
Mt Emu may represent a minor centre base (Fig. 5) to the stems (versus formation
of localised speciation given the presence of a distinct rounded tuber), the distinctive
of other endemics or near endemics, such glandular trichomes with enlarged bases that
as the tetraploid Allocasuarina emuina impart crenate to crenulated margins to the
L.A.S.Johnson (Lamont et al. 2012). These floral bracts and the greater number of flowers
authors also concluded that Mt Emu hosted in the verticillasters (16-24 versus up to 10).
refugial populations of many heathland species
Conservation status: This species occurs
during Pleistocene interglaciations when the
in a southern section of Noosa National
surrounding coastal plain was inundated. In
Park; however, there are several threatening
glacial periods during the Pleistocene or into
processes that are currently affecting it. Mt
the recent Holocene and present, the area
Emu is surrounded by housing developments
surrounding Mt Emu would have mainly
and is increasingly a popular small hill for
supported low dunefields (Lees 2006) and
people to climb with a number of existing
swamps, neither comprising suitable habitats
rough tracks from the base to the summit.
for this Plectranthus. Given the apparent
Recently one of these has been ‘upgraded’
restriction of Plectranthus acariformis to
to enable vehicle access to the summit; in
Mt Emu it can also be hypothesised that the
the process several populations of cryptic
species is an example of incipient speciation,
and geographically restricted ground orchids
but where apart from localised dispersal,
have been severely impacted with many
range expansion has not yet occurred, unlike
plants destroyed. The localised population
the case of Allocasuarina emuina. This also
of Plectranthus acariformis is restricted to
fits well with the concepts and theories of
the very summit of the hill (Fig. 2) where
Forster, Plectranthus acariformis and P. geminatus 285
most of the tracks intersect and where there indumentum, non-glandular trichomes sparse
is repeated trampling or disturbance of the and shaggy, 2-seriate, weakly divaricate
vegetation. The Plectranthus appears to (mainly held at 90° to stem), longer trichome
have been trampled out or cleared from the series 8-12-celled up to 4 mm long, shorter
tracks and ‘sitting perches’ at the summit, but trichome series 4-6-celled up to 0.4 mm long,
persists abundantly in crevices and amongst glandular trichomes dense, uniseriate, very
boulders that are too rugged for most casual short (< 0.1 mm long) although occasionally
visitors to wander over. up to 0.7 mm long, sessile glands absent or
rarely scattered to dense. Leaves discolorous,
Given the hypothesised incipient
petiolate; petioles 8-55 x 1.5-3 mm,
speciation of this species, it is likely that
channelled on top, pink-purple, non-glandular
there is little genetic variation present in
trichomes sparse and shaggy, 2-seriate,
the population; indeed it is likely that most
weakly divaricate (mainly held at 90° to
individuals (or clumps) are clonal in origin.
stem), longer trichome series 8-12-celled
An appropriate conservation status up to 4 mm long, shorter trichome series
(IUCN 2001) for Plectranthus acariformis is 4-6-celled up to < 0.5 mm long, glandular
Endangered based on the criterion D. trichomes moderately dense, generally very
short (< 0.2 mm long) although up to 0.7 mm
Etymology: The specific epithet is derived
long on occasion, sessile glands 8-celled,
from the Latin noun acarus which is derived
dense; laminae cordate-ovate, fleshy, keeled,
from Greek atari (mite) and the Latin -formis
20-65 x 15-60 mm, crenate with 10-14
(like) and is a fanciful allusion to the form of
teeth up to 4 mm long on each margin, of
the floral bracts in this species.
similar length along margin, secondary teeth
Plectranthus geminatus P.I.Forst., sp. nov. poorly developed; tip acute; base subcordate
Allied to P. caldericola P.I.Forst. but differs to truncate; upper surface somewhat glossy
in the stem bases being conspicuously olive-green, veins impressed, velutinous,
thickened-tuberous, foliage that is ± scentless non-glandular trichomes moderately dense,
and with non-glandular indumentum in two 2-seriate, long trichome series divaricate,
distinct series (versus not), the laminae are 8-10-celled and 1-4 mm long, short trichome
cordate-ovate (versus broadly ovate to almost series divaricate, 4-6-celled up to 0.8 mm
lobate) with 10-14 teeth per margin (versus long, glandular trichomes ± sessile (< 0.1
7-9), the floral bracts are broadly orbicular- mm long), sessile glands dense, 8-celled or
reniform to orbicular-obovate (versus broadly- a mixture of 4 and 8-celled; lower surface
ovate to obovate) and the corolla tube is paler green to silver-green and with a hoary
abruptly curved (versus weakly). Typus: silver frosting from indumentum, veins
Queensland. Moreton District: Lamington strongly raised, non-glandular trichomes
National Park, Cainbable Falls, 27 February dense, 2-seriate, divaricate, long trichome
2014, PI. Forster PIF40722 & G. Leiper series 8-12-celled and 1.8-3 mm long,
(holo: BRI [2 sheets + spirit]; iso: K, MEL, short trichome series 4-6-celled and < 0.5
NSW distribuendi). mm long, glandular trichomes scattered,
± sessile and < 0.1 mm long, sessile glands
Erect to decumbent subshrub (rarely a herb)
dense, 4 and 8-celled. Inflorescence up to 120
to 100 cm high; foliage ± scentless when
mm long, usually single or with 1 or 2 side
crushed, somewhat clammy; non-glandular
branches, pedunculate for up to 16 mm; axis
and glandular trichomes uncoloured, sessile
square in cross-section, pink-purple, strongly
glands 4 or 8-celled, orange-red. Roots
channelled, non-glandular trichomes dense,
thickened-tuberous, fleshy-fibrous. Stems
2-seriate, divaricate, long trichome series
square, erect to straggling, fleshy, easily
8-14-celled up to 3 mm long, short trichome
snapped, the lower parts up to 7 mm diameter
series 4-6-celled and < 0.5 mm long,
and noticeably thickened forming weak tubers
glandular trichomes moderately dense, very
from which reshooting occurs annually,
short (< 0.4 mm long), sessile glands sparse
pink-purple; upper parts with persistent
286 Austrobaileya 9(2): 279-291 (2014)
to moderately dense, 4-celled; bracts broadly Additional specimens examined: Queensland.
orbicular-reniform to orbicular-obovate, Moreton District: Canungra to Mt Tamborine Road,
Feb 2014, Forster PIF40715 & Leiper (BRI, MEL);
1.8-2.2 x 1.8-3.5 mm, initially somewhat
Lamington NP, near Plum Pudding, Feb 2014, Forster
comose, non-glandular trichomes sparse, PIF40716 & Leiper (BRI, MEL); cult. Beenleigh (ex
2-seriate, divaricate to somewhat antrorse, Numinbah Valley, S of Chesters Road), Feb 2014, Leiper
long trichome series 8-14-celled up to 2.5 s.n. (BRI [AQ837024]); Numinbah Valley, S of Chesters
mm long, short trichome series 4-6-celled up Road, Feb 2014, Forster PIF40692 & Leiper (BRI, K,
MEL, NSW); Cainbable cliffs, Lamington NP, S of
to 0.4 mm long, glandular trichomes absent,
Canungra, Jan 2000, Bean 15967A [& Leiper] (BRI);
sessile glands moderately dense, 4 and Lamington NP, Pats Bluff, Mar 2014, Forster PIF40758
8-celled; verticillasters 10-12-flowered, up & Leiper (BRI).
to 5 mm apart; pedicels 1.8-2 x c. 0.2 mm,
Distribution and habitat: Plectranthus
non-glandular trichomes occasional to sparse,
geminatus has a relatively small area of
2-seriate, divaricate, long trichome series
occurrence from south of Canungra to the
8-14-celled up to 1 mm long, short trichome
northern parts of the Lamington Plateau
series 4-6-celled and < 0.3 mm long, glandular
(Sarabah Range, western cliffs) in south¬
trichomes dense, very short (< 0.1 mm long),
east Queensland (Map 1). Three populations
sessile glands absent or occasional and 4 or
CPIF40716, PIF40722 and PIF40758) have
8-celled. Flower calyces 1.5-1.6 mm long,
been found on rock outcrops or platforms
non-glandular trichomes dense and shaggy,
derived from north-westerly basalt flows
2-seriate, divaricate to horizontal at 90° to
(Hobwee basalts of the Lamington Group)
tube, long trichome series 8-14-celled up to
from the Tweed or Mt Warning Shield
2 mm long, short trichome series 4-6-celled
Volcano caldera (Stevens 1970; Willmott
and <0.5 mm long, glandular trichomes
2004) and are generally immediately adjacent
occasional and very short (< 0.1 mm long),
to grassy woodland dominated by eucalypts
sessile glands dense, 4 or 8-celled. Corolla
(e.g. Eucalyptus banksii Maiden and E.
7.5-10 mm long, lilac-purple; tube 3.6-5
quadrangulata H.Deane & Maiden or E.
mm long, abruptly curved at 40-80° 1.8-2
crebra F.Muell. and E. melliodora A.Cunn.
mm from the base, slightly inflated upwards,
ex Schauer). Two populations (PIF40692 and
glabrous; upper lobes suborbicular, erect to
PIF40715) occur on small rhyolite outcrops
reflexed, 1.5-1.8 x 1.5-1.8 mm, non-glandular (Binna Burra rhyolites) derived from the same
trichomes sparse, divaricate, 8-14-celled up
volcano (Willmott 2004) with associated
to 2 mm long, glandular trichomes absent,
grassy woodland dominated by eucalypts (e.g.
sessile glands occasional, 4-celled; lateral
Corymbia intermedia (R.T.Baker) K.D.Hill
lobes oblong, 1.2-1.3 x 0.7-0.8 mm, glabrous, & L.A.S.Johnson, Lophostemon confertus
purple and centrally edged with white; lower
(R.Br.) Peter G.Wilson & J.T.Waterh. or E.
lobe broadly ovate, 3.5-5 x 3.2-4.5 mm, carnea R.T.Baker and E. tereticornis Sm.).
non-glandular trichomes sparse, divaricate,
These rock outcrops or platforms are often
2-4-celled and < 0.3 mm long, glandular
small in individual extent (e.g. populations
trichomes absent, sessile glands scattered, 4
sampled by PIF40692, PIF40715, PIF40716),
or 8-celled; filaments filiform, 7-11 x c. 0.2 though some are much larger (PIF40722 &
mm, lilac, fused for 3-3.5 mm from the base;
PIF40758) but tend to be mainly precipitously
anthers c. 0.4 x 0.3 mm; style filiform, 9-10 vertical in their entirety and thus difficult to
x c. 0.2 mm, lilac, bifid for c. 0.4 mm. Fruit access. Soils are skeletal to non-existent and
calyces 2.5-27 mm long; upper lobe oblong-
the plants grow mainly in humus or leaf litter
ovate, 0.8-0.9 x 0.8-0.9 mm; lateral lobes
that has accumulated in crevices or flatter
lanceolate-falcate, 1-1.2 x 0.5-0.6 mm; lower areas. At some localities, populations of P.
lobes lanceolate-falcate, 1.5-1.7 x 0.5-0.6
graveolens are close by or occasional plants
mm. Nutlets flattened convex, 07-0.8 mm
are intermingled with those of P. geminatus.
long, 07-0.8 mm wide, 0.5-0.6 mm thick,
glossy brown, weakly verrucose. Figs. 6-10.
Forster, Plectranthus acariformis and P geminatus 287
Fig. 6. Plectranthus geminatus. A. habit of flowering stem *0.5. B. adaxial leaf surface xl. C. abaxial leaf surface
xl. D. part of rhachis showing channelling and part verticillasters x4. E. floral bract x8. F. front view of flower x8. G.
lateral view of flower x8. H. lateral view of flower calyx xl2. I. lateral view of fruit calyx xl2. All from Leiper s.n.
(BRI [AQ837024]). Del. W. Smith.
288 Austrobaileya 9(2): 279-291 (2014)
Fig. 7. Plectranthus geminatus. Habit of plants in the Numinbah Valley {Forster PIF40692 & Leiper). Photo: G.
Leiper.
Fig. 8. Plectranthus geminatus. Thickened tuberous base to stems of plants from Cainbable Falls {Forster PIF40722
& Leiper). Photo: G. Leiper.