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Citation: Martine CT, Symon DE, Evans EC (2013) A new cryptically dioecious species of bush tomato (Solanum) from the Northern Territory, Australia. PhytoKeys 30: 23–32. doi: 10.3897/phytokeys.30.6003
A new species of dioecious Solanum from the Australian “Dioicum Complex” of Solanum subgenus Leptostemonum is described. Solanum cowiei Martine sp. nov., is allied with other members of this problematic lineage, but differs in its slender leaves, limited armature and diminutive habit. The species was first segregated by botanists at the Northern Territory Herbarium as Solanum sp. Litchfield (I.D. Cowie 1428); and specimens representing this species have also been referred to by Symon as Solanum sp. Fitzmaurice River. Collections suggest that this is an endemic of the sub-arid tropical zone of the Northern Territory. SEM images support initial assumptions that the new species is cryptically dioecious via production of inaperturate pollen grains in morphologically hermaphrodite flowers.
Bush tomato, Kimberley, new species, Limmen National Park, Litchfield National Park, Northern Territory, Solanum, Solanum cowiei, Solanum dioicum, Solanum sp. Litchfield , cryptic dioecy, inaperturate pollen
More than three decades ago the late David Symon published the first comprehensive monograph of Solanum in Australia (1980), a collection of species descriptions for 125 native and exotic solanums including fourteen species newly described by the author.
Research using molecular phylogenetics approaches (
The Dioicum Complex, in particular, is a taxonomically challenging group, as acknowledged by
In 2009, CTM followed up on collections by local botanists (including K. Brennan, I. Cowie, D. Lewis, and J. Westaway) of a taxon that had been segregated in the Northern Territory Herbarium as Solanum sp. Litchfield (I.D. Cowie 1428). New field collections from Litchfield National Park by CTM and colleagues were then used for molecular work (
Unfortunately, few collections had been made of this taxon that included reproductive elements and field surveys made in April-May 2009 and May 2013 located no individuals in flower or fruit. However, multiple new reproductive collections (and some older collections now recognized as this taxon) were deposited/filed at DNA between 2009 and the present day, thus allowing for a species description to now be completed.
Among the specimens now annotated as Solanum sp. Litchfield is a sheet that had been in an indet. folder until recently. This specimen, Barritt 1396, of a staminate plant in flower, was identified by the collector as Solanum dioicum. During a visit to the Northern Territory Herbarium in 2004, Symon encountered the specimen, annotated it as Solanum sp. Fitzmaurice River, and recorded a page of notes on the morphological characteristics setting this taxon apart from others. Those notes, left in the specimen folder, are here incorporated and used, in part, to describe Solanum cowiei – a posthumous contribution described further in
urn:lsid:ipni.org:names:77134228-1
http://species-id.net/wiki/Solanum_cowiei
Figs 1–2This species is distinguished from other dioecious Australian solanums by its slender leaves, fine (or absent) armature, and diminutive habit.
TYPE: AUSTRALIA. The Northern Territory: Macadam Range, 14°41'07"S, 129°44'39"E, 15 June 2007 (staminate and pistillate flowers; fruit), Kym G. Brennan 7274 (holotype: DNA! [D0182846]; isotype: PERTH).
Clonal, erect subshrub to 80 cm. Single woody stems 4–5 mm diameter from slender, scarcely-rooted underground stolons, splitting at ca. 40 cm into 2–6 branches. Overall plant aspect yellow-green to gray-green (becoming slightly red-tinged), with older stems eventually woody and gray. Stems with short, dense indumentum of stellate trichomes. Prickles straight, even throughout or slightly widened at base, fine, 5–12mm long, scattered or absent on stems, rarely dense, tending to be absent on woody growth, except near base. Leaves 4–9 cm × 5–10 (-22) mm (largest on newer resprout growth), alternate, linear – lanceolate; margins entire to wavy or rarely lobed; the base tapering to a short petiole 1–1.5 mm long, apex acute; dark green above, slightly lighter beneath, both sides slightly scabrous with short, dense trichomes; trichomes mostly short stalked, porrect-stellate with short central ray. Flowers borne on new growth. Male inflorescence a cyme to at least 6 cm long with 9–12 flowers that are shed successively, only 1–2 flowers open at a time; pedicel 5–7 mm, unarmed; calyx 7 mm long with or without a few prickles towards the base, the lobes ending with a slender filiform acumen ca. 3 mm long; petals 5, fused; corolla 1 cm long, purple, broadly stellate to rotate, acumens 0.5 mm; stamens 5, anthers 2–5 mm long, oblong-lanceolate to somewhat tapered, poricidal, filaments 2 mm; in a loose anther cone; ovary, style, and stigma vestigial and not exserted beyond the stamens. Morphologically hermaphrodite flowers solitary, functionally female with anthers producing inaperturate pollen (Fig. 1F). Female flower on short pedicel; calyx ca. 5 mm, densely armed with long, straight prickles and stellate trichomes; lobes 6 mm, unequal and linear, prickly; corolla ca. 2 cm diameter, 2 cm long, stellate-funnelform, purple; acumens ca. 2 mm; ovary glabrous, 1 mm diameter at anthesis; style erect, 10 mm (including stigmatic surfaces); bifid stigmas 1.5 mm long; stamens of same proportions as in staminate flowers. Peduncle 1.5 cm long, 1.5 mm diameter, sparsely armed with small prickles to 2 mm long. Fruit a green berry 1.2–1.5 cm diameter, globular, drying to black-green and apparently detaching and falling from calyx. Fruiting calyx 2 cm wide, 1.5 cm long, densely armed along sutures, prickles widened (0.5–1 mm) at base and 5–7 mm long, tapering to long fine tip; calyx short stellate-pubescent, more so on sutures and around bases of prickles; calyx lobes extending to slender filiform acumen 5–7 mm long, covered in fine stellate trichomes at tip of each lobe; expanding and surrounding fruit except for ca. 1.5 cm opening at mouth. Calyx retained on stem following fruit drop, at times remaining on plant into next season. Seeds 1.5–2 mm, brown, conspicuously and minutely reticulate.
A Functionally female plant with morphologically hermaphrodite flower and developing fruit (from type collection, Brennan 7274) B Close-up of functionally female flower showing bifid stigma C Mature fruit with enlarged fruiting calyx (pressed specimen) D Staminate plant in flower (also from type collection) E SEM of aperturate pollen grain of staminate flower (from herbarium specimen and partially degraded), arrows showing three germination pores F Inaperturate pollen grain of functionally female flower G Leaf showing lobing pattern and armed midvein (both infrequent). Photos A–C by Kym Brennan. SEM images by Renata Mammone.
Solanum cowiei is presently known from a handful of localities in the sub-arid tropical zone of the Northern Territory (a region known colloquially as the “Top End”), most of these habitats are classified under the Tropical eucalypt woodlands/grasslands Major Vegetation Group (
Solanum cowiei habitat near the Lost City in A unburned condition and B burned condition C Post-fire resprout growth with deep green color and widened leaves D Excavated ramet showing belowground stolon leading to additional ramets of same genet.
Most flowering specimens have been collected from October-November and March-May, with fruiting specimens collected in Jan-Feb and May. Blooming appears to occur on new shoots soon after burns, as evidenced by dozens of male plants found to be in bud within weeks of managed burns set in the Lost City area of Litchfield National Park in late May, 2013.
Solanum cowiei is named for Dr. Ian Cowie, Chief Botanist at the Northern Territory Herbarium (DNA) and one of the first to recognize the distinct nature of the taxon.
Based on IUCN Red List Categories (
AUSTRALIA. Northern Territory: Bullo River Station, 15°35'22"S, 129°29'11"E, 7 May 2008 (fl), I.D. Cowie 12068 (DNA); Bullo River Station, 15°40'14"S, 129°37'31"E, 11 May 2008 (fl), J.O. Westaway 2653 (DNA, NSW); Bullo River Station, 15°39'31"S, 129°34'57"E, 9 May 2008, I.D. Cowie 12095 (DNA, DREF); Bullo River Station, ca. 25 km NW of homestead, 15°16'15"S, 129°47'23"E, 22 March 2009, D.L. Lewis 1192 (DNA, AD); Litchfield National Park, Lost City, 13°13.137’S, 130°44.216’E, 26 May 2009 (fr), C.T. Martine 1753 (DNA, BUPL); Litchfield National Park, Lost City, 13°12'50"S, 130°44'43"E, 8 March 2006 (fr), J.L. Egan & D. Lucas 5716 (DNA); Litchfield National Park at turnoff to Florence Falls, 13°07’S, 130°48’E, 23 November 1990 (fl), I.D. Cowie 1428 & C.R. Dunlop (DNA); Litchfield National Park opposite Florence Falls Rd. turnoff, 13°07'38"S, 130°48'20"E, 20 January 2005 (fl), J.L. Egan s.n. (DNA, AD); 2 km south of Fitzmaurice River Narrows, 14°49'19"S, 129°58'42"E, 14 May 1994 (fl), I. D. Cowie 5030 & D.E. Albrecht (DNA, MEL); Fitzmaurice River, 14°47'28"S, 130°01'04"E, 14 May 1994 (fl), M.J.A. Barritt 1396 (DNA); Bradshaw Field Training Area, ca. 94 km NW of Timber Creek, 15°02'35"S, 129°52'03"E, 4 April 2007 (st), B.M. Stuckey & I.D. Cowie 106 (DNA); Keep River National Park, Spirit Hills area, ca. 27 km NW of Bulloo River Homestead, 15°18'38"S, 129°34'12"E, 18 April 2007 (fr), I.D. Cowie 11692 (DNA, AD); Macadam Range, S of Port Keats, 14°44'00"S, 129°44'00"E, 16 June 2007 (fl), J.O. Westaway 2368 (DNA); Limmen State Park, St. Vidgeons block, 65 km from ruins, 15°16'46"S, 134°31'03"E, 20 April 2009 (st), D.L. Lewis 1160 (DNA).
Solanum cowiei has been known for some time as a local morphotype, having been described by Cowie as Solanum sp. Litchfield as early as 2007. In Litchfield National Park, perhaps the most visited recreation area in the Northern Territory, three primary populations are on routes well travelled by day visitors and campers. The most collected population sits along the road to Florence Falls, with tour buses and cars passing on macadam nearly every day within 10 m of individual plants. Thanks to a series of biodiversity surveys undertaken by staff of the NT Herbarium over the last decade or so (e.g.,
Vigorous post-fire regrowth has been noted in some areas of deep sand beneath open canopies, with one apparently clonal population in a ca. 20 × 20 m area around the Lost City consisting of ca. 40 ramets (Martine, Evans and Dugan pers. obs.). Resprout growth in this grouping was vigorous and well-armed (Fig. 2C), with numerous male flower buds produced on ramets 12–15 cm tall. While other species in this burn area had also begun to resprout, most had not yet developed flower buds – leading one to believe that the flowers of Solanum cowiei, once opened, would face little local competition for pollinators. While fire is thought to influence the life histories of other species in the Dioicum Complex (
Previous molecular work (
In support of its disturbance-adapted nature, much of the biomass in populations of Solanum cowiei appears to be below-ground. Stolons function in vegetative reproduction (Fig. 2D), but are also likely important for short-term energy and water storage in the sandy soils inhabited by the species. Stolons unearthed in the field snapped crisply and bore the smell of potato starch. Root systems extending from these stolons are coarse and poorly developed.
The link of this species to fire may be the key determinant of the success of the species in individual sites. In unburned sites surveyed by the first author in the Lost City area of Litchfield National Park (in 2009 and 2013) (Fig. 2A), individual plants were difficult to locate and devoid of reproductive structures. In recently burned areas (Fig. 2B) plants were locally abundant, with budding ramets emerging from the sand at high densities.
The designation of Solanum cowiei, along with the recent description of Solanum zoeae and allied unnamed variants in the Kimberley region (
The poor resolution of the relationships among Australia’s dioecious Solanum species is a function of both overlapping morphological characteristics (see
Gemma Dugan provided critical field support in 2013, as did F. Daniel Vogt, Bill Figley and Elizabeth Lavoie in 2009. Thanks to Ian Cowie and Deborah Bisa for assistance in the Northern Territory Herbarium and Kym Brennan for photographs of the type collection. Renata Mammone, Alexandra Boni, G. Dugan and E. Lavoie made important contributions as undergraduate researchers. Funding was provided through Bucknell University via the David Burpee Endowment, the David T. Scadden Faculty Scholar Award (to CTM and ECE), and the Department of Biology Summer Undergraduate Research Fellowship program (to GD, RM and AB).