Research Article |
Corresponding author: Christopher Martine ( chris.martine@bucknell.edu ) Academic editor: Sandy Knapp
© 2016 Christopher Martine, Jason Cantley, Emma Frawley, Alice Butler, Ingrid Jordon-Thaden.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Martine CT, Cantley JT, Frawley ES, Butler AR, Jordon-Thaden IE (2016) New functionally dioecious bush tomato from northwestern Australia, Solanum ossicruentum, may utilize “trample burr” dispersal. PhytoKeys 63: 19-29. https://doi.org/10.3897/phytokeys.63.7743
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A new Australian species of functionally dioecious bush tomato of Solanum subgenus Leptostemonum is described. Solanum ossicruentum Martine & J.Cantley, sp. nov., is thought to be allied with members of the problematic “Dioicum Complex” lineage, but differs in its short silvery indumentum, long calyx lobes, larger stature, and an unusual fruit morphology that may represent “trample burr” seed dispersal. The species occurs in a range extending from the eastern Kimberley in Western Australia to far northwestern Northern Territory and has been recognized for decades as a variant of S. dioicum W.Fitzg. Specimens of this species were previously referred to by D.E. Symon and others as Solanum dioicum ‘Tanami.’ Ex situ crossing studies and SEM images of inaperturate pollen grains produced in morphologically hermaphrodite flowers indicate that this taxon is functionally dioecious. The scientific name was chosen with the help of 150 seventh grade life science students from Pennsylvania, USA.
Bush tomato, cryptic dioecy, inaperturate pollen, Keep River National Park, Kimberley, Mirima National Park, new species, Northern Territory, Solanum , Solanum dioicum , Solanum sp. Tanami, undergraduate research, Western Australia
Dioecy in Solanum (Solanaceae) is one of the more fascinating phenomena in plant reproductive biology (
Solanum ossicruentum Martine & J.Cantley, sp. nov. is one of the many recognizable variants currently included under the broad taxonomic umbrella (
Recent observations of the taxon by CTM in Mirima National Park (WA), the Carr Boyd Ranges (WA), and Keep River National Park (NT) are combined here with inferences from plants grown in cultivation from wild-collected seed and herbarium sheets held at the Northern Territory Herbarium, Palmerston (DNA). Seeds were germinated following a 24-hour soak in 1000-ppm gibberellic acid and sown in a controlled growth chamber environment as per
This species is distinguished from other dioecious solanums in northwestern Australia by its short silvery indumentum, long calyx lobes, larger and compact stature, and a bony hard mature fruit that remains enclosed in a heavily armed calyx.
AUSTRALIA. Western Australia: Mirima (Hidden Valley) National Park, below upper lookout on Derdbe-Gerring Banan Lookout Trail, 15°45.827'S, 128°45.105'E, 18 May 2014 (staminate and “female” flowers; fruit), Christopher T. Martine and Rachel F. Martine 4011 (holotype: DNA; isotypes:
Clonal, upright woody shrub to 1–2 m tall and 1–2.5 m wide. Single woody stems ca. 2.5 cm diameter from woody rootstock, splitting at about 1/3 of total height to form a Y-shaped or inverted tripod-like growth form, ultimately branching 4–10 times. Overall plant aspect silvery to bluish-green to gray-green, the young growth tomentose-lanate, with older stems woody and gray. Internodes 4.5–8 cm. Stems with short, dense indumentum of stellate trichomes. Prickles straight, long, thin, somewhat sharp, 6–8 mm long, slightly widened at base, abundant and dense (7–15 per cm of internode) on all stems including older woody growth. Leaves 13–23 cm × 4–5 cm, alternate, lanceolate, unarmed; margins entire to undulate; base truncate to rounded, asymmetrical; petiole 10–19 mm long, with scattered prickles; blade soft silvery-blue/gray-green to sage green, concolorous, both sides densely silvery-tomentose (380–560 trichomes per 0.25 cm radius leaf disk); trichomes mostly short stalked, porrect-stellate with short central ray (midpoint). Inflorescences borne on new growth.
Male inflorescence a cyme about ca. 4–5 cm long with 2–12 flowers, unbranched, typically with only 2–3 flowers open at a time; peduncle ca. 2–2.5 cm long; rachis 2–2.5 cm long; pedicels ca. 2 mm, unarmed; calyx 5-lobed with or without a few prickles towards the base, the lobes 1.2–1.5 cm long with linear acumens; corolla 3.5–3.8 cm diameter, dark violet, rotate-stellate to rotate, glabrous adaxially and abaxially except for pubescence of minute simple hairs along folds; acumens 0.75–1.25 mm; stamens 5, ca. 9 mm long, equal; anthers ca. 5 mm long, oblong-lanceolate to somewhat tapered, connivent, yellow, poricidal; filaments ca. 4 mm, connate at base; ovary, style, and stigma vestigial, non-functional, and not exserted beyond the stamens.
Solanum ossicruentum sp. nov. A Typical habitat, Mirima National Park, WA B Leaf morphology C Female individual, Mirima NP D Close-up of functionally female (morphologically hermaphrodite) flower E Abaxial side of functionally female flower showing elongated calyx lobes F Male individual, Mirima NP G Male flower, abaxial view H Developing fruit within calyx I Immature fruits showing blood-red staining at 2 minutes (lower) and 5 minutes (above) after cutting J Mature bony fruits removed from calyces and (lower right) as collected from ground beneath plant. Yellow scale bars as follows: 3 cm (B, C, F); 1 cm (D); 2 cm (E, G, H, J); 0.75 cm (I). Photos A, C, F, and J by C.T. Martine; all others by J.T. Cantley.
Morphologically hermaphrodite flowers solitary, functionally female, with anthers producing inaperturate pollen (Fig.
Fruit a berry 1.5–2.5 cm diameter, globose; immature fruit light green, fleshy, with slightly sticky flesh oxidizing from whitish-green to deep blood-red when cut; mature fruit drying to dark green, then chestnut brown, becoming leathery-reticulate in texture and bony hard, weakly six-angled, and loosely retained and partly-enclosed (±75%-enclosed) in calyx, with a 6–8 mm diameter light-colored disk-shaped abscission scar. Fruiting calyx lobes 4.5–7.25 cm long and long-acuminate (acumens breaking off with age), densely armed with sharp prickles 7–8 mm long, tapering to long fine tip, 4–5 prickles per jagged line along ribs and spreading, short stellate-pubescent, more so on calyx ribs and around bases of prickles. Calyx slightly sticky-adherent to fruit when immature, readily separating from fruit as the berry matures, hardens, and shrinks from drying. Fruit and intact calyx ultimately detaching from plant as one light brown, sharply spiny, 3.5–4.5 cm diameter dispersal unit. Seeds ca. 1.5 mm diameter, tan to brown, conspicuously and minutely reticulate, up to 500–650 per fruit.
Solanum ossicruentum is presently known from a wide range of localities in the sub-arid tropical zone of the Northern Territory and eastern Kimberley in Western Australia, including the northern edge of the Tanami Desert (Fig.
Seed dispersal appears to follow the relatively uncommon “trample burr” pattern for Solanum described by
Most flowering specimens have been collected from February-July, with fruiting specimens collected in March-September. Seeds germinated for this study were from diaspores collected at the base of plants bearing flowers and immature fruits at Mirima National Park on 1 May 2014. These were assumed to have developed in the previous growth season.
Previous phylogenetic work including accessions identified as this form (
The name Solanum ossicruentum was chosen based on suggestions from middle school students in Lewisburg, Pennsylvania, USA. In the spring of 2015, CTM presented live plants of the taxon to an assembly of 150 seventh-grade life science students at Donald H. Eichhorn Middle School. The students, with the help of Mr. Bradley Catherman, were invited to examine the plants, ask questions, and then submit an essay proposing and justifying a potential Latin name for the putative new species. Numerous students were drawn to and suggested names based on the characteristics of the fruits, which stain blood red when cut open before maturity and then mature to a dry, bony condition. Thus ossi- is used for “bone” and -cruentum for “bloody.”
Based on IUCN Red List Categories (IUCN 2011), S. ossicruentum is considered Data Deficient (DD). While the species appears to be relatively widespread over a range of approximately 90,000 km2, its range is not comprehensively understood. A relatively small number of collections, coupled with the fact that populations often consist of multiple individuals, suggest that the species is common in some localities but uncommon on the regional and global scales. Further data are required before a certain conservation status can be determined. Like other dioecious species of clonal nature, “populations” of S. ossicruentum have the potential to represent large multi-stemmed genets connected by an underground network of stolons (e.g.
AUSTRALIA. Northern Territory: Jellebra Rockhole, 19°21'45"S, 129°00'35"E, 7 June 1996, D.E. Albrecht 7756 (DNA, NT); Cockatoo Creek, Keep River area, 15°55'17"S, 129°03'31"E, 2 September 1974, Gibbs & Fox 618(DNA, NE); Spirit Hills, 15°24'58"S, 129°28'39"E, 17 April 2007, R.A. Kerrigan 1226 (DNA); 11 km east of NE Mt. Frederick, 19°37'S, 129°21'E,1 March 1981, P.K. Latz 8597 (DNA, NT); Pargee Range, 19°36'S, 129°16'E, 2 April 1981, P.K. Latz 8608 (DNA, ADW); 8 km SSW Victoria River Bridge, 15°40'47"S, 131°5'34"E, 16 April 1996, P.K. Latz 14760 (DNA, NT, AREF); Cow Creek, Victoria River, Gregory National Park, 15°52'26.8"S, 131°19'58.6"E,2 May 2001, C.P. Mangion & G. Boehme 1060 (DNA); Winnecke Hills, 18°37'11"S, 130°16'30"E, 1 May 2004, C.P. Mangion & D.L. Lewis 1607 (DNA); Nigli Gap Walk, Keep River National Park, 15°45'30.4"S, 129°05'07.4"E, 26 May 2004, C.T. Martine & W.R. Barker 772 (DNA,
A comprehensive key to the “Diocum Complex,” including numerous newly recognized species, is forthcoming (Barrett and Barrett in prep). At present, the most complete diagnostic key for the species of the Kimberley region is the key in
60a | Plants less than 1 m tall, many-branched; stems moderately prickly; leaf indumentum silvery or rusty, overall aspect silvery-green, yellowish-green, or reddish-green; stigma deeply bifurcating, lobes 2-5 mm; calyx lobes slightly exceeding corolla and enclosed fruits; fruits green and fleshy at maturity | Solanum dioicum W.V. Fitzg. |
60a | Plants 1–2 m tall, few-branched and conspicuously Y-shaped in form; stems exceptionally prickly; leaf indumentum silvery, overall aspect silvery-blue; stigma shallowly bifurcating, lobes 0.5-1 mm; calyx lobes far exceeding corolla and enclosed fruits; fruits bony and dry at maturity | Solanum ossicruentum Martine & J. Cantley |
Solanum ossicruentum has been noted for nearly 50 years as a widespread morphotype of Solanum dioicum known as ‘Tanami’ (
In overall aspect, the new species most closely resembles S. beaugleholei Symon and S. phlomoides A. Cunn. ex Benth. (both endemic to NW Australia) based on leaf morphology, tomentum, and coloration, but both of these species are less rigidly upright, have much larger (only partially enclosed) fleshy fruits, and exhibit an andromonoecious breeding system.
Recent surveys in remote regions of the Kimberley suggest that the total number of dioecious taxa in that region may be around 20 (
Rachel Martine, Isee Martine, Jackson Martine, and Erin Sullivan provided critical field support and specimen collection assistance in the field. Thanks to Ian Cowie and Deborah Bisa for assistance in the Northern Territory Herbarium. Tara Caton, Dan Hayes, and Wanda Boop provided greenhouse support at Bucknell. Helpful comments were provided by three anonymous reviewers during manuscript preparation; and communications assistance came from Jeff Canning, Heather Johns, and Andy Hirsch. Funding was provided through Bucknell via the David Burpee Endowment and the Wayne E. Manning Internship Fund (to ESF and ARB) and the Botanical Society of America Undergraduate Research Award (to ESF and ARB).