Research Article |
Corresponding author: Christopher T. Martine ( chris.martine@bucknell.edu ) Academic editor: Sandy Knapp
© 2016 Christopher T. Martine, Emma S. Frawley, Jason T. Cantley, Ingrid E. 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, Frawley ES, Cantley JT, Jordon-Thaden IE (2016) Solanum watneyi, a new bush tomato species from the Northern Territory, Australia named for Mark Watney of the book and film “The Martian”. PhytoKeys 61: 1-13. https://doi.org/10.3897/phytokeys.61.6995
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A new species of andromonoecious Solanum from the Australian “bush tomato clade” of Solanum subgenus Leptostemonum is described. Solanum watneyi Martine & Frawley, sp. nov. is closely allied with S. eburneum, and is sympatric with it in parts of its range in the Northern Territory. The new species has been recognized as a variant of S. eburneum for decades, at times being referred to by local botanists as Solanum sp. “Bullita” because of its relative abundance in the vicinity of the Bullita Station area of Judbarra/Gregory National Park. Morphometric analyses show that S. watneyi differs statistically from S. eburneum in several key reproductive and vegetative characters and field observations suggest that the two sister species may represent a case of edaphic speciation. We provide morphometric evidence for the novelty of S. watneyi, a complete description, and cite specimens for both species.
Judbarra, Gregory National Park, Solanum eburneum , Solanum sp. Bullita, Mark Watney, Matt Damon, The Martian, andromonoecy, Andy Weir
Since David Symon’s monograph of Australian Solanum L. in 1981, numerous additional species and morphospecies have been described for the continent. This has been notably true for a set of “spiny solanums” from northern Australia defined by
Later work employing molecular phylogenetics (
Apparently endemic to a small region of the Northern Territory around the East Baines River, S. eburneum appeared to Symon to be restricted to gray clay soils. Meanwhile, botanists collecting in surrounding areas, including Pete Latz (NT Herbarium, Alice Springs), had observed populations across a broader range that were recognizably distinct from the similar S. eburneum. A specimen sent by Latz to Symon in 1976 led the latter botanist to conclude that it matched “no very satisfactory name” used at the time and that he could “do no better than affin. eburneum” (excerpt from letter on specimen NTD9293, P.K. Latz 5325). Field identification was also sometimes challenging, especially along the Bullita Stock Route where the range of the apparently more widespread morphotype comes into contact with S. eburneum in Judbarra/Gregory National Park. Still, the morphotype was recognizable enough to be identified for years on collection labels as S. sp. “Bullita” (Latz 12401) in reference to Latz’s assignment of that identifier to the putative new taxon beginning in the early 1970s. Until now, however, no morphometric comparison between the two morphotypes has been undertaken.
In 2014,
In early May 2014, populations of S. eburneum were visited along the Victoria Highway corridor between Timber Creek and the Northern Territory border with Western Australia, including the type locality (
To establish populations for morphometric analyses seeds were soaked for 24 hours in 1000-ppm gibberellic acid and sown in a controlled growth chamber environment at Bucknell University. They germinated at a rate of 70-90% in 2-3 weeks, with seedlings transferred to individual pots in our research greenhouse after establishment. All plants were grown in a common soil mix under identical horticultural conditions. Thirty-eight vegetative and reproductive characters were measured across developmental stages in 41 cultivated plants. These data were analyzed using ANOVA in the statistical software JMP-Pro 12 (SAS Institute Inc., Cary, North Carolina, USA) to define characters differing between the taxa. Character differences were corroborated and “field-truthed” by examination of herbarium specimens, including accessions held at the Northern Territory Herbarium, Palmerston (
The ANOVA analyses found that of 38 discrete vegetative and reproductive characters that were measured, 17 differed with statistical significance between Solanum eburneum and S. watneyi (Table
Statistical comparison of characters, S. watneyi and S. eburneum. Single asterisk (*) indicates statistical significance with a 95-99% confidence interval; double asterisk (**) indicates statistical significance with >99% confidence interval. SD = standard deviation. All measurements in cm, except trichome density (per 0.5 cm leaf disk) and number of seeds per fruit.
S. eburneum | S. watneyi | ||||||
---|---|---|---|---|---|---|---|
Character | Average | SD | n | Average | SD | n | p-value |
internode length | 2.16 | 0.67 | 16 | 4.01 | 0.98 | 25 | <.0001** |
petiole length | 2.68 | 0.80 | 16 | 3.36 | 3.36 | 25 | <.0095** |
stem prickle length | 0.40 | 0.00 | 16 | 0.26 | 0.26 | 25 | <.0001** |
apical (upper 2-3 stems) leaf length | 11.32 | 0.10 | 16 | 12.39 | 2.5 | 25 | <.1372 |
apical leaf width | 1.41 | 0.41 | 16 | 2.47 | 0.65 | 25 | <.0001** |
basal (lower 2-3 stems) leaf length | 13.66 | 1.83 | 16 | 16.80 | 3.85 | 25 | <.0061** |
basal leaf width | 2.03 | 0.88 | 16 | 3.97 | 1.15 | 25 | <.0001** |
male corolla diameter | 3.46 | 0.31 | 16 | 4.01 | 0.62 | 25 | <.0061** |
hermaphrodite corolla diameter | 4.03 | 0.35 | 16 | 4.75 | 0.58 | 25 | <.0017** |
fruit pedicel length | 3.45 | 0.64 | 14 | 4.22 | 0.65 | 19 | <.0341* |
plant height | 43.62 | 10.86 | 16 | 45.85 | 6.90 | 25 | <.4165 |
leaf adaxial trichome density | 174 | 59.00 | 24 | 105.00 | 21.46 | 25 | <.0001** |
leaf abaxial trichome density | 194 | 26.00 | 24 | 133.00 | 27.81 | 28 | <.0004** |
fruit length | 1.80 | 0.29 | 12 | 2.13 | 0.36 | 20 | <.0058** |
fruit width | 2.20 | 0.38 | 12 | 1.89 | 0.31 | 20 | <.0364* |
fruit wall width | 0.31 | 0.09 | 5 | 0.55 | 0.09 | 5 | <.0038** |
seeds per fruit | 78 | 38.00 | 12 | 44.00 | 23.62 | 20 | <.0031** |
Selected qualitative characters found to differ conspicuously between Solanum eburneum and Solanum watneyi sp. nov.
Character | S. eburneum | S. watneyi |
---|---|---|
habit | erect, compact | sprawling/lax, open |
lobing of leaves | deep, numerous | ± shallow (if present), few |
corolla color | darker purple, ‘mauve’ | lighter purple, ‘dusty purple’ |
corolla margins | more or less flat | wavy, undulating |
fruit shape | ± globose | ± ellipsoidal |
fruit color at maturity | white, ‘creamy’ without striping | yellow, ‘light lemon’ with light brown striping |
fruit interior at maturity | liquid-filled | more or less dry |
fruit firmness at maturity | soft, squishy | firm |
fruit location | pendant from stems, but not on ground | pendant, on or near ground |
seed color at maturity | black | light to dark brown |
Solanum watneyi is distinguished from S. eburneum by its weakly erect and sprawling habit, long internodes and fruiting pedicels, often scabrous dark green leaves, dusty purple corollas, and lemon-yellow thickly-walled ellipsoidal fruits often held on or near the ground.
AUSTRALIA. Northern Territory: Judbarra/Gregory National Park, Bullita Stock Route, 6 km north of Bullita Campground turnoff, 16°03.100"S, 130°27.201"E, 6 May 2014 (staminate and hermaphrodite flowers; fruit), Christopher T. Martine and Rachel F. Martine 4065 (holotype:
Weakly erect to sprawling sub-shrub to 50–60 cm. Rhizomatous and apparently clonal. Stems slender, woody, often bending to ground, especially when weighted by fruits; initially single stemmed, with strong lateral branching beginning at ca. 5–10 cm; internode lengths on mature stems averaging about 4 cm. Overall plant aspect dark green to gray-green, with older stems eventually pea-green to yellow-brown; pubescent throughout with porrect stellate trichomes (stems, leaves, pedicels, calyces) with stalks 0–0.1 mm long, lateral rays 6–10, central ray (midpoint) 1–1.5 times as long as the lateral rays; pubescence of stems short and loose. Prickles sparse, straw-colored, straight, slightly widened at base, fine, 2–5 mm long, scattered on stems. Sympodial units difoliate, the leaves solitary or geminate. Mature leaves 12–16 cm × 2–6 cm, alternate, lanceolate-elliptic, with 6–8 pairs of primary veins; young leaves lighter green and gray-hairy but becoming dark green above, slightly paler beneath, both sides closely and densely stellate tomentose, older leaves becoming scabrous and uniformly dark on both sides, retaining dense tomentum along veins; base attenuate; margins entire, sinuate or occasionally shallowly 6–8 lobed; apex rounded, mucronate; scarcely armed along midvein beneath; petiole 3–3.5 cm long with few to no prickles. Inflorescence a supra-axillary andromonoecious cyme 9–11 cm long, consisting of a basal hermaphrodite flower and a distal group of 3–7 (usually) staminate flowers (the most basal staminate flowers occasionally expressing as hermaphrodite), typically 1–2 staminate flowers open at a time, common peduncle typically 2–5 mm (-20) long, rachis slightly less tomentose than stems. Flowers 5-merous, heterostylous. Hermaphrodite flower ca. 2.5 cm below the staminate flowers, opening first; pedicel 2–3 cm long at anthesis, elongating further after fertilization, armed with prickles 2–5 mm long; calyx lobes 5–8 mm long, armed with long, straight prickles and stellate trichomes; corolla 4–5 cm in diameter, dusty purple, rotate; acumens ca. 2 mm; ovary glabrous, ca. 2 mm diameter at anthesis; style 11–12 mm (including capitate stigma), curved; stamens equal; filaments ca. 1 mm; anthers 6 mm long, oblong-lanceolate to somewhat tapered, poricidal at the tips, in a loose anther cone. Staminate flowers with pedicels 15–16 mm long, unarmed or with few prickles; calyx lobes 7–8 mm long with a few 3–4 mm weak prickles or prickles absent, the lobes ending with a slender filiform acumen ca. 3 mm long, slightly reflexed; corolla 2.5–4.5 cm in diameter, dusty purple, broadly stellate to rotate; acumens ca. 0.5 mm; stamens of same proportions as in hermaphrodite flower; ovary, style, and stigma vestigial and not exserted beyond the stamens. Fruit an ellipsoidal berry 2–2.5 cm long, 1.5–2.2 cm wide, light green with dark green stripes when young, maturing to lemon-yellow with faint brown stripes; flesh firm, the locules 2, not liquid-filled and the internal cavity dry, the fruit wall ca. 0.5 cm thick, the fruits retained on plant after maturation. Fruiting pedicels 3.5–4.5 cm long, deflexed so fruits resting on ground at maturity. Fruiting calyx enclosing and exceeding fruit in early development, eventually covering up to 2/3 of developed fruit, the lobes long-acuminate, blunt-tipped, and weakly reflexing as fruit matures, short stellate-pubescent and armed with sharp spines 2–5 mm long, these single or paired along the calyx sutures, the lobes often fused in a 3+2 or 4+1 arrangement. Mature seeds up to ~100 per fruit, 2.5–3.5 mm, tan to dark brown, finely reticulate.
Solanum watneyi is presently known from a small range of localities in the sub-arid, monsoon-influenced, zone of northwestern Northern Territory (Fig.
The areas where S. watneyi has been collected most frequently are along graded roads (Fig.
Comparisons of Solanum eburneum and Solanum watneyi. A–C S. eburneum in habitat (gray cracked clay), in flower, and mature fruits D–F same for S. watneyi (habit showing reddish sandy loam) G corolla comparisons of staminate (upper) and hermaphrodite (lower) flowers for S. eburneum (left) and S. watneyi (right) H leaf shape across varying leaf ages for S. watneyi (top) and S. eburneum (bottom) in cultivation; I) field growth habit of S. eburneum (left) and S. watneyi (right) showing the more sprawling and prostrate nature of S. watneyi. Photos A, C, D, E, F, I by
Most flowering specimens have been collected from March-May, at the transition from the wet to dry seasons, with fruiting specimens collected in April-June. Earlier flowering collections (e.g. K. Brennan 9002, 27 Jan 2000) suggest that blooming may begin during the rainy season and extend into the dry season. Plants in cultivation began flowering about 90 days after seed germination; and fruits took about 60 days to mature following hand pollination.
The specific epithet of “watneyi” is inspired by the book and film, The Martian, in which the protagonist finds himself stranded on Mars surrounded by the planet’s harsh terrain and reddish soils. In a shelter, he manages to grow a crop of potatoes (Solanum tuberosum) before finally being rescued by his astronaut colleagues. We’ve chosen to name Solanum watneyi after this character, Mark Watney, in part because of the similarly reddish soils of its habitat and the congeneric nature of the potato – but, most notably, as a way to honor the creation of a sci-fi hero botanist by author Andy Weir (
Based on IUCN Red List Categories (
AUSTRALIA. Northern Territory: Bullita Homestead (ca. 8 km north), 16°03'--"S, 130°26'--"E, 14 Apr 1996 (fr), P.K. Latz 14752 (NT); Gregory National Park, Bullock Paddock Creek area, 16°11'21"S, 130°28'59"E, 13 Apr 1996 (fr, fl), G.J. O’Neill 3 (
Solanum watneyi has been known for some time as a recognized morphotype, having been described by Latz as Solanum sp. “Bullita” in the early 1970s. This name has been used as an identifier by other botanists since that time (e.g.
Previous studies inferred that Solanum eburneum is part of the “Bush tomato clade” (
In the western (Bullita) tract of Judbarra/Gregory National Park, S. watneyi is locally common along the roadsides of the Bullita Stock Route between the Victoria Highway and the old Bullita Homestead, where it has been collected numerous times. Its abundance along this dirt thoroughfare suggests that the species appears, like many solanums, to respond favorably to disturbance. In fact, it appears most vigorously on the edges of graded dirt roads, resprouting from rootstocks after passes from mechanized grading equipment (Martine, pers. obs.)
While our ex situ morphometric analyses and most field observations are consistent with the distinctive morphological gestalt of S. watneyi, collections from around the Bullita Station can be somewhat confusing – with vegetative characters approaching intermediacy between it and S. eburneum. A small set of ex situ crosses between them (Martine, unpublished) suggests that interspecific hybridization is possible.
Recent land use history may have brought the species into secondary contact on the north-south edge of their ranges in the central area of the Bullita Section, where an underlying geology including sandstone, siltstone, and dolomite creates an especially complex physiography (
Rachel Martine contributed the species illustration and, along with 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 Peter Jobson, Peter Latz, Ben Marsh, and four peer reviewers during manuscript preparation; and communications assistance came from Heather Johns, Jeff Canning, Andy Hirsch, Richard Hund, and Heather Cacanindin. Funding was provided through Bucknell via the David Burpee Endowment and the Wayne E. Manning Internship Fund (to ESF), plus a Botanical Society of America Undergraduate Research Award (to ESF).
Specimens examined and mapped (Fig.