Research Article |
Corresponding author: Christopher T. Martine ( chris.martine@bucknell.edu ) Academic editor: Leandro Giacomin
© 2017 L. Mae Lacey, Christopher T. Martine.
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:
Lacey LM, Cantley JT, Martine CT (2017) Solanum jobsonii, a novel andromonoecious bush tomato species from a new Australian national park. PhytoKeys 82: 1-13. https://doi.org/10.3897/phytokeys.82.12106
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A new species of Solanum from the Australian “andromonoecious bush tomato clade” of Solanum subgenus Leptostemonum is described. Solanum jobsonii Martine, J.Cantley, & L.M.Lacey, sp. nov. is part of the S. eburneum Symon species group. It most closely resembles S. eburneum and S. watneyi Martine & Frawley of the northwestern part of the Northern Territory, but is separated geographically from them by the Sturt Plateau. Morphometric analyses show that S. jobsonii differs statistically from S. eburneum, S. watneyi, and S. diversiflorum F.Muell. – a similar species in habit and leaf characters – in several key reproductive and vegetative characters. We provide morphometric evidence for the recognition of S. jobsonii, a complete description, a table of comparisons within its species group, and a map showing species group distributions. One of the first new species to be described from Limmen National Park (established 2012), S. jobsonii is a testament to the value of designating and protecting public lands, as well as supporting science relating to them.
Limmen National Park, Northern Territory, Solanum watneyi , Solanum eburneum , Solanum diversiflorum , Solanum jobsonii , Peter Jobson, andromonoecy, national parks, public lands, Australia
Solanum L. is one of the more species-rich Angiosperm genera, with representation on all continents save for Antarctica. In Australia, where upwards of 120 Solanum species are known (
However, despite the conspicuous nature of the genus in parts of Australia, new species of Solanum have continued to be discovered in recent years – especially members of the “spiny solanum” group (Solanum subgenus Leptostemonum Bitter) in the northern Australian Monsoon Tropics (
The “andromonoecious bush tomato clade” is a group of 12 currently recognized species that was recognized by Martine and colleagues based on analysis of ITS (
Reproductive populations of Solanum jobsonii piqued the curiosity of Australian botanists during 2008 and 2010 biodiversity surveys (see
Based on locality data provided on specimens available at DNA and BUPL herbaria (acronyms according to Index Herbariorum; http://sweetgum.nybg.org/science/ih/), the primary known populations of S. jobsonii were visited along the Nathan River Road in Limmen NP. Herbarium specimens, leaf material for future DNA work, and mature fruits were collected. Seeds of the putative new species were removed from fresh fruits, dried, and stored for later use in establishing a greenhouse population.
Plants were grown for use in ex situ morphometric analyses by soaking field-collected seeds in 1000-ppm gibberellic acid for 24 hours, then sowing them in a controlled growth chamber environment at Bucknell University (Pennsylvania, USA). Seeds germinated in 2-3 weeks and plants were cultured under Integrated Pest Management conditions. Twenty-six vegetative and reproductive characters were measured across developmental stages. Leaf lobe depths were based on measures from the base of the most deeply cut sinus to the tip of the nearest lobe. All morphological data were then compared against related species collected during the 2016 expedition and specimens examined during visits to the Northern Territory Herbaria at Palmerston (DNA) and Alice Springs (NT).
Comparison statistics were generated using the software package JMP Pro 12 (SAS Institute Inc., Cary, North Carolina, USA). Initial analyses were carried out on the dataset using a one-way ANOVA with Student’s t-test mean comparison with P<0.05. A Connecting Letters Report summarizes mean values of each character across the four study taxa (S. watneyi, S. eburneum, S. diversiflorum, S. jobsonii) and provided similarity comparisons based on calculated means and tests carried out. This Connecting Letters Report was utilized to investigate individual differences between species before analyzing grouping differences through multivariate morphometric analyses.
Multivariate morphometric analyses were then conducted on the entire dataset for all four species. Principal component analysis (PCA) was used to determine morphological variation pattern groupings among the four taxa. A set of variables was plotted based on corresponding eigenvalues calculated using JMP Pro, representing the original dataset with the greatest variation in a two-dimensional space.
The PCA recognized five eigenvalues above a value of 1 and these were used to determine that the data set was in its entirety five-dimensional, with principal components 1 and 2 contributing the greatest amount of variation among the points (56.6% of the variation within the data set). Figure
The PCA score plot based on all measured characters for S. watneyi, S. eburneum, S. diversiflorum, and S. jobsonii supports the relative distinctiveness of Solanum jobsonii based on character grouping when compared to the other three closely related taxa, although some overlapping with S. diversiflorum and S. eburneum variants is observed (Figure
These results, in conjunction with ANOVA comparisons of each individual character across the four taxa support the hypothesis that S. jobsonii is a distinct entity. The addition of student’s t-tests also provided a Connecting Letters Report (Table
Table
Principal components analysis score plot (Fig.
Vegetative, floral, and fruiting characters measured for S. watneyi, S. eburneum, S. diversiflorum, and S. jobsonii with associated mean (M), standard deviation (SD), sample size (n), and Connecting Letters Report (CL) which indicates distinctions among species by character. Species not connected by the same letter in a row are significantly different (p < 0.05) for that character. All measurements in cm, except seeds per fruit, seed length and fruit wall width (mm), leaf surface area (cm2), and trichome density (per 0.5 cm2 area). “Apical” refers to leaves near the tips of growing stems, while “Basal” refers to leaves borne on lower portions of the stems. The nine characters found to be significantly different in S. jobsonii when compared to the other three taxa are in bold.
Character | S. watneyi | S. eburneum | S. diversiflorum | S. jobsonii | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
M | SD | n | CL | M | SD | n | CL | M | SD | n | CL | M | SD | n | CL | |
Stem prickle length | 0,26 | 0,26 | 25 | BC | 0,40 | 0 | 16 | A | 0,22 | 0,09 | 30 | C | 0,29 | 0,12 | 54 | B |
Internode length | 4,01 | 0,98 | 25 | A | 2,16 | 0,67 | 16 | B | 2,23 | 0,91 | 30 | B | 1,48 | 0,51 | 54 | C |
Petiole length | 3,36 | 3,36 | 25 | A | 2,68 | 0,80 | 16 | B | 1,03 | 0,53 | 30 | C | 0,82 | 0,39 | 54 | C |
Apical leaf length | 12,39 | 2,50 | 25 | A | 11,32 | 0,10 | 16 | A | 2,66 | 0,77 | 25 | C | 5,13 | 1,39 | 35 | B |
Apical leaf width | 2,47 | 0,65 | 25 | A | 1,41 | 0,41 | 16 | B | 1,61 | 0,41 | 25 | B | 1,48 | 1,17 | 35 | B |
Basal leaf length | 16,80 | 3,85 | 25 | A | 13,66 | 1,83 | 16 | B | 5,80 | 1,98 | 25 | D | 9,18 | 1,87 | 29 | C |
Basal leaf width | 3,97 | 1,15 | 25 | B | 2,03 | 0,88 | 16 | D | 3,24 | 0,91 | 25 | C | 4,94 | 1,62 | 29 | A |
Apical leaf adaxial trichome density | 382,60 | 98,36 | 5 | A | 243,40 | 88,79 | 5 | B | 215,60 | 90,21 | 5 | B | 316,20 | 60,91 | 5 | AB |
Apical leaf abaxial trichome density | 518,20 | 147,30 | 5 | A | 331,00 | 137,05 | 5 | B | 420,60 | 116,48 | 5 | AB | 491,60 | 119,88 | 5 | AB |
Basal leaf adaxial trichome density | -- | -- | -- | -- | -- | -- | -- | -- | 28,40 | 3,21 | 5 | -- | 42,80 | 10,21 | 5 | -- |
Basal leaf abaxial trichome density | -- | -- | -- | -- | -- | -- | -- | -- | 116,20 | 36,92 | 5 | -- | 108,40 | 33,91 | 5 | -- |
Apical leaf depth of lobing | 0,27 | 0,36 | 10 | C | 0,61 | 0,36 | 20 | B | 0,79 | 0,24 | 15 | AB | 0,90 | 0,62 | 15 | A |
Basal leaf depth of lobing | -- | -- | -- | -- | -- | -- | -- | -- | 1,48 | 0,38 | 15 | -- | 2,01 | 0,92 | 15 | -- |
Apical leaf surface area | 10,67 | 6,54 | 25 | A | 3,49 | 2,54 | 25 | B | 2,54 | 1,17 | 25 | B | 3,02 | 1,93 | 25 | B |
Basal leaf surface area | -- | -- | -- | -- | -- | -- | -- | -- | 9,99 | 4,12 | 25 | -- | 19,86 | 7,68 | 25 | -- |
Staminate corolla diameter | 4,01 | 0,62 | 25 | A | 3,46 | 0,31 | 16 | B | 2,24 | 0,45 | 16 | D | 3,02 | 0,44 | 23 | C |
Hermaphrodite corolla diameter | 4,75 | 0,58 | 25 | A | 4,03 | 0,35 | 16 | B | 3,00 | 0,37 | 16 | D | 3,58 | 0,50 | 17 | C |
Staminate calyx lobe length | 1,13 | 0,14 | 7 | A | -- | -- | -- | -- | 0,35 | 0,09 | 15 | C | 0,88 | 0,14 | 10 | B |
Hermaphrodite calyx lobe length | 2,23 | -- | 1 | A | -- | -- | -- | -- | 0,35 | 0,09 | 6 | C | 1,16 | 0,14 | 14 | B |
Fruiting pedicel length | 4,22 | 0,65 | 19 | A | 3,45 | 0,64 | 14 | B | 2,70 | 0,18 | 13 | C | 1,65 | 0,34 | 12 | D |
Fruit length | 2,15 | 0,34 | 29 | B | 1,80 | 0,29 | 13 | C | 3,11 | 0,29 | 14 | A | 1,65 | 0,13 | 3 | C |
Fruit width | 1,96 | 0,36 | 29 | BC | 2,20 | 0,41 | 13 | B | 2,92 | 0,35 | 14 | A | 1,68 | 0,28 | 3 | C |
Seeds per fruit | 53,11 | 28,45 | 28 | C | 78,69 | 36,67 | 13 | B | 433,00 | -- | 1 | A | 101,67 | 58,60 | 3 | B |
Plant height | 45,85 | 6,90 | 25 | A | 43,62 | 10,86 | 16 | AB | 33,80 | 4,44 | 3 | BC | 34,50 | 6,26 | 7 | C |
Seed length | 3,05 | 0,18 | 20 | B | 2,84 | 0,21 | 20 | C | 4,11 | 0,25 | 15 | A | 3,09 | 0,21 | 15 | B |
Fruit wall width | 5,50 | -- | 1 | 3,10 | -- | 1 | 4,40 | -- | 1 | 2,20 | -- | 1 |
Comparison of key qualitative characters across the four closely-related taxa of the Solanum eburneum species group, including S. jobsonii.
Character | S. watneyi | S. eburneum | S. diversiflorum | S. jobsonii |
---|---|---|---|---|
Plant habit | sprawling/lax, open | erect, compact | lax branches and leaves | erect or lax, compact |
Lobing of leaves, # lobes | ± shallow (if present), few, 0–2 per leaf | deep, numerous, 6–8 per leaf | pinnatifid, 4–8 per leaf | dissected, 6–12 per leaf |
Corolla color | lighter purple, ‘dusty purple’ | darker purple, ‘mauve’ | medium purple | medium purple |
Corolla margins | wavy, undulating | more or less flat | repand | involute |
Fruit shape | ± ellipsoidal | ± globose | ± globose | ± globose |
Fruit color at maturity | yellow, ‘light lemon’ with light brown striping | white, ‘creamy’ without striping | light yellow-green with dark green striping | yellow, creamy yellow |
Fruit interior at maturity | more or less dry | liquid-filled | liquid-filled | liquid-filled |
Fruit firmness at maturity | firm | soft, squishy | firm | firm |
Fruit position at maturity | pendant, on or near ground | pendant from stems, but not on ground | pendant from stems, but not on ground | pendant from stems, but not on ground |
Seed color | light to dark brown | black | tan to light brown | dark brown to black |
Soil type | well-drained limestone based sandy- or clayey-loamy soil | gray clay soil | red sandy soil | clayey soil with laterite pebbles |
With affinity to Solanum eburneum, Solanum watneyi, and Solanum diversiflorum, but differing by the involute corolla margins, deeply dissected leaves with 6–12 lobes and smaller creamy-yellow fruits.
AUSTRALIA. The Northern Territory: Limmen National Park, on main road, 15°54'47"S, 135°31'43"E, elev. ca. 250 ft, 12 May 2010 (fl, fr), B. Stuckey & I.D. Cowie 645 (holotype [two sheets]: DNA)
Lax to weakly erect sub-shrub or short-lived perennial herb to 20–50 cm tall. Stems slender, woody, upright even when weighted by fruits; initially single stemmed, with strong lateral branching beginning at ca. 7 cm; internode length on mature stems ca. 1.5 cm. Overall plant aspect dark green to gray-green, becoming slightly more yellow-green with age; pubescence of stems short and loose; moderately to densely pubescent throughout with stellate stalked trichomes, the stalk 0.05–0.1 (rarely to 0.2) mm long, with 6–8 rays 0.2–0.4 mm long, the midpoint elongate, to 0.4 mm long. Prickles sparse to moderately dense, straw-colored, straight, slightly widened at base, fine, 1–6 mm long, scattered on stems. Sympodial units difoliate, the leaves solitary or geminate. Mature leaves 5–9 cm × 1.5–5 cm, linear to lanceolate or elliptic, with 1–4 pairs of primary veins, with only a few prickles along midvein on leaf undersides; young leaves lighter green and gray-hairy but becoming dark green above, slightly paler beneath, both sides closely and densely stellate-pubescent, the older leaves becoming scabrous and uniformly dark on both sides, retaining dense pubescence primarily only along veins; base tapering; margins deeply incised and 6–12 lobed, occasionally shallowly lobed or nearly linear; apex blunt; petiole 0.3–2.3 cm long with few to no prickles. Inflorescence a supra-axillary andromonoecious cyme 1–6.5 cm long, consisting of a basal hermaphrodite flower and a distal group of 2–5 (usually) staminate flowers; typically 2–5 staminate flowers open at a time; common peduncle typically 1.5–2.5 mm long; rachis slightly less pubescent than stems. Flowers 5-merous, heterostylous with a single hermaphroditic flower at the base of the inflorescence and the plants andromonoecious. Hermaphrodite flower ca. 1.5–3 cm below the staminate flowers, usually opening first or soon after lowest 1–2 staminate flowers; pedicel ca. 2 cm long at anthesis, elongating further after fertilization, armed with prickles 1–4 mm long; calyx lobes ca. 11–15 mm long and fused for first 2–3 mm, some pairs occasionally fused entirely with sepals arranged 2+2+1, armed with long, straight prickles and stellate trichomes; corolla 2.5–4.5 cm in diameter, medium purple, rotate, free of indumentum; stamens equal; filaments ca. 1.5 mm long; anthers 5 mm long, oblong-lanceolate to somewhat tapered, poricidal at the tips, in a tight anther cone; ovary glabrous, ca. 2 mm diameter at anthesis; style 6–11.5 mm long (including capitate stigma), curved. Staminate flowers with pedicels 9–14 mm long, unarmed or with few prickles; calyx lobes 6–10 mm long and fused for first 1–2 mm, occasionally 2+2+1 as above, with a few 1–4 mm weak prickles or prickles absent; corolla 2.5–3.5 cm in diameter, medium purple, broadly stellate to rotate; acumens ca. 0.5 mm long; stamens of same proportions as in hermaphrodite flower; ovary, style, and stigma vestigial and not exserted beyond the stamens. Fruit a globose berry 1.6–1.8 cm long, 1.5–2.0 cm wide, light green with darker green stripes when young, maturing to creamy yellow; flesh firm; locules 2, liquid-filled; fruit wall ca. 2.2 mm thick; fruits retained on plant after maturation. Fruiting pedicels 1.2–2.3 cm long. Fruiting calyx enclosing and exceeding fruit in early development, eventually covering 1/4 to 1/3 of developed fruit, the lobes narrowly triangular, long-acuminate, blunt-tipped, turning brown 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. Seeds up to ~135 per fruit, 2.8–3.6 mm long, dark brown to black, flat, reniform, finely reticulate.
Solanum jobsonii Martine, J.Cantley, and L.M.Lacey and related species. A Typical habitat in clay soils with limestone stones and laterite pebbles, Limmen National Park, NT B S. jobsonii in flower and C in mature fruit D Corolla comparisons of staminate (upper) and hermaphrodite (lower) flowers for S. jobsonii (left) and S. diversiflorum (right) E Leaf shape across varying leaf ages for S. jobsonii (top) and S. diversiflorum (bottom) F S. jobsonii immature fruit with armed calyx 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) I Seed size, shape, and color comparisons from left to right – S. jobsonii, S. diversiflorum, S. eburneum, and S. watneyi J S. jobsonii trichome density of apical adaxial leaf surface (top) and apical abaxial leaf surface (bottom). Photos A, B, C, F, G by J.T. Cantley; H by E.S. Frawley; D, E, I, J by L.M. Lacey. Yellow scale bars: B, D, F, G = 1.5 cm; C = 5 cm; E, H = 2.25 cm; I = 8 mm; J = 1.5 mm.
Solanum jobsonii is presently known mostly from a restricted range of localities in Limmen NP in the sub-arid, monsoon-influenced zone of northeastern Northern Territory (Fig.
Nothing is known about pollination biology or seed dispersal of S. jobsonii, but floral morphology aligns with the typical Solanum buzz pollination syndrome (see
Although S. jobsonii has been collected on the edges of graded roads and appears to be disturbance-adapted, the species only appears where these thoroughfares bisect otherwise suitable habitat where seasonal flooding is also apparent. Occasional bushfires figure prominently into the ecology of these sites, but the effect on S. jobsonii is unknown.
The few collections made of flowering material are from the early months of the dry season, April-June, but first flowers likely bloom during the wet season (November-March) given the observation of mature fruits in April and onward. Under greenhouse conditions S. jobsonii fruits mature around 60 days after hand pollination. Successful ex situ autogamous and geitonogamous pollinations infer that the species is self-compatible.
The specific epithet of “jobsonii” is selected to honor Peter Jobson, Senior Botanist at the Northern Territory Herbarium at Alice Springs, an expert on the Northern Territory flora and the leader of the 2016 expedition to collect this and numerous other Solanum taxa with the authors.
AUSTRALIA. Northern Territory: Limmen National Park, just north of Lorella Springs turn off, 15°54'44"S, 135°31'42"E, 17 April 2008 (fl, fr), D.J. Dixon 1745 (DNA); Limmen National Park, Nathan River Road, 3.7 km north of Lorella Springs turnoff, 15.94913°S, 135.53464°E, elev. 246 ft., 14 May 2016 (fl, fr), C.T. Martine, J.T. Cantley, L.M. Lacey and P. Jobson 4226 (DNA, BUPL); Limmen National Park, jct. Lorella Springs Rd. and Nathan River Rd., 15.91605°S, 135.52926°E, 14 May 2016 (fl, fr), C.T. Martine, J.T. Cantley, L.M. Lacey and P. Jobson 4227 (DNA, BUPL); Benmara Station, approx. 1 km west No. 38 Bore, 17°54'--"S, 136°57'--"E, 5 June 1984 (fl), Strong 253 (DNA); Limmen National Park, along main road, 16°01'39"S, 135°33'24"E, 8 May 2010 (fl, fr), B. Stuckey & I.D. Cowie 595 (DNA); Savanna Way between Nathan River and Borroloola, 15°47'44"S, 135°25'46"E, 15 July 2008 (fl), H. van der Werff & B. Gray 222501 (DNA); Limmen National Park P, Nathan River Rd., Lorella Springs turnoff, 15°54'56"S, 135°31'46"E, 12 May 2010 (fl, fr), B. Wirff 531 (DNA).
Morphological comparisons of S. jobsonii and its close relatives, S. watneyi, S. eburneum, and S. diversiflorum, demonstrate a statistically significant difference among the four taxa. Most notably, S. jobsonii differs from the other three species by its involute corolla margins, deeply dissected leaves with 6-12 lobes, smaller creamy-yellow fruits, and a set of nine morphometric characters highlighted in Table
National parks are under threat throughout the world, with federally-protected lands in places like the United States in potential danger of being left unfunded, deforested, or sold into private ownership (
Thanks to P. Jobson and D. Randall, Northern Territory Herbarium, Alice Springs, plus Limmen National Park rangers C. Parry and J. Vincent, for support during the 2016 field expedition. Several Northern Territory botanists collected critical specimens of this species in Limmen NP, including I. Cowie who brought them to CTM’s attention. D. Bisa processed a loan of associated sheets held at NT Herbarium Palmerston. T. Caton, M. Garanich, D. Hayes, M. Spiro, and W. Boop provided greenhouse support at Bucknell. Helpful comments were provided by P. Jobson and two peer reviewers during manuscript preparation. Funding was provided through Bucknell University via the David Burpee Endowment and the Wayne E. and Margaret S. Manning Internship Fund (to LML), plus a Botanical Society of America Undergraduate Research Award (to LML).