Chromosome Number and Distribution of Solanum aviculare Forst. and S. laciniatum Ait.
[Read by title and abstract before the Otago Branch on April 13, 1954; received by the Editor, April 26, 1954.]
Solanum aviculare Forst., n = 23. and S. laciniatum Ait, n = 46, are separated primarily on the basis of their difference in chromosome number, but are also distinguishable by flower and fruit characters. S. laciniatum has larger pollen grains, flowers, seeds and stone-cell masses (in the fruit pulp) than S. aviculare, its corolla is deeper in colour with relatively shallow lobes the margins of which flatten more completely, producing an emarginate apex. Both in Australia and New Zealand the species overlap in distribution but S. aviculare extends further to the northward (N. Auckland, Kermadec Is., Lord Howe I, Queensland) and S. laciniatum further to the southward (Canterbury, Otago. Tasmania).
At microsporogenesis the chromosomes of the New Zealand poroporo stain readily in aceto-carmine They are small and uniform in size but two different numbers occur, namely n = 23 or n = 46 (Plate 1).* The basic chromosome number in Solanum is × = 12 so that these are instances of secondary polyploidy—apparently the first recorded for the genus, in which however simple polyploidy is not uncommon (Darlington&Janaki-Ammal, 1945). Other morphological differences have been found constantly to accompany this difference in chromosome number, warranting the recognition of two distinct species whose genetical isolation it ensures:—
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|S. aviculare Forst., n = 23.||S. laciniatum Ait., n = 46.|
|Stems green or purplish||Stems purplish|
|Flowers lavender, usually paling towards the margins, or pure white||Flowers blue-purple|
|Corolla broadly-campanulate to rotate, to 3.5 cms. diam.||Corolla rotate up to 5 cms. diam.|
|Corolla lobes about equal to the tube in length, margins incompletely flattened, apices acute||Corolla lobes about half as long as the tube, margins flat, apices emarginated|
|Average pollen-grain diameter 25–31μ (in blue lactophenol)||Average pollen-grain diameter 36–42μ (in blue lactophenol)|
|Seeds below 2 mm. in length||Seeds 2.2–2.5 mm. long|
|Stone cell masses in ripe fruit inconspicuous, only exceeding the seeds in size when coalescent||Stone cell masses in ripe fruit conspicuous, mostly as large as or larger than the seeds|
These characters provide sufficient means of distinguishing flowering and fruiting plants in the field. Forms of S. aviculare with green stems and pure white flowers constitute Cheeseman's (1920) variety albiflora. This is not distinctive when dried, indeed the separation of the two species as herbarium specimens
[Footnote] * Dr. John Hair has kindly confirmed these counts by examination of mitosis His figures will be published elsewhere.
is often difficult. Corolla characters may be obscure or even misleading since petal apices in S. laciniatum appear acute if the margins are not fully expanded, and on the other hand pressing may split the apex of S. aviculare petals producing an emargination. Pollen-grain diameter is the most reliable character of dried flowering material and it is unaffected by slight immaturity. The grains rapidly resume their natural, approximately spherical shape in blue lactophenol (phenol 20 cc., lactic acid 20 cc., glycerine 10 cc., 0.5% aqueous analine blue 20 cc.), and this is the medium in which all measurements of fresh or dried material have been made. Fresh grains swell excessively in water.
The nomenclature and distribution of these two species needs discussion. Forster's specific epithet aviculare (1786) has priority. The description in his Prodromus is worthless but in de Plantis esculentis there is significant information, namely that the flowers were violet, about an inch in diameter, with a very short tube and folded margins to the lobes. His unpublished drawing shows acute corolla lobes, and the pollen grain diameter of his specimen in the British Museum is 25μ. There is thus no doubt that the 23-chromosome form was the basis of Forster's species, and recent collections from Trio I. and Stephen I. show that it is still present in the vicinity of the type locality which, from the date on Forster's sketch (Nov. 19), must be Queen Charlotte Sound. Aiton's description of S. laciniatum (1789) gives no useful details, but it does state that the country or origin was New Zealand and the collector Banks. There appears to be no authentic herbarium material in existence, but as Stapf (1926) points out t. 349 published in Curtis's Botanical Magazine in 1795 establishes the nature of Aiton's plant. The size, shape and colour of the corolla justify the retention of his name for the plant now found to have a haploid chromosome number of 46.
Aiton gave no reason for not adopting Forster's name for his material and most systematists have synonymized S. laciniatum with S. aviculare. But Stapf (1926) drew attention to the difference in corolla shape between Aiton's plant and that shown in Forster's and Parkinson's unpublished drawings and in Laing&Blackwell (1927). After examining herbarium sheets he concluded erroneously that this was accompanied by geographical isolation and restricted S. laciniatum to Australia, S. aviculare to New Zealand, Norfolk I., British New Guinea and Timor. To determine the true distribution of these species, herbarium specimens have been examined and plants have been grown from several collections of seed. In the citations below seed collections are indicated by an asterisk * which means also that the chromosome number has been checked as well as flower and fruit characters in vivo. New Zealand material has been divided without difficulty between the two species, but in Australia the situation is less simple. Both S. aviculare and S. laciniatum undoubtedly occur there since seed from New South Wales and Victoria respectively has produced at Dunedin plants which agree exactly with the New Zealand species. But the identity of many Australian sheets examined has seemed doubtful and they are not cited in this paper. Apart from S. simile Muell. (including S. fasciculatum Muell.) which has purplish fruits, there are, principally in the Melbourne Herbarium, specimens in which the corolla suggests S. laciniatum but the pollen diameter is only about 30μ. These may prove to be merely races of this species that have evolved a smaller pollen grain, but since pollen size is closely related to chromosome number in Solanum they merit further investigation. The wide range of pollen diameter (21μ–39μ) in the material referred to S. simile is also suggestive.
The specimens listed below indicate that both in New Zealand and Australia the areas of S. aviculare and S. laciniatum overlap, that of S. aviculare extending to the northward (N. Auckland, Kermadec Is., Lord Howe I., Queensland), that of S. laciniatum to the southward (Canterbury, Otago, Tasmania) of a common area which in New Zealand lies between Auckland and the Marlborough Sounds and in Australia covers Victoria and the southern part of both New South Wales and South Australia. Most herbarium sheets are without notes on flower colour, but it is doubtful if more than one or two of the S. aviculare collections, other than those so designated, are of the variety albiflora which appears to be rare and confined to New Zealand.
Solanum aviculare Forst.
Lectotype in British Museum Herbarium “107 Solanum aviculare—G. Forster's Herbarium,” Queen Charlotte Sd., New Zealand.
Kermadec Is.: Sunday I.: 8/1887: Cheeseman; Ak. Mus. 7599.2.
Three Kings Is.: *Great I.; 1/1950, 2/1951; Baylis; O.U. 938, 927, 939.
South-West I.; 1/1950, 1/1951; Baylis; O.U. 928, 926.
North I.: Kaiaka, Mangonui; 12/1906; Carse 1208/2/8; Ch. Mus.
Poor Knights Is.; 1/1954; Baylis; O.U. 1498 (var. albiflora).
Little Barrier I.; Moore; B.D. 44638.
Great Barrier I.; 1/1919; Matthews; Ak. Mus. 739, 740.
* Fanal I.; 2/1952; Baylis; O.U. 924, 925, 929.
* Anawhata, Ak.; Farnell; O.U. 1650 (var. albiflora).
Karekare, Ak.; 11/1914; Petrie; Dom. Mus. 858.
* Huia, Ak.; 3/1953; Wood; O.U. 934 (var. albiflora).
North Hd., Ak.; Cheeseman; Ak. Mus. 7600.
Mt. Eden, Ak.; Kirk; Dom. Mus. 833.
Pukekohe, Ak.; Townson; Ak. Mus. 7601 (type of var. albiflora).
Pukekohe, Ak.; Townson; Ak. Mus. 7602.
Coromandel, Ak.; 12/1900; Petrie; Dom. Mus. 862.
Mauku, Ak.; 2/1901, 11/1901; Carse; 1208/3/6; Ch. Mus.
Mauku, Ak.; 4/1941; Slade; O.U. 936.
Tauhei, Piako; 11/1923; Brown&Carse; 1208/4; Ch. Mus.
Tauranga; 2/1934; Oliver; Dom. Mus. 851, 852.
Tolaga Bay; 12/1953; Baylis; O.U. 1497.
Taupo; 2/1949; Walker; B.D. 78174.
Pukeatua, W. Taupo; 1/1917; Petrie; Dom. Mus. 837, 856.
Makaretu, Hawke's Bay; Petrie; Dom. Mus. 834, 857.
Waipawa, Hawke's Bay; 2/1940; Oliver; Dom. Mus. 846.
Kaitoke; Aston; Dom. Mus. 839.
* Paraparaumu; 2/1953; Baylis; O.U. 940.
Upper Horokiwi Va.; 5/1953; Baylis; O.U. 933.
Otaki Gorge; 12/1928; Zotov; B.D. 499.
Wellington; Kirk; Ch. Mus. 571.
Wellington (cult); 12/1952; Seed; B.D. 79949.
Crow's Nest, Wgtn.; 3/1891; Kirk; Dom. Mus. 835, 836.
Kelburn, Wgtn. (cult.); 7/1920; Aston; Dom. Mus. 855.
Butterfly Cr., Wgtn.; 1/1938 Oliver; Dom. Mus. 853.
[Footnote] * Chromosome number checked in material from this locality.
South I.: Trio I., Cook St.; 12/1953; Dawson; O.U. 931.
Stephen's I., Cook St.; 12/1953; Dawson; O.U. 930.
Chatham Is.: Travers; Dom. Mus. 847, 848, 849.
Uncertain: 1769–70; Banks&Solander; Ak. Mus. ex Brit. Mus.
Queensland: Eumundi; 9/1911; Staer; Nat. Herb. N.S.W. 23469.
Brisbane; Henne; Nat. Herb. Melb.
Warwick; Nat. Herb. Melb.
Acacia Cr. Killarney; 9/1905; Dunn; Nat. Herb. N.S.W. 23471.
New South Wales: Sieber No. 255; Nat. Herb. Melb.
Hastings R. (2 collections); Nat. Herb. Melb.
Lower Hastings R.; 11/1897; Maiden; Nat. Herb. N.S.W. 23473.
Nov. Holl.; Mueller; Nat. Herb. Melb.
Ash I.; Woolls, Nat. Herb. Melb.
Morpeth; Leichhardt; Nat. Herb. N.S.W. 23475.
Richmond R.; 1876; Fawcett; Nat. Herb. N.S.W. 23485.
Bolaro Mt., Nelligen; Baverlen; 10/1890; Nat. Herb. N.S.W. 23488.
Tumut; 8/1903; Maiden&Boorman; Nat. Herb. N.S.W. 23487.
Eden; 4/1936; Nat. Herb. N.S.W. 23486.
Mandurama; 8/1946; Brough; Nat. Herb. N.S.W. 1917.
*Narromine; 9/1952; McLennan; Nat. Herb. N.S.W. 23489; O.U. 1495.
* Warren; 4/1952; Constable; Nat. Herb. N.S.W. 20340; O.U. 932, 1496.
Victoria: Wycheproof; 4/1917; Watts; Nat. Herb. Melb.
Fern Tree Gully; 1/1900; Nat. Herb. Melb.
S. Australia: Mt. Gambier; Mueller; Nat Herb. Melb.
Lord Howe I.: 1937; McComish; Ak. Mus.
Solanum laciniatum Ait.
Lectotype t. 349 in Bot. Mag 1795. Ex New Zealand Coll. Banks&Solander.
North I.: *Kingseat, Ak.; 1/1953; Baylis; O.U. 935.
Feilding; Allan; B.D. 10925.
Crofton; Kirk; Dom. Mus. 838.
* Karori, Wgtn.; 2/1953; Baylis; O.U. 944.
Wellington (cult.); 12/1952; Seed; B.D. 79948.
Wellington (cult.); 4/1935; Aston; Dom. Mus. 844.
South I.: *Glenavy, Cty.; 2/1953; Baylis; O.U. 945.
Dunedin; 1890; Petrie; Dom. Mus. 859, 860, 861.
* Dunedin; 12/1951, 2/1952, 11/1952, 5/1953, 2/1954; Baylis; O.U. 946, 943, 942, 941, 1616.
New South Wales: Shoalhaven; 9/1884; Banerton 673; Nat. Herb. Melb.
Victoria: Dividing Ra.; 11/1898; Walker; Nat. Herb. Melb.
Fern Tree Gulley; 11/1905; Nat. Herb. Melb.
Yarra R.; Brown; Nat. Herb. Melb.
Austr. felix; Mueller; Nat. Herb. Melb.
[Footnote] * Chromosome number checked in material from this locality.
1 S. aviculare pollen mother cell first metaphase n. = 23. New Zealand (Fanal 1) × 2750 2. S. laciniatum p.m c. second metaphase. n. = 46. Australia (S. Oakleigh) × 2750. 3. S. laciniatum p. m c first metaphase n. = 46 New Zealand (Dunedin) × 2750.4 S. aviculare seed and stone-cells from a single fruit New Zealand (Three Kings Is) × 1 5. Ditto S. laciniatum New Zealand (Dunedin) × 1
Frankston; 1933; Calvert; D.P.I. Cbra. 7874.
* S. Oakleigh; 4/1953; Willis; O.U. 1617.
S. Australia: Port Lincoln; 11/1903; Black; Nat. Herb. N.S.W. 23472.
Tasmania: Harford; 9/1932; Hamilton 84; D.P.I. Cbra. 7875.
Cape Deslaco; 8/1931; Long; D.P.I. Cbra. 7876.
Tunbridge; 1/1931; Rodway; D.P.I. Cbra. 7877.
I am indebted to the Directors of the institutions in New Zealand and Australia whose collections are cited for lending herbarium material and to Mrs. P. Hynes, Mrs. K. Wood, Mr. J. W. Dawson and Mr. J. H. Willis for special collections. Mr. Wm. T. Stearn of the British Museum very kindly examined material there on my behalf and loaned fragments from Forster's sheets. Mr. R. Carey supplied excerpts from Solander's unpublished manuscripts in the Dominion Museum Library, and the Director of Kew Gardens sent copies of Aiton's and Stapf's descriptions.
Aiton, W., 1789. Hortus Kewensis, 1, 247.
Cheeseman, T. F., 1920. Contributions to a fuller knowledge of the N. Z. flora: no. 7, Trans. Roy. Soc. N.Z., 5, 2, 9–16.
Curtis, W., 1795. Solanum laciniatum. Cut-leaved nightshade, Bot Mag., 10, 349.
Darlington, C. D., and Janaki-Ammal, E. K., 1945. Chromosome atlas of cultivated plants, 254–257
Laing, R. M., and Blackwell, E. W., 1927. Plants of New Zealand Ed. 3. fig. 135.
Forster, G., 1786. Florulae insulanum Australium prodromus, p. 18
—— 1786. De plantis esculentis insularum oceani Australis, 42, 43
Stapf, O, 1926. Solanum laciniatum, Bot Mag. 152, tab 9154.
[Footnote] Chromosome number checked in material from this locality.