Chromosome Numbers in New Zealand Ferns
[Received by the Editor, June 27, 1957]
Haploid chromosome numbers are given for 42 species and one variety of New Zealand ferns. From these indications are given of possible taxonomic problems which it is hoped to investigate fully at a later date.
Cytological studies of fern floras have been made previously for the British Isles and Madeira (Manton, 1950), for Ceylon (Manton and Sledge, 1954), for the region around Toronto, Canada (Britton, 1953) and for a greater number of North American ferns by Wagner (1955). Chromosome numbers for a considerable number of Malayan ferns have also been published (Manton, 1954). It is hoped that a similar study of a southern hemisphere flora will help towards a more complete picture of phylogeny within various fern groups. This is particularly important if the theory of an Antarctic origin of many modern ferns, propounded by Copeland (1947), is also considered.
The present paper lists all the New Zealand ferns in which chromosome numbers have been established since the publication of two earlier papers (Brownlie, 1954 and 1957).
Throughout these investigations the methods used were those described by Manton (1950).
The order of genera in the following list is that used in the revised edition of Dobbie (1951).
|Species||Locality||Author's Collection No||Chromosome No.|
|Botrychium australe R. Br.||Cass||1||n = 45|
|Ophioglossum coriaceum A Cunn.||Lyttelton, Port Hills||151||n = ca. 360|
|Leptopteris hymenophylloides (A. Rich). Presl.||Kaituna||13||n = 22|
|Leptopteris superba (Col.) Presl.||Lake Brunner||102||n = 22|
|Gleichenia circinata (Sw.) C. Christen.||Kumara||129||n = 20|
|Sticherus cunninghamii (Hew ex Hook) Ching||Buller Gorge||64||n = 34|
|Mecodium dilatatum (Forst) Copeland||North Westland||76||n = 36|
|Mecodium scabrum (A. Rich.) Copeland||North Westland||75||n = 36|
|Mecodium demissum (Forst.) Copeland||Queen Charlotte Sound||39||n = 36|
|Sphaerocionium ferrugineum (Colla) Copeland||Buller Gorge||168||n = 36|
|Hymenophyllum revolutum Col.||Buller Gorge||69||n = 22|
|Hymenophyllum peltatum Desv.||Cass||134||n = 11|
|Meringium bivalve (Forst.) Copeland||North Westland||137||n = 22|
|Cardiomanes reniforme (Forst. f.) Presl.||North Westland||127||n = 36|
|Vandenboschia colensoi (Hook. f.) Copeland||Buller Gorge||164||n = 36|
|Lindsaea linearis Swartz||Takaka||177||n = 34|
|Hypolepis millefolium Hook||Arthurs Pass||91||n = 52|
|Anogramma leptophylla (Swartz) Link||Lyttelton, Port Hills||152||n = 29|
|Adiantum aethiopicum Linn.||Piha, Auckland||141||n = 60|
|Cyathea dealbata Swartz||Queen Charlotte Sound||57||n = 69|
|Cyathea colensoi (Hook. f.) Domin.||Arthurs Pass||94||n = 69|
|Cyathea smithii (Hook.) Domin.||Kaituna||29||n = 69|
|Arthropteris tenella (Forst. f.) J. Smith||Nelson||108||n = ca. 42|
|Polystichum richardi (Hook.) J. Smith||Lyttelton, Port Hills||7||n = 82|
|Polystichum cystostegia (Hook.) J. B. Armst.||Porters Pass||144||n = 82|
|Rumohra adiantiformis (Forst. f.) Ching||Westport||62||n = 41|
|Rumohra hispida (Sw.) Copeland||North Westland||142||n = 41|
|Ctenitis glabella (A. Cunn.) Copeland||Stewart Island||114||n = 82|
|Ctenitis velutina (A. Rich.) Copeland||Queen Charlotte Sound||47||n = 41|
|Cystopteris fragilis Bernh.||Cass||125||n = 84|
|Athyrium australe (R. Br.) Presl.||Waitomo||175||n = 123|
|Asplenium flabellifolium Cav.||Lyttelton, Port Hills||6||n = ca. 270|
|Asplenium obtusatum Forst. f.||Stewart Island||115||n = 72|
|Asplenium lucidum Forst. f.||Queen Charlotte Sound||48||n = 72|
|Asplenium lucidum var. lyallii Hook. f.||Lyttelton, Port Hills||150||n = 144|
|Asplenium anomodum Col.||Weka Pass||122||n = 144|
|Asplenium colensoi Col.||Akaroa||132||n = 72|
|Pleurosorus rutifolius (R. Br.) Fée||Lyttelton, Port Hills||112||n = 72|
|Microsorium pustulatum (Forst. f.) Copeland||Queen Charlotte Sound||60||n = 37|
|Grammitis billardieri Willd.||Lyttelton, Port Hills||20||n = 37|
|Grammitis pumila Armstr.||Porters Pass||133||n = 37|
|Anarthropteris dictyopteris (Mett.) Copeland||Queen Charlotte Sound||59||n = 37|
|Ctenopteris heterophylla (Labill.) Tindale||Bluff||120||n = 37|
Notes on the Families
Like other species of the genus the New Zealand Ophioglossum coriaceum cannot be counted with accuracy, the figure n = 360 being only very approximate. On the basis of figures given by Manton and Sledge (1954) this species would be hexaploid. Botrychium australe is in accord with figures for European, Ceylon and North American species of the genus and may be described as diploid.
As was to be expected, wild material of the two species of Leptopteris is typical of the family, and examination merely confirmed the figures given by Manton (1950) for plants grown at Kew.
The two genera examined show no relationship to one another either in chromosome number or in chromosome size. Individual bivalents of Gleichenia circinata are several times larger than those of Sticherus cunninghamii. No accurate count has yet been obtained from the local Dicranopteris linearis, but the chromosomes of this fern are similar in size to those of Sticherus.
Hymenophyllaceae (Figs. 1, 3)
This family is probably one of the most interesting groups in New Zealand from the viewpoint of cyto-taxonomy. Most interest centres in the species placed in Hymenophyllum and Meringium by Copeland. Meringium multifidum has n = 26 (Brownlie, 1954), and thus is the only New Zealand species showing similarity with
Hymenophyllum tunbridgense (n = 13). Meringium bivalve, however, with n = 22 shows relationship not with the other species of Meringium but with Hymenophyllum revolutum and H. peltatum. It is intended to carry out a more detailed examination of these two genera later. The writer believes that the number of n = 11 in Hymenophyllum peltatum is the lowest yet recorded for any fern. All other New Zealand members of this family examined show n = 36 (72 in Mecodium sanguinolentum), a very consistent figure for such morphologically diverse genera as Mecodium, Cardiomanes and Vandenboschia. It is perhaps significant that the variation in chromosome numbers around 22 and 36 reported for both Malaya and Ceylon by Manton, appears to be absent in New Zealand.
The most significant new feature in this group is the figure n = 34 for Lindsaea linearis which is not in accord either with the group based on the low 40's (Manton and Sledge, 1954; Brownlie, 1957) or that based on 50 (Manton and Sledge, 1954). This genus is one which would very well repay an intensive examination.
Cytologically Anogramma leptophylla is in accord with other Gymnogrammoid ferns, and the species of Hypolepis and Adiantum listed are in no way unusual.
Cyatheaceae (Fig. 2)
This report corrects an error which was published earlier (Brownlie, 1954) in that the content of Cyathea dealbata is n = 69. These ferns are amongst the most difficult to count accurately, the chromosomes being small and seldom staining intensely. Of the other two species mentioned one each belongs to the old genera Hemitelia and Alsophila and as these are cytologically indistinguishable from Cyathea, support is given to Copeland's scheme of incorporating them in that genus.
The only member of this family examined, Arthropteris tenella, is identical with Australian material of the same species recorded by Manton and Sledge (1954).
All species of Polystichum, Rumohra, Ctenitis and Cystopteris examined are completely in accord with all previous findings, so that interest in this group is confined to the systematic position of Athyrium australe. This species with n = 123 is in line with the base number of 41 for Diplazium as noted by Manton and Sledge (1954). As these workers also noted Athyrium constant with a base number of 40, it is suggested that it would be better to regard the New Zealand fern as a Diplazium.
Two interesting features emerge from the work on this family. The first is the unusually high chromosome content (n = ca. 270) and consequent high degree of polyploidy in Asplenium flabellifolium. The other is the distinctness of Asplenium lucidum var. lyallii (n = 144) from Asplenium lucidum (n = 72), and its similarity to Asplenium anomodum. It seems possible that A. anomodum with its recognised restriction to limestone is merely a form of A. lucidum var. lyallii and that both are separate from A. lucidum. In frond shape also both ferns show great similarities.
PolypodLaceae (Fig. 4)
With all local genera except Pyrrosia examined, this family shows extreme consistency with n = 37 in all cases. Cytologically there is nothing to distinguish Holttum's Grammitidaceae (Grammitis and Ctenopteris) from Microsorium and Anarthropteris.
The New Zealand species assigned to Microsorium by Copeland are distinct cytologically from both Microsorium (n = 36) and Phymatodes (n = 36) of Holttum as recorded by Manton (1954) and Manton and Sledge (1954). It is intended also to examine this group in greater detail.
The retention of a particular base number within a genus is as marked in the New Zealand fern flora as in that of Ceylon as noted by Manton and Sledge (1954), but the variability around particular numbers recorded for the Hymenophyllaceae and the Polypodiaceae of Ceylon and Malaya appears to be completely absent.
Although the cytological method is only one of several that may help towards the elucidation of taxonomic problems it appears that a thorough analysis of the genus Lindsaea is necessary. Apart from this genus the cytological discontinuity in Copeland's Pteridaceae is similar in New Zealand (Brownlie, 1957) to that found elsewhere. On the one hand we have Pteris, the Gymnogrammoid ferns and Adiantum, and on the other Paesia, Hypolepis and Pteridium. Examination of a much wider range of genera within this family is, however, needed before any very clear relationships can be seen.
With the publication of the above list we have added to the previously low chromosome numbers (n = 13 in Hymenophyllum tunbridgense and n = 26 in Matonia) the very low figure n = 11 for Hymenophyllum peltatum, and n = 20 for Gleichenia circinata. Not enough information is yet available for the Gleicheniaceae, but cytological relationships within the Hymenophyllaceae now appear more complex with base numbers of 11, 13 and 18. In New Zealand the greatest cytotaxonomic difficulty lies in the species placed by Copeland in Hymenophyllum and Meringium. It may well be that the three figures 9, 11 and 13 were the widespread basic numbers in the past history of the modern fern groups.
I am indebted to the Research Committee of the University of New Zealand for a travelling grant for the purpose of collecting material for this research. I wish also to thank Mr. J. D. Lovis and Miss J. Palmer for collecting some of the material used in this work.
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University of Canterbury,