New Zealand Journal of Botany abstracts
Contributions to a chromosome atlas of the New Zealand flora—39.
Orchidaceae
Murray I. Dawson
Allan Herbarium
Landcare Research
PO Box 40
Lincoln 7640, New Zealand
Brian P. J. Molloy
Research Associate
Landcare Research
PO Box 40
Lincoln 7640, New Zealand
Ernst J. Beuzenberg*
of the former Botany Division
Department of Scientific and Industrial Research
Christchurch, New Zealand
*Present address: Nelson, New Zealand.
Abstract Somatic chromosome numbers are documented for the
majority of the New Zealand indigenous Orchidaceae, with counts for 80
species, 23 taxonomically indeterminate taxa, and 3 hybrids in 34
genera. Related chromosome counts are provided from elsewhere for
comparison: 43 species, 12 taxonomically indeterminate taxa, and 4
hybrids in 17 genera from Australia; 1 species from Lord Howe Island;
and 4 species in 3 genera from New Caledonia. A wide diversity of
chromosome morphology and primary and secondary basic numbers among
genera is reported (e.g., x/x2 = 11, 12, 13,
14, 15, 17, 18, 19, 20, 21, 22, 25, 26, 27). Relatively limited
polyploidy was uncovered, confirmed for New Zealand representatives to
the tetraploid level (e.g., for the Nematoceras trilobum agg., 2n
= 2x2 = 36 → 2n = 4x2 = 72; Drymoanthus,
2n = 2x = 38 → 2n = 4x = 76; and Microtis,
2n = 2x/2x2 = 44 → 2n = 4x/4x2
= 88; in these examples diploid taxa also occur). Amphidiploidy
(allopolyploidy) is reported within one genus only, Thelymitra,
where it is extensive. Reticulate cytoevolution in Thelymitra
is discussed, and the highest chromosome number obtained in this
study is 2n = 93 for T. luteocilium from
Australia. Extensive aneuploidy appears to be a feature of the
Australasian Orchidaceae. Aneuploidy occurs at several levels:
within a species (Stegostyla lyallii, 2n = 47, 48; Pterostylis
aff. montana agg., 2n = 43, 44; Earina mucronata,
2n = 40, 41, 42; Petalochilus chlorostylus, 2n =
39, 40, 41); between species in the same genus (Hymenochilus, x/x2
of 27→26(→24?); Prasophyllum, x/x2 of
22→21; Adelopetalum, x/x2 of 19→18; Thelymitra,
x/x2 of 14→13; Calochilus, x/x2
of 12→11); between subgenera (Pterostylis subg. Pterostylis,
x2 = 21, derived from x/x2
= 22 found in the other two subgenera); and between related genera
(e.g., Molloybas and Singularybas, x2
= 17, from x = 18 elsewhere in the Corybas alliance;
Calochilus, x2 = 12, derived from x2
= 13 as found in Thelymitra). The diversity of chromosome
morphology and numbers documented here provide independent and
informative characters to test the integrity of the recent and
extensive generic recircumscriptions of the Australasian Orchidaceae,
based on plant macromorphology and molecular sequence data. In
many cases, the chromosome evidence strongly supports recognition of
segregate genera (e.g., for some of the segregate genera of Caladenia,
Corybas, Prasophyllum, and Pterostylis) and
their subtribal and phylogenetic placements. In other
circumstances, the chromosome evidence is uninformative (e.g., for the
segregate genera Adelopetalum, Ichthyostomum, and Winika),
or else there are indications that certain genera and subtribes remain
cytologically heterogeneous and may not be monophyletic (e.g., within Prasophyllum
as currently circumscribed).
Keywords chromosome numbers; aneuploidy; polyploidy;
allopolyploidy; amphidiploidy; hybrids; orchids; Orchidaceae; Acianthus;
Adelopetalum; Adenochilus; Anzybas; Aporostylis;
Calochilus; Corunastylis; Corybas; Cryptostylis;
Cyrtostylis; Danhatchia; Diplodium; Diuris;
Drymoanthus; Earina; Gastrodia; Hymenochilus;
Ichthyostomum; Linguella; Lyperanthus;
Microtis; Molloybas; Myrmechila; Nematoceras;
Orthoceras; Petalochilus; Plumatichilos; Prasophyllum;
Pterostylis; Sarcochilus; Simpliglottis; Singularybas;
Spiranthes; Stegostyla; Sullivania; Thelymitra;
Townsonia; Waireia; Winika; New Zealand flora;
Australasia
B07010; Online publication date 3 December 2007; Received 18 April
2007; accepted 19 November 2007
New Zealand Journal of Botany, 2007, Vol. 45: 611–684
0028–825X/07/4504–0611 © The Royal Society of New Zealand 2007
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