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Re: fern breeding

  • Subject: Re: [ferns] fern breeding
  • From: "Tom Stuart" tstuart@westnet.com
  • Date: Thu, 06 Jan 2005 18:31:45 -0500
  • Content-description: Mail message body

A few years ago on the Alpine-L list a member asked, "When you encounter a new 
plant, how do you tell whether it's a perennial or an annual?"

That list has over a thousand members. There was no answer. Maybe some thought 
it was a dumb question, but the more I rolled it around, the more complicated 
the answer seemed. By a long measure, it was the most interesting unanswered 
question of the year.

Two weeks ago here Tony Avent asked,

> does anyone know of a list of apogamous ferns...especially winter hardy ones? 

Yes, this is also an interesting question, even though it isn't about 
Platycerium.  :-)

It is interesting horticulturally because apogamy guarantees the fern comes 
true to form, the offspring of a cultivar being precisely that cultivar. 

Moreover, apogamous ferns, bypassing the sexual phase, produce new sporophytes 

Taxonomically, the question is of interest because apogamy poses a number of 
riddles. How does apogamy coexist with evolution? Why are some genera loaded 
with apogamous species, others not at all? Sometimes loaded genera are 
phyletically far removed from each other, so did this set of characteristics 
arise many times in evolution?

As an aside, apogamy requires two separate events. First the normal meiotic 
division in the sporangium is corrupted (two paths are known), producing 2n 
chromosomes in the spores instead of n chromosomes. Second, the spore 
germinates and the resulting gamete independently produces a sporeling without 
any fertilization or concurrent recombination.

Cyrtomium is largely, not entirely, apogamous. Did this arise once or many 
times? If once, how did new species evolve? If many times, is apogamy a dead-
end evolutionally?

Why is apogamy relatively common among Japanese ferns (estimated at 13%) while 
in New Zealand it is much less common (2-3% of species)?
Its high incidence among some cheilanthoids (Cheilanthes, Pellaea, Astrolepis) 
is theorized to have an advantage in desert climates due to rapid establishment 
of the new plant after a rainfall. What is the advantage in woodlands?

The list below is preliminary. Partly this comes from a choice to start with 
the genera reflected in the temperate flora -- though not restricted to just 
the temperate species. Partly it is the lack of experimental data in much of 
the world (North America, Europe, Japan, New Zealand, Sri Lanka floras are well 
represented, other areas not). Australian ferns have been examined, but I do 
not have access to the results. Perhaps someone here has a key to:

Another digression. Apogamy can be induced by chemical means or by the stress 
of preventing fertilization.  Can someone enlighten us as to whether these 
means are strictly exploratory or already have practical application? In any 
case I strove to exclude such reports.

The marking 'both' in the list below means the species reproduces both by 
apogamy and sexual means. The two methods are sometimes reflected in separate 
subtaxa, sometimes by geographical origin, or the cytology may not be reflected 
in either morphological or geographical differences; the reference (see below) 
may have the details. An absence of 'both' only means no test has yet confirmed 
sexual propagation.

The first list of apogamous ferns was produced by the mother of cytology, Irene 
Manton, in 1950. An update:

First, temperate genera with no demonstrated apogamy:

Arachniodes, Aspidotis, Athyrium, Blechnum, Cryptogramma, Cystopteris, 
Dennstaedtia, Deparia, Gymnocarpium, Lygodium, Matteuccia, Onoclea, Oreopteris, 
Osmunda, Pentagramma, Pityrogramma, Pleopeltis, Pteridium, Pyrrosia, Woodsia, 

Genera where apogamy is rare or singular contain these species:

Adiantum caudatum (both), hispidulum, philippense
Argyrochosma limitanea
Ophioglossum coriaceum (both)
Phegopteris connectilis (both)
Polypodium scouleri (both)
Thelypteris glanduligera and parasitica

Genera where the incidence is moderate or high:

Asplenium aethiopicum, apogamum, cheilosorum (both), cataractarum, 
Asplenium filipes (both), hondoense (both), mertensianum, A . monanthes
Asplenium resiliens, and A. W heteroresiliens

Astrolepis cochiensis (both), crassifolia, integerrima, sinuata (both)

Cheilanthes alabamensis,  arizonica, bonariensis, eatonii, feei
Cheilanthes farinosa (both), kaulfussii, lindheimeri, sieberi, tomentosa
Cheilanthes villosa, wootonii

Cyrtomium caryotideum, falcatum (both), fortunei, macrophyllum

Diplazium dilatatum var.dilatatum (both) and var. heterolepia
Diplazium hachijoense, kawakamii var. kawakamii, doederleinii, donianum
Diplazium procumbens, simplicivenium
Diplazium virescens var. virescens, var. conterminum, var. okinawaense, and two 
other unnamed varieties
Diplazium taiwanense, D.Wkawabatae, D.Wtakii, and D.Wnakamurae

Dryopteris acutodentata, affinis (both), basisora, blanfordii, bissetiana
Dryopteris championii (both), chinensis, cycadina, cystolepidota, decipiens, 
Dryopteris dickinsii, erythrosora, formosana, fuscipes, gymnosora
Dryopteris hadanoi, hakonecola, hondoensis, indusiata, integriloba
Dryopteris juxtaposita, khullarii, kuratae, lepidopoda (both)
Dryopteris namegatae, neorosthorni, odontoloma, pacifica, parrisiae
Dryopteris purpurella, pseudo-filix-mas, pycnopteroides, remota, ryo-itoana
Dryopteris sacrosancta, shibipedis, silvaticum, simasakii, sparsa (both)
Dryopteris stewartii, subbipinnata, sublacera, subtriangularis 
Dryopteris tsugiwoi, tsutsuiana, varia, wallichiana (both), yakusilvicola

Notholaena aliena, N. aschenborniana, N. californica (both), N. grayi, N. 

Pellaea andromedifolia (both), P. atropurpurea, P. boivini, gastonyi
Pellaea glabella (both), intermedia (both), lyngholmii, ovata (both)

Polystichum kiusiuense, luctuosum (both), monticola, neolobatum
Polystichum rigens, tsus-simense, xiphophyllum
(most of Polystichum is tropical montane, most untested, fertile ground)

Pteris biaurita, cretica, cadieri, excelsa, esquirolii, fauriei (both)
Pteris grevilleana, kiuschiuensis, linearis, natiensis, setuloso-costulata

A majority of references for these taxa can be found on the web. For a copy of 
the list write to me privately. And, of course, please add to or correct the 
above, publicly or privately.

Yes, an interesting question.

Tom Stuart, New York

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