Chromosomes of North American grapeferns and moonworts (Ophioglossaceae: Botrychium)

10 Pages·1993·4.6 MB·English

by  F S Wagner

Contr.Univ.MichiganHerb.19:83-92.1993.
CHROMOSOMESOFNORTHAMERICANGRAPEFERNS
ANDMOONWORTS(OPHIOGLOSSACEAE:BOTRYCHIUM)
FlorenceS.Wagner
HerbariumandDepartmentofBiology
UniversityofMichigan
AnnArbor,MI48109
Because of rarity and small size, and the resulting inconspicuousness, the
diversity ofmoonwort species {Botrychium subg. Botrychium) has been largely
overlooked by botanists, until the last 15 years. Intensive work since 1977 has
resulted in discoveries, descriptions, and reinterpretations of 16 species to be
addedtothesevenknownbefore.
Scattered reports of chromosome numbers in a few of the more common
moonworts have appeared inthepast. Manyofthese,however, havebeenpub-
lished without voucher citations and have lacked illustrations of the chromo-
somes.Table1 giveschromosomenumbersforallofthedescribedNorthAmeri-
can botrychiums,withthe exceptionofBotrychiumgallicomontanum (Farrar &
Johnson-Groh 1991). Photographs and, in two cases, interpretive drawings of
thosetaxanotpreviouslyillustratedareshowninFigs.1-4.
Anumberofthenewspecieswhosechromosomenumbersaregivenhereare
found only inthewestern mountainsofNorthAmerica, andmanygrow athigh
altitudes.Thestagesofsporogenesissuitableformeioticcountsoccurearlyinthe
spring, and in the mountain habitats, snow-covered roads make collectingchro-
mosome material prohibitive. Inordertosolve thisproblemourmethodwasto
collectclumpsofsoilcontainingmaturemoonwortsduringthesummercollecting
fieldwork.ThesoilclumpsinplasticbagswerekeptinaColdTemperatureRoom
(40°F)duringthewinter,andinthespringplacedinemptycoveredglassaquaria
outdoors. Each clump was watered on alternate days. The botrychiums would
emerge,produceyoungsporangia,whichwerefixedinNewcomer'sSolution,and
then be collected asvouchersifthey matured. We have found itdifficult, ifnot
impossible,tocultivatetheseplantsformorethanayear,butwewereultimately
successful usingthis method inobtainingchromosome numbersforallthewest-
ernspeciesandalsoforthosethatoccurintheLakeSuperiorarea.
The cytological procedure consistedofplacingyoungsporangiaon amicro-
scopeslideinadropofACH(50% aceto-carmine,50% Hoyer'sSolution),teas-
ingandremovingthesporangialwalls,and,aftercoveringwithacoverslip,gently
squashingtheremainingcontents. Goodfigureswerephotographedwithacom-
pound microscope under an oil immersion lOOx objective, or a 40x high dry
objective if the figure was too large. Interpretive drawings were made with a
drawingtubetofacilitatecountingthechromosomes.Slidesweresealedfirstwith
nail polish and then, after a week, with Glyptal (a sealant made by General
Electric).InthecaseofB.montanum,theonlyfigureobtainedwasphotographed
butcouldnotbedrawn;thenumberisthereforeapproximate.Thechromosomes
of B. crenulatLim, on the other hand, are shown in a drawing, the figure not
survivingtobephotographed.
83
84 CONTR.UNIVERSITYOFMIC'HIGANHERBARIUM VOLUME19
TABII- I.CliromosomcluimbcrsinNorthAmericanbotrychiums.AllWagnervouchers
aredepositedatMIC'11.
Speeies Locality Chromosome Ploidal Reference
Number Level
Bolrychiiiin subu. Osniundonieris
B.viri^inianum MI:WashtenawCo. n= 92 4.V Wagner1955
(L.)Sw. Warneron
May151954
Rotrvchinni subg. Sccplrid'niiu
B.hilcrmiliifn (Sav. IN:JeltersonCo. n= 45 Zv Wauner1963
I,.Underw. Warner9273
B.(lissccluni Spreng. Briiion.v./;. /)= 45 2.Y Brillon1953
B.jcnmanii AL:MobileCo.. n= 90 4.x Wagner1963
I..Underw. Bcihcl9213
B.iiiuUifidtiiu (Gmel MI:WashtenawCo. «= 45 2.V Wagner1955
Rupr. Wiij^iieron
22June1954
B.Hoiowuisdecnsc (Ciilb. MI:WWdainsnherteinna1w95C4o.. n= 45 2.V Wagner1955
B.nii^idosutn MI:MonroeCo. n= 45 2x Wagner&
W*.H.Wagner Wo^incr9067 Wagner19S2
B.luiuirioidc.s AL:LeeCo., n= 45 2x Wagner1963
(Michx.)Sw. \Vui^ncr9l95
Borrvchiiiin subg. Botrvccnhiiini
B.Wac.iiHn.iuWiaatguinner MI:WaAfligiewrrC8o5.0,43 n= 90 4.1: WaWgangenre&r1990b
B.ciscctidcns OR:WallowaCo. n- 90 4.1 Wagner&
W.H.Wagner Wagner83363 Wagner1986
B.vainpcslre W.H. MI:LeelanauCo. n= 45 Zv Wagner&
Wagner&Farrar Wagner85025 Wagner1986
B.Wcr.cnHi.ildWiaugtnner CAC:o.S.anKiBeefrenrarodnint) /;= 45 2.V WaWgangenre&r1981
15Aug1963
B.echo W.H.Wagner CO:ClearCreekCo. n=: 90 Ax Wagner&
Wagner82135 Wagner1983
B.gaUiconiontatnim MIN;NormanCo. unknown Ax Farrar&
Farrar&John.son- Johnson-Ciroh
Oroh 1991
1993 F.S.WAGNER:BOTRYCHIUM 85
Table lcontinued.
B.hesperium (Maxon CO:ClearCreekCo., «= 90 4x Wagner&
&Clausen)W.H. Wagner82136 Wagner1983
Wagner&Lellinger
B.lanceolatum WA:SkamaniaCo., «- 45 2x WagnerinFabbri
(Gmel.)Angstr.ssp. Wagner63112 1963
lanceolatum
B.lanceolatum ssp. MI:EmmetCo., n= 45 2x Wagner1955
angustisegmenturn E.G.Voss on
(Pease&Moore) 15May1954
Clausen
B.lunaria (L.)Sw. MI:ChippewaCo. n= 45 2x Wagner&Lord
Wagner8199 1956
B.matricariifolium MI:EmmetCo., n= 90 4a Wagner&Lord
A.Br. Wagnerin1955 1956
B.minganense MI:ChippewaCo. n= 90 4.x Wagner&Lord
Victorin Wagner8200 1956
B.rnontanum MT:LakeCo., 2n= ca.90 2x Wagner&
W.H.Wagner Wagner80110 Wagner1981
B.mormo MN:ClearwaterCo. 2n= 90 2a- Wagner&
W.H.Wagner Wagner77326 Wagner1981
B.pallidum MI:ChippewaCo., 2n= 90 2a- Wagner&
W.H.Wagner Wagner89041 Wagner1990a
B.paradoxum AB:WatertonLakes n- 90 Ax Wagner&
W.H.Wagner NWaatgl.nePrar8k33,31 Wagner1981
B.peduncitlosum OR:WallowaCo., n= 90 4.V Wagner&
W.H.Wagner Wagr\er83361 Wagner1986
B.pinnatum St.John WA:SkamaniaCo. n= 90 4v WagnerinFabbri
Wagner63111 1963
B.pseiidopinnatum ON:ThunderBayDist., n= 135 6a Wagner&
W.H.Wagner Drifein1989 Wagner1990b
B.pumicola Coville OR:KlamathCo., n^ 45 2a Wagner1955
R.M.Brown in1954
B.simplex E.Hitchc. MLWashtenawCo., n= 45 2a Wagner1955
Wagner8142
B.spathidaturn ON:ThunderBayDist. n= 90 4a Wagner&
W.H.Wagner Wagrter88036 Wagner1990a
B.xwatertonense AB:WatertonLakes 2n= 180 4a Wagnerelal.1984
W.H.Wagner Natl.Park, (meiosis
{hesperium x Wagner83332 irreg.)
paradoxum
)
86 CONlR.UNIVERSITYOFMICHIGANHERBARIUM VOLUME19
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n=45.E.B.echo,n=90.F.B.asccnih-ii.s,n=90.
1993 F.S.WAGNER:BOTRYCHIUM 87
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FIG.2.MeioticchromosomesofBotrychium:localitiesandvouchernumbersareshowninTable1.
A.Botrychiumhcsperium,n =90. B. B. paradoxum,n =90. C. B. pedunciilostiin,n =90. D. B.
xwatertonense,ca.41 ITs,99Vs.(ExplanatorydrawinginFig.4B).E.B.lamcolaliimsubsp.lanceo-
laliim,n=45.F.B.pinnatmn,n=90.
88 CONTR.IJNIVFRSITYOFMICHIGANHERBARIUM VOLUMF 19
^~/\
^
^ Y F tj^^«fi
FIG. 3. Mcioticand somaticchri)mosomcsofHolrychliuii: li)caliticsand vouchernumbersare
shownin Table 1.A.Boirvch/iuncampcstre.n=45.B.H.mormo,2n=MO.C.B.ptillitlinn.In^90.
D.B.monliiniini,2n^ca.90.F.B.spathulaiiini.n=90.F.B.luuminaiitm.ii=90.
1993 F.S.WAGNER:BOTRYCHIUM 89
—
Off-
At>'^
^
B '^
FIG.4.A.ChromosomesofBotrychiiiincreniilaliim,2n=90;localityandvouchernumberare
showninTable1.B.ExplanatorydrawingofFig.2D,chromosomesofB.xwatcnoncnse.ca.44IFs
and99Fs.
The three subgenera of Botrychium in North America are Osmiindopteris,
Sceptridium, and Botrychium. (A fourthsubgenus,Japanobotrychium, occurs in
theOldWorldtropics.)
SubgenusOsmundopteris:Botrychiumvirginianum(L.)Sw.,themostfamiliar
and one of the most widespread species in the genus, occurs in Asia, Europe,
North America, and extends as a morphological cline into South America. The
chromosomenumberistetraploid,with«=92(x=46),anunusualbasenumber,
theonlyonein agenus inwhich almostallofthe numbers arc basedonx=45.
Theothermemberofsubg. Osmundopteris,B.strictumL.Underw.,fromeastern
Asia,alsohasanaberrantnumber,n=AA(Sahashi 1982).
Subgenus Sceptridium: The evergreen grapeferns number approximately 25
species,seven ofwhich occur in North America. Six ofthese are diploidwith a
chromosome number of« - 45. The seventh, Botrychiumjenmanii L. Underw.
(syn. B. alabamense Maxon), is a tetraploid with n = 90, a presumed ancient
allopolyploidhybridofthe diploidspecies, B. biternatiwi (Sav.) L. Underw. and
B. limarioides (Michx.) Sw. (Wagner 1963). It occurs also in the Caribbean and
Central America. Nootherpotential hybrids are known in the North American
membersofthesubgenus.Thereis,however,anundescribedtaxonofSceptridium
in KentuckyandTennessee,whosechromosomenumberandploidallevelare as
yetundetermined.
SubgenusBotrychium:All23taxaofthemoonwortshavechromosomenum-
bers based on 45. Surprisingly, half ofthe members of the subgenus are tetra-
ploids,and one isahcxaploid. Until fairly recentlyonly five taxaofmoonworts
wereknownineasternNorthAmerica,B.simplexE.Hitchc,B. hmaria(L.)Sw.,
B.lanceolatum(Gmel.)Angstr.(subsp.angustisegmentum(Pease&Moore)Clausen),
B. matricariifoUumA. Br.,andB. minganenseVictorin,andthreeintheWest,B.
lanceolatum (subsp.lanceolatiun),B.pumicolaCoville,andB.pinnatumSt.John
(formerlyconfusedwithB.borealeMildeoftheOldWorld).Manyofthe 16new
species were simply overlooked or thought to be forms of the more common
90 CONTR.UNIVERSITYOFMICHICiANHERBARIUM VOLUME 19
Table2.SterilehybridbotrvchiunisinNorthAmerica.
Species Locahty Reference
B.uscemlciis xcrcniilaliim OR:WallowaCo. Wagner&Wagner1986
WagnerH3363a
B.echo Xmini^iiiu'iise AZ:ApacheCo. Wagner&Wagner1983
WagmTH2I()4
B.liinccolaliini xmiiii^aiwiise CO:(lunnisonC\). Wagner&Wagner1988
WagnerH212I
B.lanceoldtuiu ssp. MI:AlgerCo. Wagner&Wagner1988
angitstisegmenliim x /-).Uenson2300
matr'uariifoliiiin
B.htnariii xpiiuiatuin BC:BryanBoruCk. (Unreported)
J.W.Easton (UBC)
B.hiiuiria x simplex MI:DeltaCo. Wagner&Wagner1988
R.B.Wilson iniyf-i4
B.lii/niiia x spathuliidu ON:ThunderBayDist. Wagner&Wagner1988
WagnerH7237
B.inatricariifolitiiu x MI:SchoolcraftCo. Wagner&Wagner1988
/ningiificnse WagnerH1045
B.matricariifoliiini xsimplex MI:MidlandCo. Wagner1980,1991
Wagner8997
B.pciliiniiilosum x piniuiiiiiii OR:WaWganlelroSw3a36C/o. Wagnerc^:;Wagner1986
B.{xhwcaiscpretnoiuimcnsxepaWii.uUlo.xWitatgu)ner ABP:arWkaterWtaognnLearkSe3s3N3a2tl. Wagnerelal.1984
species, usually B. limaria or B. inatlcariifolium. One ofthe helpful elements in
recognizingthe distinction ofthenewspecieshasbeentheploidal level,empha-
sizingthedifferences,forexample,betweenB.limaria^2.y,andB.ininganense.4a-,
andbetweenB.matricariifolium,4.v.andB.pseiidopmnatumW.H.Wagner,6.v.
Although for many years, authors believed that interspecific hybridization
doesnotoccurintheseplants,wehavemuchevidencenowthatitdoes(Wagner
etal. 1985). Indeed,wehavenowencounteredtendifferentwidelyscatteredand
sporadic types that appear to be intermediate between well-known species and
that possess abortive spores. These are listed in Table 2. We have very little
evidenceoftheirchromosomebehavior;however,themisshapenandhighlyvari-
ablespores,oftenverylargeandsphericalamongmanysmallandshriveledones,
presentstrongevidencethatmeiosisisirregular.
HybridsinBotrychiumarerare,however;usuallyonlyasingleplantisfound
amonghundreds.Thesehavemoreoftenbeenrecognizedonlyafterlargecollec-
tions havebeenmade andsorted,when theystandoutasmorphologically inter-
mediateanddifficulttoassigntoknownspecies.Sofarwehaveidentifiedonlya
1993 F.S.WAGNER:BOTRYCHIUM 91
TABLE 3.Hypotheticalparentsforpolyploidbotrychiums.
Hypotheticalparents Presumednothospecies
(Allorthospeciesexcept B.pinna(nm)
B.hiternalum xhmurioides B.jenmanii
B.campestre x lanceolatum B.echo
B.campestre x lunaria B.spathulatum
B.campestre x simplex B.gallicomontanum
B.cremdatimi x montamim B.ascendens
B.lanceolatum x lunaria B.pinnatum
B.larjceolatiim x montanum B.peduncidosum
B.lanceolatum x pallidum B.—matricariifoliutn
>B.acuminatum (metaspecies)
B.lanceolatum x simplex B.hesperium
B.lunaria x pallidum B.minganense
B.pmnatum x simplex B.pseudopinnatum
fewhybridsinthefieldand,withoneexception,wehavenotsucceededinobtain-
ing meiotic material of hybrids for chromosome study. In order to do so the
putativehybridsmustbeidentifiedasmatureplantsinthefield,wellpastmeiotic
stages ofsporogenesis, and tagged in the hope they will reappearthe following
spring, or the clump collected and overwintered as described above. The one
exception is Botrychium xwatertonense W. H. Wagner, the hybrid between B.
hesperium (Maxon&Clausen)W.H.Wagner&LellingerandB.paradoxumW.
H.Wagner,discussedindetailinWagneretal.1984.MeioticcountsofB.xwater-
tonensewere obtainedbythelattermethod.Meiosisprovedtobeirregularwith
the number ofpairs ofchromosomes ranging from 36 to41 and the number of
unpairedchromosomesfrom99to110,the totalsbeingapproximately 180chro-
mosomes.
The major question involving the polyploids in Botrychium is whether they
are autopolyploids from single pre-existing divergent species (orthospecies), or
allopolyploidsofinterspecifichybrids(nothospecies).Thefirstauthortosuggest
thataspeciesofmoonwortwasactuallyapolyploidhybridwasMeyer(1981).He
proposedthat B. matricariifolium originated asthesterile hybridofB. lanceola-
tum and B. lunaria (1981, pp. 613 ff., figs. 2, 3). His hypothesis, however, is
unlikely, because a numberofmorphological characters do not conformto this
interpretation.
Using such characters as (1) trophophore blade cutting and (2) shape; (3)
relativedevelopmentofthebasalpinnapair;(4)marginaldenticulation;(5)vena-
tionpattern; (6) epicuticularwax; (7) relativelengthofsporophore;and (8)pin-
nationofsporophore,originsofsomeofthepolyploidtaxacanbehypothesized.
Forsome ofthepolyploidsthere are no obviouscandidates aspossible parents.
OneoftheseisB.acuminatumW.H.Wagner,ararespeciesoftheLakeSuperior
region. ItisveryclosemorphologicallyinmostcharacterstoB.matricariifolium,
with which it co-occurs. Botrychium acuminatum may represent an example of
metaspeciationinwhichdivergentevolutionhastakenplacefromanallopolyploid
nothospecies,inthiscase,B.matricariifolium.
92 CONTR.UNIVERSITYOFMICHIGANHERBARIUM VOLUME19
Themostrcmarkablt;polyploidisB.paradoxumW.H.Wagner,whichdiffers
from all other known species, diploid or polyploid, and forwhich there arc no
knownrelativesorpostulatedparentalcombinations.
Hypotheses of reticulate origin for the various polyploid taxa are listed in
Table 3.They are presented here in the hope that theywill be tested in various
ways, including observations on chromosome pairing behavior in natural back-
crosses, comparisons of isozyme patterns of the postulated parents and their
allopolyploidpresumeddescendants,andobservationsonchloroplastDNA. Also
theoreticallyat least, it should be possible to reproduce the proposed hybridiza-
tionsexperimentally.
ACKNOWLEDGMENTS
MuchotthechromosomeresearchreportedherewascarriedoutduringthetenureofNational
SvacriieonucsewFaoyusndfartoimonW.grFIa.ntWsagDnEeBr-,8a0n0d55fo3r6thaendsugDgEeBs-t8i2on(s)2m7a6d8e.bIyahmimesapnedciablylyD.grRa.teFfaurlralrorcohnecleprni-n
ingthederivationsofpolyploidspecies.IamalsoindebtedtoDavidBayforphotographichelp.
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