Brief information about the species status of Utricularia cornigera Studnicka

2013·1.8 MB·English

by  Miloslav Studnicka

TechnicalRefereed Contribution
Brief information about the species status of
Utricularia cornigera Studnicka
Miloslav Studnicka • Liberec Botanic Gardens • Purkynova 630/1 • CZ-460 01 Liberec • Czech
Republic • [email protected]
Keywords: Utricularia cornigera, hybrid, heterosis, apomixis
Abstract: The carnivorousplant Utricularia cornigera Studnickawas describedin2009, butauthor-
ities ofthe International Carnivorous Plant Societypublishedanopinionthatitis notatrue species,
but only a natural hybrid of U. reniformis and U. nelumbifolia. The role ofheterosis is discussed,
because U. cornigera is much largerthan boththeoreticalparents. Seedlings, the very characteristic
feature ofbladderworts (Utricularia), are different in all the bladderworts described, that is, in the
named species and in artificial hybrids of U. nelumbifolia and U. reniformis. No support for the
hypothesis supposing ahybrid origin ofU. cornigera was found.
Introduction
Recentlyahypothesisappearedthat Utriculariacornigera StudnickacouldbeahybridofU. nelum-
bifolia Gardn. x U reniformis St.Hil. (Schlauer 2011; Fleischmann 2012). Consequentially, the new
specieswasrejectedfromtheCarnivorousPlantDatabase(Schlauer2011).Neverthelessitwasaccepted
inthe International PlantName Index (IPNI 2005). This articlepresents the results ofnew experiments
withartificialcrossingsofboththeoreticalparentsproposedbythe authors.
Themannerofgerminationandspecificallytheappearanceoftheseedlingsarecrucialphenomenain
thelife strategyofbladderworts. Inthe Utricularia speciesfromthesectionIperuatherearetwodifferent
ways ofgermination: either by floating seedlings (e.g. U. cornigera, U. nelumbifolia), or by terrestrial
U
seedlings(e.g. U. geminiloba, U. nephrophylla, andthetrue reniformis).
ThedifferencewasdescribedandpicturedasaveryimportantdiacriticalattributeofU. cornigeraas
comparedwith U. reniformis (Studnicka 2009).As mentionedintheprevious paper, U. reniformis does
nothavewhorl-shapedseedlings anditcannotgerminate inwater, but U. cornigera germinates inwater.
Thefloatingwhorl-shapedseedlingsofU cornigeraarerathersimilartothealsowhorl-shapedseedlings
ofthe Brazilian U. nelumbifolia andtheVenezuelan U. humboldtii Schomb. These species canusephy-
totelmeswithinthe leafrosettesofcertainhostplantstogerminate(Taylor 1989; Studnicka2011).
Methods
Cultivatedplantswereusedformanualhybridization,whichwascarriedoutduringJulyandAugust
2012 inLiberecBotanicGardens. SpecificidentityofU. reniformisisgrantedbyapreviousstudymade
usingthe same material(Studnicka2009). Specific identity ofU. nelumbifolia is clearbecausethe sto-
loniferous plants distributed in European botanic gardens are ofnatural origin. Numerous fresh seeds
(thewholecontentofatleast2fullseedcapsulesofeachspeciesorhybrid)wereputintowaterinaglass
and cultivated in a greenhouse. The seeds of U. reniformis, which couldnot germinate in such condi-
tions, werealsoplacedonawetsoilmixofpeatanddriedSphagnummoss 1:1 andwere alsocultivated
inthe greenhouse. Justthe soil surfaceprovides suitable conditions for U. reniformisto germinate.
Volume 42 March 2013 15
The seedlings ofU. reniformis, U. nelumbifolia, U. nelumbifolia x U. reniformis, and U. reniformis
mm
x U. nelumbifoliawere documentedbyphotographstakenusingaPentax35 macrolens.The float-
ing hybrid seedlings were compared with the seedlings of U. cornigera formerly used to describe the
species (Studnicka2009).
Possible heterosis was evaluated according to the maximal size ofthe leafblades found. The blad-
derwort U. cornigera was measured in natural localities as well as in cultivated specimens, both giant
(Studnicka 2009). The species U. nelumbifolia found thanks to F. Rivadavia nearTeresopolis in Serra
dos Orgaoswasmuchsmallerthanthe specimens cultivatedinLiberec Botanic Gardens, whichiswhy
Ipresent a measurement ofa cultivatedplanthere. The leafofthe flowering cultivated specimen ofU.
reniformisusedinthis researchwas also measuredandcomparedwiththe largest leaffoundinnatural
conditions (cf Studnicka2009).
Results
The question is whether the prospective hy-
bridtheoreticallyresulting in U. cornigera would
be an F generation or a descendant ofmultiple
1
breeding. To assess this problem measurements
ofthe largestknown leaves in allthree species in
questionareneeded. Icangivethesedimensions:
U cornigera 24.4 x 20.7 cm (cultivated speci-
men), but also up to 17.5 x 13.0 cm in natural
conditions; U. reniformis9.2 x7.5 cm(cultivated
specimen),buteven 10.5 x8.5 cminnaturalcon-
ditions; U. nelumbifolia 9.9 x 9.6 cm (cultivated
specimen), butdistinctly smallerspecimenswere
seen in natural conditions. The preserved leafof
U. cornigeraphotographedinthis article is locat-
ed in the PRC herbarium; the leaves ofthe other
species are found in Liberec Botanic Gardens
(www.botaniliberec.cz). It was documented that
theleaflaminasofthetheoreticalparentalspecies
arebothabouthalfthesizeofthoseofU. cornige-
ra (Fig. 1-3). IfU. nelumbifolia and U. reniformis
weretheparents ofU. cornigera the giant size of
,
its leaflaminawouldbe asignofheterosis.
The seedlings of all three species are very
characteristic. Are the juvenile hybrids of U.
nelumbifolia x U. reniformis (and conversely)
similar to U. cornigera? The results of crossing
experiments are documentedbelow(Fig. 4-8).
Discussion
Figures 1-3: Leaves of luxurious specimens The bladderwort U. cornigera is much more
of cultivated bladderworts. The scale is in vigorous than both U. nelumbifolia and U. reni-
centimeters.
16 Carnivorous Plant Newsletter
Figures 4-5: Floating seedlings of Utricularia nelumbifolia (left) and terrestrial seedlings
of U. reniformis (right). These theoretical parents of U. cornigera were crossed artificially.
(See the following figures.)
' A
/> -7*
.
x
'
ri *
A
V v-W
a *
9
Xx,
V
r
Figures 6-7: Seedlings of the hybrid Utricularia nelumbifolia 9 x U. reniformiswith 4-5 leaf
primordia (left) and of the hybrid U. reniformis 9 x U. nelumbifolia with 3-4 leaf primordia
(right).
formis. Therefore, the heterosis effect in the FI
crossbredgenerationshouldbenoted, ifU. corni-
gem were to be considered as a hybrid. The het-
erosis effect is, however, unsustainable in subse-
quentgenerations. The gigantism in U. cornigera
(considered a hybrid) would be stable solely by
two prerequisites: 1. It is a primary hybrid; 2. It
propagates onlyasexually.
U. cornigera produces viable seeds, but they
could theoretically be a result ofapomixis. Nev-
Figure 8: Seedlings of Utricularia cornigera ertheless, research of seedlings made by cross-
with 6-8 leaf primordia are dissimilar to the
breeding experiments between U. nelumbifolia
hybrids pictured above.
and U. reniformis indicates lowernumbers ofleaf
primordia in these hybrids in comparison with U. cornigera. This is clear evidence that the seedlings
of U. cornigera cannot be an apomictic derivate ofthe hybrids U. nelumbifolia x U. reniformis or U.
reniformis x U. nelumbifolia. Experience with a cultivated U. cornigera indicates thatmanual pollina-
tionisnecessaryto obtainseedsandseedlings.Thatis also a signofnormal sexualpropagation.Asthe
aforementioned prerequisites are not fulfilled, the idea that U. cornigera originated as a hybrid is not
supported. According to this preliminary result, U. cornigera arose due to reproductive isolation, like
other endemic plants restricted to the same area, ratherthan from ahybrid origin. The future study of
Volume 42 March 2013 17
traps, and or fertility/sterility in mature hybrids would also be interesting corroboration ofthe species
status ofU. cornigera.
Conclusions
1. The seedlings originating from both crossings of U. nelumbifolia and U. reniformis are dis-
similarto seedlings ofU. cornigera.
2. This fact excludes the possibility that U. cornigera couldbe an apomictic primary hybrid.
3. The bladderwort U. cornigera is the most vigorous species ofthe three named bladderworts,
but no heterosis could survive inmany generations ofthe sexuallymultiplying bladderwort. That is
why it canhardly be a stabilizedhybrid ofmuch smallerparents.
Acknowledgement: I wish to thank Professor R. J. Valka Alves, University Federal do Rio de Ja-
neiro, forhis helpful suggestions.
References
Fleischmann,A. 2012.Thenew Utricularia speciesdescribedsincePeterTaylor’smonograph. Camiv.
PI. Newslett. 41: 67-76.
IPNI. 2005. The International PlantNames Index, http://www.ipni.org/ipni/plantnamesearchpage.do,
accessed 17 July2012.
Schlauer, J. 2012. Carnivorous Plant Database, http://www.omnisterra.com/bot/cp_home.cgi, ac-
cessed 17 July2012.
Studnicka, M. 2009. Brazilian bladderwort Utricularia reniformis is a blend oftwo species. Thaiszia
-J.Bot. 19: 131-143.
Studnicka, M. 2011. Surprising phenomena in the life strategy of Utricularia reniformis in Brazil.
Thaiszia-J. Bot. 21: 37-43.
Taylor, P. 1989. The genus Utricularia - a taxonomic monograph. Kew Bull. Additional Ser. XIV,
Royal Bot. Gardens, Kew. 723 p.
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