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2003]regardlessofthetypeofinflorescence,i.e.araceme,panicleandumbel
[Hirabayashietal.2006].
Manypapershavereportedthetraitsoffloralmorphology(e.g.flowersize,
numberofpollengrainsperflower,pollen/ovuleratio,nectarvolume)associated
withthematingsystemofaspecies[Ornduff1969,Cruden1977,2000,Spira
1980,Preston1986,DamgaardandLoeschcke1994a,Bennett2001,Takahataet
al.2008,Takahata2009,MichalskiandDurka2009].Amongthem,thepol-
len/ovuleratio(P/O)providesthebestinsight[Cruden1977,2000,Plitmannand
Levin1990].AccordingtoCruden[1977,2000],P/Oscorrelatewiththeinci-
denceofoutcrossingbecausetheyreflectpollinationefficiency;i.e.thelikeli-
hoodofapollengrainreachingthestigma.Hereportedasubstantialdecreasein
P/Ofromxenogamytofacultativexenogamytoautogamy.However,thepolli-
nationefficiencyhypothesishasbeencriticized.Charnov[1982]arguedthatP/O
ratioisgovernedbytheallocationofresourcestomaleandfemalesexfunction
(sex-allocationtheory),asrepresentedbythenumberandsizeofpollengrains
andseeds.ThetheoriesofCrudenandCharnovarenotmutuallyexclusiveand
Götzenbergeretal.[2006]proposedthatbothsexallocationandpollination
efficiencycontributetothevariationintheP/Oratio.Anumberofstudieshave
verifiedthecorrelationbetweenmatingsystemsandP/Os[e.g.Jürgensetal.
2002,MichalskiandDurka2009],includingincrucifers[Preston1986,Taka-
hataetal.2008].Afterastudyon66taxa,Preston[1986]reportedthatP/Osof
allogamouscrucifersaretypicallygreaterthan3500,thatthoseofautogamous
crucifersaretypicallylessthan1000,andthatthesestandardscanbeusedfor
indicatingthematingsystemoftheBrassicaceaespecies.AccordingtoTakahata
etal.[2008],among53speciesofBrassicaandalliedgenera,thelowestP/Os
werefoundintheobligateautogamousspecies,whilethexenogamousspecies
showedhigher,butmorefluctuatingP/Os.TheyfoundthattheP/Oratioof
B.junceawas3137;amongSinapisspeciesitvariedwidelyfrom11900(S.alba
S02)to2800(S.pubescensS07).ThereisevidencethatP/Osarealsoaffected
bythesexualsystem,thepollenvectors(i.e.windoranimals),lifeformand
ecologicalfactors(e.g.habitatdisturbance)[Cruden2000,ErbarandLanglotz
2005,Götzenbergeretal.2008].
Angiospermflowersareverydiverseinboththeirphenotypicfeaturesand
theirpollinationmodes.Theyvaryincolour,scent,size,morphology,andinthe
typeandamountofrewardtheyoffertopollinatinganimals.Complexcombina-
tionsofflowertraitsaregenerallyinterpretedasadaptationsforattractingand
exploringcertaintypesofpollinators.Thisviewiscodifiedintheconceptof
‘pollinationsyndromes’[FægriandvanderPijl1979,Proctoretal.1996,for
recentcommentaryseeArmbrusteretal.2000,OllertonandWatts2000,Fenster
etal.2004.Ollertonetal.2007,2009].Pollinationsyndromesaresuitesofcon-
vergentphenotypicfloraltraitshypothesizedtoadoptdistantlyrelatedspeciesto
particulartypeofpollenvectors,abiotic(windorwater)aswellasbiotic
(abroadgroupofanimalssuchasbees,butterfliesorbirds).Toincreaseattrac-
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