Page & Erickson (198S) showed that such worker-produced drones ..... vaiualrlr-- discus-sion,.. atiil fol :'errr.lrrrtl ri\ hal iinl)irt, lisfred t.lata ()n thc ci'ossing-r:r'cl f ...
Heredity73 (1994) 98-102 O T h eG e n e t i c aSl o c i e t vo f G r e a tB r i t a i n
Received 28 January 7994
Lackof meioticrecombination in thelytokous parthenogenesis of layingworkersof Apis melliferacapensrb(the Capehoneybee) R O B I NF .A . M O R I T Z& * M I C H A EH L ABERLT lnstitut für Biologie, Technische Universität Berlin, Franklinstrasse 28129, D 10587 Berlin, Germanv
OfTspringof thelytokouslayingworkers of Apis melliferac'apensis were screenedusingmultilocus DNA fingerprintingwith the (GATA)l oligonucleotide. All screenedoffspringworkersrevealedan identicalDNA fingerprintpattern,lackingevidenceof any meiotic recombination. This finding supportsearliercytologicalstudiesthat postulateda centralfusionin the automicticthelytokous parthenogenesis of honeybees. Furthermore, cnrssing-over did not contributeto detectable senetic v a r i a h i l i ti yn t h i ss t u d y . Keywords: Apis ntelliferucapensi.s,automixis,DNA fingerprinting,parthenogenesis, recombination.relationship.
Introduction In a queenrightcolony the queenis usuallythe only reproductive female.Shesuppresses the rearingof new queens(not in the swarmingseason)and the ovary developmentof the workers through pheromone acticrn(Butleret ul., 7961).In queenless colonies,however,this suppression is no longereffective,and the workerswill either start rearingemcrgencyqueens,if appropriately ageclbrood is available, or developtheir ovariesand becomelayingworkers.Layingworkersin honeybeesusually produce unfertilized eggs that developinto male offspring.Page& Erickson(198S) showedthat suchworker-produced dronescan contributesubstantially to the senepool in the population.in the Cape honeybee(Apis melliferu capensisEsch.), however,layingworkersare known to producefemale offspring(Onions,1912;Anderson, 1968).The fertilizationmode of thelytokousparthenogenesis in honeybees was first discussedby Tucker (1958), whcr suggestedan automixiswith fusion of the two central nuclei.The locationof the meioticnucleiin queen-laid eggsdiffers significantlyfrom that in worker-laid eggs in A. m. c'upen.sis.In queeneggsthe two pairsof nuclei are arrangedperpendicularto the eeg surface(Snodgrass,1925;DuPraw,196l). Verma& Ruttner(1983) 'r'Co rrcs non de n cc. iCurrcnl adclrcss: Zoologisches lnstitut. Universität Miinchcn. L o u i s c n s t r a s s el . l . 1 . i 0 3 3 3M i i n c h e n . G e r m a n v .
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observed that the four nuclei are serially arrtrnged, parallel to the egg surface, in eggs of laying workers of the Cape honeybee. Only the two centrarllylocated nuclei fuse to form automictically a diploid nucleus. These observations confirmed Tucker's theoretical concept of trn automixis with central fusion in an empirical cytological study. The genetical consequencesof the central fusion automixis are clear.giving r i s el r l t w o p r e d i c l i o n s . 1 There is no random recombination of the parental chromosomes. 2 Gene recombination can occur only through crossing-over (Greeff & Villet, 1993 ). Both hypotheses can be readily tested by scrcening offspring of laying workers. given there are suitable geneticmarkers to analysegeneticrecombination. Phenotyprc mutant markers which can be used to study recombination in worker offspring produccd by A. m. cupensrsworkers are potentially availablein the honeybee (Tucker, 1986). The use of mutant markers for such a study is, however, laborious.Laying workers of the mutant strainsperform arrhenotokousparthenogenesisand do not produce female offspring. Therefore the mutant allele has tcl be introduced into the A. ru. aches to test the parthenogeneticmode in laying t'upen,sisworkers. Multilocus DNA fingerprinting with the (GATA)', probe (Epplen, 19BB)has been shown to reveal intracolonial genetic variability among workers i M o r i t z e r a l . , 1 9 9 I ) . H a b e r l & M o r i t z ( 1 9 9 . 1 )u s e dt h i s t.echniqueto determine the degree of polyandry in a colonv of honevbees.Here we use this technique to rel'eal the cytogenetical mechanism which underlies the parthenogenesis of laying A. nt, c'apensrs'workers.
Materialsand methods
For blockingreagent(BoehringerMannhcim) (pF{7"-i1. labr:llcdi(iAl A )t hybridizationthe dLJ'fP*digoxigenin (Fresenius) was addedto the preh'vbridrzalion solution fot"at to a final concentrationof 5 nnt and incub;.rte
