Crossing experiments with Philaenus spumarius (Homoptera).

HERE 56-28 CROSSING EXPERIMENTS WITH PHILAENUS SPUMARIUS (HOMOPTERA) By 0. HALKKA, LllSA HEINONEN, M. RAATIKAINEN and A R J A VAS -4 R A1 N E N DEPARTMENT OF GENETICS, UNIVERSITY OF HELSINKI, AND DEPARTMENT OF PEST INVESTIGATION, AGRICULTURAL RESEARCH CENTRE, TIKKURILA, FINLAND (Recei ed Sep embe lG h, 1966) INTRODUCTION OLYMORPHISM in ield popula ions o Philaenus spuma ius has P been s udied by a numbe o au ho s, and he equencies o he di e en colou o ms ha e been epo ed in abou 20 publica ions. Al hough, om esul s ob ained wi h na u al popula ions, i has been in e ed ha he colou polymo phism is genically de e mined, c ucial p oo om c ossing expe imen s has been wan ing. In he USA, C. R. WEAVER has succeeded in ob aining o sp ing om known emales wi h unknown ma ing pa ne s, and has ound ha he o ms end o e- p oduce hemsel es (see OWEN and WIEGERT, 1962). Simila expe i- men s we e pe o med by he p esen au ho s in he au umn o 1964. In hese expe imen s, emales ep esen ing he colou o ms ma ginella and leucoph halma we e ound o p oduce among hei o sp ing daugh- e s like hei mo he , in addi ion o males and emales belonging o he colou o m ypica. Pic u es o he colou o ms as dis inguished by us, ha e been published by HALKKA (1964). Ma e ial and me hods All he emales and mos o he males used o c osses we e isola ed as la ae. The isola ion wo k was done in he o es and ga den a ea su ounding he "Nu mija i A" ield, which ha bou s one o he na u al popula ions s udied by he senio au ho (HALKKA, 1964). The o hy spi le masses p oduced by he la ae usually con ained a single speci- men only. Al oge he , 49 species o plan s we e used as ood sou ces by Philaenus la ae in he Nu mija i a ea. A de ailed epo on he dis i- CROSSING EXPERIMENTS WITH PHILAENUS 307 bu ion o he di e en colou o ms on hese plan s will be published elsewhe e. He e i will su ice o say ha he dis ibu ion appea s o be pe ec ly andom. In July 1965, 60 pai s we e placed in cages con aining po ed T i o- lium p a ense (“Tammis o” p oduc ) and A ena sa iua (Swedish “Sol”). The clo e was in ended o se e as ood, he oa s mainly as a si e o o iposi ion. The lowe po s we e sunk in o he soil up o he im, he lowe pa o he nylon cage ne su ounding he po . Apa om oc- casional wa e ing, he cages we e un ended, un il 15 o hem we e mo ed in o a g eenhouse on Decembe 31, 1965, and he emaining 45 on Feb ua y 26, 1966. The cages we e main ained a he Ag icul u al Resea ch Cen e. The win e o 1965-1966 was unusually se e e in Finland. A Tik- ku ila, he mean empe a u es o Janua y and Feb ua y we e - 13.9’ C and - 13.5O C, espec i ely. The cages, howe e , we e ai ly well p o- ec ed by abou 110 cm o snow on he g ound. In he g eenhouse, a empe a u e ange be ween 18 and 25 deg ees cen ig ade was main- ained and humidi y was kep a ound 75 %. High humidi y is essen ial o success ul ea ing o Philaenus. O he 60 pai s, 24 p oduced a leas one o sp ing, while 36 we e ailu es. Mos o he ailu es we e no due o inabili y o Phi aenus eggs o hibe na e bu o high la al mo ali y esul ing om poo hibe na- ion o he T i olium used as ood plan . Spi le masses we e obse ed in many o he cages which la e ailed o p oduce adul s. A o al o 234 F, o sp ing we e ob ained, 118 emales and 116 males. RESULTS The c osses, oge he wi h hei F, o sp ing, a e epo ed in Table 1. The o m ilinea a is a e a Nu mija i, and he isola ions did no p oduce enough males belonging o his o m. In ac , all he i inea a male pa en s o he success ul c osses o igina ed om ield collec ions. The ypica and populi males and he di e en emale o ms we e isola ed om al oge he 12 species o ood plan s. A he ime o isola- ion, he male and emale pa en s o c osses 9, 41, 57 and 59 we e li ing oge he as la ae in a common spi le mass. In Table 1 and in he ol- lowing epo , he c osses a e g ouped in o h ee sec ions acco ding o he o m o he male pa en : 308 HALKKA, HEINONEN, RAATIKAINEN AND VASARAINEN (1) Wi h ypica CIS he male pa en : In c osses 9 and 57 he emale, oo, belonged o ypica, and in bo h cases bo h pa en s we e isola ed om he same spi le mass. Only ypica o sp ing we e p oduced. In c osses 5, 23 and 59 he emale belonged o ilinea a. The pooled esul o hese c osses is 18 ilinea a and 16 ypica specimens. In c osses 1 and 30, he emale belonged o ma ginella. In addi ion o ma ginella and ypica specimens, c oss 30 includes in he F, gene a ion ou leucoph halma emales, wo o which bea small whi e spo s on hei ely ae and may be e be assigned o he o m albomacula a. The male pa en o his c oss ob iously bo e a gene esponsible o he leucoph halma pheno ype in one o his ch omosomes, al hough his gene was no exp essed in his pheno ype. The wo albomacula a speci- mens may ha e esul ed om a ia ion in he exp essi i y o his gene in he emale sex. I his explana ion is co ec , c osses 1 and 30 demon- s a e he exis ence o wo majo genes, which a e he e p o isionally named ma and lop. C oss 32, wi h la e alis as he emale pa en , p oduced a emale like he mo he and a male like his a he . In c osses 27 and 50, he emale belonged o lauicollis. Al oge he 17 F, o sp ing we e ob ained, all ypica. The ailu e o hese c osses o p oduce la icollis may be due o chance, since only 7 emales we e ound in he F, o he wo c osses combined. In c oss 31, he emale belonged o leucocephala. Two emales, one o hodox leucocephala and one wi h wo small whi e spo s on bo h ely ae, we e ob ained. This la e specimen di e s om a ue laui- collis pheno ypically and is bes in e p e ed as esul ing om a ia ion in he exp essi i y o a majo gene esponsible o he leucocephala pheno ype. This gene is he e p o isionally named Ice. In c osses 20, 25 and 41, he emale belonged o leucoph halma. Only leucoph halma and ypica o sp ing we e ound in he F, gene a ion. The gene esponsible o he o ally black leucoph halma pheno ype is ob iously exp essed only in he emale sex, a esul indica ed by he combined in o ma ion om c osses 30, 20, 25 and 41. I he lop gene eally is sex-con olled, he black males encoun e ed p inia ily in no h- e n Finland ha e a di e en geno ype. I is, o cou se, also possible ha he same gene is sex-con olled only in some pa s o i s dis ibu ion a ea. CROSSING EXPERIMENTS WITH PHILAENUS 309 TABLE 1. The esul s o c osses be ween Philaenus colou o ms. i 2 yp 2 - i 7 yp 6 ~- C oss no. i 3 i 2 i 4 yp 8 i 3 yp 1 la 3 i 2 yp 2 i 2 yp 1 Female Male pa en pa en i 1 yp 2 i 6 yp 1 i 1 yp 1 To al F, o sp ing 3 44 9 57 Y P i Y P i Y P ma YP i 1 yp ma I YP _____ 7 2 25 5 23 59 1 30 32 1 14 2 8 9 27 50 31 YP 2 YP 5 Ice 1 “ la” 1 I- 2 1 1 11 3 20 25 41 - lop 1 lop 5 yp 1 YP 5 1 YP1 - YP I POP yp I i i I i YP 2 1 YP 1 yp 4 i 3 I yp 2 i 5 7 54 14 48 i 2 yp 1 1 i 3 yp 1 39 40 ma 1 - i 3 yp 1 I YP 1 ma ~~ la Ila i la 1 i la i ]a 3 i 7 yp 7 I i 4 yp 6 la 2 i 8 i 2 yp 9 27 21 47 49 19 44 46 7 14 5 234 24 118 I 116 (2) Wi h populi as he mule pa en : The o sp ing om he single c oss (c oss numbe 7) wi h populi as he male pa en and ypica as he emale con ained only ypica speci- mens. (3) Wi h ilinea a as he male pa en : C oss 54, wi h ypica as he emale pa en , is ecip ocal o c osses 5, 23 and 59. Again, as in hese c osses, ypica and ilinea a pheno ypes a e equally common in bo h males and emales. This ac p o es, ha i is an au osomal gene, since Philaenus males a e XO as ega ds sex de e mina ion. The combined in o ma ion om c osses 5, 23, 59, 54 and 310 HALPKA. HEINONEN, RAATIKAINEN AND VASARAINEN 48 shows, ha he i gene is dominan in bo h sexes. In c oss 48, ilinea a pa en s p oduced bo h ilinea a and ypica o sp ing. The o sp ing o c osses 39 and 40, be ween a ma ginella emale and a ilinea a male, shows he ecessi eness o he ypica condi ion o- wa ds he e ec o he ma and i genes. The wo c osses, 47 and 49, bo h p oduced equen o sp ing, includ- ing, in addi ion o he pa en al ypes la e alis and ilinea a, a numbe o ypica specimens. The o sp ing om c osses 47 and 49, oge he wi h he esul o c oss 32, p o e he exis ence o a gene, la , esponsible o he la e alis pheno ype. C osses 19, 44 and 46 all p oduced ilinea a (pa e nal pheno ype) and ypica emales and males. The ma e nal pheno ype la icollis was ob ained in c oss 44 only. The exis ence o a gene o his pheno ype, la, seems unques ionable, bu ei he he gene in ques ion has a low pene ance o he la icollis pheno ype may also be caused by he ac ion o o he genes. DISCUSSION The esul s o he c osses desc ibed abo e show con incingly ha each o he dis inc ly colou ed and eadily dis inguished pheno ypes is de e mined by a pa icula majo gene. Mos o he genes a e egula ly exp essed in he emales bu p ac ically ne e in he males. This is ue o he exp ession o he majo genes ma , la , Ice and lop. The i gene, in con as , is exp essed in bo h sexes. A i h sex-con olled gene, he exp ession o which is con ined o he emale sex, la, also exis s. How- e e , he dependence o he la icollis pheno ype on he p esence o he la gene is pe haps no so clea -cu as in he case o he o he ou genes and hei espec i e pheno ypes. Samples collec ed om he ield e eal he ex eme a iabili y and ob ious he e ogenei y o he basic colou o m, ypica. Ob iously a g ea numbe o modi ying colou genes, he e ec o some o which is p obably u he modi iable by ex e nal ac o s, combine o c ea e he long a ay o pheno ypes om uni o mly ligh o uni o mly da k o ms. Many o hese modi ying genes a e no allelomo phs o he majo colou pa e n genes. Al hough i is likely ha he i, ma , la , la, Ice and lop genes a e allelomo phs o closely linked loci, and ha hey a e all au o- somal, e en his has no been conclusi ely es ablished. Fo his eason, neu al and noncommi al symbols o hese loci o genes a e used h oughou his pape . CROSSING EXPERIMENTS WITH PHILAENUS 311 P o ided ha he pene ance o he colou genes is comple e, he dominance o he i, ma , la , la, Ice and lop genes makes es ima ion o 2pq equencies ai ly easy in popula ions in which he pheno ypes a e sha ply dema ca ed. Fo hese genes, he 2pq equencies a y be- ween 1 % and 7 % in mos popula ions in Finland. The homozygo es hus con ibu e insigni ican ly o he gene equencies in hese popula- ions. A he p esen phase o gene ical wo k on Philaenus i is no known whe he some o he genes a e possibly le hal when homozygous. We also know no hing o he o de o dominance o epis asis in his a ay o colou genes. The expe imen al p og am o ob aining F, is being ex ended by us and s eps o p oducing Fa ha e been aken. In many espec s, colou polymo phism in Philaenus a o ds an in e es ing compa ison wi h wha is known o balanced polymo phisms in he Lepidop e a. As wi h he bu e lies, polymo phism in he meadow spi lebug is la gely sex-con olled. I seems ha many o he ules go e ning polymo phism in he Lepidop e a may also be alid in his Homop e an. A e a long pe iod o pe sis en and pains aking wo k, bo h he gene ics and ecology o ce ain bu e lies a e now being in es iga ed a a a he ad anced s age (e.6. SHEPPARD, 1961). Wi h Philaenus, ecological wo k synch onized and pa allel wi h gene ic anal- ysis has been ba ely begun by us. Philaenus a o ds a ou able ma e ial o s udies on sex-con olled inhe i ance and also o in es iga ions on he e olu ion o dominance.' Acknowledgemen s. - The English o he manusc ip was checked by M s. JEAN MARGARET PERTTUNEN, M.A., o whom ou since e hanks a e due. G an s o he s udy ha e been ecei ed om he Uni e si y o Helsinki and om he Na ional Resea ch Council o Sciences. SUMMARY The mode o inhe i ance o he di e en genes de e mining he coIou o ms o Philaenus spuma ius was s udied a he F, gene a ion le el. Six majo genes, each one esponsible o a dis inc colou pa e n, we e obse ed in his wo k. In a single dose, i e o hese genes, he e p o isionally named ma , la , la, Ice and lop, always mani es hei ' No e added in p oo : The i s adul specimens belonging o he Fa gene a ion eme ged in No embe 1966. They show dominan ansmission o he genes i and lop and s eng hen he iew ha in he emales yp is he bo om ecessi e in a dominance hie a chy se ies. A de ailed accoun o he F, p ogeny will be published in ano he con ex . 312 HALEKA, HEINONEN. RAATIEAINEN AND VASARAINEN e ec s in he emales bu ne e in he males. The six h gene, i, has a dominan mode o inhe i ance in bo h sexes. The la icollis pheno ype may pe haps ha e h ee al e na i e gene ic backg ounds: a) he la gene, b) ac ion o da kening modi ie s on he ypica gene ic condi ion and c) ac ion o genes nonallelic wi h lu o Ice and epis a ically causing he appea ance o wo whi e spo s on bo h ely ae o an indi idual wi h a Ice gene in he geno ype. The six majo genes may be allelomo phic wi h each o he . The exp essi i y o he six majo genes is ema kably independen o ex e nal ac o s, including ood plan s o he P and F, gene a ions. The possibiIi y ha he six majo genes cons i u e a dominance hie a chy is being u he s udied, oge he wi h he ecologicd aspec s o he sex-con olled inhe i ance o he colou genes. Li e a u e ci ed IIALKKA, 0. 1964. Geog aphical, spa ial and empo al a iabili y in he balanced poly- OWEN, D. F. and WIEGERT, R. G. 1962. Balanced polymo phism in he meadow SHEPPARD, P. M. 1961. Recen gene ical wo k on polymo phic mime ic Papilios. - mo phism o Philaenus spuma ius. - He edi y 19: 383-401. spi lebug, Philaenus spuma ius. - Ame . Na . 96: 353-359. Symp. Royal En om. SOC. London I: 20-29.