ELBA BI OFLU X
Ex t r em e Life , Biospe olog y & Ast r obiology
I nt e r n at iona l Jour na l of t he Biof lu x Socie t y
D e scr ibin g h e a d sh ap e s of w h it e st e m b or e r s
(
Sch ir p oph a ga inn ot a t a
W a lk e r ) t ha t a r e a ble t o
su r vive on diffe r e n t r ice t ype s u sin g La n dm a r k
b a se d g e om e t r ic m or p h om e t r ics
Queenily n B. Albut ra, Mark Ant hony J. Tor res, and Cesar G. Dem ay o
Dep art m ent of Biological Scien ces, College of Science and Math em at ics, MSU- I lig an I n st it ute of Tech nology, I ligan Cit y, Phillipp in es. Corresponding auth or: Queen ilyn B.
Albut ra q ueenilyn_albut ra@yahoo. com
Abst r a ct. Rice st em bor er s ar e consider ed as t he m ost seri ous insect pest of r ice in Asi a. I t i nfect s i ts plant host by bur r ow ing i nt o t he st em usi ng it s m andi ble. How ev er , apar t fr om t he m andibl e, t he head of ri ce st em bor er s is also associat ed in t he i ncur sion pr ocess si nce it facilit at es t he ent r y of l ar v ae t o t he r ice plant. Di ffer ences in t he head capsul es hav e a dir ect effect on t he abilit y of t he i nsects t o ingest har d foods r apidly. Differ ent rice v ari et ies i n t he Philippi nes ser v e as plant host f or t his pest and inf est ation occur r ed in differ ent geogr aphical locati on. Var iati ons in habitat and plant host w er e t hought t o gener at e env ir onm ent al v ariat ion i n m or phom et ri c t r ait s and host adapt ed her biv or e phenot y pe r espectivel y . Landm ar k based geom et r ic m or phom et r ic analysi s w as used t o assess t he hy pot hesis t hat t he head shape of w hit e st em bor er di ffer bet w een populat ions wit h r espect t o differ ent rice var ieti es and geogr aphical locati on w her e it w as obt ained. Relati v e w ar p analy sis show ed v ari ation in t he head shape bet w een differ ent w hit e st em bor er (Schir pophaga innot at a Walk er ) popul at ions i nf esting differ ent v ari eties of rice. Non- si gnificant head shape v ari ations w er e obt ained betw een geogr aphicall y separ at ed popul at ions.These r esult s indicat e t hat t he rice host var ieti es play an im por t ant r ole i n t he sel ecti on of individuals t hat ar e able t o count er act t he r esist ance fact or s in pl ant s.
Key w or ds: Schir pophag a inn ot at a, Landm ar k based geom et ric m or phom et ri c anal ysis, Relat iv e w ar p analy sis, MANOVA.
su fficient d ifferences am ong variet ies t o m ake variet al resist ance an im p ort ant fact or in insect cont rol (Chandler 1967 ) . According t o Fordyce et al ( 20 06 ) , p lant t rait s th at confer resist ance against herbivores can serve as st rong select ive ag en t s on h erbivore physiology, life hist ory, behaviou r, and m orphology. Variat ion in plant resist ance t rait s can lead t o locally adapted herbivore ph en ot ypes.
I t w as also arg ued t hat populat ions of t he pest s differ b et w een g eograp hical locat ions t hus m ay exp lain variat ions in t h e response of t he rice h ost s t o t he in sect p est s. Since st em borers are h ighly m ob ile p ests, variat ion in t h e qualit y of habit at s m ay also b e ab le t o gen erat e en vironm en t al variat ion in m orph om et ric t rait s of t he p est s ( Sm ith & Pat t on 1 988) . I t is for t his reason t h at g eog rap hic variat ion could h ave locally ad ap t ed p opulat ion s that follow uniqu e and d iverg en t evolu t ionary pat h ( Thom pson 1988) . Analyses of g eog raphic variat ion in b od y size and th e size of ot her fu nct ional p art s are im p ort an t for underst anding locally variable ad ap t at ion s, wh ich m ay produ ce m orph olog ical diversit y w it hin insect species and pot en t ially m ay lead t o speciat ion . I t is on t h is cont ext that w e invest ig at ed t he sh ap e of t he head of rice st em borer ’s larvae t h at n ot on ly associat ed w ith th e rice variet y it infests but th e geograph ical locat ion w h ere th ey w ere collect ed. We applied t he Land m ark- based m eth od in g eom et ric m orph om et ric ( GM) analysis t o d et erm in e h ead shape variat ion bet w een p op ulat ion s of w h it e st em b orer. The m eth od of GM is con sidered one of the best app roaches t o h ave a b ett er com parison of sh apes and w ould no longer rely on qualit at ive d escript ions th at u sually are being int erpret ed differen t ly by individual scient ist s ( Ad am s et al 2004) . By t h e u se of quant it ative app roach like GM in d escrib ing m orph olog ical variat ions, it w ill b e easier t o d et erm ine relat ionships b et w een m orph olog y and ot her variab les thu s on e could m ake m ore in form ed dedu ct ion on organism ’s evolut ion (Ad am s 1999 ).
M a t e r ials and M e t h od s. Th e white stem borer larvae w ere collect ed from d ifferent sam p ling sites in t hree provinces of Mind an ao. Th ey w ere Lan ao del Nort e, Misam is Occid en t al and Z am boang a del Sur respect ively ( Fig. 1) . Aside from d ifferen t sam pling areas, sam p les w ere also obt ain ed from different variet ies of rice p lant as shown in Table 1 . A m ature st age of rice plan t w as ch osen in each of t he sam pling sit e. Rice st alks w h ich app eared w hit e in color and bearing n o rice g rains com p ared t o the ot hers w ere uproot ed . With the aid of a knife, each st alk w as longit udinally d ivided . Thus, revealing a colony of st em b orer’s larvae insid e. The sam p les w ere th en preserved in 95% ethyl alcohol.
Tab le 1 List of PSB/ BPI / NSI C/ I R rice variet y and th eir correspond ing ch aract erist ics
Rice Variet y Ave. Yield ( t / h a)
Grow t h Du rat ion Heigh t ( cm ) Suscep t ib ilit y
I R 72 5 112 88 MS
PSB Rc 1 8 5.1 123 102 I
PSB Rc 2 6H 5.6 110 88 I
BPI Ri 10 4.7 108 84 MR
NSI C Rc 158 7 113 NA MR
Legen d: MR- Moder at ely Resist ant ; I – I nt er m ediat e; MS – Moder at ely Suscept i ble.
For sim plicit y, different populat ion s w ere labeled as Kap158, Kap18, Kap10, Kum 26, Pla158, Pla26 and Pla72. Kap , Kum and Pla st and s for Kap at ag an , Kum alarang and Plarid el respect ively w h ere the sam ples w ere t aken. 158, 18, 1 0, 26 and 72 st and s for t h e NSI C Rc 15 8, PSB Rc 18, BPI Ri 10, PSB Rc 26H and I R 72 rice variet ies respect ively w h ich serve as plant h ost of th e wh it e st em borer larvae.
Each larva w as p lace in t he t est t ube wh ich con t ains 5% sod iu m hydroxid e. A st ereom icroscope w as u sed t o m agn ify t h e ant erior p ort ion of the larva. The im age of t h e larvae’s h ead cap su le w as capt u red u sing m icronCAM at t ached t o t he st ereom icroscop e.
Figur e 2. Digit ized im age of w hit e st em bor er ’s head show ing t he locat ion of 37 anat om ical landm ar ks.
Landm ark based geom et ric m orphom et ric analysis w as em ployed in th is stud y t o d eterm ine and com pare t he shape of t he head bet w een popu lat ions of S. inn ot at a t aken from differen t localit ies and in fest d ifferent varieties of rice. Tw o- dim ensional Cart esian coord inat es of t he selected landm arks in t he head capsu le of t he w hit e st em b orer’s larvae w ere dig it ized u sing t he p rog ram tpsDI G version 2 .12 ( Roh lf 2008 a). The raw coord inat e dat a w ere then subj ect ed t o generalized Procru st es analysis ( GPA) t o superim pose the land m ark configu rat ion s u sing least - squ ares est im at es for t ran slat ion and rot at ion p aram eters ( Ad am s et al 2004) . GPA is an im p ort ant procedu re because it elim inat es any variat ion du e t o differences in t ranslat ion, orient at ion, and size, and w ould superim pose th e ob j ect s in a com m on coord inate syst em .
p rod uces th e part ial- w arp scores, which describe t h eir d eviat ions from the referen ce configu rat ion and that can be used as variables in sub sequent m ult ivariat e st at ist ical analyses ( Roh lf 1999, 20 04) .
Th e relat ive w arp scores w ere subj ect ed t o MANOVA and Kruskal- Wallis t est using PAST soft w are version 1 .91 (Ham m er et al 2 00 1) t o det erm in e w hether t he head shape of w hit e st em borer differ significant ly bet w een d ifferent popu lat ions. Wh en MANOVA sh ow ed sign ificant resu lt s, t he analysis w ould proceed t o Hot elling’s pairw ise com p arison s ( p ost -h oc) t est . Kru skal- Wallis t est w as also done t o det erm in e w het her t h e sh ap e variat ion s observed in each of t he sign ificant relat ive w arps are also con sidered st at ist ically sig nificant .
Re su lt s and D iscu ssion. Using the t hirt y- seven landm arks, t he CVA scatt erplot s revealed no significant variat ions betw een g eograph ically d ifferent populat ions of t h e st em b orer at t acking variet ies of the sam e rice variet y ( Fig. 3A,B, Table 2 ). How ever, w h en populat ion s of t h e st em borer at t acking d ifferent variet ies w ere com pared, variat ion s in the head sh ap es observed ( Fig. 3C, D, Table 2) . Com parison of head sh ap es are d escribed based from t he relat ive w arp analysis (Fig s 4 and 5 , Table 3) . Kru skal-Wallis t est w as em ployed t o verify w heth er th e sh ap e variat ion s ob served in each of th e significant relat ive w arp s can b e considered st at ist ically sign ificant . Th e result of t he t est is sh own in Tab le 4.
Tab le 2 Resu lts of MANOVA t est for significant variat ion in t h e head shape b etw een
d ifferen t p opulat ions of w hit e st em borer
Wilk’s
Lam bda df1 df2 F p( sam e)
Bet w een Kap158 and Pla158 populat ion 0.1018 60 15 2.794 0. 05673
Bet w een Kum 26 and Pla26 populat ion 0.1172 60 16 2.005 0. 06187
Bet w een Kap158, Kap18 and Kap10
populat ion 0.05808 100 110 3.545 1 .2 6 5 E- 1 0
Bet w een Pla158, Pla26 and Pla72 populat ion 0.09518 100 118 2.645
2 .5 4 3 E- 0 7
Tab le 3 Variat ion in the h ead sh ap e bet ween w hit e st em borer popu lations th at host different rice
variet ies as explained by each of t h e sign ificant relat ive w arps and it s corresponding percen t age variance
RW % Var iance
Kap158 v s. Kap18 v s. Kap10 % Var i ance
Pl a158 v s. Pla26 v s. Pl a72
1 26. 36% Var iat ion in t he base of t he v er t ex and locati on of t he f r ons of t he head. Am ong t he t hr ee populat ions, Kap18 has t he m ost v aried vert ex and fr ons. Kap18 populat i on has head char act eri zed w it h less define cur v at ur e in t he base of t he v er t ex and w it h fr ons shi ft ed t ow ar d t he cent er .
26.95% Var i ation i n t he shape of ant er ior r egi on and base of t he v er t ex . Pl a158 populati on has head char act er ized w it h point ed ant er ior r egi on and m or e def ined cur v at ur e i n t he base of t he ver t ex com par ed t o Pla26 and Pla72 w it h slightly r ounded ant er ior r egion and less defi ned cur vat ur e in t he base of t he v er t ex .
2 14. 90% Var iat ion i n t he shape of ant er ior r egi on and wi dt h of t he head. Kap18 populati on has sl ender head w it h m or e point ed ant eri or r egion com par ed t o Kap1 58 and Ka10 populati ons.
13.66% Var i ation i n t he shape of t he ant er ior r egi on and position of t he fr ons. The Pl a158 and Pl a26 populati ons shar e t he sam e head feat ur e wit h slightly bl unt ant eri or r egion and fr ons shift ed t ow ar ds t he ant er i or r egion. Pl a72 populati on i s slight ly differ ent w it h head havi ng point ed ant er ior r egi on and fr ons shift ed near t he cent er of t he head.
3 9.47% Var iat ion in t he w idt h of t he head. Kap10 populat ion show ed a w ider head com par ed t o Kap158 and Kap 18 populati ons.
9. 21% Var i ation in t he dim ension of fr ons and wi dt h of t he head. Pl a158 populati on i s char act erized w it h sl ender head com par ed t o Pla26 and Pl a72 populati ons.
4 6.85% Var iat ion i n t he dim ensi on of t he f r ons and wi dt h of t he head. Kap10 populati on has sl ender head w it h l ar ger fr ons com par ed t o Kap18 populati ons wit h lar ger fr ons and br oader head. Kap158 populat ion has t he av er age head shape.
7. 51% Var i ation i n wi dt h of t he head. Ther e is no consider able v ariati on i n t he w idt h of t he head betw een populati ons. The pr esence of outlier s i n Pla26 and Pla72 popul ations m ade t he popul at ions v ari ed in t his r el ati ve w ar p.
5 6.28% Var iat ion i n t he shape of ant er ior r egi on and w idt h of t he head. Kap10 and Kap158 popul at ions hav e sl ender head w it h poi nt ed ant erior m ar gin com par ed t o Kap1 8 popul at ions t hat hav e w ider head w it h sli ghtly blunt ant er i or r egion.
5. 26% Var i ation i n t he shape of t he ant er ior r egi on and base of t he v er t ex . Pl a158 populati on has head char act eri zed wit h m or e point ed ant er i or r egion and less defi ned cur v at ur e i n t he base of t he v er t ex com par ed t o Pla26 and Pl a72 populati ons.
Figur e 4. Sum m ar y of Landm ar k based geom et r ic m orphom et r ic analysis show ing t he consensus m or phology ( upper m ost panels) and t he v ar iat ion i n t he shape of head bet w een Kap158, Kap18 and Kap10 popul at ion of w hit e st em bor er as explain ed by each of t he significant r elat ive w ar ps.
Tab le 4
Results of Kru skal- Wallis t est evaluat ing for sign ifican t variat ion in t he head sh ap e b et w een p opu lat ions of whit e stem borer t hat h ost d ifferent rice variet ies b ased on each
sign ificant relat ive w arps
Var iat ion Bet w een Kap158, Kap18 and Kap10
Relat ive War p p- v alue Mann- Whit ney Pair wise Com par ison
Kap158 vs. Kap18 Kap158 vs. Kap10 Kap18 vs. Kap10
1 0 .0 1 7 7 4 0 .0 2 3 4 9 0.3129 0 .0 0 8 0 2 9
2 0.09965 0.05737 0.1461 0. 2324
3 0.5217 0.7902 0.3441 0. 3483
4 7 .9 3 1 x 1 0- 5 0 .0 4 3 1 6 0 .0 0 0 9 4 4 0 .0 0 0 3 6 6
5 8 .7 9 x1 0- 5 5 . 6 3 7 x 1 0- 5 0. 736 0 .0 0 2 9 8 1
6 0 .0 0 1 7 4 3 0 .0 0 1 6 4 8 0. 962 0 .0 0 1 0 5 3
Var iat ion Bet w een Pla158, Pla26 and Pla72
Relat ive War p p- v alue Mann- Whit ney Pair wise Com par ison
Pla158 vs. Pla26 Pla158 vs. Pla72 Pla26 vs. Pla72
1 4 .0 8 4 x 1 0- 5 0 .0 4 6 1 5 .2 4 4 x 1 0- 6 0 . 0 3 8 5 9
2 0.07973 0.7639 0.07119 0 . 0 4 2 5 5
3 0 .0 0 7 1 9 0 .0 0 4 3 8 0 .0 2 5 6 9 0. 1569
4 0.1426 0.07804 0. 131 0. 5479
5 0 .0 0 8 3 3 0.5595 0 .0 1 8 4 4 0 . 0 4 4 3 5
I t can be seen from t he resu lt s t hat differen ces in rice variet ies w ere t h e m aj or fact ors t h at d et erm ined variat ion s in t he h ead shap e of w h it e st em b orers. Variat ion due t o d ifferences in t he rice variet y of plan t host is associat ed w it h the varying resist ance of t h e d ifferent rice variet ies against the pest . St at ist ical and relat ive w arp an alysis showed significant variat ion in the h ead shap e betw een t he p op ulat ion s th at h ost m oderat ely resist ant rice variet y and suscep t ib le rice variet y e.g. b etw een Kap 10 and Kap1 8 p opulat ion s. As sh own in t ab le 1 , BPI Ri10 rice variet y is m ore resist an t ag ainst st em b orer at t acks com pared t o PSB Rc 18. The p opu lat ion of w h it e stem b orer that in fest m oderat ely resist ant rice variet y h as an evid en tly slender h ead w ith poin t ed an terior region w h ile t hose th at in fest suscept ib le rice variet y h as w id er head w it h rou nd er ant erior region.
Accord ing t o Fordyce et al (2 00 6) , plan t t raits t h at confer resist ance ag ainst h erb ivores can serve as st rong select ive agent s on herbivore physiolog y, life h ist ory, b eh aviour, and m orphology. Variat ion in plan t resist an ce t raits can lead t o locally adapt ed h erb ivore ph en ot yp es. Various m orph ological and anat om ical plan t ch aract ers w ere correlat ed w ith st em b orer su scept ibilit y. Tall p lant s w ith w ide leaves and thick st em s w ere m ore suscept ible t o st em borer d am age. Wh ereas variet ies w it h vascular bundles arranged closer t han the w id th of t he larval head offered resist ance t o larval b oring (Chand ler 196 7) . I n a st ud y on rice plan t s against st rip ed st em borer (Ch ilo
supp ressalis) , the int eract ion of leaf b lade w ith a hairy upper surface, t igh t leaf sheat h
w rapp ing, sm all st em w ith rig id su rface and th icker hyp od erm al layers w ere associat ed w it h resist an t rice variet y ( Pat an akam j orn 1 965 ). Resist ant rice variet ies have t hinn er st em diam et er com pared t o t he su scept ible variet ies ( Ch and ler 1967; Hosseini et al 2 01 1). For t he larvae t o su ccessfully penet rat e it s h ost p lant w it h thinn er st em diam eter, it m u st press it self in t o t he sm aller h ole causing its head t o becom e slender and poin t ed. When an in sect popu lat ion h as tw o or m ore host sp ecies, th e p ossib ilit y arises t hat gen e flow is rest rict ed betw een g roups on d ifferent host s t hat are subj ect ed t o d ivergent n atu ral select ion for host ad ap t at ions (Berlocher & Feder 2002 ) as sh own in t h is stud y.
d ifferences in th e rice variet y w as associat ed w it h t he varyin g resist an ce of th e d ifferent rice variet ies against st em borer at t acks. Morph olog ical charact erist ics of t he variet y an d alt h ough not in vest ig at ed in t his st udy t he b ioch em ical charact erist ics of t he p lant s w ere responsib le for the variat ion s ob served in th e head shape.
Ack n ow leg de m e n t s. Th e auth or w ould like t o t hank Prof. Sharon Rose M. Tabugo and Mr. Mich ael Muh m in E. Man t ing for the t echnical assist ance and esp ecially t o t he DOST-SEI ( ASTHRDP) for t he sch olarship gran t and t o t h e Philippine Rice Research I n st itu t e ( PhilRice) for add it ional supp ort .
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Receiv ed: 25 April 2012. Accept ed: 05 June 2012. Published onli ne: 06 June 2012. Aut hor s:
Queenily n B. Albut r a, Depar t m ent of Biological Sciences, College of Sci ence and Mat hem atics, MSU- I ligan I nst it ut e of Technol ogy , I ligan Cit y , Phillippi nes, e- m ail: queenil yn_albut r a@y ahoo.com
Mar k Ant hony J. Tor r es, Depar t m ent of Biol ogical Sci ences, Coll ege of Science and Mat hem at ics, MSU- I ligan I nst it ut e of Technol ogy , I ligan Cit y , Phillippi nes.
Cesar G. Dem ay o, Depar t m ent of Bi ological Sciences, College of Sci ence and Mat hem atics, MSU- I ligan I nstit ut e of Technology , I ligan Ci t y, Phillippines, e- m ail : cgdem ay o@gm ail. com
How t o cit e t his ar ticle:
Albut r a Q. B., Tor r es M. A. J. , Dem ay o C. G., 2012 Describi ng head shapes of w hit e st em bor er s (Schir pophaga innot at a Walk er) t hat ar e abl e t o sur vi ve on diff er ent rice t y pes using Landm ar k based geom et ri c
