Nutlet production and germination in female and hermaphrodite plants of Thymus albicans Hoffmanns. & Link (Lamiaceae)

Beni o Valdés, Zoila Diaz Li an e & Raquel Pa a Nu le p oduc ion and ge nina ion in e nale and he naph odi e plan s o Thymus albicans Ho nanns. & Link (Lamiaceae) In oduc ion Abs ac Valdés, 8., Diaz Li an e, Z. & Pa a, R.: Nu le p oduc ion and ge nina ion in emale and he - maph odi e plan s o Thymus albicans Ho manns. & Link (Lamiaceae ). -Boeeonea 13: 353- 360.2001. -ISSN 1120-4060. Some ep oduc i e aspec s a e s udied in Thymus albicans Ho manns. & Link, endemie o SW Ibe ian Peninsula. Pe een age o he naph odi e plan s ui se , nu le p oduc ion, seed se , ep oduc i e e ieiency and pe c en age o ge nina ion o seeds p oduced by emale and he - maph odi e plan s a e s udied. Pe cen age o emale and he naph odi e plan s is e y a iable be ween popula ions. Nu le p odue ion and ep odue i e e iciency a e highe in emale han in he naph odi e plan s, and his, oge he wi h a sligh ly ad aneed ge nina ion o seed p o-. duced by emales, may ine ease emale i ness in na u al popula ions. Gynodioecy is he occu ence o emale and he naph odi e indi iduals in he same na - u al popula ions o a species. I is equen ly he esul o he egula occu ence o male s e ile genes in o he wise he naph odi e popula ions (Richa ds 1986). Female plan s can be conside ed as he naph odi es ha ha e los hei male unc ion, a p ocess in which bo h nuclea and cy oplasmic genes may be in ol ed (Belhassen & al. 1991). Gynodioecy can be conside ed a well-s ablished b eeding sys em in he Lamiaceae; wi hin a popula ion, equencies o he naph odi e and emale plan s show li le a ia ion wi h ime (Richa ds 1986). Models o gynodioecy in ol ing he e ec s o sel ing pos u- la e ha emale a e main ained in he popula ion because hei o sp ing a e obliga o y ou - c ossed and hence mo e i han he p ogeny o he naph odi es o en esul ing om sel - e iliza ion (Cox 1988). Gynodioecy occu s in mos species o Thymus (Mo ales 1986) and has been s udied in de ail in T ulga is L. by Dommee & al. (1978) and Assouad & al. (1978). As in many o he gynodioecious Angiospe ns (Delph 1996), he co olla in ~male lowe s is smalle han in he naph odi e lowe s, and while in he la e he e is a well ma ked p o and y, wi h he s igma becoming ecep i e ou days a e an hesis, in emale lowe s he s igma is ecep i e inmedia ely a e lowe opening (Mo ales 1986). Thymus albicans Ho nanns. & Link is one o he wo Ibe ian Peninsula species o sec . 354 Valdés & al.: Nu le p oduc ion and ge mina ion in Thymus Mas ichina (Mi11e ) Ben ham, cha ac e ized by hei la lea es, which a e ne e cilia e a he base, and capi uli o m lowe -heads wi h small whi e lowe s wi h cilia e calyx- ee h. T albicans di e s om he o he species in he sec ion, T mas ichina (L.) L. , by he size o he calyx, highe in T albicans, and size o calyx ee h, as long as o sho e han ube in T mas ichina, bu qui e longe han he ube in T albicans. I is a gynodioecious endan- ge ed species endemie o SW Ibe ian Peninsula whe e i li es in coas al sandy soils o a educed a ea in S Po ugal a ound Fa o (Alga e) and in Cadiz p o ince (Spain), whe e i s dis ibu ion a ea is now in eg esion. Hs p esence in Huel a and Se i11a p o inces (Mo ales 1986) has no been ecen ly con i med. The aims o his pape is o quan i y he sexual ep oduc i e capaci y o his species. Sex dis ibu ion, nu le p oduc ion, ep oduc i e e iciency and seed ge mina ion capaci y ha e been s udied in se e al popula ions. Possible di e ences be ween emale and he - maph odi e plan s o hese pa ame e s ha e been checked. Ma e ia) and Me hods Fi e popula ions we e chosen nea Chiclana (Oidiz p o ince) (Fig. 1), a11 li ing on sandy soils wi h simila clima ic condi ions. Popula ions l, 2 and 3 g ow as pa o he Fig. l. Gene ai dis ibu ion o Thymus albicans Ho nanns. & Link. and o igin o he popula ions s udied. Bocconea 13 -2001 355 open unde sc ub o Pinus pinea o es , and popula ions 4 and 5 in open and sunny a eas a ound he o es . Pe cen age o emale and he map odi e plan s was es ima ed by coun ing ali specimens in ou popula ions. F ui se (% l l), nu le p oduc ion, seed se (% S/O) and pe cen age o abo ion was measu ed in se e al emale and he map odi e plan s in he ou popula ions in 1995 and 1996. Plan s o simila size, sepa a e o an equi alen dis ance and dis ibu ed a andom in each popula ion we e chosen. Fi e eplica es o 50 calyces pe ('lan , ali sepa a e a an- dom, we e used o e alua e hese pa ame e s. F ui se was es ima ed as pe cen age o lowe s which p oduced ui ing calyces, his is, wi h a leas one nu le . Nu le p oduc ion pe calyx was es ima ed as numbe o nu le s p oduced by each ui ing calyx. Seed se was es ima ed as pe cen age o o ules which p oduced nu le s. Pe cen age o abo ion e e s o ali ui ing calyces s udi ed; abo ed e ilized o ules we e ecognizable as seedless nu le s, which we e always smalle han ipe ones. Rep oduc i e e iciency was measu ed acco d- ing o Wiens & al. (1987) as % S/O x l l. Pe cen age and dynamic o ge mina ion o seeds p oduced by emale and he maph o- di e plan s o ou popula ions we e s udi ed in labo a o y condi ions. Fou eplica es o each sample, o 25 nu le s each, we e sown in Oc obe 1995 and Decembe 1996, in s e - ile Pe i dishes wi h we il e pape . Seeds we e g own in na u al day ligh wi h empe a- u es anging om 18 o 28°C. Seed ge mina ion was ollowed daily du ing 40 days. The numbe o days elapsed om sowing o ge mina ion o he i s seed ( O) and om sowing o 50% ge mina ion ( 50) ha e been used as indica o s o ge mina on dynamic. Resul s Pe cen ages oJ gynodioecy. -Size o popula ion, numbe o plan s, densi y and sex dis- ibu ion in he i e popula ions s udi ed a e indica ed in able 1. Pe cen age o he maph o- di e and emale plan s is e y a iable om one popula ion o ano he , anging om 39.13% o 63.15% o he maph odi es. In hese pe ennial plan s, no di e ences in sex pe - cen ages ha e been obse ed in wo consecu i e yea s (1995 and 1996) excep o popu- la ion l, which was pa ially des oyed by building ac i i ies in he sp ing o 1996. F uc i ica ion.- F ui se , nu le p oduc ion, seed se , ep oduc i e e iciency (PERS) and pe cen age o abo ion in emale and he maph odi e plan s o he ou popula ions Table l. Densi y and sex dis ibu ion in he popula ion s udi ed. Popula ion Su ace (m2) N° plan s N° plan s/m2 % He maph odi e 360 61 0.16 46. 15 2 675 83 0.12 39.13 3 372 95 0. 25 40.47 4 42 19 0.45 63 . 15 5 4234 2032 0.47 62.22 356 Valdés & al.: Nu le p oduc ion and gennina ion in Thymus Table 2. F uc i ica ion in 1995 and 1996 in emale (F) and he maph odi e (H) plan s o he popula- ions 1,3,4 and 5. N, numbe o plan s s udied . A) 1995 Popula ion N % / l nu le s/ cal yx %S /O PERS % (mean ± s.d.) abo ion 3-F 3 }' 0.39 4.20 0.38 9.71 1.01 57.63 3-H 4 12.41 7.29 0.60 15.25 1.89 40.46 4-F 4 57.19 16.59 0.65 16.29 9.31 40.68 4-H l 11.36 4.10 0.41 10.40 1.18 58.32 5-F 5 29.34 13.42 0.68 17.24 5.06 38.70 5-H 4 13 . 61 8.13 0.29 7.08 0.96 70.68 B) 1996 Popula ion N % l l nu le s/calyx %S/O PERS % (mean ± s.d.) abo ion l - F 4 17.62 5.55 0.48 11.98 2.1/ 52.06 l - H 4 10.15 6.86 0.42 10 . 58 1.07 41.03 3-F 9 36.68 10.67 0.64 15.91 5.84 34.60 3 -H 9 20.24 9.58 0.37 9.28 1.88 54.90 5-F 4 14.28 1.42 0.39 9.75 1.39 60.99 5 - H 4 20.78 10.34 0.39 9.82 2.04 54.47 s udi ed in 1995 and 1996 a e indica ed in able 2. Pe cen ages o ui ing calyces wi h O, l and 2 ipe nu le s in emale and hennaph odi e plan s a e shown in Figs. 2a and 2b. No s a- is ical es s ha e been ca ied ou owed o he he e ogenei y in he numbe o plan s s ud- ied in each popula ion. In popula ions l and 4 nu le p oduc ion and ep oduc i e e iciency a e highe in emale han ÌÌì'~ennap h odi e plan s. In popula ions 3 and 5, whe e hese alues we e es i- ma ed o wo consecu i e yea s, esul s a e a he con adic o y. In popula ion 3 bo h nu - le p oduc ion pe ui ing calyx and ui se we e 10we in emale han in hennaph odi e plan s in 1995, bu conside ably highe in 1996. In popula ion 5, on he con a y, bo h pa ame e s we e qui e 'highe in emale han in hennaph odi e plan s in 1995, while hey we e e y simila in 1996. As shown in Figs, 2a and 2b, he numbe o ipe nu le s pe calyx is a he low, wi h a educed pe cen age o calyces wi h wo ipe nu le s. No calyx was ound wi h h ee o ou Bocconea 13 -2001 357 ipe nu le s. Numbe o nu le s p oduced by ipe calyx ends o. be highe in emale han in he map odi e plan s. Seed ge mina ion.- Pe cen age and dynamics o ge mina ion o seeds o ou popula- ions s udi ed and le el o s a is ic signi ican di e ences o Iukey HSD es a e gi en in able 3. Ihe e a e no s a is ically signi ican di e ences be ween popula ions 3 and 4 as s udi ed in 1995. In 1996 only popula ion 1 showed a pe cen age o seed ge mina ion sig- % % 10 8 6 4 2 10 O 8 O 6 O 4 O 2 O 3-F 3-H 1-F 1-H a) 4-F 4-H b) 3-F 3-H 5-F 5-F D O nu ~ 1 nu .2 nu 5-H D Onu ~ 1 nu .2 nu 5-H Fig. 2. Pe cen age o ui ing calyces wi h 0, l and 2 nu le s in emale (F) and he maph odi e (H) plan s: a, da a o popula ions 3, 4 and 5 (1995); b, da a o popula ions I, 3 and 5 (1996). 358 Valdés & al.: Nu le p oduc ion and ge mina ion in Thymus ni ican ly lowe han in popula ions 3 and 5, which did no di e one om he o he . No di e ences ha e been ound ei he be ween 1995 and 1996 in popula ion 2. Da a o emale and he maph odi e plan s o hese popula ions a e shown sepa a ely in able 3. The s a is i c compa ison be ween pai s o means in emale e sus he maph odi e plan s (Mann-Whi ney-U non pa ame i c es ) has shown only signi ican ly di e ences a he 0.05 le el in popula ion 3 o 1995, bu a he 0.1 le el in popula ion 5 o 1996, wi h a lowe pe cen age in emale e sus he maph odi e plan s. Da a on dynamics o ge mina ion o seeds a e also gi en in able 3, whe e he pa ame- e s O and 50 ha e been indica ed. Ge mina ion usually begins ea lie in nu le s p oduced by emale han by he maph odi e plan s, bu in popula ions 3 no di e ence was ound in 1996. The pa ame e 50 is ussually eached 1-3 days ea lie in nu le s p oduced by emales han in hose p oduced by he maph odi es, bu once mo e popula ion 3 di e s a his espec . Table 3. Pe cen age (%) and dynamics ( O and 50, in days) o ge mina ion o seeds in emale (F) and he maph odi e (H) plan s om popula ions 1,3, 4 and 5. Mean and s anda d de ia ion (in b acke s) o % ge mina ion, and mean and ange o a ia ion (in b acke s) o O and 50, a e indica ed. The same le e uppe means implies s a is ic di e ences wi h signi icance a le e I as ollows: a= p< O.OI, b= p< O.OOI [Tukey HSD es ]; x= p< 0.05, y= p<O.1 [Mann-Whi ney-U]. Popula ion yea sex % O 50 nO eplico l 1996 F 49.0 (8.9) 3 (2 -5) 7 (4-8) 4 H 44.0 (-) 4 (4) 5 (5) l To al 48.0 a,b (0.8) 5 3 1995 F 59.0 x (22.2) 3 (3) 4 (4) 4 H 84.0 x (3.3) 3.5 (3-4) 7 (7) 4 To al 71.5 (20.0) 8 1996 F 81.0 (7.6) 3 (3) 4.5 (4-6) 4 H 85.0 (8.2) 3 (3) 4 .2 5 (3-5) 4 To al 82.8 a (7.6) 8 4 1995 F 83.0 (8.9) 3.5 (3-4) 6.2(4-7) 4 H 68 .6 (14. 1) 4 (4) 10.5 (7-14) 2 To al 78.8 (11.6) 6 5 1996 F 78 .0 y (4.0) 2.5 (2-3) 3 (3) 4 H 86.0 y (6.9) 2 (2) 4 (3 -5) 4 To al 82.0 b (16.4) 8 Bocconea 13 - 2001 359 Discussion The e is a wide a iabili y in he uc i ica ion pa ame e s analyzed, which oge he wi h he di e ences in numbe o indi idua1s s udi ed om each popu1a ion comp1ica es s a is ical compa isons. Howe e , da a sugges ha pe cen age o uc i ica ion is e y low in ali popula ions. Pe cen age o au ogamy in he maph odi e plan s is equally e y low, as i has been obse ed a pe cen age o uc i ica ion lowe han 5%, wi h a PERS o c. 0.1 (unpublished da a). This indica es he low su i al po enciali y o his species. Seed abo ion, some imes as high as 70%, seems o g ea ly a ec ui se , and he e is a nega i e co ela ion be ween numbe o nu le s pe calyx and deg ee o seed abo ion, as deduced om able 2. Besides, a high, bu no e alua ed, s yle p eda ion by smallia ae has been obse ed in mos emale and he maph odi e plan s. Bo hseed abo ion and s yle p eda ion could explain he low ui se obse ed, and also he di e ences ound in a pa - icula popula ion in consecu i e yea s. On he o he hand he esul s show a gene ai endency o a highe nu le p oduc ion and ep oduc i e e iciency in emale han in he maph odi e plan s, which ag ee wi h he gen- e ai endency ound in gynodioecious popula ions o o he species o Thymus (Dommèe & al. 1978, Assouad & al. 1978), and wi h esul s ound by se e al au ho s in o he g oups (Maki 1993, Eckha 1992). Seed ge mina ion pe cen age is gene ally high, wi h a o al mean o c. 74%. This indi- ca es ha he e a e no special equi emen s o seed ge mina ion and ha his does no make any p oblem o he su i al o his species. Popula ion l is he only one which sig- ni ican ly di e s om he o he s by i s low ge mina ion pe cen age, bu no logical expla- na ion has been ound o his di e ence, as popula ion l is no he smalles and occupies a simila habi a ha he o he h ee. A he o he side, as deduced om able 3, he e is no ela ionship be ween pe cen age o ge mina ion and sexuali y. Only signi ican di e ences a e ound in popula ion 3 in 1995, bu no in he same popula ion in 1996. As indica ed abo e, nu le s p oduced by emale plan s seem o ge mina e ea lie han hose p oduce by he maph odi es. As ge mina ion occu s a e Au umn ain all, his di - e ence in ge mina ion may a ou emale o sp ing. Howe e , u he obse a ions could con i m his endency. Re e ences Assouad, M.W., Dommèe, B., Luma e , R. & Valdey on, G. 1978: Rep oduc i e capaci i es in he sexual o ms o he gynodioecious species Thymus ulga is L.-Bo . J. Linn. Soc. 77: 29-39. Belhassen, E., Dommèe, B., A lan, A., Gouyon, P. H ., Pomen e, D., Assouad, M. W. & Cou e , D. 1991: Complex de e mina ion o male s e ili y in Thymus ulga is L.: gene ic and molecula analysis. -Theo . Appl. Gene . 82: 137-143. Cox, P. A. 1988: Monomo phic and dimo phic sexual s a egies: a modula app oach.- Pp. 80-97 in: Dous , J. L. (ed.), Plan ep oduc i e ecology. Pa ems and s a egies. -Ox o d. Delph, L. F. 1996: Flowe size dimo phism in plan s wi h unisexual lowe s. -Pp. 217-237 in: Lloyd, D. G. & S. C. H. Ba e (eds.), Fio ai biology. -New Yo k. Dommèe, B., Assouad, M. W. & Valdey on, G: 1978: Na u al selec ion and gynodioecy in Thymus ulga is L. -Bo . J. Linn. Soc. 77: 17-28. Eckha , V. M. 1992: Resou ce compensa ion and he e olu ion o gynodioecy in Phacelia linea is (Hyd ophyllaceae). -E olu ion 46: 1313-1328. 360 Valdés & al.: Nu le p oduc ion and ge mina ion in Thymus Maki, Y. 1993: Ou c ossing and ecundi y ad an age o emales in ginodioecious Chionog aphis japonica a o ku ohimensis (Liliaceae). -Am. J. Bo . 80: 629-634. Mo ales, R. 1986: Taxonomia de los géne os Thymus (exc uida la secci6n Se pyllum) y Th ymb a en la Peninsula Ibé ica .. -Ruizia 3: 1-324. Richa ds, A. J. 1986: Plan b eeding sys ems. -London. Wiens, D., Cal in, C. L., Wilson, C. A., Da en, C. L, F ank, D. & Sea ey, S. K. 1987: Rep oduc i e success, spon aneous abo ion, and gene ic load in lowe ing plan s. - Oecologia (Be l.) 71 : 501-782. Add ess o he au ho s: Valdés, B., Dia z Li an e, Z. & Pa a R.: Dp o. Biologia Vege ai y Ecologia, Facul ad de Biologia, A da. Reina Me cedes sin. Apdo. co eos 1095.41080 Se illa, Spain.