Documents

A New Look at Darwinian Sexual Selection.doc

Description
Download A New Look at Darwinian Sexual Selection.doc
Categories
Published
of 5
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Related Documents
Share
Transcript
   A New Look at Darwinian Sexual Selection Keywords: Darwin, male ornamentation, fancy male species, food-courtship theory, peafowls, bower birds. MERLE JACOBS   Note 1 Goshen College, Goshen, IN ! #!, $%& , merleej@goshen.eduReceived e!ruar 1#, 1$$$, %u!lished &arch 1', 1$$$   Introduction (o ex%lain the srcin o) the ostentatious %lumage o) the males o) )anc *male !irds%ecies and the !right coloration o) males o) non*avian s%ecies, +harles Darwin%ro%osed the theor o) sexual selection 1-. e argued that the ornate )eatures o) males are a conse/uence o) )emale mate selection !ased on an a!stract aesthetic sense. Darwin likened this %rocess to animal !reeders %roducing )anc *male varieties o) %igeons ! a %rocess o) conscious arti)icial selection. Al)red 0allace, Darwins colla!orator and a student o) wildli)e !ehavior, suggested an alternative ex%lanation. &ale adornment, he noted, was associated with heightened %h sical activit and he %ro%osed that !ecause o) their greater energ the most highl adorned males are a!le to win out in the com%etition with rival males 2-.3n the 1$4's, 5ulian uxle 4- and R.0.6. ingston 7- %ointed out that male adornment is itsel) instrumental in esta!lishing dominance relationshi%s among males. 0hen so em%lo ed, adornment actuall reduces the %h sical activit necessar to intimidate rivals.3n the earl 1$8's, as a graduate student, 3 examined the %rocess o) )emale choice in studies o) the dragon)lies 'erithemis tenera  and 'lathemis lydia  8-, )ruit )lies Drosophila melanogaster   9- and other organisms #-. & o!servationsled me to the conclusion that what a%%eared to !e choice o) an adorned male ! a )emale was reall a mutual attraction o) !oth sexes to a %articular t %e o) re%roductive site. (hus mate selection re/uired not an aesthetic sense, onl an awareness o) )eatures characteristic o) a suita!le !reeding site, which might !e mirrored in the ornamentation o) the male. According to this view, mate selection is related directl to ada%tive niche s%eciali:ation. rom this insight, 3 went on to a career in )ield and la!orator studies leading to the develo%ment o) a )ood*courtshi% theor o) mate selection. The food-courtship theory Li)e on earth is driven ! solar energ as )ound in )ood molecules in various ecological niches. ;rganisms com%ete )or these niches. (hat %o%ulation most e))icient in use o) the energ availa!le in a %articular niche will !e the )ittest to survive there. (hrough natural selection, organisms will tend to !ecome s%eciali:ed to )orm isolated %o%ulations, each ada%ted to make the most  e))icient use o) energ availa!le in a %articular niche. (his %rocess o) segregation and s%eciali:ation o) %o%ulations is )acilitated ! em%lo ing in the mating %rocess sam%les o) the )ood availa!le in the %re)erred niche. 3n %articular cases, the male ma dis%la the )ood to the )emale or )eed it to her in the courtshi% ceremon . Among !irds, the male ma !ear %ermanent re%resentations o) s%eci)ic )oods on his %lumage. 3n this case, the )emale ma !e attracted to the male !ecause she is attracted to these re%resentations o) the territorial )oods. (his %rocess, !ringing together males and )emales o) similar tastes and %h siologies, ma lead to s%eciation. Some o) the male dis%la )eatures ma come to !e involved in s%ecies identi)ication. &ale adornment could have a dual )unction, re%elling rival males as well as attracting )emales. +lari)ication o) the role o) male ornamentation thus %resents a huge challenge to investigators.(he )ood*courtshi% theor ma !e a%%lied to the case )or mate choice among %ea)owls 'a(o cristatus.  (he <e es%ots< on the tail )eathers o) the male !ear a striking resem!lance to !lue !erries. (hus, according to the )ood*courtshi% theor , it is !ecause their %lumage !ears re%resentations o) )ood that %eacocks attract %eahens. (his is consistent with the )inding o) =etrie et al. >- that males with the most <e es%ots< on their tail have the greatest mating success. urthermore, it is not inconsistent with a %ossi!le role o) the <e es%ots< in re%roductive com%etition among males $-. &oreover, this ex%lanation seems more %lausi!le than the suggestion that ! selecting mates according to the %er)ection o) their tail*)eather <e es%ots,< %eahens are a!le to identi) mates with the greatest <)itness< 1'-.?ecause male !ower!irds %lace )ruit and )lower arrangements in their court ards and %aint the walls o) their !owers with colored )ruit %ul%, the are considered to have the most highl develo%ed aesthetic sense among the !irds.?ut according to m o!servations, it is more %lausi!le to ex%lain the mating !ehavior o) this s%ecies in terms o) the )ood*courtshi% theor .(he male satin !ower!ird 'tilinorhynchus (iolaceus,  which has !lue %lumage and !lue e e irises, %laces !lue )ruits and )lowers sometimes )acsimiles o) such!lue )oods- in his court ard. e also %aints the inner walls o) his !ower with !luish regurgitated )ruit residues. 3s it not %ossi!le, there)ore, that the colored o!jects in the court re%resent )avorite )ruits o) the s%ecies, and the chewed materials %ainted on the walls re%resent such )oods hung out to dr in a more %ermanent )orm3n northeastern Australias &ount Lewis, 3 studied the satin !ower!ird. arl in the da , the male chewed u% materials in the court ard, then immediatel regurgitated a viscous su!stance and a%%lied it with his !ill onto the inner walls o) his !ower. e later occasionall %ecked at this as i) tasting it. 0hen a )emale arrived she )ed on materials in the males court. (he male then chewed )oods in the court while making loud coughing sounds while regurgitating the viscous su!stance )rom his !eak in the %resence o) the )emale. 0hen the )emale a%%roached him and started to enter his !ower, he charged her. She )led, onl to return later, and the entire %er)ormance was re%eated #-.   A %u!lished videota%e 11-, shows !oth male and )emale satin !ower!irds %ecking at the <%ainted< walls o) the !ower within which mating occurs. ?ull dog ants swarm over these walls as i) )inding something edi!le thereon. (he same videota%e shows the regent !ower!ird, %ericulus chrysocephalis,  which has ellow %atches on his %lumage and ellow e e irises, using ellow )ruits much as the satin !ower!ird uses !lue )ruits.(he !ower!ird ha!it o) s%reading )ood remnants around the nest ma !e o!served among other !irds. 3t has !een re%orted that among the !ird*o)*%aradise, 'arotia lawsii,  the male in his court, ru!s chalk )rom a chalk cli)) over his dis%la %erch. (he visiting )emales eat the chalk, which is rich in calcium 12-.(he North American white*!reasted nuthatch %itta carolinensis  %er)orms similar )ood*smearing !ehavior at the nesting hole. (hese !irds swi%e their !ills againstthe !ark around their nesting holes while holding )ood items in their !ills. xamination o) the !ark around the holes reveals %arts o) insects and s%iders #-. Some o) these materials are retrieved later and used in mate*)eeding or )eeding oung. An im%lication o) the )ood*courtshi% theor is that the selective %ressures associated with )ood %re)erence, ha!itat choice, courtshi% !ehavior, and male coloration will tend to !e mutuall rein)orcing. (his ma ex%lain wh so man )ruit*eating !irds !ear <)lorid< or <)ruit < %lumage. or exam%le, the crested guan 'enelope purpurascens  o) +osta Rica has a red throat %ouch, giving the im%ression that the throat contains a red )ruit o) the t %e %roduced ! the %alms on which the !irds )eed. (he keel*!illed toucan )amphastos sulfuratus  and chestnut mandi!led toucan )amphastos swainsonii   )eeding on the same )ruits have red undertails and !ill markings again closel resem!ling these )ruits. (he &onte:uma oro%endolas 'sarocolius monte*uma  )eeding on these )ruits have red ti%s on their !ills. 0hen the male )eeds the )emale during courtshi%, it is di))icult to know whether he has, or has not, red )ruit %ul% in his !eak #-.David Snow, an avid student o) tro%ical American !irds, was one o) the )irst to link color)ul %lumage o) certain !irds with the )ruit*eating ha!it 14-. Another such student, Steven ilt , agrees with Snows assessmentB <? almost an measure, the most color)ul tro%ical !irds are usuall )ruit*eating and nectar*)eeding s%ecies. (hese are )ollowed in color)ulness ranking ! %artl )ruit*eating!irds, while the legions o) dull*colored s%ecies are drawn mostl )rom the ranks o) insect*eating !irds.< 17-.Not onl tro%ical !irds, !ut also those o) tem%erate regions, demonstrate a correlation !etween color)ul %lumage and the )ruit*eating ha!it. Among the )inch*like !irds in the vicinit o) m home in 3ndiana, those !edecked in red are )re/uentl seen eating red !erries, such as staghorn sumac )hus typhina,  scarlet elder %abucus racemosa,  and hawthorn Crataegus  s%. (hese !irds include the cardinal )ichmonena cardinalis,  rose*!reasted gros!eak <=heucticus ludovicianus<, %ur%le )inch +ar%odacus %ur%ureus, and house )inch Carpodacus me+icanus.  ;n the other hand, !lack*!rown*streaked )inch*like  !irds, such as song s%arrows elospi*a melodia  are seldom i) ever seen )eeding on red !erries. References 1- Darwin, +.A. 1>#1. (he descent o) man and selection in relation to sex. 5ohn &urra , LondonC A.L. ?urt =u!l., 2nd d., 1>#7, New ork.2- 0allace, A.R. 1>>$. Darwinism. 4rd dn. &acmillan, London.4- uxle , 5.S. 1$4>. Darwins theor o) sexual selection and the data su!sumed ! it in the light o) recent research. American Naturalist #2B719*744.7- ingston, R.0.6. 1$44. (he meaning o) animal colour and adornment. dward Arnold, London.8- 5aco!s, &.. 1$88. Studies on territorialism and sexual selection in dragon)lies. colog 49B899*8>9.9- 5aco!s, &.. 1$#>. 3n)luence o) !eta*alanine on mating and territorialism in Drosophila melanogaster.  ?ehavior 6enetics >B7>#*8'2.#- 5aco!s, &.. 1$$$. &r. Darwin misread &iss =eacocks mindB a new look at mate selection in light o) lessons )rom nature. Nature?ooks.>- =etrie, &., (. allida and +. Sanders. 1$$1. =eahens %re)er %eacocks with ela!orate trains. Animal ?ehaviour 71B424*441.$- Andersson, &. 1$$7. Sexual selection. =rinceton Eniversit =ress, =rinceton, New 5erse .1'- Fahavi, A. and A. Fahavi. 1$$#. (he handica% %rinci%le. ;x)ord Eniversit =ress, ;x)ord and New ork.11- Gau)man, . 1$$#. ?ower !ird !lues. Hideota%e- Hideo Nature Li!rar , (hirteenI0N( )or ??+ (H in association with =artridge ilms, xecutive =roducers 5ohn S%arks and &ichael Rosen!erg, =roduced ! +live ?romhall, ilmed ! 6len (hre)lo and Neil ?romhall, 0ritten ! ?arr =aine-.12- =ruett*5ones, S.6. and &.A. =ruett*5ones. 1$>>. (he use o) court o!jects ! Lawes 'arotia.  +ondor $'B84$*878.14- Snow, D.0. 1$#9. (he we! o) ada%tationB !ird studies in the American tro%ics. (he New ork (imes ?ook +o., New ork.17- ilt , S. 1$$7. ?irds o) tro%ical America. +ha%ters =u!l. Ltd., Shel!urne, Hermont. About the Author  1  &erle . 5aco!s is Research =ro)essor meritus in Foolog , 6oshen +ollege, 6oshen, 3ndiana. is !ook r. Darwin isread iss 'eacocs ind: & New /oo at ate %election in /ight of /essons 0rom Nature  was %u!lished this ear ! Nature?ooks. 3n)ormation a!out this !ook 3S?NB '*$998$19*1*8, 27> %ages, hardcover- is availa!le )rom the author at 2217 South &ain Street,6oshen, 3N 79829, ESA merleej@goshen.edu, %honeB 21$ 844*2#29- or )rom the
Search
Tags
Related Search
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks