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   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$19*1*8, 27> %ages, hardcover- is availa!le )rom the author at 2217 South &ain Street,6oshen, 3N 79829, ESA , %honeB 21$ 844*2#29- or )rom the
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