Vlitt.Münch.Ent.Ges. 86 79-98 München,15.12.1996 ISSN0340-4943 Colour polymorphism of Callimorpha dominula (Li.waels, 1758) in Italy, and the problem of polytopic subspecies (Lepidoptera, Arctiidae, Callimorphinae) Von Alberto Zill/ Abstract RelictpopulationsofCallimorphadominula(Llsnaels,1758)fromSicilyarecharacterizedbyindividualsvirtually indistinguishable from those occurring in the Alps and northwards. This is in profound contrast with the phenotvpesfoundinpeninsularItalyfsubsp.personaHlbner,1790).Thenominatesubspeciesbecomes,therefore, a fx>lytopic subspecies. A general revie\%'ofthecolour polymorphism ofthespecies in Italy isalso provided. Following a critical discussion ofsome pathways through which reoccurrence ofcharacters between distant fX)pulationsofasamespeciesmayoccur,particularemphasisislaid uponthepossibilitythat,inspecialcases, thereoccurrenceisnotindependent,asclaimedsofar.Itisputforvvardthatsomecasesofpolytopismmightbe parsimoniouslvexplained consideringtheshifttoward a differentarrayofcharactersofthepojnilationsinter- posed bet^veen others, subject to stabilizing selection. It is suggested that archaic dominula populations in peninsularItalvundervventmelanismandflavism,asnowobser\'edinpersona,andstartedbeinginvolv^edwith a'southem'.Vlüllerianmimicryringbasedonyellowandblackpatterrts.Becauseofthepaucityoftheday-flying mothsbearingthevellow/blackpatteminSicily,duetoalackofcolonizationfromthemainland,thedominula populationsintheislandwouldnothavemettheproperecologicalcontextforundergoingasimilarshift.Abrief discussiononthesubspeciesconceprttriestoshowhovvmisusedthesubspeciescategoryisintaxonomy,notleast becauseofconfusionbetweeninductiveanddeductivep>rocesseswhilecircumscribingsubspeciesanddeficien- cies in the concept itself. Events of character reoccurrence, and hence polytopic subspecies, are belie\'ed to represent a valid reason for abandoning the use of the subspecies category as scarcely informative or even misleading. Contents 1 Introduction 2 TheItalianpopulations 2.1 SituationinNorthItalyandperiphery Z2 SituationinpeninsularItaly 13 SituationinSicily 2-3.1 Literaturedata 232 Helddata 3 Polytopicsubspecies 3.1 Originofcharacterreoccurrence 3.1.1 Ecologicaldeterminismfselection) 3.1.2 En\'ironmentalinductionduringde%'elofmient 3.13 Chance(probabilistice\'ents) 3.1.4 Commongenealog)'(phylogenesis) 3.1.4.1 Geographievicariance 3.1.4.2 Dispersal 3.1-43 "Shift"ofthein-betweenpopulations 4 HowtoexplainthepresenceofnominatedominulainSicily? 4.1 .Melanismandtheshiftred-yellowinApenninicday-flyingmoths 3 Remarksonthesubspeciesconcept 5.1 Polytopicsubspedesandtheiroutshotsonthesubspedesconcept 79 1 Introduction TheScarletTigerMoth, Callimorpha domuiula (Linnaeus, 1758), is a well-known and outstanding western palaearcticspecieswhichhasbeertafavouritesubjectforgeneticalandpopulationalstudies. Infact,after thepioneeristicworkbySTANDFuss(1896),muchresearchhasbeencarriedoutontheformalandecological genetics of domimtla, among the others by eminent researchers such as Clarke, Goldschmidt, Cockayne, Kettlewell, FisHER, FoRD, OwEN, and Sheppard. Detailsonthebionomicsofthespeciescanbedrawnfromseveralsources(e.g.Wenzel1936,Kettlewell 1943, Fisher & Ford 1947, Cook 1959, 1961a, 1961b, 1961c, 1962a, Cook & Kettlewell 1960, Owen 1993, 1994, 1996),howeveritisofinteresttostresstwomainfeatures,namelytheday-flyinghabitsofthemoth (whichisalsopartiallynight-active)andthetendencytoformlocal,isolatedcolonies(Kettlewell1943,Ford 1971).Inparticular,aspotteddistributionofthepopulationsiswell-pronouncedalongpeninsularItaly,the speciestherebecomingdecisivelylinked tomountainousareasasitdoesnottoleratethexericconditions characteristicoflowaltitudemediterranean-typeecosystems. Thecxitstandingpatternoidomuiula(fig. 1)and thewayofbeingdisplayed,e.g.whileflyingorresting uponflowersinthesunshine,areparticularlycharacteristicofadistasteful,aposematicorganism.Thespecies wasinfactshowntobeprovidedwithtoxicsubstances(Rothschild1961,Kayetal. 1969,Edgaretal. 1980) and,accordingly,isrejectedbynaturalpredatorssuchasbirds(Frazer&Rothschild1960,Rothschild1985). According torecentrevisionarywork (Freina & Witt 1987), the EuropeanpopulationsofC. dominula shouldbesplitintofourwelldelimitedsubspecies,namely(fo»H'H///rt(s.str.),powpalisWitsche,'[926,persona (Hübner,1790),andbithynicaStaudincer,1871 Themaindifferencesbetweenthesesubspeciesaresumma- . risedintable1.Exceptforbitln/iiica,theotherthreesubspeciesmeetinNorthernItaly,originatingPolymorphie populationsinthecontactzones(Rocci1913,Turati1919,1923,Kettlewell1943,Cook1962b,E. Bertaccini, in Utt.) (fig. 1). TheremarkabledistributionofthecolourpolymorphismshownbytheScarletTigerMothgivesafine opportunityofreviewingthepuzzlingphenomenon ofthepolytopicsubspeciesand itsconsequencesin taxonomy. 2 The Italian populations Broadlyspeaking,nominatedominulaoccursinNorth-WestItaly,whereasmelanicpopulations(ssp.pompalis Nitsche, 1926) are found more easterly along the Alpine ränge, in the Dolomites and surroundings. Callimorphadominulapersona(Hübner,1790)isexclusivetopeninsularItaly,rangingfromtheTusco-Aemilian Apennines to Calabria (fig. 1). Thepersonaphenotypesgreatlydifferfromthoseoftheothereuropeansubspecies,beingcharacterized byhindwingsandabdomeninwhichtheusualredcolourofthebackgroundisreplacedbyyellowandby much more conspicuous black markings. The melanism of persona is clearly polygenic, in fact several phenotypicclassesalongacontinuumcanberecognized,andintheextremeformstheblackmarkingsare entirelyspreadoverthehindwingsandtheabdomen.Theforewingapexisalsostatedtobemoreacutethan inthenominatesubspecies(Freina&Witt1987),butthistraitissounconstantthatotherauthorsmaintained thecontrary (e.g. Treitschke 1834). Also the forewings areaffected by the melanism, as evidenced by the reduced size of their pale spots, but only to a limited extent. Because of the striking phenotypic differences between persona and nominate dominula some earlier Table 1. Maindifferencesbetween the European subspeciesofCalliinorplm doiuimiln (Linnaeus) currentlyrecog- nized. FW, forewing; HW, hindwing. subsp. FW spots HWcolour abdominalstripe HW melanism domiinila no yes yes no 80 authors even put forward that they reprcsent two distinct species (e.g. Esper 1794, Boisduval 1834, 1840, Tkfitschke 1834, Dui'Onchei, 1836, Herrich-Schäffer 1845). Kettlewell's (1943) credit is to have critically weighted thetwoalternativehvpothesesabouttheconspecificityoidoiuiiuilaandpcrsojinthrougharemark- ablyelegantreasoning froma methodological Standpoint,which isherebrieflysummarised. Objecti\'elv,someevidencewouldagreewiththeexistenceoftwospecies,aboveallthelowfertilityand larval \'iabilitvoithecrossesdoiniiniln (s.str.) x persona,aswell astheassortativematingsoccurringwhen doiiiiinilii (s.str.) males are given the choice between both types offemales (Standfuss 1896, Goldschmidt 1924). Ün theotherhand, theoccurrenceoverlargeextensionsofNorth Italyofpopulationsinwhichthe diagnosticcharactersofpersoiiti, i.e. melanismandflavism,arenomorelinked isdefinetelyunsubstantial withtheexistenceofmorethanonespecies(Kettlewell1943).Asamatteroffact,polymorphicpopulations with yellow unmelanic individuals are known in both the western and eastern districts of North Italy (Piedmontand Friuli),whercasponipalifipopulations,inshort'redpersona ,occurovermostofthecentral- eastern Alpine sector (Rocx 1913, Nitsche 1926, Dannehl 1928, Kettlewell 1943, Cook 1962b, Freina & i Witt1987).Lastbutnot\east,doniinulamalesareinanycaseattractedhypiersonafemales,wheneverdonü)nda femalesshouldbeabsent,andcopulatewiththemproducingsomeviableoffspring,alsoobtainablethrough the reverse crosses (Kettlewell 1943). Owing to thescantydataavailable,itcannotbeascertained whethertheassortativematingsbetween doiiiiniilaandpersona,aswellasthelowerfertilityoftheircrosses,revealtheoccurrenceoftwodifferentiated evolutionarylineages.TheSituationmightinfactrepresentnomorethanasimpledistanceeffectindependent ofthesubspeciesidentifiedbytaxonomists,e.g.acaseofoutbreedingdepressionComingoutfromthecross of differently coadapted genotypes sampled from distant populations (cf. Oliver 1972, Endler 1977, Templetonetal. 1986).ResearchonthecourtshipbehaviouroftheScarletTigerMoth,involvingacomplex arrayofVisual,chemicalandacousticSignals(cf.Brakefield&Liebert1985:238),andcrossingexperiments betweensamephenotypes(e.g.dontiniila xdonüntila)fromdifferentareaswouldbedecisive.Interestingly, someexperimentsonmatechoiceinadominulapopulation from England evidenced preferentialmatings betweendifferentgenotypes(Sheppard1951, 1952,Sheppard&Cook1962,Ford1971),beingoneofthefew known cases of disassortative mating (Partridge 1983). DespitetheremarkableamountofworkonthegeneticsoidoininnlainEngland,althoughcontradictory (e.g. Cockayne 1928, Kettlewell 1943, Fisher & Ford 1947, Wright 1948, 1978, Sheppard 1951, 1952, 1953, 1956,Kettlewell1952,Cook&Kettlewell1960,Williamson1960,Sheppard&Cook1962,Ford&Sheppard 1969, Lees 1970, Ford 1971, White 1985, Jones 1989, 1993, Clarke et al. 1990, 1991, 1993, Owen & Clarke 1993, Owen & Goulson 1994), far fewer data are available on the colour polymorphism of the Italian populations.Frommuseummaterialitisevidentthatmanyamateurshadjustcrossedspecimensnorthand southoftheAlpstoobtainbeautifulhybridsfortheircollections.Howevermorerationalapproacheswere followed by Standfuss (1896), Oberthur (1911), Goldschmidt (1924), Cockayne (1928) and Kettlewell (1943). Unfortunately, most of the experimental crosses were partial or with contradictory results, so a thoroughpictureofthegeneticsofthecolourpolymorphisminItalyisstillwanting.Itisnottheaimofthis paper to summariseagain the old data available (cf. forreviews Cook 1962b, Ford 1971, Robinson 1971), ne\'ertheless,attentionshouldbefocusedonthenormalredcolouroidominulawhichisseeminglyincom- pletelvdominantovertheyellowoftheItalianforms(thetrueSituationbeingprobablyquitecomplex),while thegeneresponsiblefortheyellowaberrationsoidoiniiiiila(s.str.),occurringthroughoutthespecies"ränge, behavesasttHallyrecessive.Itremainstobeascertained,therefore,whetherthegeneresponsibleoftheyellow oftheItalian formsisactuallydifferentfromthedominulayellowgene,assuggestedbyKettlewell(1943), possiblymorethanonegenebeinginvolved,orthediscrepancymaybeduetodifferentialexpressionofthe samegeneindifferentiatedgenecomplexessuchasthoseofdistantpopulations,asmootedbyFord(1937). Regardingthemelanismoipersona,thetraitisfairlywelldescribedbyincompletelydominantgeneswith additiveeffectsinatwo-lociSystem(Goi.dschmidt1924).However,Kettlewell(1943)stressedthedifference betweenyellowdominulaandunmelanic/vrsoHrt,namelytheenlargedblackdorsalstripeoftheabdomenof theiatter(oftenblackeningtotallytheurites),and referred tothatcharacter,exclusivetomostoftheItalian populations, as a "primary melanistic factor". This factor is usually associated with 'secondary" ones, i.e. thosedarkeningthehindwings,butitisinheritedindependently. Owingtothegreatvariabilityofthespecies,affectingalsomanyothertraitssuchasforewingSpotting (e.g.number,shape,size,colour,etc.),severalauthorstriedtodistinguishbynomenclatureanykindofform (cf.Biok1937).Thenameswereoftenmisapplied,sometimesconferringtoanindividualaberrationtherole ofa geographical raceor,converselv,applvingthenameofa localracetovaguelyresemblingaberrations collectedelsewhere.Othersourcesoferr(.)rswerehonnMiymsusedtodepictdifferentforms,misidentifications 81 and iipplic.ilion Id wild spriimtMis ot iiiimcs llic iisc ol wliu li slioiiKI li.uc hfcn icstrirlcd lo l.ibor.ilory liybrids.Theni.iincdiisciuicikristh.il i(is.idillu iill l.iskI(hI.i\' lolr\'locliuul.ilclowImlipliciiolv|>u il.isscs Ix'lon^i'dspcvinuMisivported ini.uinislii-liU'r.iluii-vviliioiil.ulc'(.|ii.ilc'iiluslMlions. I orIhcs.ikcolclcirnossit isliu'ivlorrsii^^i'stedavoidingusingnamesotIhctornisand lodircvllyivlatt'lotlu'irmorphologicalIvaliires. Morc'ovt'r,niislabellingotbredsptvinicnspivscrvfd inmuscums,parliciil.ulv inthocaseofaiiilicialhybrids (o.g.lrc>ating(/(ij/;/;;////; xjH'l^solun^sil Ihcywcrccolk-ttt-d inUu-wildorinllu'[iLufol ivsidencool tlu'bivt'dcr), is also sonii'lhin;!, llial [HCJiK-litrs a tari'hi! appiriiaiion ol llu' atIn.il dislnbiilion ol Ihf rolour loinis. 2.1 Situation in North Italy aiui [icriphory Asatistactorypictiireofthecok)urpolyniorphisniinNorlii It.ilywillhcprt)bablyncverattainedasihfciirrent patti'rn ot gcographic Variation siiggusts coniplcx ilynaniics in spacc ^nd tinic. Ihe dislribiilion of thc nu'l.niisni,inparticnlar,isclcarlymosaic-likoinaspatiallyiH'ti'rogiMU'ousaroasuchasthatotthosouthorn Alps.Wetindpolymorphicpopulationswithspecimcnsrangingtroni mn-mMdoiiiiiiuln[opoiiipnliseastand westofthecoreareaoftheso-calledssp.paiiipnlis(e.g. iTiiili; I.onibanlia aml Ticino). Asonemightexpect, normaliloiuiiiiiliidoalsooccnrwithin therangi>of/'(i/;;/'/(/;s(Danni in l''?.S,('ook l%2b)and viccversa, i.e. pi'iiipuli:. phi'holypes weil t)nlsid(' ils piilaluc iani',f (Tukaii (^ Vikii^ \'->\'1, \\. Hi kiai i ini, in liü., A. /ii ii pers.t)bs.in Liguria).pA'eninthepopulationselearlyreterabletont)niinale(/()»/;///////honi l'iednionl,nul l'riiili a number of the individiials show one or nioreof Kini iwii i's melanistie laelors. Regardingthered/yellowpolymorphism,yellowspccimensha\'eollenIh'i'iireportedtromi'iedmontand l.iguria CruKATi & Vfritv 1'^)12, Roh i 1913, Ki rriivviii \94^) anii .uf so Ireqiient in F-riuli that yellow monomorphic populations aic llie rnle lor nian\' .neas (C'iuik I''(i2b, C . Mokandini pers. conini.). Iti.^nalsobenoted thatallIheunniel.iniespt'iimiMissoulhol IheAlps,whencompared tosamplesnorth ol Ihe alpnie ränge (e.g. North Swil/erland, Haxaria), show soine redn(lioii ol Ihe si/e ol lorewingspots. C oneerning thesituatimiofcolom^polvniorphism in areas pi-ripheral to italy, mostol thepopulations correspond to the nt)minate subspeeies. II niighl be worth noting, however, that specimens with golden forewing spots are reported froni Wallis (Ki i ii i\\i i i l'*4.'^) and in part of Slovenjia orange hindwinged individualsare prosent. Thespecies has also beeii re|>orled in C'orsiea (I'kiina & Wii r 1487: h3\), but this datuni has not been confirmed by Runc;s (19HS). lhuler llu'secircumstancesitshould berlear how niisU'.ulinr, Nie naniingot subspeeiesis fora eorri'it iippreeialion ot thegeographic wiri.ilion ol IheSiark't liger Molli in n.ilnri', 2.2 Situation in peninsular llaly Roughly south oftheTusco-Aemilian Apenninie watershed the Situation is i|uite simple, as only persona phenotvpi'SarefounduptoCalabria (e.g.Cosia IS42,Stani)iuss ISSS,C'ai hi ki \ ISS7,SiAnnFk 1916,Fki:ina i<i Wii I \'-)H7,ßikiACClNietal. 1994). Differeneestlohowt'vi'riKiurbelween po|>iil.ilions.isloIhi'Irequeney ot the various melanistie morphs. Despitesomeredorreddishspecimenspreser\eil in publii aiul prixaleiollections,cleare\ick'nu'ol .mv of such individuals collected in the wild south of the very northern Apennines seemingly exists only in StaljhI'R's (192.^) report. This was believed by Kiniii':wi1 1 (1943) to ri'(-iresi'nt a new mutation. The rare occurrence of reddish specimens due lo norlhein alleles in peninsiiLn lLil\ is, oii Ihe contrarv, well in agreementwithpopulationalthinking. 23 Situation in Siciiy Iherecent rediscoveryofpopulationsol IheScaiiel 1 iger Molh inSuilvga\i'im|-ielusloi'xaluatecritically Ihe theori'ticil problems ot Ihe pt)lvlopic subspi'ciesand ol Ihen laxonoinu licalnu'nl. 82 2.3.1 LilcTdlure data Asbasc'd on litcrature,onlyonespccimciiofthcScarlct Ii^crMolh liad cvcrbecnCDÜected withcertainty in Sicily (Makiam 1937). Mowuvlt, pcrsoini had becn generically rL'ported forSicily by Dui'onc iihi. (18%), Spui.kk (1906) and Kirniwi.ii. (1941), all of whom sccmingly madc rufcrcncc to Hsi-i.k's (1794) and Ti<ii- TSCHKi's(1834)quotations.Neverthclcss,thercisslrongcvidcnccthat,ashappened ina longlistofnominal taxa, thcauthors wereconfusingSouth llalyand Sicilybccausctheseregionsonccjointly bclongcd tothe SingleKingdomofthetwoSicilies,beingnonethelessknownalsoasIheKingdomofNaplcsandtheKingdom ofSicily. TKiiiTscuKi- (1834) did notexplicitlyState thatpersona wasoccurring in Sicily, but that thedealer G. Da(ii obtaincd somespecimensbredexlarvaeafterhisexpeditionsinSouth ItalyandSicily("inNeapel und Sicilien"). TheexactcollectingsiteofDaiii. istherefore unknown. Asa matteroffact, nospecimen in Tki.nstiiKi.'scollection(Natural IlistoryMuseum, Budapest)islabelled"Sicilien"asotherspeciescollected byDaiii.inSicilyared..Ronkay,inlitt.).Hi;iiMi<(1790,quoted byOiiiimiiik,1911),whoapparentlyexamined the same material in coli. j.C. Gikninc, (Frankfurt) like Esru< (1794) did later, was more precise in stating thatthespecimensofpersonahad beenscntfrom thedistrictofNaplestoFrankfurtbytheKingandQueen ofthetwoSicilies. ftisimportanttonotethatnospecimeno(personafromSicilyhasbeenfound uptonow in theNatural History MuseumofVienna, wherethematerial byGi-kmnc. ispreserved (Hoknetal. 1990). Makiam's (1937) record is froma beechwood ofM. Soroat m 1700a.s.l. in the Nebrodi ränge (North- WestSicily).Thisrecord waslargelyoverlooked duetoboth thescantycirculationoftherelevantbulletin andMakiam'smisidentifications.Thisled thesingletontobelinked tossp./^r'rso/w,sinceatthatümL-persona wasprobablyacriticallyconsidered asthevalid nameforeverypopulation southoftheFo Valley. In fact, Makiam(1937)firstidentifiedthespecimenasro/z/rt/zoi'/(nameofsomehybridst/()/»;;/»/rt x persona),and later considered it to represent a variety of persona (Makiani 1939, and specimen's label). Contrary to the expectations,thatspecimen(preservedinMuseoCivicodiStoriaNaturalediTerrasini,prov.Falermo)fully conforms to nominaledominula, asalsoevidenced by Mariani's (1937) description and illustration. 2.3.2 Field data Recently,severalspecimensoftheScarletTigerMothhavebeencollectedinSicilybyS.Btu.A,E. Bektaccini, G. FiLMi, B. Giandolio, W. Hocems,and F.F. Romano, all from Nebrodi Mts, and correspond todoniinuln (s.str.) (e.g. Bektaccini et al. 1994). Asa matteroffact,theSicilianspecimens,beingcharacteristicofthenominatesubspecies,arenotonly 'taxonomically' unrelated topersona, still present in thesouthernmost tip ofCalabria (Sialuek 1916), but alsototheothertwored-hindwingedsouthernsubspecies,vi'/..ponipalisandhithyuiai.Therängei)hiominula (s.str.), hence, passes over peninsular italy and includesSicily (at least some part of the Island), For that reason C. dominula dominula (Linnaeus 1758) becomes a polytopic subspecies. Lastbutnotleast,theSicilianspecimensshowtraitscharacteristicofdominulanorthoftheAlps.Infact, featureslikethewideforewingspots,theverysmallblackspotsofthehindwingand theextremelynarrow black abdominal stripeareall unusual characteristics forany dominula population from .\'orth Italy. 3 Polytopic subspecies In a polytypic species, a subspeciesshould bedefined as polytopic when it reoccurs in widely separated areasamongwhich populationsbelongingtoothersubspeciesarefound.Suchareoccurrenceissaidtobe independentaccordingtoWilson & Bwjwn (1957), Mayk (1963)and Mayk& Asm/xk(1991). In particular, Mayk(1963)States:"...Thedistributionofthesubspecieswillbedeterminedlargelybythecorrelationbetween thediagnosticcharactersand theenvironment;consequentlytherängeofa subspeciesmaysometimesbe disct)ntinuous (polytopic subspecies).". Successively Mayk (1969) writes: "...it may happen that several unrelatedand moreorlesswidelyseparated populationsacquireanidentical phenotype.Theevolutionist knowsthat such populationsare not identical genetically, butsincethesubspeciesis notanevolutionary concept,taxonomistssometimescombinesuchvisuallyidenticalpopulationsintoaSinglesubspccifictaxon. Suchageographicallyheterogeneoussubspeciesiscaliedapolytopicsubspecies.Theonlyalternativetoits recognition is not to recognizeany subspecies in sucha species.". 83 In modern evolutionary biology the subspecies concept is generally thought to have outlived its usefulness (e.g. Wilson& Brown 1953, Minelli 1994),beingofsomeuseonlyfortaxonomicconvenience, e.g. in the Classification of population samples (Mayr 1969), to depict cases of categorical geographic Variation(Thorpe1987)orsubjectivelyperceived partitionsofcontinuousvariability(Cracraft1992).The conceptual difficultiesengendered by thetraditional subspeciesconcept led Böhme (1978, 1979) to revisit it from an ecological pointofview, aiming atestabUsliing a new role, possibly more linked to the reahty ofbiological phenomena. Alternatively,sometaxonomistsrefused a priori thesubspeciesasa taxonomic categorywithoutnatviralcounterpartinthewild (e.g.Poole1989).Nevertheless,thestudyofintraspecific geographic Variation is of great evolutionary interest. Within this context, a rather neglected issue is represented by thecharacterstates (hereafter 'characters', forthe sake ofbrevity) which are only shared by distant populations ofa species. 3.1 Origin ofcharacterreoccurrence It is evident that only the polytopism of the characters can be observed in nature; any reference to subspecificentitieswould infactrepresentanabstractionsubjecttoseverecriticism(e.g.Wilson&Brown 1953). Therefore,forthesakeofnaturalness, thepresentsectionischieflydevoted tocharactersand their States.Nevertheless,toalloweffectiveextensionofanycommenttothesubspeciesproblem,thediscussion is restricted to characters discontinuously varying on a regional scale (e.g. Leucodonta bicoloria [Denis & Schiffermüller],1775,acrossthePalaearcticRegion,cf.Schintlmeister1989),eventhough,possibly,through transitionzoneswithpolymorphicpopulationsorintermediateindividuals.Infact,imderthesecircumstanc- esthegeographicrecjuisitesnecessaryfordelimitingsubspeciesareclearlymet.Aimingatcircumventingthe conceptualandoperationaldifficultiesforsubspeciesrecognitiondueto theexistenceoftransitionzones, it is worth noting the arbitrary proposal of the so called 'seventy-five per cent rule', that is to say the recognition of different subspecies in case at least 75 % of the individuals of adjacent subspecies are determinable (Amadon 1949). Inothercases,thedistributionofdifferentmorphscanbemosaic-likeaccordingtotheunevenpresence ofsomealternativeecologicalfactorsonalocalscale(e.g.f.staticesandf.henseriofProcrisstaticesLinnaeus, 1758,cf.Reiche1964,Alberti1978,Tarmann1979).Suchatightcorrespondencemaybedueeithertodirect habitat selection by the relevant genotypes, or to habitat correlation induced by external agents (e.g. differentialpredationonalternativephenotypesaccordingtotheenvironmentalpatcheswhicharechosenfor resting,environmentalinduction,etc.)(Weins1976,Aldridgeetal.1993,Jonesetal. 1993,Fraiersetal.1994). Intheextremecasestheseprocessescanevenleadcontiguouspopulationstoshowsharpdiscontinuitiesas tostrikingcharacters,butthecanonicalgeographica!requisitesfordelimitingsubspeciesareclearlymissing. Fromatheoreticalpointofview,anywithin-speciesreoccurrenceofcharactersindistantpopulationscan be due to: ecological determinism, environmental induction during development, chance, and common genealogy.Suchcauseswillnowbereviewedseparately,althoughJointpresenceoroverlapsbetweenthem might theoretically occur in nature, not least when more than two sites are involved. 3.1.1 Ecological determinism (selection) This point corresponds to Mayr's (1963, 1969) idea. The independent evolution of identical traits due to similarselectivepressuresisarathercommonphenomenonand mostofthetaxonomists" polytopicsub- speciesderivefromthiskindofevents.Kudrna(1977)definesthesamebasicphenomenonas "pseudopoly- typism", hopefully tocircumvent theconceptual problems arising when a taxonomist finds itdifficult to make a decision. Almostanycharacterisapossiblecandidateforpolytopism,includingphysiologicalandbiochemical ones.However,theeffectsofecologicaldeterminismareeasilyobserved incertaincrypticmothschoosing stones forresting which, matching with the local rockcolours, may show recurrent "adjustment toback- ground' (cf. Ford1955) (e.g. speciesundergoingalbinism when theysettleincalcareousorchalkyareas). Amodelfortheevolutionofphenotypicsimilarityiswellrepresentedbysomebark-camouflagingspecies thatindependentlydevelopedmelanicpatternsinseveralindustrializeddistrictsofEurope(cf.Kettlewell 1973). Episodes of altitudinal or thermal melanism (Mani 1968, Kettlewell 1973), if not exclusively due to environmental induction, can also produce similarity through selectionistic processes (e.g. between separated mountain populations in contrast with lowland ones). 84 Character polytopism, determined by Community differences between areas, can occur in Batesian mimics,vvhene\'ermatchingwithdifferentmodeis,oreiseMülleriancomimics,possiblyfollowingdifferential selectionassociated with changesofthe abundance ofthedifferent pattern types in which thecomimics themselvesareinvoh'ed. Theselectionresponsibleofthecharacterreoccurrencemavacteitherondifferentgenesproducingan equivalentphenotypiceffectoronasameunit(e.g.ararebutvvidelydistributedallele)whichistherefore fixed in two ormore distantareas. It is noteworthy that many earlierauthors admitted that phenotypes characteristicofparticulargeographicracesoccurredelsevvhereasaberrationsacrossthespecies"ranges.An excellentaccountonthedilemmabetweenhomologousandanalogousgenesdeterminingcharacterreoccur- rence within- and between species is Lattin's (1961). 3.1.2 Environmental induction during development Totalh' different kind of environmental intluences capable of leading to phenotypic similarity between separatedareasisex'idencedbvtraitswhichrepresentproductsorbv-productsoftheinteractionbetween genesandexternalfactorsduringtheorganisms"de\elopmentalpathways.Themorphologicalresponseto environmentalStimulicanfallwithinthelimitsofthenormofreactionofgivengenotypesorrepresenttrue phenocopies,i.e.developmentalaberrationswhichoftenresemblewildmutantsorphenotypesparticularto specialregions(Nijholt1991).Laboratoryexperiencesdemonstratedthepossibilityofobtainingimagines resembling thoseparticulartogivenregionsbymanipulating parameterssuchaslight, temperatureand humidity(Standflss1896,Kohler&Feldotto1935,Robinson 1971).Depositionofmelaninaswellasother pigmentsisoftencorrelated withphotoperiodicresponseorfluctuationsofotherfactors(Vltllalme1969, Watt1969,Hoffnlann 1973,Kettlewell1973,Shafiro1976,Douglas&Grlla1978,Br.akefield&Mazzotta 1995).Similarly,thepresenceortheabsenceofgivensubstancesinthedietcandeterminedramaticphenotypic effects (PiCTET 1905, Wigglesworth 1972, Wilson 1985, 1986). Therefore, should therängeofspecies show aparticularshape,thereoccurrenceofagivencharactermightbeduetodifferentialexpression(switching, penetrance,etc.)ofgenesaccordingtoexternalfactorsvaryinggeographically,sothatsimilarepiphenotypes are locall\" produced on a scattered basis. 3.1.3 Chance (probabilistic events) Althoughstochasticeventsshouldalwavsbeconsideredaspossibledeterminantsofbiologicalphenomena, the probabilityofcharacterpolytopism exclusively due to chance appears decisivelylow. An accidental arousal ofa trait common to otherpopulations might theoretically happen in a popuIation (concordant mutation).However,thatcharacterwillbelikelytofacedifferentselectiveregimesbecauseofthediversity ofthe relexant ecological scenarios. Accordinglv, should that character increase in frequency and attain fixation,morelikelvecologicalexplanationsshouldbetested,unlessitisaneutralcharacter,viz.notaffecting theadaptivelevelsofitsbearers. Hvpotheticallv,neutralcharacterscouldpersistinsomepopulationsand e\enattainfixationbvgeneticdriftor,followingthedifferentrouteoffounder'seffect,anewcolonycould originate frombearers ofthemutant trait. Thereare, however, conceptualand operational difficultiesin establishingwhetherornotonecharacterisadaptive.Inanycasegeneticanalysesshouldbecarriedoutto ascertainthepossibilitx'oflinkagebetweentherelevantgenes(possiblvevenslightlydisadvantageous)and othersgreatlyenhancingthefitnessofthebearers(e.g.somephvsiologicaltrait),inwhichcaseselectionists hypotheses would again explain the phenomenon (cf. Koiima & Lewontin 1970). Contrarytoa longheld opinion,thereissomeevidencethatgenitalicpiecesnotinvolved inlock-and- keymechanisms(orinchoosingsubstrataforo\iposition)donothaveahighadapti\esignificance(Cesarom etal. 1994),beingcomparativelvfreefromfunctionalrestraints.Therefore,toacertainextenttheyshould be unaffected by strong selective pressures such as those modelling other characters, e.g. wing pattern characteristics, which areamongst the most important ones in relating an indi\idual to its environment (abiotic,biotic,andsexual).Therefore, thevcould theoreticallvbeselected tofeststochastichypothesesof characterreoccurrencebetween distant populations. However, this would requiretheexistenceofsharp discontinuityinthegenitaliabetweenadjacentpopulationsofthesamespecies,whichisinconflictwithbeing recognizedasconspecific.Infact,duetotheclearh-polvgenicnatureofsuchmorphologicaltraits,anyabrupt gapbetweenmorph typesprovidesindirecte\idenceofgeneticdivergenceofacertainextent. 85 3.1.4 Commongenealogy(phylogenesis) Thepossibilityofcloserkinshipbetweensomewidelyseparatedpopvilationsratherthantheneighbouring onesisnotnecessarilyinvalid.ItfoUowsthatthereoccurrenceofcharactersisnotindependent,asclaimed byWilson&Brown(1953),Mayr(1963,1969)andMayr&Ashlock(1991),butderivesfromatightergenetic and phylogeneticcontinuityatinfraspecificlevel. Atleastthreemodeiscanbeproposed. 3.1.4.1 Geographie vicariance Sharingthesametraitswouldbetheresultofpastgeneflowwithinonegroupofpopulations,uponwhich ordinarybiogeographiceventsactedbyfragmentingitsrängeandallowingthederivedsubgroupstocontact otherconspecificpopulations. From theoriginal groupofpopulationsderivetwoormoreseparatedsub- groups,scatteredinacontinuumofconspecificbutlesserrelatedpopulationshavingexperiencedpartially differenthistories.Theclosergenealogyamongthesub-groupsisinferred,indeed,bythecharacterswhich remain shared, at least for some time. 3.1.4.2 Dispersal When long distance dispersal is taken into account, the possible Constitution of a polytopic complex is evident. For example, following prevailing wind directions a given territory canbe colonized notby the nearmostpopulations,butbyindividualsfromdistantpopulationswhichthenceintroducethecharacters oftheirown population (founder'seffect). 3.1.4.3 'Shift' of the in-between populations Itisunnecessaryalwaystoinvokemovingindividualsorcomplexrängedynamicstoexplainnon-independ- entcharacterreoccurrence.Givenageographiccontinuumofhomogeneouspopulations,apseudovicariant pattern may arise from the shift of the middle ones toward a different array of characters, with the populationsatbothextremitiesremainingunaffected. Thephenomenoniscomplementarywiththeoneaccounted forbyecologicaldeterminism,although decisivelymoreprobable.Infact,insteadofbeingtwodistantgroupsofpopulationsconverginginresponse to similar selective pressures, it is the group in-between which undergoes changes because of different ecological conditions. Ecologystill playsa majorrole,butdoes notproduceindependentpolytopismbut rather the diversification of some populations interposed between conservative ones, at the same time becomingapolytopiccomplex. Underthesecircumstancesitisafruitlessdiscussiontoseparatepaleoeco- logicalfactors(i.e.historicaltypes)fromcurrentecology,asthisdistinctionhindersthetemporalcontinuity ofasamephenomenon.Aprogressivelychangingecologicalbackgroundallowsboththeshifttowardnew characterstatesand theirmaintenance. AsimilarreasoningwasfollowedbySheppardetal.(1985)whilereconstructingthehypotheticalancestral pattern of Heliavüiis mclpoiuciic (Linnaeus, 1758) and H. craio (Linnaeus, 1758). The authors rejected consideringthepatternsoccurringintheAmazonbasinasancestral,notleastbecauseofthesimilarityof patternsbetweenpopulationsnorthandsouthofthatbasin.Infact,ifthissimilarityhadbeenindependent, it would have required admitting highly improbable phenomena of convergence and assuming, if not independent,dispersaloverthousandsofkilometresalongtheAndeanrimofthebasin.Sheppardetal.(1985) parsimoniouslyconcludedthattheAmazonianpatternsweresecondarilyderivedandtheextra-Amazonian onesclosetotheancestral. 4 How to explain the presence of nominate doininiiln in Sicily? Itshould benoted thatauthoritativediscussionson thepolytopicsubspecies (e.g. Mayretal. 1953, Mayr & Ashlock1991)did noteventakeintoaccountthepossibilityofcharacterreoccurrenceinmorethanone character, since reoccurrence of more characters would have represented a probabilistic and biological nbsurdity.TheclosematchingbetweentheSicilianandnorthernspecimens,whencomparedtopersona,is thereforeparticularlysurprising,whenconsideringthenumberofthecharactersinvolvedand thedegree ot their genetic/ontogenetic independence (hindwing background colour, width of theabdominal black stripe, hindwing mclanism and width ofthe forewingspots). Thorpe (1987), in fact, hasproperlypointed outthatwhilestudyinggeographicvariabihtytheactualcongruenceofdifferentcharactersisofvalueonly if they are geneticallv/ontogenetically independent. Moreover, with characters mutually independent, liighlevelsofcongruencebetweensamplesfronidistantareaswouldsuggestunderlyingvicariance-events asresponsible(viz.phylogenetickinship),whereaslowcongruencewouldindicatecontrolbypresent-day ecological factors (Thorpe 1987). ToInterprettheoccurrenceofdoiiiiiiiila phenotypes in Sicily, what is known about thegenetics ofthe colour forms and the presence of pcrscvuj phenotvpes in the southernmost tip of Calabria immediately permitdiscardinganyhypothesisofenvironmentalinduction.Stochasticexplanationsarealsohazardous, asthecharactersinvolvedaresomanv-Therefore,assuminganarchaicpresenceoipersonaontheNebrodi Mts, to return back to nominate doniiiiula would have required too many character reversals. Nevertheless,according tothecanonicalworkinghypothesisforthecharacterpolytopism,analogous selectiveregimeswouldhaveengenderedtheproperecologicalcontextforsuchcharacterreversals.Forthis tobetrue,itwouldhaverequiredsuchmarkedecologicalsimilaritiesbetweentheSicilianbiotopesandthe main Europeanpartofthespecies' rängethatallthetraitscharacterizingpersonawouldhavebeensubject to strong directional selection to obtain a "new' donünnia on the Island. Nonetheless, the number of the charactersinvolved,aswellastheirgenetic/ontogeneticindependence,makeagainapreciseturningback todo)ninnln fromperso)iaa highly improbableevent. As for the remaining hypotheses, the proposal ofa vicariance model would require an exageratedly complicated theoryofcrustalmovementsand landbridges,notsupportedbythetertiaryandquaternary geological history ofthe Central Mediterranean (cf. Azzaroli & Cita 1980, Catalano et al. 1995). As the ScarletTigerMothisabsentinthecentralandsouthernIberianPeninsulaandthewholeofNorthAfrica,a colonization of Sicily from the south can reasonably be excluded. The species is also absent from other Mediterranean islandsand in the Hast Mediterranean itshowsa differentcombination ofcharacters. The possibilityofaccidentalintroductionisalsolessened,astheSicilianrecordsarenotfromcoastalareasnear portsandtowns,butfromwellpreservedinnermountainzones. Itshouldalsobenoted thatthelarvaedo notfeed upon treesused inreforestation. Accordingtothe'shiftofthein-betweenmodel",theNebrodipopulationswouldrepresentthedescend- antsofnormalredunmelanicdominulawhich,spreadingfromthenorth,colonizedwholepeninsularItaly andSicilv.Infact,severalnorthernspeciesreachedSicilythroughtheApenninicrängeandcurrentlysurvive ontheIsland"smountainmassiveswithrelictpopulations.OncethecolonizationofSicilywasassessed,it wouldhavebeentheApenninicgroupofpopulationsthatdiverged,givingrisetoVnepersonaphenotypes. Therefore, instead ofclaiming highly improbable theories in order to Interpret the presence ofnominate dominulainSicily,thequestionbasicallymovestotheoriginofpersonainpeninsularItaly,amoreparsimo- nioushypothesiswhichwillbetentativelvdiscussedinthenextparagraph. 4.1 Melanism and the shift red-yellow in Apenninic day-flying moths TheoriginoipersojwinpeninsularItalystillneedsadequateexplanation;nevertheless,somebizarrecongru- enceswhichoccurintheApenninesthrowsomelightonthephenomenon.IntheItalianPeninsula,infact, two otheraposematicday-flying mothsreplaced an archaicred/black-unmelanic pattern (R/m), widely spreadinthenorthernareasoftheirranges,withayellow/black-melanicone(Y/M),namelyZi/gaenaephialtes (Li.WAELS,1767)andZ.transalpina(Esper,1782).ThefactthatinbothspeciestheY/Mpatternismorerecent thantheR/monecaneasilybeinferredthroughoutgroupcomparisonwiththepatternscharacteristicofother Zygaenaspecies,particularlvthosemorerelated phvlogenetically.Asamatteroffact,bothZygaeiiadori/enii OcHSENHEiMER, 1808 (sister species of Z. ephialtes) and Z. angeticae Ochsenheimhr, 1808 + Z. hippocrepidis (Hüb.ner, [1799]) (making up an Artenkreis together with Z. transalpina) (cf. Naumann & Tremevvan 1984, HiLLE & Naumann 1992) show the pattern R/m. In Zygaena ephialtes thearchaic R/m pattern is widespread from Francetocentral Asia, even though populationswithindividualsbearingaY/mpatternarefoundoccasionally.WiththeexceptionoftheTurkish populations(R/m),themelanicpatterns(R/MandY/M)arecharacteristicofthesouthernpartofthespecies" ränge,fromSpaintosouthernRussia. However,thefourmainpatternsoiephialtes(R/m,R/M,Y/M,and. 87 scarcer, Y/m) coexist over large extensions, the species showing also many more types of pattern in particularcontactzones,e.g. intermediatemelanicsororangespecimensduetomultiallelism withdiffer- ential penetrance and the disruption ofdifferently coadapted genotypes (Bovey 1941, 1966, 1983, Reichl 1958, 1959, Dryja 1959, Bullini et al. 1969, Gabriele 1990). As for Italy, the Situation is rather simple throughout the peninsula. Apart from some "relictuar presenceoftheR/M pattern inNorthTuscany(Verity 1930),allalongtheApenninesmonomorphicY/M populations occur (the polymorphism relevant to the number of forewing spots not being considered here). Thedistribution ofthe colourpolymorphism in North Italy is more mosaic-like, with Y/M, R/M, and, occasionally in the western Alps, even R/m populations (Gabriele 1990) (fig. 2). TheSituationoiZygaenatransalpinainItalyis,onthecontrary,remarkablycomplexasthecontactzone between northern (R/m) and southern patterns (Y/M) is somehow streaked along the Apennines. R/m patternscharacteristicofcentralEuropeandtheAlpsdoapproximatelyoccurovermostofNorthandCentral ItalyuptotheTiberValley. Itisnoteworthythat,likeiordojuimila,inFriulipolymorphicpopulationswith red/yellow and unmelanic/melanic individuals occur (Reiche 1962, Bovey 1981) (interestingly, in the surroundingsofTarnovaalsoZ.tvigclicncshowspopulationswithabundantY/mindividuals,L.Morinpers. comm.).FromCentralItalysouthwards,theR/mpatternbecomesprogressivelyrestrictedtoinnermountain andeasternzones,leavingoutthewesternpartofthepeninsula.Accordingly,Y/Mand R/Mpatternsare increasinglyfrequent from thewestern hillsofcentral Italyto themountains ofSouth Italy (fig. 3). Because of the spacial heterogeneity due to the orientation of Apenninic ridges, Isolation effects or geographicallyasymmetricgeneflow,aswellasthepolygenicnatureofthemelanismandmultiallelismfor backgroundcolouration(Bovey1981,Reiche1992),eachtransalpinapopulationshowsinpracticeapeculiar combinationofphenotypic freciuenciesofcolour forms. Highly polymorphic populations with all sortof intermediatesareparticularlyfrec]uentalongthesouthernhalft^fthePeninsulawherethetwomainbulks ofpopulations meet. Twomoreaspectsdeservefurtherattention,i.e.thepresenceofR/Mpopulationschieflylinked tolow altitudeareasfromLiguriatoTuscany,similartomanyotherspeciesofZi/gaena,andmainlyconsistingof stout-bodied individuals (Costantini 1916, Verity 1930, Burceff 1951, Alberti 1971), and of relict R/m offshoots ofthese populations in somelittoral localities ofcentral Italy. Despitethecomplexity ofthecolourpolymorphism ofthe Italian transalpina, thereislittledoubt that theY/MpatternsrepresentapurelysouthernSituation,thepresenceofyellowandofmelanicphenotypes beingpositivelyassociated with warmerand southernareas. Thisisalsodemonstrated bya transectina favourable area at the border between Latium and the Abruzzi, where two parallel mountain ridges, respectivelywestandeastofRovetoValley,showaNW-SEorientation. Atthesouth-westernfoothillsof bothridges,noticeablywarmerthanthenorth-easternones,Y/Mindividualsprevail.Thefrequencyofyellow specimens, as well as melanic ones (both R/M and Y/M),decreases goingup themountains. On the top and onthecoolernorth-easternslopesofboth ridgesR/m individualsaredistinctlymoreabimdant. Theecologicalbackground allowingtheshiftofthe R/mpatternofZi/gacnaephialtcstoward theY/M onewasidentifiedasachangeoftherelativeabundanceoftwoMüllerianmimicryringsduringthePleistocene period.Accordingtotheproposedmodel,inSouthItalycpJiialteswouldhavedivergedfromamainEuropean ring,involvingseveralspeciesoiZygaenasharingaR/mpattern,andenteredintoamoreMediterraneanring basedonaY/Mpattern,inwhichthemostabundantcomimicsarethermophilousspeciesbelongingtothe genusSyntomis(Bullinietal.1969,Turner1971,Sbordonietal.1979).Thereisstrongevidencethatthesame basicphenomenonhasoccurredmZygaenatransalpi)m,althoughincompletely. ThegeneralappearanceoiCalliinorpliadoininiilaobjectivelylooksquitedifferentfromthatcharacteristic oftheZygaenaortheSyntomisspecies,particularlyinsize.Nevertheless,biochemical,eco-ethological,and colourpatterncongruences(Frazer&Rothschild1960,Rothschild1961,1985,Kayetal. 1969)suggestthat theyareall involved in thesameMüllerian rings. As a matteroffact, Rothschild& Lane (1960) showed thatsomeinsectivorousspeciesofbirdsareunabletoperceivethedifferencebetweenC.domiindaandspecies oiZygaenaandTyriajacohaeae(Linnaeus,1758),sothebirds,havingexperiencedthelatterspecies,trytoreject orevenescapewheneitherdominulaorspeciesofZygaenaareoffered to them. InpeninsularItaly,thetwoalternativemimicryringsarenotmutuallyexclusive,butcoexistoverlarge extensions.However,asthereisadistincttrendfortheY/Mringtobecomeprogressivelyscarcernorthwards orathigheraltitudes,itcanbesupposedthatitattaineditscurrentspeciescomposition,includingancestral dominulapopulationswhichoncewereredunmelanic,inxerothermicrefugialareasofsouthernItalyduring thePleistoceneglaciations.ItisnoteworthythatSicilyremainedunaffectedbytheshiftR/m-Y/M,apparently because of unsuccessful colonization by some species. In fact, if is compared the lepidopteran species