Biochemical Analysis of Relationships of Mediterranean Alectoris Partridges

The Auk 109(2):358-367, 1992

BIOCHEMICAL ANALYSIS OF RELATIONSHIPS OF MEDITERRANEAN ALECTORIS PARTRIDGES

ETTORERANDI, 1 ALBERTOMERIGGI, 2 RITA LORENZINI,1 GEA FUSCO,1 AND PHILIP U. ALKON 3 lIstitutoNazionale de Biologiadella Selvaggina via, Cd Fornacetta,9, 40064 Ozzanodell'Emilia (Bo), Italy; 2Dipartimentodi Biologia Animale, Universitd di Pavia,Piazza Botta, 9, 27100Pavia, Italy; and 3JacobBlaustein Institute for DesertResearch, Ben-Gurion University of theNegev, SedeBoqer Campus 84990, Israel

ABSTRACT.--TheMediterranean Alectoris (including A. rufa, A. graeca,A. chukar,and A. barbara)comprise a groupof closelyrelated and morphologicallyuniform partridgeswith largely allopatricdistributions and instancesof natural hybridizationin parapatriccontact zones. Their taxonomic status and evolution are controversial. We have used multilocus proteinelectrophoresis to estimatethe extentof geneticdivergence among nominal Alectoris speciesand within A. chukar,A. graecaand A. rufa.The averageNei's (1978)genetic distance amongconspecific populations (• = 0.008;range 0.003-0.021) was 26 timessmaller than amongspecies (• = 0.208;range 0.071-0.312). The most genetically similar species were A. rufaand A. graeca(/• = 0.081);A. barbaraand A. chukarwere the most divergent (/• = 0.303). The F•, valuesamong species (F•, = 0.75) were more than eight times larger than among conspecificpopulations (Fs, = 0.09). The gap in D and F•, values for intraspecificand inter- specificcomparisons indicates a prolonged interruption of gene flow among speciesand independentevolution of their genepools. Dendrograms summarizing genetic distance ma- tricesand cladisticanalyses of discretecharacter states suggested that A. rufaand A. graeca are sisterspecies of recentorigin, followed by the mostdistantly related and ancientA. chukar and A. barbara.Because protein electrophoresisresults are concordantwith biogeographical and paleontologicalinformation, we constructa hypothesisfor the evolution of the Medi- terraneanAlectoris. Received 2 May 1991,accepted 13 January1992.

THE AL•CTORISpartridges (Galliformes, Pha- Most Alectorisspecies are very similar mor- sianidae)are distributedwidely in the Palaearc- phologically,differing only with respectto sub- tic (Fig. 1). They present intriguing and chal- tle but diagnosticface and throat plumagepat- lenging questionswith regard to taxonomicand terns(Johnsgard 1988). Their naturalranges (Fig. evolutionary relationships. Peters (1934) in- 1) are largely allopatric, except for sympatry cluded graeca,chukar, and magnaas subspecies between melanocephalaand philbyiin southern of A. graeca,a taxonomythat was followed by Arabia. Parapatriccontact zones exist between Dementiev and Gladkov (1952). Voous (1960) chukarand graecaat the border of Greece and largely accepted this classification,but ques- Bulgaria,between rufa and graecain the French tioned the separatespecies rank assignedto A. Alps, and probablybetween magnaand chukar rufa. From ethological evidence, Menzdorf in central China (Watson 1962a, Bernard-Lau- (1984) agreed that graeca,chukar, and rufa had rent 1984).Only two zonesof overlap and hy- not yet attainedtrue speciesstatus. Vaurie (1959), bridization (sensu Short 1969) have been re- on the contrary, argued that these forms com- ported: a well-documented rufa and graeca prisedseparate species owing to diagnosticdif- hybrid zone in the southernFrench Alps (Ber- ferences in facial plumage and vocalizations. nard-Laurent1984); and an unconfirmedgraeca This view was supportedby Watson(1962a, b), and chukarhybrid zone in Thrace south of the who offeredadditional evidence of species-spe- Rhodope Mountains (Dragoev 1974). Extant cific plumage characters,and of behavioraland Alectoris populations of Mediterranean and ecological separationamong parapatric popu- North Atlantic islandsprobably resultedfrom lations. The Vaurie (1959) and Watson (1962a, human introductions (Watson 1962b, Blondel b) view of sevenclosely related Alectoris species 1988). The present pattern of only one species is now widely accepted(Cramp and Simmons per island may representthe outcomeof com- 1980, Johnsgard1988). petitive exclusionamong two or more species 358 April1992] BiochemicalGenetics ofPartridges 359 followingrepeated introductions (Blondel 1988). tein evolution was used to estimatedivergence Therefore, several lines of evidence, including times, which have been related to current evo- allopatricdistributions, natural hybridization, lutionary and biogeographicalhypotheses. ecologicalexclusion, and morphologicalsimi- larity havebeen used in supportof hypotheses MATERIAL AND METHODS of a recent radiation, and perhapsincomplete speciation,of the MediterraneanAlectoris par- We analyzed 117 specimensbelonging to the fol- tridges(Voous 1960, Watson 1962a,b, Blondel lowingpopulations: A. tufapopulation 1 (n = 12,wild, SW Spain);A. tufa 2 (n = 20, captive-reared,Italy); A. 1988). graeca1 (n = 10, wild, E Alps, Italy); A. graeca2 (n = Two conflicting models have been recently 20, captive-reared,Italy); A. chukar1 (n = 20, wild, proposedto explain evolution and speciation China); A. chukar2 (n = 5, captive-reared,Bulgaria); in Alectoris(Fig. 1). Watson(1962a) argued that and A. chukar3 (n = 20, wild, central Israel); A. barbara Alectoriscomprises: (1) the "superspecies"grae- (n = 20, wild, Sardinia,Italy). Captive specimenswere ca (encompassinggraeca, and magna);(2) the obtained from pure-bred, [arm-reared stocks.Given "superspecies"chukar (encompassing chukar, the recent[oundation of the captivestocks, and their philbyi,barbara, and tufa); and (3) melanocepha- derivation from more than 20 breeding pairs, there la,a separateand moredistantly related species. was little likelihood that the sourcepopulations were subjectto substantialinbreeding. Wild birdswere col- From morphologicaland biogeographicalevi- lected [rom localities at which there have been no dence, Watson argued that graecawas the an- restockingwith reared birds. We alsoanalyzed tissues cestorof the chukarlineage, and that rufaevolved of Gray Partridge (Perdixperdix, n = 2) and Ring- recently in southwesternEurope after barbara necked Pheasant (Phasianuscolchicus, n = 2) as out- crossedthe Straits of Gibraltar. Span0 (1975) groupsfor rooting phylogenetictrees. criticized Watson'smodel and suggestedclose Liver and heart sampleswere dissectedfrom fresh- relationshipsof chukarwith graecaand rufa,but ly-killed birds, storedat -20øC for severalhours after not with barbaraand philbyi.Bernard-Laurent death, and then stored at -80øC until processing.We (1984) and Blondel (1988) cited extant zones of separatelyhomogenated about 0.5 g of each tissuein overlapand hybridization for includinggraeca, 1 ml of 0.01 M Tris/HC1 pH 7.5, 0.001 M Na2.EDTA, rufa,and chukar in a singlesuperspecies of which and 0.001 M B-mercaptoethanolbuffer and centri- fuged for 15 rain at 13,000rpm. Supernatantswere graecawas the ancestralform. Accordingto these diluted in one volume o[ a 40% glycerol solution, authors, barbara never crossed Gibraltar to Eu- aliquotedin Microtiter plates,and frozen at -80øC rope and is only distantly related to graeca. until used. Vertical polyacrylamidegel electropho- We used multilocusprotein electrophoresis resis(concentration of 7.5% monomersin the contin- to estimate the extent of genetic divergence uoussystems) was usedto resolve33 loci. Staining amongthe four Mediterraneanspecies of Alec- recipeswere adaptedfrom Harris and Hopkinson toris:Red-legged Partridge (A. rufa), Rock Par- (1976).Electromorphs were presumedto have a sim- tridge (A. graeca),Chukar (A. chukar),and Bar- ple geneticbasis, and were consideredas alleles. A1- bary Partridge (A. barbara).In particular, we leles were codedby their mobility from the starting line, with the most anodal allele coded as "a." examined the following hypothesesposed by The BIOSYS-1 program (Swofford and Selander previous authors:(1) the Mediterranean Alec- 1989) was used to computepercent polymorphic loci torisspeciated very recently(Watson 1962a) and, (P) and heterozygosity(H) values. Agreement with perhaps, incompletely (Voous 1960, Blondel Hardy-Weinberg expectationswas tested using chi- 1988);(2) graecawas the ancestralform of a su- squareanalysis (Sokal and Rohlf 1981). Other statis- perspeciesfrom which chukarand rufa origi- tical proceduresincluded: contingency tests of allelic nated at the eastern and western range bound- heterogeneity among populations (Workman and aries, respectively (Bernard-Laurent 1984, Niswander 1970); Nei's (1978) and Rogers' (1972) ge- Blondel 1988); or, alternatively, (3) chukar,bar- netic distancematrices, UPGMA phenograms(Sneath bara,and rufa constitutea superspecies,with and Sokal 1973); and Wagner networks (Swofford rufa originating from barbaraafter crossingGi- 1981). We have computedF-statistics (Wright 1978) within and among nominal species.These provided braltar (Watson 1962a). Genetic distanceswere two lines of evidence (i.e. genetic distancesand F•,) used to estimate levels of divergence among on the extent of genetic divergenceat different tax- conspecificpopulations and among species, and onomical levels (Corbin 1987). Cladistic trees were to obtain dendrogramsshowing phenetic and constructedusing the programPAUP (Swofford1985) phylogenetic relationshipsamong species.A after coding alleles as present or absentaccording to tentativecalibration of the averagerate of pro- the independent-allele model (Buth 1984). The SPSS 360 RANDI•r AL. [Auk, Vol. 109

Fig. 1. Distributionof partridgesof genusAlectoris (adapted from Watson1962a and Blondel 1988).Con- tinuouslines indicatethe evolutionaryrelationships among species as suggested by Watson(1962a, b). Broken lines indicateevolutionary relationships as hypothesizedby Blondel (1988).

(Nie et al. 1975)package was used to computea Mann- higher than the average F•, among conspecific Whitney U-testof differenceof heterozygosityamong populations (0.09). populations. There were no fixed allelic differences between rufa and graeca.We found that chukarhad RESULTS fixed allelic differencesat 12%of loci from rufa and graeca,while there were 24% fixed allelic We were able to resolve33 presumedgenetic differencesbetween barbaraand the rufa-graeca loci among eight populations of Mediterranean pair. There were 27%fixed differencesbetween Alectoris,and the Perdixperdix and Phasianuscol- chukarand barbara.Allele frequenciesof rufaand chicusoutgroups (Table 1). Observed hetero- graecadiffered significantly (single-locuscon- zygosityranged from 0.018(rufa 1) to 0.085(chu- tingency x2-test)at six (18%) of their polymor- kar3), and percentpolymorphic loci rangedfrom phic loci. Major differencesin allele frequencies 6.1 (barbara)to 39.4 (chukar2, Table 2). Similar between these two speciesoccurred at EST-2, levelsof geneticvariability have beenobserved sGOT, and sME. The mean F•, between them in many other bird species(Corbin 1987,Evans was 0.572,as comparedto only 0.063 and 0.076 1987). Heterozygosity did not differ between among the two rufa and the two graecapopu- wild and captive populationsof the samespe- lations, respectively.Intraspecific heterogene- cies(Mann-Whitney U-test,P < 0.05). All poly- ity wasgreater among chukar populations (i•st = morphicloci were at Hardy-Weinberg equilib- 0.159). rium, excepting sME in rufa 2 and PEP-2 in Nei's (1978) standard unbiased genetic dis- chukar 3 (P < 0.01; x2-test with Levene's [1949] tancesaveraged 26 times larger amongnominal correctionfor small samplesize, and exactprob- Alectorisspecies (b = 0.208;range 0.071-0.312) ability test).A positivefixation index F (Wright thanamong conspecific populations (/• = 0.008; 1965) indicated a significant deficiency of het- range 0.003-0.021; Table 3). Interspecific ge- erozygotesin both cases. netic distanceswere lowestbetween A. rufa and Allele frequenciesover all polymorphic loci A. graeca,but even these values (9 = 0.081;range differed significantly among all species(P < 0.071-0.091) were 18 times larger than the av- 0.01;contingency x2-test), and amongthe three erage interpopulation genetic distancewithin populations of chukar(P < 0.01) and two pop- thetwo species (b -- 0.0045;range 0.003-0.006). ulation of graeca(P < 0.05). The average F• The largest genetic distance of the study was among specieswas 0.75, more than eight times betweenbarbara and chukar(/• = 0.303),which April 1992] BiochemicalGenetics ofPartridges 361

is one of the highestD-values obtained between than 0.02 (Barrowclough1983). Exceptions have what are consideredto be congenericbird spe- been found recently in someNeotropical birds, cies (Zink 1988, Gill and Gerwin 1989). which had comparativelylarge genetic dis- A phenogram was generated with the un- tances:(a) among conspecificpopulations oc- weighted pair-group method using arithmetic cupyingseparate Amazon banks (e.g. b = 0.040 averages(UPGMA) of Nei's distances(Fig. 2A). between trans-Amazonianpopulations of Pipra A Wagner network (Fig. 2B) was derived using coronata;Capparella 1988); (b) among subspe- Rogers'(1972) distances.Nei's D, a nonmetric cies(e.g. /• = 0.066among subspecies of Chi- distancemeasure, has been widely applied in roxiphiapareola; Capparella 1988);and (c) among ornithologicalresearch and, therefore, enabled species(Hackett and Rosenberg1990). These us to compareour results with previous work. phenomena have been attributed to mecha- Moreover, Nei's D is intended to estimate the nisms of geographic variation and speciation proportion of mutational divergence among that may be peculiar to South American birds pairs of lineages, and is related to the time of (Capparella1988). Hackett and Rosenberg(1990) divergencefrom the last common ancestorin have suggestedthe findingsmay indicatethat caseof regular ratesof molecularevolution (Nei a reconsiderationof the taxonomyof Neotrop- 1978).The two dendrogramswere topologically ical birds is warranted. identical. They indicated that rufa and graeca While theory providesno absolutethresholds are most similar, linked at 0.081, followed by of geneticdistance for ranking bird taxa(John- chukar at 0.168, and barbara at 0.282. To construct sonand Zink 1983),the large body of empirical the Wagner tree, we usedPerdix perdix and Phasi- evidence provides useful guidance. Corbin anuscolchicus as outgroups to root the multiple- (1987) described the occurrence of different addition-criterianetwork. We optimized branch slopesof the regressionline of D on F•tbetween lengths to maximize goodness-of-fitstatistics. conspecificpopulations or between species. Similar lengthsamong sister branches suggest- Large, abrupt differencesin D and F•tbetween ed a regular rate of protein divergenceamong intraspecific and interspecific levels suggest the lineages.A relative rate test (Beverleyand historicalinterruption of geneflow amongtaxa Wilson 1984)was performedusing Perdix perdix and reorganizationof the genomes(e.g. found- and Phasianuscolchicus as outgroups.The aver- er effect, random drift, natural selection), and ageratio of branchlengths among lineages was indicate speciation. 1.0133 + 0.0039,confirming the idea of a reg- The averagegenetic distance among Alectoris ular rate of protein evolution. Parsimonytrees (b = 0.208)was substantially higher than values (not shown) were derived by cladisticanalysis obtainedfor mostother congenericbird species (PAUP) of allele distribution among species. (Gill and Gerwin 1989). However, the low av- These agreed in topographywith the dendro- eragedifference among conspecific populations gramsshown in Figure 2. of ourstudy (t3 = 0.008)is typicalof birdsin general, and of galliforms in particular. Inter- DISCUSSION specificgenetic distance between Lagopus lagopus and L. mutusin Scandinaviawas 0.046, as Applications of multilocus protein electro- comparedto an averageof only 0.0035and 0.0009 phoresisin the study of avian evolution have among their conspecificpopulations, respec- consistentlyindicated a comparativelyslow rate tively (Gyllenstenet al. 1985).The averagege- of geneticdivergence among avian taxa. Avise netic distanceamong seven populations of Cal- and Aquadro (1982) derived an average Nei's lipeplacalifornica was 0.005 (Zink et al. 1987), (1972)b of 0.08among 173 congeneric species and their estimatedlevel of gene flow of 5.5 of birds, an order of magnitudelower than the birds per generationwas nearly identicalto the averageof other vertebrates.Variation of pair- rate estimatedamong three populationsof Coli- wise interspecific genetic distancesis large, nusvirginianus (Ellsworth et al. 1989). ranging from 0.00 to 0.39 (Gill and Gerwin 1989, Intraspecific genetic distances among the Zink and Avise 1990). Many conspecificbird Alectorispopulations of this studyranged from populations are little differentiated, and it is 0.003to 0.021,and were only about 5% of the difficult to find local populationsor subspecies average interspecificgenetic distanceof 0.208. with F•,-valuesgreater than 0.05 and D greater The Fs,-valuesamong Alectoris species were more 362 RA•r• E'rAt. [Auk,Vol. 109 April 1992] BiochemicalGenetics ofPartridges 363

TABLœ2. Genetic variability at 33 loci in Mediter- ranean Alectorispartridges.

Percent

morphicpoly- Heterozygosity Population loci Observed Expected A. rufa I 12.1 0.018 0.017 A. rufa2 18.2 0.029 0.039 A. graecaI 21.2 0.052 0.051 A. graeca2 21.2 0.042 0.053 A. chukar I 15.2 0.050 0.047 A. chukar 2 12.1 0.048 0.042 A. chukar 3 39.4 0.085 0.100 A. barbara 6.1 0.030 0.028

than eight times higher than amongconspecific populations.We found rufaand graecato be the leastdivergent species, with an averagegenetic distanceof 0.081, 18 times larger than their average interpopulation distance of 0.0045. Ge- netic distancesand F•,within and betweenspe- cies of Alectorisare comparable to the values found in Palaearctic and North American birds (Corbin 1987, Evans 1987). The relatively large gapbetween the populationand the specieslev- els suggestsan extendedinterruption of gene flow and an independentevolution amongthe vv vv various Alectorisgene pools. The genetic distances(/• = 0.303)between barbara and chukar populationsare very high for congenericbirds. The extentof geneticheterogeneity among chu- karpopulations (F, = 0.159)is three to five times larger than the valuesusually observed among conspecificbird populations,and indicatesthe existenceof significantgeographic divergence within the chukarrange. The pattern of phylogeneticrelationships de- picted by our dendrogramsand cladistic trees (Fig. 2) suggeststhat Alectorisspecies did not result from contemporaneousepisodes of speciation (i.e. as consequenceof the fragmenta- tion of an ancestralpopulation). Rather, they arosefrom at least three waves of speciation. Therefore, the two reported hybrid zones in- volve sistertaxa (rufaand graeca)and nonsister taxa(chukar and graeca).The ability to hybridize is most probably attributableto the conserva- tive morpho-anatomical evolution and conse- quent retention of ancestral characters,rather than to incomplete speciation (McKitrick and Zink 1988, Cracraft 1983, 1989). The rare instancesof natural hybridization (which do not compromisethe evolutionary independenceof the rufa,graeca, and chukargenomes), the large 364 RANr•XET AL. [Auk, Vol. 109

TABLE3. Nei's (1978)genetic distances (lower left) and Rogers'(1972) genetic distances (upper right) among Mediterranean Alectorispartridges and the outgroupsPerdix perdix and Phasianuscolchicus.

A B C D E F G H I L A A. rufa1 -- 0.019 0.114 0.108 0.181 0.159 0.183 0.249 0.605 0.572 B A. rufa2 0.003 -- 0.107 0.100 0.177 0.155 0.176 0.245 0.601 0.566 C A. graeca1 0.091 0.074 -- 0.035 0.210 0.194 0.188 0.252 0.592 0.563 D A. graeca2 0.087 0.071 0.006 -- 0.197 0.177 0.179 0.253 0.605 0.563 E A. chukar 1 0.181 0.171 0.211 0.193 -- 0.042 0.059 0.284 0.628 0.567 F A. chukar 2 0.154 0.144 0.184 0.162 0.008 -- 0.065 0.270 0.626 0.566 G A. chukar 3 0.161 0.151 0.161 0.147 0.021 0.017 -- 0.287 0.628 0.571 H A. barbara 0.272 0.263 0.266 0.267 0.312 0.297 0.300 -- 0.599 0.568 I Perdixperdix 0.926 0.920 0.898 0.924 0.994 0.990 0.993 0.917 -- 0.394 L Phasianus colchicus 0.849 0.838 0.831 0.830 0.839 0.836 0.839 0.843 0.501 -- gap between interpopulation and interspecies Comparisons of sister-branch lengths in genetic distances,and the existence of diag- UPGMA and Wagner dendrograms (Fig. 2), as nostic phenotypic charactersindicate that the well as the relative rate test, indicate a rela- Mediterranean Alectorisare composedof what tively constantrate of proteinevolution in Alec- can be considered good evolutionary species. toris.Therefore, we can attempt a calibration of the molecular clock in order to date the divergence times of Alectorisspecies. Based on a gal- liform fossil (the odontophorin North Ameri- A chukar1 can quail Cyrtonyxcooki), Gutierrez et al. (1983) chukar2 proposed Nei's values of 1 D = 23.6 million chukar3 years (myr). Marten and Johnson(1986) pro- graeca1 vided a similarestimate of 1 D = 19.7myr. These graeca2 rateshave proved useful in estimatingtimes of ru•a1 evolutionary branchingsin several bird taxa (Johnsonand Zink 1983, Zink and Johnson1984, Randi et al. 1991b), and also approximate the Perdix rate of mtDNA evolution in Ammodramus(Zink Phasianu$ and Avise 1990). From multiple comparisonsof nDNA (Helm-Bychowskiand Wilson 1986)and 1.00 0.83 0,67 0.50 0,33 0.17 0.00 Nei's D enzyme phylogenetictrees, as well as several informative fossils, Randi et al. (1991a) derived the calibration 1 D = 22.9 myr for phasianid chukar 1 birds. Assumingthis rate, we derived the fol- chukar 2 lowing divergence times (Fig. 2A); (1) an initial chukar 3 splitting of the ancestralAlectoris into the pres- graeca 1 graeca 2 ent barbaraand chukarlineage about 6.4 million

rufa 1 years ago (mya); (2) a secondsplitting of the rufa 2 chukarand graeca-rufalineages about 3.8 mya; barbara (3) a final splitting of graecaand rufa only 1.8 Perd•x mya. Phaslanu$ Our results indicate that genetic divergence among the Mediterranean Alectorisis great and 0'.00'0107 • 0113' 0•.20• 0•,27' 0133' 0•.40 that they can be consideredgood evolutionary Distancefrom the Root Rogers' D species,as proposedby Vaurie (1959) and Wat- Fig.2. (A) UPGMA dendrogramof Nei's standard son(1962a, b). Phylogeneticrelationships among unbiasedgenetic distances (Table 3) amongMediter- raneanAlectoris and outgroupsPerdix perdix and Phasi- the speciesas indicated by our studiesdo not anuscolchicus. Cophenetic correlation is 0.994. Time supportthe evolutionaryscenarios proposed by scalecomputed using calibration 1 D = 22.9 myr. (B) Watson (1962a) and Blondel (1988): chukaris not Wagner tree obtained from Rogers'genetic distances strictly related to barbaraand rufa;graeca is not (Table 3). Copheneticcorrelation is 0.999. the ancestral form of a superspeciesencom- April1992] BiochemicalGenetics ofPartridges 365 passingrufa and chukar;and barbarais not the throughout the Mediterranean basin favored stem speciesof rufa. Evolution and speciation expansionof the Europeanand Middle-Eastern of Alectoris are not recent Pleistocene events as populationsof rufa,graeca, and chukar.They be- supposedby Watson (1962a);based on our es- cameparapatric, and originatedthe actualzones timated divergence times, speciation events of overlapping and hybridization. could span from the Miocene-Pliocenebound- The model is consistent with available fossil, ary to early Pleistocene.The conservativemor- biogeographicand genetic information on the phology and the small plumage differenceare Mediterranean Alectoris. It also leads to the fol- consistentwith a slow rate of morphologic evo- lowing hypotheticalpredictions for other Alec- lution and not with recent origins of thesespe- torisspecies: (1) First, melanocephalaand philbyi, cies. the only two sympatricAlectoris (Watson 1962a), We proposethe following model of Alectoris aroseduring the first wave of speciationfrom evolution,substantially concordant with Span0 anciently separated lineages. They came into (1975),and characterizedby at leastthree waves extensive contact in the Arabian Peninsula, and of speciation.About 6 mya, at the Miocene-Plio- evolved character displacement and ecological cene boundary,and ancestralspecies split into compatibility (Watson 1962a), allowing their barbaraand in the chukarlineage. This division sympatry. From plumage characters(Watson occurredduring a period of climatic warming 1962a),we hypothesizethat melanocephalais re- and aridity that resulted in the closureof the lated to the barbaralineage, and that philbyiis Mediterranean Sea at Gibraltar and its subse- related to the chukarlineage. (2) Second,magna quent dessication(Voous 1974). Concurrently, arosefrom ancientfragmentation of chukarpop- uplift of the Carpathian Mountains created an ulations in China. Plumage similarities be- east-westdivide of the central European plains, tween magnaand graecaresulted from conver- and separatedthe Sarmatic Sea from the Med- gence rather than from common ancestry.This iterranean (Voous 1974). The climate probably is in contrast to Watson's (1962a) argument favored the spread of birds adapted to arid and that magnais a relic population of a widespread steppe habitats, such as barbaraand chukar.We ancestral graeca lineage. Our model indicates supposethat geologicevents resulted in an east- that graecanever reached central Asia. These west splitting of the ancestral populations in hypothesesare amenableto testing by expand- which the chukarlineage spreadeastward around ing biochemical genetic researchto all seven the SarmaticSea, while barbaraspread westward extant speciesof Alectoris. along the Mediterranean littoral of the Middle East and Africa. Following speciation,barbara ACKNOWLEDGMENTS eventually crossedthe Straits of Gibraltar, and then spreadeastward along the EuropeanMed- We thank Ariane Bernard-Laurent and T. Crowe iterranean coasts,thereby explaining the pres- for the comments and suggestionsthat greatly im- enceof fossilbarbara in Franceup to the middle proved an early version of the manuscript. We are Pleistocene (Mourer-Chauvir• 1975). Then, indebted to J. Blondel and S. J. Hackett for the ex- about 4 mya (early Pliocene),the ancestralchu- cellent reviews of the paper. kar populations,spreading westward, gave rise to the graeca-rufalineage. Finally, at the start of LITERATURE CITED the Pleistoceneglaciations, about 1.8 mya, chukar populations in western Europe survived in AVISE,J. C., ANDC. F. AQUADRO.1982. A comparative fragmented populations, which probably un- summaryof genetic distancesin the vertebrates. derwent repeated contraction and expansion Evol. Biol. 15:151-158. accordingto climatic changes.The fossil record BARROWCLOUGH,G. F. 1983. Biochemical studies of indicatesthat barbaradisappeared from Europe microevolutionary processes.Pages 223-261 in during the middle Pleistocene,while both rufa Perspectivesin ornithology (A. H. Brushand G. A. Clark, Jr., Eds.). Cambridge Univ. Press,Cam- and graecaoccurred in France (Mourer-Chau- bridge. vir• 1975). The origin of graecaand rufa was BERNARD-LAURENT,A. 1984. 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