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Home , Black bittern, Dwarf bittern, Gorsachius, Nyctanassa, Rufescent tiger heron, Tigrisoma

The Auk 112(3):672-679, 1995

PHYLOGENETIC RELATIONSHIPS OF THE ZIGZAG (ZEBRILUS UNDULATUS) AND WHITE-CRESTED (TIGRIORNIS LEUCOLOPHUS) ESTIMATED BY DNA-DNA HYBRIDIZATION

FREDERICKH. SHELDONl, KEVIN G. MCCRACKEN2, AND KEELEY D. STUEBING 1 •Museuraof Natural Science,Louisiana State University, BatonRouge, Louisiana 70803, USA; and 2LouisianaCooperative and WildlifeResearch Unit, Schoolof Forestry,Wildlife, and Fisheries, LouisianaState University, Baton Rouge, Louisiana 70803, USA

ASSTRACT.--Recently,we acquiredDNA of two rare speciesof heron, the NeotropicalZigzag Heron (Zebrilusundulatus) and the African White-crestedBittern (Tigriornisleucolophus). To estimatetheir phylogenetic relationshipsto other , we comparedthese specieswith representativesof the major heron cladesusing DNA-DNA hybridization. Even though the resemblesa tiger-heron in its barred plumage and forest habitat, it is most closelyrelated to .The White-crestedBittern is monophyleticwith the New World tiger-herons ()and, thus, is better termed the White-crestedTiger-Heron. These findings accordwell with phylogeneticanalyses based on osteology.The remaining uncer- taintiesin higher-level heron phylogenyare principally: (1) the positionand composition of someenigmatic genera (e.g. Gorsachius,Agamia, Pilherodius, and Ardeola);and (2) the iden- tification of the basal heron lineage, which appearsto be either tiger-heronsor the Boat- billed Heron (Cochlearius).Received 15 June1994, accepted 27 January1995.

THE HERONS(Ciconiiformes: Ardeidae) may groups, the tiger-herons. This study supple- be divided ecologicallyinto groupsthat: (1) feed mentsa previousDNA-DNA hybridization ef- largely in openareas either by day (e.g.Egretta, fort to estimatethe intergenericphylogenetic Ardea,Bubulcus, and Butorides)or night (Nyctic- relationshipsof herons(Sheldon 1987a,see also orax, Nyctanassa,and Cochlearius);(2) live and Sheldon and Kinnarney 1993). At the time of nest in marshes (bitterns); or (3) live in forested the 1987 study, DNA was available from only areas (tiger-herons and Gorsachiusnight-her- one tiger-heron --theRufescent Tiger- ons). Of these groups, the least known are the Heron (Tigrisomalineatum)--and, as a result, lit- forest-dwellingspecies, which generallyare rare tle could be said about the relationshipsamong and difficult to observe.In comparisonto other members of this group. Also, becausethe de- herons,they are poorly representedin museum termination of the position of the tiger-heron collections,have received little ecologicaland cladewithin the heronfamily relied on a single behavioral study, and have obscurephyloge- species,the overall estimateof heron phylog- netic relationships (Payne and Risley 1976, eny potentially sufferedfrom the limited sam- Hancock and Elliott 1978, Hancock and Kushlan ple representing this important group. Since 1984). They also exemplify some intriguing the earlier study,we haveobtained DNA of two evolutionary issues and problems. Forest- more tiger-herongenera (sensu lato): the White- dwelling heronshave undergone marked adap- crestedBittern (Tigriornisleucolophus) of Africa tive changesin apparent responseto their hab- and the Zigzag Heron (Zebrilusundulatus) of itat (especiallyin terms of their plumage),and South America. With Tigrisomalineatum, these they have relictual tropical distributions--the new speciesconstitute three of the four tradi- tiger-heronsoccur in the Neotropics,Africa, and tional tiger-heron genera. Unfortunately, a New , and Gorsachius occurs in Africa sampleof the fourth tiger-heron,the ForestBit- and . tern (Zonerodiusheliosylus) of New Guinea, is In this paper we present DNA-DNA hybrid- still lacking. ization evidenceof the phylogeneticrelation- The inclusionof two more tiger-herongenera ships of membersof one of these little-known not only improvesthe likely accuracyand use- 672 July 1995] HeronPhylogeny 673

TAnLEI. Speciesand samplesused in study.

Name Country Preparation no. Egrettathula (Snowy ) USA 3705 Cochleariuscochlearius (Boat-billed Heron) 3281 Tigrisomalineatum (Rufescent Tiger-Heron) Ecuador 3165, 4507 Tigriornisleucolophus (White-crested Bittern) 1910 Zebrilusundulatus (Zigzag Heron) Ecuador 3170 Ixobrychusexilis () USA 409 Plegadisfalcinellus (Glossy Ibis) USA 852

fulness of the DNA-DNA estimate of phylog- ization estimatesof phylogeny (e.g. Sheldon 1994, eny, but it permits a more substantialcompar- Slikas et al. 1996). ison between the DNA-DNA hybridization re- With the exceptionof Tigrisoma,only one individ- ual of eachspecies was compared.For Tigriornisand suitsand other studiesof heron phylogeny (e.g. Zebrilus,only one sample was available; for the other Bock1956, Curry-Lindahl 1971,Payne and Ris- species,samples from more individuals were avail- ley 1976). Payne and Risley's (1976) study is able, but degrees of individual variation were ex- particularlyuseful as a soundingboard, because pectedto be well below genetic differencesamong it is a thorough cladisticand phenetic analysis species(Sheldon 1987a,Bleiweiss and Kirsch 1993, of heron osteologyand, thus,may be compared Sheldon and Winkler 1993). We comparedtwo in- to the DNA-DNA hybridization resultsvia tax- dividuals of EcuadorJanTigrisoma: one from the east- onomic congruenceanalysis (e.g. Cracraft and ern (Amazonian) lowlands (tissue no. 3165; ANSP Mindell 1989, Bledsoe and Raikow 1990). catalog183558); and one from 1,500 m elevation on theeastern slopes of theAndes (tissue no. 4507; ANSP METHODS catalogno. 185105).DNA of the latter was received late in the study and was included becausewe be- The taxa and samplesused in this study are listed lieved it to representa separatespecies, the Fasciated in Table 1. Becauseof the n2 problem noted by Bar- Tiger-Heron (T. fasciaturn).Now, we are not certain rowclough (1992), in which the required number of about the speciesof the specimen,but suspectit to pairwise DNA-DNA hybridization comparisonsin- be lineatum.This individual is a juvenile , whose creasesgeometrically with the number of taxa (n), we powderdown pattern suggestslineatum, but was col- limited the number of speciesin this study to save lected at an altitude more typical of fasciaturn.We money and time. Our selectionof speciesfor com- include its data in this paper becausethe specimen parison (in addition to Tigrisomalineatum, Tigriornis ultimately will be identified. leucolophus,and Zebrilusundulatus) was based on the Methods of DNA preparationand hybridization following observations. Sheldon (1987a) identified were basedon thoseof Sibley and Ahlquist (1990), three fundamentallineages of herons:"typical" her- with the modificationsof Sheldon and Winklet (1993) ons (including day-herons and night-herons); bit- and Slikaset al. (1996). Hybrids were fractionatedin terns; and tiger-herons. Therefore, we decided to in- a 35-column machine from 60ø-95øC in 2.5øC incre- clude representativesof each of theseclades. Egretta ments.All DNA sampleswere radiolabeledand com- thulawas selected because it is a commontypical her- pared as drivers (targets),except for Tigrisomasample on. Similarly, Ixobrychusexilis is a common bittern. 4507, which was radiolabeled but not used as a driver Sheldon (1987a) also found that Cochleariuscochlearius in reciprocalcomparisons. Data are availablefrom the was geneticallyremote from other heronsand pos- authors. sibly monophyleticwith tiger-herons.Thus, Coch- The indexesof hybrid stability(Tin, Tmoa,, ATe, and leariuswas includedin the study.Night-herons were ATmoa,)and normalized percent reassociation(NPR) excludedbecause they were found to be unambigu- were computedby the methodsof Sheldonand Bled- ouslymonophyletic with day-heronsand distantfrom soe (1989). Individual hybrids were excluded from all other lineages,including Cochlearius(contra Bock further analysisif they exhibited technical problems 1956,Cracraft 1967,Payne and Risley 1976).Finally, or less than 60% NPR (rationale discussedin Sheldon the GlossyIbis (Plegadisfalcinellus) was selected as an and Winklet 1993).Trees were built using the Fitch, outgroup; DNA-DNA hybridization studiesof vari- Kitch, and neighbor-joiningoptions of PHYLIP 3.4 ous ciconiiform suggestthat ibisesare as close (Felsenstein 1989). Becausemeasurement error is not or closerto heronsthan any group of birds (Sibley correlatedwith geneticdistance (Fig. IA), the fitting and Ahlquist 1990, Sheldon and Kinnarney 1993). option was set to unweighted least squares(Cavalli- Moreover,within reason,outgroup choice appears to Sforza and Edwards 1967). Branch robustness was have remarkablylittle effect on DNA-DNA hybrid- testedby bootstrappingwith the programof A. Dick- 674 SHELDON,McCRAc•cEN, AND STUEBINC [Auk, Vol. 112

I I

III July1995] HeronPhylogeny 675

0.50 12

0.45 lO 0.40

0.35 ø 8 0.30

0.25 o 6 o•_ ø 0.20 4 0.15 0 00 0 0 O.lO 0 00 0 0 0 2

0.05 o

0.00 [ I o I I I 0 • I I I I 0 2 4 6 6 10 12 0 2 4 6 6 10 12 /I Tmod, /I Tmod, Fig. 1. (A) ATmoa,versus standard deviation for each ATmod,value (from Table 2). (B) AT•oa,versus ATe, showinghigh correlationbetween the two distancemeasures (R = 0.995,n = 49). erman(pers. comm.; Krajewski and Dickerman1990) building methods produced a single, fully re- and jackknifing(Lanyon 1985). solvedbranching pattern (Fig. 2). This tree de- pictstwo majorheron groups--tiger-herons and RESULTS other herons. The tiger-heron clade includes Tigrisomaand Tigriornis.The other herons are The phylogeneticanalysis was basedon 467 divided into three clades:Cochlearius, Egretta, hybrids consistingof 7,005 thermal fractions. and /Zebrilus.Egretta is the sistertax- BecauseAT= and AT=oa,were highly correlated on of Ixobrychus/Zebrilusand togetherthey form (Fig. lB), we summarize in Table 2 only the the sistergroup of Cochlearius. AT=oa,values, which have somebetter proper- A relative-rate test (Sarich and Wilson 1967) ties(e.g. Sarich et al. 1989).All Fitchand neigh- was performed with Plegadisas the outgroup. bor-joiningtrees and testsof branchrobustness Ixobrychusappears to have evolved faster, and (bootstrappingand jackknifing) using those tree- Cochleariusand tiger-heronsslower, than Egretta (ANOVA, P < 0.001). This result is concordant with previous determinations of heron rates Egre• 0.74 2.52 Ixobrychus -- Egreffa thula -- Egretta caerulea 0.30 1.81 Zebrilus -- Syrlgmeslblletrix -- Ardea herodias 2.40 Cochlearlus Casmerodlus albus Bubulcus Ibis 0.61 Butorldes striat•s TigrisomaI Nyctanassa vlolacea Tlgrisoma2 Nyct•coraxnyc•comx Bot•urus lan•glnosus 0.27 2.33 Ixobrychusexllls Tlgriornls Zebr#us undulates

6,48 Cochleaflus cochleaflus Plegadls TlgrisomaIlnea•um Fig. 2. Estimateof heron phylogeny. Modal dis- Tlgrlornlsleucolophus tancesfitted by unweighted least squaresusing the Fitchprogram of Felsenstein(1989). All branches100% Plegadls falclnellus resolvedafter bootstrapping1,000 times and jack- Fig. 3. Consensustree derivedby mergingtree in knifing. Figure 3 with tree in Sheldon(1987a:fig. 1). 676 S•mDOU,McCRAClqJq, aND STUEmNG [Auk,Vol. 112

Syrigma sibilatrix Payne & Risley Hybridization Egretta thula (t976)

DNA~DNAEgretta caerulea

Bubulcus ibis

Butorides striatus

Ardea herodias

Casmerodius albus

Nyctanassa violacea

Nycticorax

Botaurus lentiginosus

Ixobrychus exilis

Zebrilus undulatus

Cochlearius cochlearius --

Tigrisoma lineatum

Tigr•ornis leucolophus Fig. 4. Comparisonof tree in Figure 3 and tree basedon cladisticosteological analyses of Payneand Risley (1976:figs.34 and 35).

(Sheldon 1987b,Sheldon and Kinnarney 1993). hybridization, as long as the data are fitted to However, Zebrilus,which is monophyleticwith a branchingpattern without assuminga con- Ixobrychus,does not exhibit the fast rate found stant (or monotonic)evolutionary rate. DNA- in other bitterns. Becauseof the variability in DNA hybridizationdistances are inherently hi- rates of evolution, we did not use the Kitch erarchicaland appearmainly to reflectphylog- option in PHYLIP, which assumesa molecular eny (e.g. Springerand Krajewski1989, Bledsoe clock. and Sheldon 1990, Sheldon 1994). The two fundamentaldiscoveries of our study DISCUSSION are supportedby congruencewith Payne and Risley's(1976) phylogeny: Tigrisoma and Tigrior- The only other rigorouseffort to estimateher- nisare sistertaxa; and Zebrilusis monophyletic on phylogenywas the osteologicalcladistic and with bitterns. pheneticstudy of Payne and Risley (1976).Giv- That Tigriornisis a tiger-heron(sensu stricto) en the importance of tree congruencein as- is expected.Although Tigriornisdiffers from sessingthe accuracyof phylogenetic estimates other large tiger-heronsin sometraditionally (e.g. Cracraft and Mindell 1989, Bledsoeand important morphologicalcharacters (e.g. it has Raikow 1990, Swofford 1991), we have aligned two insteadof three powderdownpatches and our tree (Fig. 3) with a consensustree (Fig. 4) a particularlydistinct sternum), it is united with derived from the most-parsimoniousWagner Tigrisomaby a seriesof osteologicalsynapo- trees of Payne and Risley (1976:figs.34 and 35) morphies (e.g. sacral parapophyseswith the to determinethe extent of agreement.In Figure synsacrumand ligamental furrow of the hu- 4, we used Payne and Risley's (1976) cladistic merus;Payne and Risley 1976),as well as other parsimonyresults for this comparison,instead characters(e.g. nesting;see below). Given the of their phenetic trees, becausephenetic anal- relationshipbetween Tigriornis and other large ysesof morphologyare not generallyuseful in tiger-herons,the commonname of this species estimating phylogeny. Such analysesfail be- ought to be White-crestedTiger-Heron, not causeoverall similarity in morphology is not White-crestedBittern as in Sibleyand Monroe distributedhierarchically according to phylog- (1990). eny (e.g. Ridley 1986). The sameis not true of The discoverythat Zebrilusand bitterns are molecular-distance methods, such as DNA-DNA monophyleticalso is not surprising,despite the July1995] HeronPhylogeny 677 resemblanceof Zebrilusto large tiger-heronsin herons;(2) night-herons are not monophyletic plumageand foresthabitat, and the uniqueness with bitterns;and (3) tiger-heronsand day-her- of someof its osteologicalfeatures (e.g. small ons are not sistertaxa. Following this reanalysis, size,shape of the bill, angle of the bill with the the only major discrepancybetween Payne and skull, and form of the sternalkeel; Payneand Risley's(1976) resultsand the DNA-DNA hy- Risley 1976). Like bitterns, Zebrilushas 10 tail bridization findings concernsthe monophyly feathers, instead of the normal 12, and it has of day- and night-herons. The DNA-DNA hy- scutellatetarsi (Payne and Risley 1976). In ad- bridization data indicate that day- and night- dition, Zebrilusand bitterns have pure white herons are sister taxa, and Payne and Risley's eggs(Hancock and Elliott 1978,English 1991). (1976) data do not. Large tiger-herons,in contrast,have eggsthat Our current study disagreeswith Sheldon are coloredand blotched(e.g. beige-yellow with (1987a)in one respect.Formerly, Cochleariusap- reddishbrown or violet blotchesin Tigriornis peared as the sister taxon of Tigrisoma;now it [Brownet al. 1982]and bluishwhite with pale- appearsas the sistertaxon of the lineage com- violet blotchesin Tigrisornalineaturn [Hancock prising bitterns/Zebrilusand "typical" herons. and Elliot 1978]). The nest of Zebrilus also is Becauseof this discrepancy,we have depicted remarkablysimilar in somerespects to thoseof the node from which Cochlearius,tiger-herons, certainbittern species.Zebrilus constructs a shal- and bitterns/typical herons emerge as a mul- low round platform in trees or bushesbetween tifurcation in Figures 3 and 4. In terms of evo- 1 and 3 m above water. Four of the five Zebrilus lution, the discrepancybetween the two DNA- nestsfound by English (1991) were weaved with DNA hybridization studiesmay simply reflect thorns to form an edge barrier. At least two the inability of the technique to resolve this speciesof forest-stream-dwellingbitterns, the node given rapid origination of the three major African Dwarf Bittern (Ixobrychussturrnii) and heron groups over a short period of time (e.g. the Black Bittern (I. fiavicollis),are known to Sheldon 1987a). In terms of phylogenetic-re- build nests in thorn bushesover water (Han- constructiontechnique, the discrepancymay be cock and Elliot 1978). Tiger-heronsconstruct the result of taxonomicsampling. In the 1987 nestsin treesbetween 6 m (Tigriornis;Brown et study, fewer taxa bore on this node (viz. only al. 1982) and 15 m (Tigrisornamexicanurn; Han- one tiger-heron). Such incongruenciesempha- cockand Elliot 1978)above the groundor water. size the need for as complete a set of taxa in Although DNA-DNA hybridization and mor- phylogenetic reconstructionsas possible (e.g. phologicalstudies concur as to the phylogenetic Lanyon 1994).Unfortunately, becauseCochlear- positionof Zebrilusand Tigriornis,they disagree ius is monotypic and genetically distant from in the placement of several other heron taxa. all other herons,and only one more tiger-heron Payneand Risley's(1976) tree depictsCochlear- (Zonerodius)can be brought to bear on ius, night-herons,and bitterns (including Ze- the problem, we cannot expect to increaseour brilus) as monophyletic. It also indicates the taxonomic sample substantially. monophylyof day-and tiger-herons.DNA~DNA Several groups of birds are distributed pan- hybridizationsuggests a more asymmetrical tree. tropically, including tiger-herons,storks, fin- In particular, day- and night-heronsare mono- foots, jacanas,trogons, and barbets.The cause phyletic; bitterns (including Zebrilus)are their of this distribution is one of the great mysteries sistertaxon; and Cochleariusand tiger-heronsare of bird evolution. Moreover, certain of these basalto thesetwo groups.Although thesedif- groups are represented only by relicts (most ferencesbetween the morphologicaland DNA notably the tiger-herons and finfoots), which studiesindicate substantial incongruence, in fact raisestangential questionsabout the age of taxa they arenot well-founded.We havereanalyzed and whether the same fundamental forces are Payne and Risley's(1976) data (McCrackenand responsiblefor shaping their distributions.At Sheldon unpubl. analysis)using PAUP (Swof- present,phylogenetic data are being gathered ford 1993),a programthat was not availableto on all of thesegroups (Sibley and Ahlquist 1990, Payneand Risley.This reanalysisindicates that: Lanyon and Hall 1994, Houde et al. 1995, B. (1) Cochleariusis highly diverged from other Slikas pers. comm., S. Emlen pets. comm.), and herons, including night-herons;indeed, based the possibilityof substantivecomparative anal- on morphology and a thorough consideration ysesof branching patternsand geneticdistanc- of outgroups,it is not even monophyleticwith es is on the horizon. 678 SHELDON,McCRACr,•N, AND S?UESING [Auk, Vol. 112

ACKNOWLEDGMENTS A comparisonof solution and membrane-bound DNAx DNA hybridization,as used to infer phy- We owe particularthanks to R. Dickermanand G. logeny. J. Mol. Evol. 40:678-688. Barrowclough(American Museum of Natural Histo- KRAIEWSm,C., AND A. W. DICKERMAN. 1990. Boot- ry) for providingtissues of Tigriornisand to M. Rob- strapanalysis of phylogenetictrees derived from bins (Academyof Natural Sciencesof Philadelphia, DNA hybridization distances.Syst. Zool. 39:383- ANSP) for supplyingtissues of Zebrilusand Tigrisoma. 390. ANSP'sprogram in Ecuador,where the Robbin'stis- LANYON,S.M. 1985. Detectinginternal inconsisten- sueswere collected,was supported by the MacArthur ciesin distancedata. Syst.Zool. 34:397-403. Foundation. Laboratory work was kindly performed LANYON,S. M. 1994. Polyphylyof the blackbirdge- by M. Kinnarneyand wasfunded by the Academyof nus Agelaiusand the importanceof assumptions Natural Sciencesand NSF grants BSR-8806890and of monophylyin comparativestudies. Evolution BSR-9020183. 48:679-693. LANYON,S. M., AND J. G. HALL. 1994. Reexamination of barbetmonophyly using mitochondrial-DNA L•UP, E CITED sequencedata. Auk 111:389-397. PAYNE,R. B., ANDC. J. RIsLme.1976. Systematicsand BARROWCLOUGH,G. F. 1992. Biochemical studies of evolutionary relationships among the herons the higher level systematicsof birds. Bull. Br. (Ardeidae). Misc. Publ. Univ. Mich. Mus. Zool. Ornithol. Club 112a:39-52. 150:1-115. BLEDSOE,A. H., •ND R. J. RAIKOW. 1990. A quanti- RIDLIne,M. 1986. Evolution and classification.Long- tative assessmento _ongruencebetween molec- man, London. ular and nonmolecularestimates of phylogeny. SARICH, V. M., C. W. SCHMID, AND J. MARKS. 1989. J. Mol. Evol. 30:247-259. DNA hybridizationas a guideto phylogenies:A BLEDSOE,A. H., AND F. H. SHELDON. 1990. Molecular critical analysis.Cladistics 5:3-32. hornologyand DNA hybridization.J. Mol. Evol. SARICH, V. M., AND A. C. WruSON. 1967. Immuno- 30:425-433. logical time scale for hominoid evolution. Sci- BtmIW•ISS,R., AND J. A. W. KIRSCH. 1993. Experi- ence 158:1200-1203. mental analysisof variancefor DNA hybridiza- SHELDON,F. H. 1987a. Phylogenyof heronsesti- tion: II. Precision. J. Mol. Evol. 37:514-524. matedfrom DNA-DNA hybridizationdata. Auk Boot, W. J. 1956. A generic review of the family 104:97-108. Ardeidae (Aves). Am. Mus. Novit. 1779:1-49. SHELDON,F. H. 1987b. Ratesof single-copyDNA BROWN, L. H., E. K. URBAN, AND K. NEWMAN. 1982. evolution in herons. Mol. Biol. EvoL 4:56-69. The birds of Africa, vol. 1. Academic Press, Lon- SHELDON,F. H. 1994. Advancesin the theory and don. practiceof DNA hybridization as a systematic CAVALLI-SFOP,ZA, L. L., AND A. W. F. EDWARDS. 1967. method.Pages 284-297 in Molecularapproaches Phylogeneticanalysis: Models and estimation to ecologyand evolution(B. Schierwater, B. Streit, procedures.Evolution 21:550-570. G. P. Wagner,and R. DeSalle,Eds.). Birkhauser CRACRAFr,J. 1967. On the systematicposition of the Verlag, Basel,Switzerland. Boat-billed Heron. Auk 84:529-533. SHELDON, F. H., AND A. H. BLEDSOE. 1989. Indexes CRACP,Ar'r, J., AND D. P. MINDELL. 1989. The early to the reassociationand stability of solutionDNA history of modern birds: A comparisonof mo- hybrids. J. Mol. Evol. 29:328-343. lecularand morphologicalevidence. Pages 389- SHELDON,F. H., AND M. KINNARNEV. 1993. The effect 403 in The hierarchyof life (B. Fernholm, K. Bre- of sequenceremoval on DNA-hybridization es- mer, and H. Jornvall, Eds.).Exerpta Medica, Am- timatesof distance,phylogeny, and ratesof evo- sterdam. lution. Syst. Biol. 42:32-48. CURR¾-LINDAI-IL,K. 1971. Systematicrelationships SHELDON, F. H., AND D. W. WINICLER. 1993. Inter- in herons(Ardeidae), based on comparativestud- genericphylogenetic relationships of swallows iesof behaviorand ecology.Ostrich (suppl.) 9:53- estimatedby DNA-DNA hybridization.Auk 110: 70. 798-824. ENGLISH,P. 1991. The voice and first nestingrecords SISLEV,C. G., AND J. E. AHLQUIS?.1990. Phylogeny of the ZigzagHeron in Ecuador.Wilson Bull. 103: and classification of birds. Yale Univ. Press, New 661-664. Haven, Connecticut. FELSENSTEIN,J. 1989. PHYLIP--Phylogeny infer- SIBLEY,C. G., AND B. L. MONROE. 1990. Distribution encepackage (vet. 3.2). Cladistics5:164-166. and taxonomyof birds of the world. Yale Univ. HANCOCK,J., AND H. ELLIOtt. 1978. The herons of Press, New Haven, Connecticut. the world. Harper and Row, London. SLIt,AS, B., F. H. SHELDON,AND F. B. GILL. 1996. Phy- HANcocIc, J., AND J. KUSHrAN. 1984. The herons logenyof titmice(Paridae) I: DNA-DNA hybrid- handbook.Harper and Row, New York. ization estimateof relationshipsamong subgen- HOUDE, P., F. H. SHELDON,AND M. KREITMAN. 1995. era. J. Avian Biol. In press. July1995] HeronPhylogeny 679

SPRINGER,M., AND C. KRAJEWSKI.1989. DNA hy- analysisof DNA sequences(M. M. Miyamoto and bridizationin :A critiquefrom J. Cracraft, Eds.). Oxford Univ. Press, New York. first principles.Q. Rev. Biol. 64:291-318. SWOFFORD,D.L. 1993. PAUP: Phylogeneticanalysis SWOFFORD,D. L. 1991. When are phylogeny esti- using parsimony, 3.1. Illinois Natural History mates from molecular and morphological data Survey, Champaign. incongruent? Pages 295-333 in Phylogenetic