ORNITOLOGIA NEOTROPICAL 16: 347–359, 2005© The Neotropical Ornithological Society

INDEPENDENT EVOLUTION OF TWO DARWINIAN MARSH-DWELLING OVENBIRDS (FURNARIIDAE: LIMNORNIS,

LIMNOCTITES)

Storrs L. Olson1, Martin Irestedt2, 3, Per G. P. Ericson2, & Jon Fjeldså4

1Division of Birds, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington, DC 20013-7012, U.S.A. E-mail: olsons@si.edu

2Department of Vertebrate Zoology and Molecular Systematics Laboratory, Swedish Museum of Natural History, P.O. Box 50007, SE–104 05 Stockholm, Sweden.

E-mail: martin.irestedt@nrm.se & per.ericson@nrm.se3Department of Zoology, University of Stockholm, SE–106 91 Stockholm, Sweden.

4Vertebrate Department, Zoological Museum, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark. E-mail: jfjeldsaa@zmuc.ku.dk

Resumen. – Evolución independiente de dos horneros de pantano (Furnariidae: Limnornis, Limnoc-tites). – La Pajonalera Pico Curvo (Limnornis curvirostris) y la Pajonalera Pico Recto (Limnoctites rectirostris)son dos especies de hornero de pantano colectados por primera vez por Charles Darwin en Uruguay.Ambas tienen una distribución limitada a Uruguay, el sur de Brasil y el norte de Argentina, área en la cualocupan hábitat muy diferentes. Descritas originalmente como congéneres debido a sus similitudes en plu-maje, las dos especies han sido consideradas parientes cercanas a pesar de diferencias estructurales obviasentre ambas. Analizamos secuencias de ADN de tres genes de estas dos especies y las comparamos conuna amplia variedad de otras especies de Furnariidae y varios grupos externos. Limnoctites rectirostris perte-nece al grupo de especies tradicionalmente agrupadas en Cranoleuca, estando más cercanamente relacio-nada al Curutié Ocráceo (C. sulphurifera) entre las especies muestreadas. Estos resultados están respaldadospor vocalizaciones y nidificación. Limnornis curvirostris forma un clado con el Junquero (Phleocryptes mela-nops); este clado tiene al Macuquiño (Lochmias nematura) como grupo hermano. Una relación cercana entreLimnornis y Phleocryptes es respaldada por el color azul de los huevos y la arquitectura del nido, la cual es apa-rentemente única en estos dos géneros.

Abstract. – The Curve-billed Reedhaunter (Limnornis curvirostris) and the Straight-billed Reedhaunter (Lim-noctites rectirostris) are marsh-dwelling ovenbirds that were first collected by Charles Darwin in Uruguay.Each has a limited distribution in southernmost Brazil, Uruguay, and northern Argentina, within which thebirds occupy very distinct habitats. Originally described as congeners because of overall similarity of plum-age, the two species have been treated as close relatives through most of their history despite obviousstructural differences. We analyzed DNA sequences from three different genes of these species, compar-ing them with a wide variety of other species of Furnariidae and several outgroup taxa. Limnoctites rectirostrisbelongs among the species traditionally placed in Cranioleuca, being most closely related to the marsh-dwelling Sulphur-throated Spinetail (C. sulphurifera) among the species we sampled. This is supported byvocalizations and nidification. Limnornis curvirostris forms a clade with the Wren-like Rushbird (Phleocryptesmelanops), with the Sharp-tailed Streamcreeper (Lochmias nematura) as a rather distant sister-taxon. A closerelationship between Limnornis and Phleocryptes is supported by the apparently unique nest architecture andblue-green egg color. Accepted 5 April 2005.

Key words: Furnariidae, Limnoctites, Limnornis, molecular systematics, nidification, ovenbirds.

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INTRODUCTION

Charles Darwin was the first naturalist to col-lect two paludicolous species of ovenbirdsthat are now known to be of very limited dis-tribution in southeastern South America.These were obtained in June 1833 (Steinhe-imer 2004; not 1832 as per Vaurie 1980: 211)in what is now the province of Maldonado inthe Republica Oriental del Uruguay. WhenJohn Gould (1839: 80–81, pll. 25–26) identi-fied and described the birds from the voyageof H. M. S. Beagle, he created a new genus,Limnornis, for these two species, calling thefirst L. rectirostris, for its very straight, pointedbill, and the second L. curvirostris, for its billwith a more typically curved tip. In Englishthese species are now called the Straight-billed and the Curve-billed reedhaunters,respectively.

Both species were said by Darwin (inGould 1839:80–81) to live in the same habitat“amongst the reeds on the borders of lakes”and that he was “unable to point out any dif-ferences” in the habits of the two. This mis-taken impression probably colored much ofthe subsequent thinking about these birds.Apart from the supposedly shared habitat, themain similarity between the two reedhauntersis in general coloration and plumage pattern.This is doubtless what lead Gould (1839) tohis original decision to place them both in thesame genus and also why Vaurie (1980) rathervigorously defended this course. On the otherhand, there are manifest differences betweenthe two, so that they have most often beenplaced in separate monotypic genera (Limnor-nis and Limnoctites). Regardless, the tworeedhaunters first collected by Darwin havelong been regarded as each other’s closest rel-ative. This also appeared to receive supportfrom a phylogenetic analysis of nest structure(Zyskowski & Prum 1999) in which Limnornisand Limnoctites were said to form a group withthe Wren-like Rushbird (Phleocryptes melanops).

We decided to test this hypothesis by review-ing the information on morphology, ecology,and nidification, and by comparing this withnew molecular evidence.

SYNOPSIS OF MORPHOLOGY ANDNOMENCLATURAL HISTORY

Both reedhaunters are plain brownish or dullrufous above, with rufous tails, dull whitishundersides, and no adornment apart from awhitish superciliary stripe. Limnornis curviros-tris is a reasonably robust bird (26.7–33.3 g,mean 29.0 g, n = 10, according to USNMspecimen data; mean of 21 eggs 24.6 x 17.9mm, according to Narosky et al. 1983) with alongish, rounded tail and a stout, curved bill.It has very much the appearance of a drabversion of one of the smaller species of Fur-narius. Limnoctites rectirostris is a much slighterbird (15.6–24.5 g, mean 19.2 g, n = 5, accord-ing to USNM specimen data [the heaviest wasa very fat laying female]; mean of 3 eggs 20.3X 15.3 mm, according to Ricci & Ricci 1984)with an extremely long, straight, slender bill,and a shorter, graduated tail with verypointed, usually worn, rectrices. The nomen-clatural history of the two species hasrevolved around whether to emphasize theirsimilarities or their differences.

Gould (1839) did not designate a typespecies for Limnornis and Gray (1840) subse-quently selected L. curvirostris as the genotype.Sclater (1889) overlooked Gray’s action andapplied a new name, Limnophyes, to L. curviros-tris, reserving the name Limnornis for L. rec-tirostris. But Limnophyes was preoccupied by agenus of Diptera, so Oberholser (1899) pro-posed Thryolegus as a replacement. Hellmayr(1925) pointed out Gray’s (1840) type desig-nation, returned curvirostris to Limnornis, andproposed the new generic name Limnoctitesfor L. rectirostris. Since then, most authorshave maintained the two species in monotypicgenera, usually placing them next to one

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another. The first exception appears to be Esteban

(1949), who advocated removing Limnoctitesrectirostris to the subfamily Synallaxinae nearCerthiaxis, presumably leaving Limnornis curvi-rostris in the Philydorinae, where both wereplaced by Sclater (1890). Peters (1951) alsodissociated the two, placing Limnornis immedi-ately after Furnarius, with 12 genera between itand Limnoctites, which was placed between Cer-thiaxis and Poecilurus/Cranioleuca. AlthoughMeyer de Schauensee (1966) followed Peters’sequence almost exactly, one of his few depar-tures was to place Limnoctites immediately afterLimnornis. Vaurie (1971, 1980) and Sibley &Monroe (1990) returned to the original Goul-dian nomenclature and combined both spe-cies in Limnornis. Other authors (e.g., Ridgely& Tudor 1994) have preferred to emphasizedifferences by recognizing two genera for thereed-haunters, although still maintaining theirclose association. Remsen (2003) maintainedthem as adjacent in his linear sequence butnoted that differences in tail structure, nestingmaterials, and egg color called into questiontheir proposed sister relationship.

DISTRIBUTION AND HABITAT

For nearly a century, Darwin’s original twospecimens of L. rectirostris were the only onesknown. Sanborn (1929) next obtained thespecies at another locality in Uruguay in 1926.Gradually, its range was extended from theprovinces of Entre Rios and Buenos Aires,Argentina, to Rio Grande do Sul and SantaCatarina, in southernmost Brazil, and the spe-cies was also found more extensively in Uru-guay (Daguerre 1933, Pereyra 1938, Esteban1949, Escalante 1956, Gerzenstein & Achaval1967, Zorilla de San Martin 1963, Alda doRosário 1996, Babarskas & Fraga 1998).

After Darwin’s original collection, Limnor-nis curvirostris was next collected from 1866 to1868 at Conchitas, Buenos Aires Province,

Argentina, by W. H. Hudson (Sclater & Salvin1868). Durnford (1877: 182) found the spe-cies common in the same province and was“at a loss to understand how this bird couldhave escaped the observation of naturalists tillMr. Darwin’s visit to South America.” Addi-tional specimens were obtained in Uruguay(Sclater & Hudson 1888, Sclater 1890, Hell-mayr 1925), Sanborn’s (1929) assertion thathis 1926 specimens from Uruguay were thefirst since Darwin being erroneous. By 1899,the range of the species was extended to RioGrande do Sul, Brazil (Ihering 1899).

Although Darwin stated (in Gould 1839)that the two reedhaunters occurred togetherand Vaurie (1980: 212) asserted that “L. rec-tirostris shares the same habitat [as L. curviros-tris], but its requirements are less rigid,” this isnot, in fact, the case. Ridgely & Tudor (1994:61) note that the two species “appear never tooccur together in the same marsh.” Belton(1984: 622) shows no overlap in rangebetween the species in Rio Grande do Sul,Brazil. Olson has experience with L. curviros-tris in Argentina, and with both speciesthrough much of Uruguay, and has not yetvisited a site where both species might beexpected to occur in proximity.

Limnoctites rectirostris typically occurs inmarshes. Although a variety of plants mayoccur in such sites, particularly at the edges,the bird is found only where the spiny cara-guatá, Eryngium spp., dominates. In the orni-thological literature this plant has erroneouslybeen referred to as a sedge (e.g., Ridgely &Tudor 1994, Remsen 2003: 226, but correctlyas an “apiaceous herb” on 261) or a grass(Gerzenstein & Achaval 1967, Vaurie 1980,Babarskas & Fraga 1998). It is actually a dicotthat belongs in the carrot family (Apiaceae orUmbelliferae). Ricci & Ricci (1984: 205) cor-rectly describe the plants as growing in “bro-meliad-like rosettes,” the leaves of which arebeset with sharp spines that make the pursuitof birds in this habitat a decided challenge to

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the ornithologist’s flesh and clothing. Thespecies that have been mentioned in connec-tion with Limnoctites are Eryngium horridum(Belton 1984, Remsen 2003), E. pandanifolium(Gerzenstein & Achaval 1967, Babarskas &Fraga 1998, Remsen 2003), and E. eburneum(Ricci & Ricci 1984). The ranges of theseplants are given as southern Brazil to NEArgentina, with the last two extending to Par-aguay (Cabrera 1965).

That the birds are tied to the plant andnot necessarily to marshy environments isshown by their occurrence at 200 to 250 m inrocky scrub forest where Eryngium pandanifo-lium occurs in 5 to 20 m wide patches alongstreams (Gerzenstein & Achaval 1967). ThatL. rectirostris occurs as high as 1100 m (Ridgely& Tudor 1994, BirdLife International 2000,Remsen 2003) is presumably based on thepopulations in Aparados da Serra NationalPark mentioned by Belton (1984: 621),though no substantive documentation of theiroccurring so high appears to exist.

Although also a marsh bird, L. curvirostrisis found in extensive reedbeds, especially ofthe giant sedge or pajonal (Scirpus giganteus),the grass known as espadaña (Zizaniopsis bona-riensis), and also cattails (Typha). Although itsbriefly stated range from Rio Grande do Sulto Buenos Aires is the same as that of L. rec-tirostris, within that area it is much the moreabundant and widespread of the two speciesbecause of the greater extent of its habitat.

In summary, although the distributions ofthe two reedhaunters are superficially similar,they are adapted to distinct habitats and areprobably never syntopic.

NIDIFICATION

Nest structure in the Furnariidae is extremelydiverse and has been used to devise a phylog-eny of the family (Zyskowski & Prum 1999).In this phylogeny, Limnornis and Limnoctiteswere grouped with Phleocryptes melanops on the

basis of their supposedly building a domednest with “a small awning over the nestentrance” (p. 899). The nest of Limnornis curvi-rostris is described by von Ihering (1902) andBelton (1984); that of Limnoctites rectirostris byDaguerre (1933), Ricci & Ricci (1984) andSick (1993); and those of both species in Vau-rie (1980) and Narosky et al. (1983). Includedhere are all the references cited by Zyskowski& Prum (1999), plus some others, but nonementions an awning over the entrance of thenest of Limnoctites. This error came aboutfrom misinterpretation (K. Zyskowski pers.com. to Olson, June 2004) of photographs ofthe nest of Phylloscartes ventralis in the articlepreceding the paper by Ricci & Ricci thatwere erroneously captioned as Limnoctites.Zyskowski (pers. com. ibid.) has since foundand photographed a nest of L. rectirostris inUruguay and confirmed that it does not havean awning. Remsen (2003) took his descrip-tions of the nests of both reedhaunters ashaving awnings from Zyskowski & Prum(1999).

The first mention of an “awning” beingconstructed by Limnornis curvirostris appears tobe that in one of two nests of described byNarosky (in Vaurie 1980: 213). Later, Naroskyet al. (1983: 36) confirmed that the nest of L.curvirostris “possesses, like that of the junqueroPh[leocryptes] melanops, a 3 cm projection oreave above the mouth of the entrance” (ourtranslation).

On the other hand, it does seem that thebasic nest structure of Limnornis and Phleo-cryptes is similar, best exemplified by Narosky’sdescriptions in Vaurie (1980). Phleocryptes pre-sents a presumably more derived condition incovering its nest with mud.

The vast majority of species of Furnari-idae have pure white eggs, although the eggsin a few species of Synallaxis may have a lightbluish, greenish or yellowish cast (Schönwet-ter & Meise 1967: 12, Sick 1993: 428). In con-trast, the eggs of Limnornis curvirostris and

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STABLE 1. Specimen data and Genbank accession numbers for samples used in the study. Family and subfamily designations are given according to twoalternative classification schemes. Acronyms: AMNH = American Museum of Natural History, New York; NRM = Swedish Museum of Natural History;USN rsity of Copenhagen.

Spec tochrome b Myoglobin G3PDHCincFurnFurnUpuAutoLochPhilyThriAnuAsthCoryCranCranCranSynaLimLimPhleoGeosSclerDrymXiphDendSittaChamPteroScyta

Y590044d

Y064279c

Y065700a

Y590048d

Y065699a

Y065702a

Y065701a

Y065709a

Y065705a

Y065710a

Y065708a

Y065707a

Y590043d

Y065715a

Y065711a

Y065712a

Y065713b

Y065714a

Y065718a

Y065717a

Y065716a

AY590054d

AY064255c

AY065756a

AY590058d

AY065755a

AY065758a

AY065757a

AY065765a

AY065761a

AY065766a

AY065764a

AY065763a

AY590053d

AY065772a

AY065768a

AY065769 a

AY065770b

AY065771a

AY065776a

AY065774a

AY065773a

AY590065d

AY590066d

AY590078d

AY590081d

AY590076d

AY590077d

AY590072d

AY590070d

AY590073d

AY590069d

AY590068d

AY590063d

AY590080d

AY590088d

AY590093d

AY590087d

AY590092d

AY590095d

AY590096d

AY590097

Refe

M = National Museum of Natural History, Smithsonian Institution; ZMUC = Zoological Museum of the Unive

ies Classif. by Irestedt et al. (2002, in press) Classif. by Remsen (2003) Voucher no. Cylodes fuscusarius cristatusarius leucopuscerthia jelskiimolus leucophthalmusmias nematurador atricapilluspadectes flammulatusmbius annumbi (*)enes cactorumphistera alaudinaioleuca albicapillaioleuca pyrrhophiaioleuca sulphuriferallaxis ruficapillanocites rectirostrisnornis curvirostriscryptes melanopsitta tenuirostrisurus scansor ornis bridgesiiocolaptes majorrocincla tyranninasomus griseicapillus aeza meruloides

ptochos tarniilopus spillmanni

Furnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: SclerurinaeFurnariidae: SclerurinaeFurnariidae: DendrocolaptinaeFurnariidae: DendrocolaptinaeFurnariidae: DendrocolaptinaeFurnariidae: DendrocolaptinaeFormicariidae RhinocryptidaeRhinocryptidae

Furnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: FurnariinaeFurnariidae: PhilydorinaeFurnariidae: PhilydorinaeFurnariidae: PhilydorinaeFurnariidae: PhilydorinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: SynallaxinaeFurnariidae: FurnariinaeFurnariidae: PhilydorinaeDendrocolaptidaeDendrocolaptidaeDendrocolaptidaeDendrocolaptidaeFormicariidae RhinocryptidaeRhinocryptidae

ZMUC S220NRM 966772

ZMUC 125590ZMUC S439NRM 937251ZMUC S2577NRM 937334ZMUC S428NRM 966903ZMUC S150NRM 966910

ZMUC 124797NRM 966821

USNM B17199NRM 956643

USNM B14895USNM B2735USNM B2734ZMUC S292NRM 937258NRM 966930NRM 966847NRM 976662NRM 967031ZMUC S2053

AMNH RTC467ZMUC S540

AA

AAAAAAAA

A

A

AAAAAAAAA

rences: aIrestedt et al. (2001), bIrestedt et al. (in press), cEricson et al. (2002), dFjeldså et al. (2005).

OLSON ET AL.

Phleocryptes melanops are a deep greenish-blue(Schönwetter & Meise 1967: 12; Vaurie 1980).We reviewed the egg color of at least 32 gen-era of Furnariidae, mainly based on the col-lections of the British Museum (MichaelWalters, pers. com. to Olson, June 2004) andscattered references in more recent literatureand found no exceptions to the precedingobservations. Thus, the decidedly greenishblue eggs of Limnornis curvirostris and Phleoc-ryptes appear to be unique within the Furnari-idae, a similarity noticed at least as early asPereyra (1938).

In contrast, the nest and eggs of Limnoc-tites rectirostris have been likened to that ofCranioleuca. “The [white] eggs and nest moreclosely resemble those of C. sulphurifera thanthose of L. curvirostris, whose eggs are bluishgreen and the nest [of L. curvirostris], althoughspherical with a lateral entrance, is more con-spicuous for being constructed at consider-able height (up to 1.6 m), and is without muchdifferentiation between the external materialand the lining” (translated from López-Lanúset al. 1999: 63).

Within the Furnariidae the white eggs andless elaborate nest of L. rectirostris are proba-bly plesiomorphic states, or relatively so in thecase of the nest, the apparently uniqueawninged nest and blue-green eggs of L. curvi-rostris and Phleocryptes are derived conditionsthat argue for a sister-group relationship forthese two taxa.

MOLECULAR SYSTEMATICS

Materials and methods. Twenty species of oven-birds and four woodcreepers were selectedfor the molecular analysis. In addition to Lim-nornis and Limnoctites, we included representa-tives of all major clades of furnariidsidentified by Fjeldså et al. (2005), as well as thegenera Sclerurus and Geositta, which form thesister group to a clade consisting of all theother ovenbirds (called “core ovenbirds”

herein) and the woodcreepers (Irestedt et al.2002, Chesser 2004, Fjeldså et al. 2005). Serv-ing as outgroups are three representatives ofthe proposed sister clade of Furnariidae(Irestedt et al., 2002, Chesser 2004): Pteropto-chos tarnii and Scytalopus spillmanni (family Rhi-nocryptidae) and Chamaeza meruloides (familyFormicariidae). Sample identifications andGenBank accession numbers are given inTable 1.

We sequenced the complete myoglobinintron 2 (along with 13 bp and 10 bp of theflanking regions of exons 2 and 3, respec-tively), the complete glyceraldehydes-3-phos-phodehydrogenase (G3PDH) intron 11(along with 36 bp and 18 bp of exons 11 and12, respectively), and 999 bp from the cyto-chrome b gene (see Ericson et al. 2002,Irestedt et al. 2002, and Fjeldså et al. 2003,2004, for primer sequences and procedures).Positions where the nucleotide could not bedetermined with certainty were coded withthe appropriate IUPAC code. Due to thelow number of insertions in the introns,the combined sequences could easily bealigned by eye. All gaps in the myoglobin andthe G3PDH sequences were treated as miss-ing data in the analyses. No insertions, dele-tions, stop or nonsense codons wereobserved in any of the cytochrome bsequences.

ModelTest 3.06 (Posada & Crandall 1998)in conjunction with PAUP* (Swofford 1998)was used to evaluate the fit of the data to dif-ferent models for nucleotide substitutions.The GTR+I+Γ model has the best fit for thecombined data set and for the cytochrome bpartition, while GTR+G was selected forboth the myoglobin intron 2 and the G3PDHintron 11 partitions. These models wereused in the analyses of the individual genes, aswell in the analysis of the combined data set.The posterior probabilities of trees andparameters in the substitution modelswere approximated with Markov chain

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Monte Carlo and Metropolis coupling usingthe program MrBayes (Huelsenbeck & Ron-quist 2001, Ronquist & Huelsenbeck 2003).

We ran two analyses of 500,000 genera-tions for each gene with trees sampled every100 generation. The parameter estimates fromthe two separate MCMC runs for each dataset were compared and found to be very simi-lar, thus allowing an inference from the con-catenated output. Posterior probabilities forthe individual genes were based on a total of9000 trees saved after discarding the treessaved during the “burnin phase” (as estimatedgraphically) in each analysis. The analysis ofthe combined data set was conducted in thesame manner as for the individual genesexcept that the number of generations in eachrun was two millions. The 50% majority-ruleconsensus trees were identical in the runs andthe posterior probabilities are based on a totalof 390,000 saved trees.

Results. The concatenated sequences became2164 basepairs long after alignment. Withinthe ingroup (all ovenbirds and woodcreepers)the lengths of the myoglobin sequences rangefrom 677 in Philydor to 701 bp in Geositta, andthe lengths of the G3PDH sequences rangefrom 349 in Dendrocincla to 401 bp in Xiphoco-laptes. The myoglobin intron is the least varia-ble among the three genetic markers studiedherein (Table 2). The observed substitutionrate is larger in the mitochondrial cytochromeb gene, in accordance with previous studies(Irestedt et al. 2004). The alignment of the

myoglobin intron 2 and G3PDH intron 11sequences requires postulation of a few inser-tions and deletion events (indels) among thecore ovenbirds, most of which involve only asingle basepair (singletons) and/or are foundonly in a single taxon (autapomorphic).

The phylogenetic trees obtained from theBayesian analyses of the individual geneticmarkers, as well as of the combined data set,are generally similar (Figs 1A-C and 2). Theanalyses also agree well on the systematicpositions of Limnornis and Limnoctites, whichclearly are not sister taxa. Most major group-ings of ingroup taxa are recovered by all datapartitions and receive generally high supports(Table 3). Monophyly of the ingroup isstrongly corroborated, as is the basal positionof Geositta and Sclerurus relative to the coreovenbirds and woodcreepers, which in turnare recovered as sister groups. All data parti-tions except cytochrome b also support abasal position among the core ovenbirds of aclade consisting of Automolus, Thripadectes andPhilydor. Although the cytochrome b data setalso recognizes monophyly of this clade, itleaves the group unresolved in relation to theother core ovenbirds. The remaining coreovenbirds are divided into two clades thatreceive strong support in the analyses ofmost data partitions. Limnornis groups withPhleocryptes with 100% posterior probabilitiesin the analyses of both myoglobin and thegenes combined. The analyses of cytochromeb and G3PDH also suggest a Limnornis-Phleo-cryptes clade, albeit with weaker support.

TABLE 2. Descriptive statistics for the observed pairwise, uncorrected sequence divergencies (p-distances)between selected groups of taxa. Larger distances suggest higher rates of nucleotide substitutions.

Cytochrome b Myoglobin intron 2 G3PDH intron 11Mean Min. Max. Mean Min. Max. Mean Min. Max.

Within core ovenbirdsCore ovenbirds vs woodcreepersCore ovenbirds vs Sclerurus/Geositta-cladeCore ovenbirds vs Outgroups

12.6314.5315.5717.7

2.412.2113.5115.84

15.6217.1218.1220.32

2.34.173.777.09

0.292.962.85.67

3.625.164.928.6

5.166.847.719.31

0.764.594.536.68

7.738.839.6311.54

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OLSON ET AL.

Cinclodes, Lochmias, Upucerthia and the twospecies of Furnarius are the other membersof this larger group of core ovenbirds.The other group consists of the threespecies of Cranioleuca, Limnoctites, Synallaxis,

Asthenes, Anumbius and Coryphistera. Limnoctitesfalls well within the Cranioleuca clade, butit groups with different species of Cranio-leuca depending on which genetic marker isstudied.

FIG. 1. Majority-rule consensus trees obtained from Bayesian analyses of three genetic markers: A. cyto-chrome b, B. myoglobin intron 2, C. glyceraldehydes-3-phosphodehydrogenase (G3PDH) intron 11. Pos-terior probabilities are indicated at the nodes.

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DISCUSSION

DNA sequence data unambiguously showthat Limnornis curvirostris and Limnoctites rectiros-tris are not particularly closely related. Limnoc-tites falls out among the species of Cranioleuca

and within the sample we tested was closest tothe Sulphur-throated Spinetail C. sulphurifera.This is another marsh-inhabiting species witha distribution similar to the two reedhaunters,except that it also occurs farther inland and tothe south in Argentina (Remsen 2003). As

FIG. 2. Maximum-likelihood tree calculated from the combined data set (cytochrome b, myoglobin intron2 and glyceraldehydes-3-phosphodehydrogenase intron 11). Posterior probabilities from the Bayesiananalysis are indicated at the nodes.

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recounted above, Esteban (1949) advocatedputting Limnoctites in the Synallaxinae.Gerzenstein & Acheval (1967), followed byRicci & Ricci (1984), noted its general similar-ity in appearance to Cranioleuca sulphurifera.López-Lanús et al. (1999) concurred and alsoconsidered that the vocalizations, nest, andeggs of Limnoctites were more similar to C. sul-phurifera than to Limnornis curvirostris.

In the straight bill and in tail and rectrixshape, Limnoctites agrees better with Cranio-leuca than with Limnornis. The juvenal plumageof C. sulphurifera, which lacks the breaststreaks and yellow throat of the adult, is likethat of Limnoctites in every respect except forits rufous and black pattern in the wing.

Similarities extend to vocalizations as well.“L. rectirostris gives a hissing trill Ti-ti-ti-ti-titititritriiiii, accelerating at the end. This ismaintained at a stable frequency of between 4and 6.5 kHz, lasting about 2.5 and 3.5 s, com-posed of 14 to 18 elements, varying up to 22... . The territorial advertising vocalization ofthis species is well differentiated from that ofL. curvirostris, whose song sounds rough andfaltering. On the other hand, it could be con-founded by an untrained ear with that of C.

sulphurifera, which gives a vocalization of simi-lar length (between 2.5 and 3.5 s) but with awider frequency range (between 1 and 6.5kHz) and a greater and more complex quan-tity of elements” (translated from López-Lanús et al. 1999: 62).

In our molecular phylogeny Limnornis iswell separated from Limnoctites and its closestrelative among the taxa we sampled is theWren-like Rushbird Phleocryptes melanops, withthe Sharp-tailed Streamcreeper Lochmias ne-matura as the closest outlying sister group.There is nothing in the external morphologyof these three genera that suggests a particu-larly close relationship. An obligate inhabitantof streams in dense forests (Remsen 2003 ),Lochmias differs strikingly from the other twoin its habits.

Phleocryptes, like Limnornis, inhabits marshyreedbeds and the two may occur together inthe same marsh, although Phleocryptes is muchmore widely distributed, from Pacific Ecua-dor to Chile and east across parts of Bolivia,Paraguay, most of Argentina, Uruguay andsouthern Brazil (Remsen 2003). It is a smallerbird with a much more variegated plumagethan Limnornis. Apart from DNA sequences,

TABLE 3. Posterior probabilities for selected nodes obtained in analyses of different data partitions.

Combined data set

Cytochrome b Myoglobin intron 2

G3PDH 11

Monophyly of Furnariidae (ovenbirds and woodcreepers)

Basal position of a Sclerurus/Geositta-cladeMonophyly of core-ovenbirdsBasal position of Automolus, Thripadectes and

Philydor among core-ovenbirdsMonophyly of a Cranioleuca spp. and Limnoc-

tites cladeSister group relationship between Limnoctites

and Cranioleuca sulphurifera

Sister group relationship of Limnornis and Phleocryptes

100%

100%100%100%

100%

100%

100%

100%

98%100%

No support, but no contradition

99%

100%

76%

100%

100%100%92%

100%

100%

100%

100%

90%100%93%

100%

Alternative tree topology

suggested61%

356

EVOLUTION OF TWO MARSH-DWELLING OVENBIRDS

the best evidence for a relationship betweenthese two genera comes from the nests andeggs, as outlined above.

CONCLUSIONS

The available molecular, morphological, andbehavioral data all indicate that Limnoctites rec-tirostris belongs among the species currentlyincluded in the genus Cranioleuca, within whichit appears to be most closely related toanother marsh-dwelling species, C. sulphurifera.Thus it appears possible that Limnoctites rec-tirostris may be a large, paedomorphic (inplumage) derivative of C. sulphurifera thatmoved out of reedbeds and became adaptedto marshes of Eryngium, where its long,straight bill is possibly an adaptation forextracting prey from the spiny rosettes of thatplant, as suggested by Ricci & Ricci (1984).

It would be premature, however, to makeany taxonomic or nomenclatural recommen-dations until the systematics of the entiregenus Cranioleuca has been undertaken.Zyskowski & Prum (1999) indicate that thereare two distinct groups within Cranioleucabased on nest structure, which they designateas the albiceps group and the pyrrhophia group.Limnoctites and C. sulphurifera belong to thepyrrhophia group. The type species of Cranio-leuca is C. albiceps and there does not seem tobe any previously recognized generic nameavailable for the pyrrhophia group (Hellmayr1925). Thus, if this group were to be sepa-rated generically from Cranioleuca, the 8 spe-cies now in it would presumably have to takethe name Limnoctites, which would certainly bean ironic turn of events. Another possibility isthat L. rectirostris and C. sulphurifera may besufficiently distinct as to be separated in Lim-noctites, so that the rest of the pyrrhophia groupwould require a new name.

Our molecular evidence indicates that theprevious intimation of a relationship betweenLimnornis and Phleocryptes is correct. This

hypothesis is corroborated by the similar neststructure, egg coloration, and to some extentby the similarity in microhabitat. These twotaxa otherwise appear to be sufficiently dis-tinct from one another morphologically andmolecularly to justify the recognition of sepa-rate monotypic genera.

ACKNOWLEDGMENTS

For assistance in the field in Argentina andUruguay, we are greatly indebted to JoaquinAldabe, J. Phillip Angle, Luis Chiappe, MiguelClara, Santiago Claramunt, Christina Geb-hard, and Christopher Milensky. JorgeCravino, Director, Departamento de Fauna,Montevideo was instrumental in providingpermits and critical information as well asarranging for accommodations for fieldworkon numerous estancias in Uruguay, to whosegenerous owners we are most grateful.George and Janet Winter provided a sumptu-ous base of operations for fieldwork in Uru-guay in 2002. J. V. Remsen, Michael Walters,and Kristof Zyskowski provided much usefulinformation and references. Field work inArgentina and Uruguay was supported by theVirginia Y. Hendry Fund and the AlexanderWetmore Endowment Fund, SmithsonianInstitution, respectively. Samples owned bythe Swedish Museum of Natural History werecollected in Paraguay in collaboration with theMuseo Nacional de Historia Natural del Para-guay, San Lorenzo. The Swedish ResearchCouncil (grant no. 621-2001-2773 to P.E.)funded the laboratory work. We thank J. V.Remsen and Frank Steinheimer for many use-ful comments on the manuscript.

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