Y:/Lund University/jav/articles/JAV3313/jav3313.3d[x] Thursday, 30th October 2003 18:42:0

Reflections Reflections are short contributions (5/2 printed pages, about 1200Á/1500 words) in which an editor and/ or a reviewer comments on, and provides a perspective on one of the published papers in the same issue. An abstract is not required.

JOURNAL OF AVIAN BIOLOGY 00: 1Á/3, 2003

The ‘‘Coerebidae’’: a polyphyletic taxon that dramatizes historical over-emphasis on bill shape as a taxonomic character

J. V. Remsen, Jr., Museum of Natural Science, Foster Hall 119, Louisiana State University, Baton Rouge, Louisiana 70803, USA. E-mail: [email protected]

Because the core body shapes of birds are relatively for whom plasticity of bill shape in Galapagos ‘‘finches’’ conservative (Hafner et al. 1984), differences in bill shape catalyzed his famous ideas, would presumably have and size account for much of the variation among birds warned ornithologists against using bill shape as a that we humans perceive. Although tail and leg size and character, but many bird families were and continue to shape may vary almost as much, the bill may exert more be defined, at least in part, by bill shape. This criterion influence on our cognitive perception because of its ‘‘works’’ well for some groups with unique bills, such as proximity to the bird’s face. The close association of bill ducks, flamingos, parrots, and woodpeckers. In many size and shape with food type and feeding behavior adds other cases, however, over-emphasis on bill shape, or additional weight to the ornithologist’s perception of skeletal and muscle characters that co-vary with bill their ‘‘importance.’’ For these reasons, it is perhaps no shape (Bock 1964), has produced taxa that are either not surprise that bird bills have played a prominent role in monophyletic or if so, merely arbitrary breaks inflicted their classification. on continuous variation (Storer 1969). Burns et al.’s For the Passeriformes known as nine-primaried os- research is the most recent of several studies that indicate cines, bill characters historically have been used fre- that perhaps the worst case of over-emphasis on bill quently in determining family boundaries. For example, shape is in the group known as the New World nine- Ridgway’s (1901) classic treatment used bill characters in primaried oscines, the ones included in Ridgway’s key. virtually every line of his dichotomous key for the six Burns et al.’s analysis of mitochondrial sequences New World families that he recognized: Fringillidae for shows beyond a doubt that the ‘‘Coerebidae’’ actually finches (all the conical-billed species), ‘‘Tanagridae’’ consists of multiple independent lineages. In fact, of the

(/ Thraupidae) for tanagers, ‘‘Mniotiltidae’’ (/ Par- 10 original genera in that family, the new genetic data ulidae) for warblers, Icteridae for blackbirds, Catam- can confirm that only three pairs are each others’ closest blyrhynchidae for one species, the plushcap relatives (Chlorophanes and Iridophanes, Conirostrum Catamblyrhynchus diadema, with an unusual bill, and and Oreomanes, and Dacnis and Cyanerpes), and that Coerebidae for honeycreepers, which were those species the ‘‘honeycreeper’’ ecotype evolved a minimum of six that had bill shapes or tongues associated with flower- times within the tanager-finch lineage. In three of those feeding. Yet Ridgway himself recognized that his key cases, the sister genera are not of the omnivore didn’t work for some species, especially some of the ‘‘tanager’’ ecotype but rather of the ‘‘finch’’ ecotype, honeycreepers, and his accompanying text was sprinkled e.g., Coereba and a Tiaris grassquit. Burns et al. did not with cautionary sentences and pleas for additional data. data from enough species of Diglossa to determine He astutely noted that some species that he placed in the whether that genus is polyphyletic, as is strongly Coerebidae might actually be warblers or tanagers. suggested by morphological data (Bock 1985). A century later, Kevin Burns, Shannon Hackett and All this reflects the ongoing overhaul of family the late Nedra Klein (2003, see pp. xx-yy in this issue) boundaries within the New World nine-primaried os- have hammered the final nail into the coffin of the cines. Long-suspected of taxon boundary problems ‘‘Coerebidae’’. The importance of the dismantling of the (Sclater 1886, Storer 1969), the tanagers (Thraupidae) ‘‘Coerebidae’’, which actually began more than 50 years and sparrows (Emberizidae) were identified as paraphy- ago with Beecher’s anatomical studies, reaches beyond letic taxa by DNA hybridization studies of Bledsoe the boundariesUNCORRECTED of phylogenetic classification. Darwin, (1988) and Sibley and PROOF Ahlquist (1990). Although DNA

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hybridization data have often been harshly criticized, the tanagers and relatives, it will be possible to analyze results from such studies often have been vindicated by these lineages to quantify and identify where morphol- subsequent, different genetic techniques, and this would ogy has masked phylogeny. Such analyses so far in birds now include the results of Burns et al. (2003). Currently, have shown that plasticity and convergence in characters the delimitation of monophyletic groups in the New associated with feeding, namely the head and bill in World nine-primaried oscines is undergoing systematic herons (McCracken and Sheldon 1998) and the legs in and thorough investigation, with at least four research diving ducks (McCracken et al. 1999), are largely teams actively working together on this group, each with responsible for the differences in phylogenies based on a different taxon focus. With the probable exception of morphology versus genetics. Convergence among the Icteridae, the other four ‘‘families’’ contain multiple lineages that are obviously distantly related has been genera that actually belong in other groups. For example, recognized for more than a century. For example, the the ‘‘tanager’’ genera Euphonia and Chlorophonia have extreme ‘‘honeycreeper’’ ecotype, namely small birds already been excised from the Thraupidae and deported with strongly decurved bills and bright plumage, has to the Fringillidae (Burns 1997, Klicka et al. 2000, Yuri evolved at least five times in the Passeriformes: Cya- and Mindell 2002, Banks et al. 2003). The eventual nerpes in the Thraupidae, Myzomela and perhaps others taxonomic realignments will have important effects on in the Meliphagidae, Vestiaria and Drepanis in the research on these taxa, which are frequently studied by Fringillidae, Neodrepanis in the Philepittidae, and al- bird biologists because of their abundance and ubiquity. most all Nectariniidae. However, many cases of poly- By now, all avian biologists recognize that controlling for phyly as a consequence of past taxonomic over-emphasis phylogenetic effects is critical to the interpretation of all on bill shape and other plastic morphological characters comparative data (e.g., Lanyon 1993). doubtless remain to be discovered. The contrast between the fates of the Coerebidae and the Icteridae are striking and are worth exploring. The Icteridae has included species with somewhat curved bills used for flower-probing (some Icterus orioles) as References well as some taxa with conical, seed-crushing bills Banks, R. C., Cicero, C., Dunn, J. L., Kratter, A. W., (Molothrus ater, Dolichonyx), yet with one exception Rasmussen, P. C., Remsen, J. V., Jr., Rising, J. A. and Stotz, (below), the monophyly has never been seriously ques- D. F. 2003. Forty-fourth supplement to the American Ornithologists’ Union Check-list of North American Birds. tioned. The Icteridae as defined by Ridgway (1901) and Á/ Auk 120: 923Á/931. Hellmayr (1937) remains 100% intact, whereas the Bledsoe, A. H. 1988. Nuclear DNA evolution and phylogeny of Coerebidae, as defined by Ridgway (1901), Hellmayr the New World nine-primaried oscines. Á/ Auk 105: 504Á/ 515. (1935), Wetmore (1960), and Meyer de Schauensee Bock, W. J. 1964. Bill shape as a generic character in the (1966), no longer exists. Assuming that further investiga- cardinals. Á/ Wilson Bulletin 76: 50Á/61. tions continue to show that the Icteridae is a mono- Bock, W. J. 1985. Is Diglossa (?Thraupinae) monophyletic? Á/ phyletic, the reasons for the ‘‘resiliency’’ of the Icteridae In: Buckley, P. A., Foster, M. S., Morton, E. S., Ridgely, F. G. and Buckley, F. G. (eds), Neotropical Ornithology. are presumably: (1) plumage patterns in the Icteridae are Ornithological Monographs no. 36, pp. 319Á/332. relatively conservative (e.g., Omland and Lanyon 2000) Burns, K. J. 1997. Molecular systematics of tanagers (Thraupi- and are unlike those of most other New World nine- nae): Evolution and biogeography of a diverse radiation of Neotropical birds. Á/ Mol. Phyl. Evol. 8: 334Á/348. primaried oscines; (2) most species in the Icteridae are Burns, K. J., Hackett, S. J. and Klein, N. J. 2003. Phylogenetic above the range in body size shown in the other families; relationships of Neotropical honeycreepers and the evolu- and (3) within the genera that deviate from the straight, tion of feeding morphology. Á/ J. Avian Biol. 34: xxÁ/yy. Hafner, M. S., Remsen, J. V., Jr. and Lanyon, S. M. 1984. Bird pointed bill with elevated culmen (often with associated versus mammal morphological differentiation. Á/ Evolution with ‘‘gaping’’ feeding behavior) that typifies most 38: 1154Á/1156. Icteridae, intermediates between the typical and atypical Hellmayr, C. E. 1935. Catalogue of birds of the Americas. Alaudidae to Compsothlypidae. Á/ Field Mus. Nat. Hist. shapes exist so that the extremes are not isolated but Publ., Zool. Ser., vol. 13., pt. 8. 541 pp. seem part of a continuum. The one exception, the Hellmayr, C. E. 1937. Catalogue of birds of the Americas. bobolink D. oryzivorus in the monotypic genus Dolicho- Icteridae. Á/ Field Mus. Nat. Hist. Publ., Zool. Ser., vol. 13., pt. 10. 228 pp. nyx, has produced the only challenge to the family’s Klicka, J., Johnson, K. P. and Lanyon, S. M. 2000. New World monophyly and often has been placed in a separate nine-primaried oscine relationships: constructing a mito- subfamily within the Icteridae, mainly because of lack of chondrial DNA framework. Á/ Auk 117: 321Á/326. intermediates between it and more typical Icteridae. Lanyon, S. M. 1993. Phylogenetic frameworks-towards a firmer foundation for the comparative approach. Á/ Biol. J. Linnean Recent genetic results (Lanyon and Omland 1999), Soc. 49: 45Á/61. however, clearly show that it is embedded deep within Lanyon, S. M. and Omland, K. E. 1999. A molecular phylogeny the Icteridae and does not warrant subfamily status. of the blackbirds (Icteridae): five lineages revealed by cytochrome-b sequence data. Á/ Auk 116: 629Á/639. As Burns and others firm up the branching pattern McCracken, K. G., Harshman, J., McClellan, D. and Afton, A. within theUNCORRECTED species-rich and morphologically diverse D. 1999. Data set incongruencePROOF and correlated character

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evolution: an example of functional convergence in the hind- Sclater, P. L. 1886. Á/ Catalogue of the birds of the British limbs of stifftail diving ducks. Á/ Syst. Biol. 48: 683Á/714. Museum 11: 1Á/431. McCracken, K. G. and Sheldon, F. H. 1998. Molecular and Sibley, C. G. and Ahlquist, J. E. 1990. Phylogeny and osteological heron phylogenies: sources of incongruence. Á/ classification of birds. Á/ Yale Univ. Press, New Haven, Auk 115: 127Á/141. Connecticut. Meyer de Schauensee, R. 1966. The species of birds of South Storer, R. W. 1969. What is a tanager? Á/ Living Bird 8: 127Á/ America and their distribution. Á/ Livingston Publ. Co., 136. Narberth, Pennsylvania. Wetmore, A. 1960. A classification of the birds of the world. - Omland, K. E. and Lanyon, S. M. 2000. Reconstructing Smithsonian Misc. Á/ Coll. 139: 1Á/37. plumage evolution in orioles (Icterus): repeated convergence Yuri, T. and Mindell, D. P. 2002. Molecular phylogenetic and reversal in patterns. Á/ Evolution 54: 2119Á/2133. analysis of Fringillidae, ‘‘New World nine-primaried os- Ridgway, R. 1901. The birds of North and Middle America. Á/ cines’’ (Aves: Passeriformes). Á/ Mol. Phyl. Evol. 23: 229Á/ Bull. U. S. Nat. Mus., no. 50, pt. 1. 243.

UNCORRECTED PROOF

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