Proposal (264) to South American Classification Committee

Incluir el género Oryzoborus dentro de Sporophila

El género Oryzoborus comprende un grupo de cuatro pequeños Emberizidae de pico muy robusto. Actualmente, todas las guías de aves sudamericanas lo consideran un género aparte de Sporophila (pero muy afín) e incluso ha sido sugerido que no debería ser incluido en Sporophila por las diferencias en el tamaño del pico (Stiles 1996) y por las características del esqueleto (Webster y Webster 1999). Otros autores, sin embargo, han sugerido que debería ser incluido en Sporophila (Olson 1981, Sato et al. 2001, Burns et al. 2002.).

Nuevos datos: Lijtmaer et al. (2004), usaron dos fragmentos diferentes de mitocondrial DNA para realizar un análisis filogenético de Sporophila y géneros afines (Volatinia, Tiaris y Oryzoborus). Concluyeron que Oryzoborus está incluido dentro de un bien soportado clade conteniendo a todas las especies de Sporophila, lo cual sugiere fuertemente la unión de los dos géneros.

Sin embargo, viendo los diferentes árboles originados en el análisis, llama la atención que las dos especies de Oryzoborus usadas (angolensis y crassirostris) están casi siempre separadas por especies de Sporophila, y a veces muy separadas como se aprecia en la Fig. 4. De aceptarse esta propuesta, esto crea un problema para ubicación de las especies dentro de la secuencia.

Yo voto SI a esta propuesta.

Literatura citada

Burns, K. J., Hackett, S. J., y Klein, N. K. 2002. Phylogenetic relationship and morphological diversity in Darwin´s finches and their relatives. Evolution 56: 1240-1252.

Lijtmaer, D. A. N. M. Sharpr, P. L. Tubaro y S. C. Lougheed. 2004. Molecular phylogenetics and diversification of the genus Sporophila (Aves: Passeriformes). Mol. Philo. Evol. 33:562-579.

Olson, S. L. 1981. A revision of the species of Sporophila (Oryzoborus) angolensis (Aves: Emberizinae). Proc. Bio. Soc. Wash. 94:43-51.

Sato, A., Tychi, H., O´h Uigin, C., Grant, P. R., Grant, B. R. y Klein, J. 2001. On the origin of Darwin´s finches. Mol. Biol. Evol. 18:299-311.

Stiles, F. G. 1996. When black plus white equals gray: the nature of variation in the variable seedeater complex (Emberizinae: Sporophila). Orn. Neotrop. 7:75-107.

Webster, J. D. y J. R. Webster. 1999. Skeletons and the genera of sparrows (Emberizinae). Auk 116:1054-1074.

Manuel Nores, Marzo 2007

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Comments from Remsen: "YES. Although taxon-sampling in the genetic data are weak, the burden of proof, in my opinion, now falls on those who would recognize Oryzoborus. That Oryzoborus, as currently defined, is likely not monophyletic further suggest that the best thing to do for now is to dump them all into a broadly defined Sporophila."

Comments from Cadena: "NO. Manuel may well be right, but none of the relevant nodes in the molecular studies that have considered this question are well-supported. Oryzoborus and Sporophila (and Dolospingus, too) are clearly very closely related, but the available data cannot reject the hypothesis that these three genera are monophyletic. Thus, as mentioned by Robbins et al. (2005, Ibis), "...whether to group these genera on the basis of genetic similarity or retain them on the basis of diagnostic bill and skull differences will remain a matter of preference until a more fully resolved phylogeny of the seed-finch clade is achieved...". For the sake of stability, I'd rather retain Oryzoborus until more data are available to sort out relationships with more confidence."

Comments from Robbins: "NO, the molecular results presented by Litmaer et al. (2004) are not well supported, and we concluded (Robbins et al. 2005) that a more complete molecular data set is needed within the seed-finch clade before any changes should be made."

Comments from Stiles: "NO. I agree with Daniel and Mark that more complete taxon sampling will be required before making this move."

Comments from Zimmer: "NO. I'd rather wait. In addition to morphological distinctions, I think vocal differences might be suggestive that these shouldn't be merged."

Comments from Jaramillo: "NO - I am swayed by the comments from Daniel and Mark. This is a difficult group, with various issues going on here. The only resolution will be for someone to tackle this with dense taxon sampling, multiple genes, etc. Bill size is highly plastic in finches, I would not at all be surprised if Oryzoborus are in fact nested within Sporophila, but want stronger data before I accept that arrangement."

Comments from Pacheco: "YES. Embora os resultados de Lijtmaer et al. (2004) não sejam irrefutáveis, eu considero que estes combinados com sugestões prévias independentes (sobretudo, Olson 1981) indicam claramente que Oryzoborus não se sustenta em separado. Um oportuno trabalho (com boa cobertura) acerca da filogenia do atual parafilético gênero Sporophila deverá se ocupar, oportunamente, da subordinação mais apropriada dos táxons tradicionalmente listados sob Oryzoborus."