Conservation taxonomy of the Greater Antillean Oriole (<em>Icterus dominicensis</em>): diagnosable plumage variation among allopatric populations supports species status

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Melissa R. Price
William K. Hayes

Keywords

Abstract

Abstract: Allopatric populations, such as those present on islands, pose special challenges to identifying taxonomic boundaries which can be practically addressed using diagnostic criteria. To assess the taxonomic and, hence, conservation status of the four island populations of the Greater Antillean Oriole (Icterus dominicensis), we examined 156 male specimens of I. dominicensis for six discrete and three continuous plumage characters. The four island populations proved to be 100% diagnosable. Icterus d. northropi differed from all other taxa by having the greatest extent of yellow on the venter (non-overlapping with other taxa). Icterus d. portoricensis was distinguished from all other taxa by the presence of a black upper rump (yellow in other taxa) and the least extent of yellow on the rump (non-overlapping with other taxa). Icterus d. melanopsis and I. d. dominicensis were fully discriminated from I. d. northropi and I. d. portoricensis by the aforementioned characters and from each other by upper-tail covert color (black and r 50% yellow, respectively). Our findings support recent studies suggesting that the four island groups represent distinct allospecies consistent with interpretations of both the phylogenetic and evolutionary species concepts. With elevation to full species, conservation priorities need to be revisited, particularly for the critically endangered Bahamas taxon (I. d. northropi).


Keywords: conservation taxonomy, Greater Antillean Oriole, Icterus dominicensis, plumage variation, species limits, West Indies islands


Resumen: Taxonomía para la conservación de Icterus dominicensis: una variación diagnosticable en el plumaje entre poblaciones alopátricas apoya el estado específico- Poblaciones alopátricas, como las presentes en las islas, plantean desafíos especiales a la identificación de los límites taxonómicos que pueden abordarse en la práctica con criterios de diagnóstico. Para evaluar la taxonomía y, por tanto, el estado de conservación de las cuatro poblaciones isleñas de Icterus dominicensis se examinaron 156 ejemplares machos para seis caracteres discretos y tres caracteres continuos del plumaje. Las cuatro poblaciones insulares demostraron ser 100% diagnosticables. Icterus d. northropi difería de todos los restantes taxones por tener el mayor grado de amarillo en el vientre (que no se traslapan con otros grupos taxonómicos). Icterus d. portoricensis se distinguió de todos los otros grupos taxonómicos por la presencia de una rabadilla negra (de color amarillo en otros taxones) y el menor grado de amarillo en la parte posterior (que no se traslapan con otros grupos taxonómicos). Icterus d. melanopsis y I. d. dominicensis fueron totalmente discriminados de I. d. northropi y de I. d. portoricensis por los caracteres mencionados y entre ellos por el color de la parte superior de la rabadilla (negro y amarillo r 50%, respectivamente). Los resultados respaldan estudios recientes que sugieren que los cuatro grupos de las islas representan distintas aloespecies, coherente con la interpretación de ambos conceptos de especie, el filogenético y el evolutivo. Con la elevación al nivel de especies, las prioridades de conservación necesitan ser revisadas, en particular para el taxón en peligro crítico de Bahamas (I. d. northropi).


Palabras clave: Icterus dominicensis, islas de las Indias Occidentales, límites de las especies, taxonomía para la conservación, variación de plumaje


Résumé: Taxonomie et conservation de l’Oriole à capuchon (Icterus dominicensis): le diagnostic des variations de plumage dans les populations allopatriques confirme le statut d’espèce- Les populations allopatriques, telles que les populations insulaires, offrent des défis particuliers quant à l’identification de limites taxonomiques grâce à des critères de diagnostic. Afin d’évaluer la taxonomie et le statut de conservation de quatre populations insulaires d’Oriole à capuchon (Icterus dominicensis), nous avons relevé sur 156 spécimens mâles de I. dominicensis 9 variables du plumage : six variables discrètes et trois continues. Les quatre populations insulaires s’avèrent être 100% diagnostiquées. Icterus d. northropi diffère de tous les autres taxons par une plus grande étendue de couleur jaune sur le ventre (sans chevauchement avec d’autres taxons). Icterus d. portoricensis se distinguait de tous les autres taxons par la présence de couleur noire sur le haut du croupion (jaune chez les autres taxons) et moins de jaune sur le croupion (sans chevauchement avec d’autres taxons). Icterus d. melanopsis et I. d. dominicensis étaient totalement séparés de I. d. northropi et I. d. portoricensis par les variables précitées et séparées l’un de l’autre par la couleur des couvertures sus-caudales (noir et r 50% jaune, respectivement). Nos résultats étayent les études récentes qui suggèrent que les quatre groupes insulaires représentent des espèces allopatriques distinctes, en cohérence avec les interprétations phylogénétiques et évolutives. En élevant le statut des sous-espèces à celui d’espèces, les priorités de conservation doivent être revues, en particulier pour le taxon Bahamas (I. d. northropi) en danger d’extinction. 


Mots clés: Antilles, conservation de la taxonomie, Icterus dominicensis, Oriole à capuchon, variation de plumage, limites spécifiques

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