RESUMEN
Molecular phylogenetic studies have resolved placental mammals into four major groups, but have not established the full hierarchy of interordinal relationships, including the position of the root. The latter is critical for understanding the early biogeographic history of placentals. We investigated placental phylogeny using Bayesian and maximum-likelihood methods and a 16.4-kilobase molecular data set. Interordinal relationships are almost entirely resolved. The basal split is between Afrotheria and other placentals, at about 103 million years, and may be accounted for by the separation of South America and Africa in the Cretaceous. Crown-group Eutheria may have their most recent common ancestry in the Southern Hemisphere (Gondwana).
Asunto(s)
Teorema de Bayes , Mamíferos/clasificación , Mamíferos/genética , Filogenia , África , Animales , Emparejamiento Base , Evolución Biológica , Núcleo Celular/genética , Ecosistema , Fósiles , Genes , Genes de ARNr , Funciones de Verosimilitud , Cadenas de Markov , Marsupiales/clasificación , Marsupiales/genética , Mitocondrias/genética , Método de Montecarlo , Placenta , Probabilidad , Análisis de Secuencia de ADN , América del SurRESUMEN
The hoatzin (Opisthocomus hoazin) lives in the humid lowlands of northern and central South America, often in riparian habitats. It is a slender bird approximately 65 cm in length, brownish with lighter streaks and buffy tips to the long tail feathers. The small head has a ragged, bristly crest of reddish-brown feathers, and the bare skin of the face is bright blue. It resembles a chachalaca (Ortalis, Cracidae) in size and shape, but its plumage and markings are similar to those of the smaller guira cuckoo (Guira guira). The hoatzin (pronounced Watson) has been a taxonomic puzzle since it was described in 1776. It usually has been viewed as related to the gallinaceous birds, but alliances to other groups have been suggested, including the cuckoos. We present DNA sequence evidence from the 12S and 16S rRNA mitochondrial genes, and from the nuclear gene that codes for the eye lens protein, alpha A-crystallin. The results indicate that the hoatzin is most closely related to the typical cuckoos and that the divergence occurred at or near the base of the cuculiform phylogenetic tree.
Asunto(s)
Aves/clasificación , Cristalinas/genética , Mitocondrias/genética , ARN Ribosómico 16S/genética , ARN Ribosómico/genética , Animales , Secuencia de Bases , Aves/genética , Datos de Secuencia Molecular , Filogenia , América del SurRESUMEN
Summary The phylogenetic relationship between the members of the super-order Paenungulata, the manatees, elephants and hyraces were investigated using amino acid sequence analysis of the oc A crystallin of the eye lenses of these animals. The analysis confirms the monophyletic origin of the orders Hyracoidea, Sirenia and Proboscidea and places the edentates as the oldest offshoot from the main eutherian stem, followed by the Paenungulates as the next branch. The results suggest that the manatee may be closer to the hyrax than to the elephant due to the presence of 72-Leu in the hyrax and the manatee but not in the elephant. Morphological evidence would indicate a closer relationship between the elephant and the manatee which, if true, would require a back-substitution of 72 Leu Val in the elephant oc A chain or two parallel substitutions 72 Val Leu in the hyrax and manatee.
Resumo As relações filogenéticas entre os membros da super-ordem Paenungulata, os peixes-bois, elefantes e "hyraxes", foram investigadas, utilizando-se a seqüência de análises de aminoácidos da proteína oc A do cristalino da lente dos olhos destes animais. As análises confirmam a origem monofilética das ordens Hyracoidea, Sirenia e Proboscidea e colocam os edentatas como os mais antigos do ramo da linha principal dos euterianos, seguidos pelos Paenungulatas como ramo mais próximo. Os resultados sugerem que os peixes-bois podem estar mais próximos dos hyraxes que dos elefantes dada a presença dos 72-Leu nos hyraxes e peixes-bois, mas não nos elefantes. Evidências morfológicas indicariam uma relação mais próxima entre o elefante e peixe-boi, as quais, se verdadeira, exigirão uma retrossubstituição do 72-Leu Val na cadeia oc A dos elefantes ou 2 substituições paralelas na 72-Val Leu nos hyraxes e peixes-bois.
RESUMEN
Summary The phylogenetic relationship between the members of the super-order Paenungulata, the manatees, elephants and hyraces were investigated using amino acid sequence analysis of the oc A crystallin of the eye lenses of these animals. The analysis confirms the monophyletic origin of the orders Hyracoidea, Sirenia and Proboscidea and places the edentates as the oldest offshoot from the main eutherian stem, followed by the Paenungulates as the next branch. The results suggest that the manatee may be closer to the hyrax than to the elephant due to the presence of 72-Leu in the hyrax and the manatee but not in the elephant. Morphological evidence would indicate a closer relationship between the elephant and the manatee which, if true, would require a back-substitution of 72 Leu Val in the elephant oc A chain or two parallel substitutions 72 Val Leu in the hyrax and manatee.
Resumo As relações filogenéticas entre os membros da super-ordem Paenungulata, os peixes-bois, elefantes e "hyraxes", foram investigadas, utilizando-se a seqüência de análises de aminoácidos da proteína oc A do cristalino da lente dos olhos destes animais. As análises confirmam a origem monofilética das ordens Hyracoidea, Sirenia e Proboscidea e colocam os edentatas como os mais antigos do ramo da linha principal dos euterianos, seguidos pelos Paenungulatas como ramo mais próximo. Os resultados sugerem que os peixes-bois podem estar mais próximos dos hyraxes que dos elefantes dada a presença dos 72-Leu nos hyraxes e peixes-bois, mas não nos elefantes. Evidências morfológicas indicariam uma relação mais próxima entre o elefante e peixe-boi, as quais, se verdadeira, exigirão uma retrossubstituição do 72-Leu Val na cadeia oc A dos elefantes ou 2 substituições paralelas na 72-Val Leu nos hyraxes e peixes-bois.