Diversification of Ramphastinae (Aves, Ramphastidae) prior to the Cretaceous/Tertiary boundary as shown by molecular clock of mtDNA sequences

Partial cytochrome b and 12S rDNA mitochondrial DNA sequences of eight representatives of the Ramphastidae family were analyzed. We applied the linearized tree method to identify sequences evolving at similar rates and estimated the divergence times among some of the taxa analyzed. After excluding Ramphastos tucanus and Capito dayi from our data set, the remaining taxa presented a constant rate of DNA substitution, and branch lengths could be re-estimated with a clock constraint using the maximum likelihood method. Branch lengths were calibrated assuming that Galliformes and Piciformes split around 100 million years ago (mya). Our results indicate that Ramphastinae, and probably Capitoninae, diverged from other Piciformes in the Late Cretaceous (82 mya), suggesting that Piciformes is another avian order that survived the mass extinction event occurred 65 mya at the Cretaceous/Tertiary (K/T) boundary. The divergence times estimated within the Ramphastinae genera cover the period from the Middle Eocene (around 47 mya) through the Late Miocene (9.5 mya). Our estimate of divergence time is coincidental with the split of the African and the South American continents and other intense geologic activities and modifications of the areas which correspond to the current Neotropics. These events might have influenced the diversification of Ramphastinae in South America.

Mitochondrial genome organization and vertebrate phylogenetics

Com o advento das técnicas de seqüenciamento de DNA, a organizaçäo do genoma mitocondrial de vertebrados mostrou variaçäo entre níveis taxonômicos superiores. A organizaçäo "conservada" é encontrada em mamíferos placentários, tartarugas, peixes, alguns lagartos e Xenopus. As aves, outras espécies de lagartos, crocodilianos, mamíferos marsupiais, cobras, tuatara, lampréia, uma espécie de peixe e alguns outros anfíbios apresentam ordens que diferem do que foi inicialmente considerado a "ordem gênica conservada". O mecanismo mais provável de novos rearranjos gênicos parece ser duplicaçäo in tandem e múltiplos eventos de deleçäo, sempre associados com seqüências de tRNAs. Alguns novos rearranjos parecem ser típicos de grupos monofiléticos e o uso destes dados pode ser útil em questöes de filogenia envolvendo níveis taxonômicos superiores. Outros aspectos como a estrutura secundária de tRNA e códons de início e de parada de transcriçäo de genes codificantes para proteínas podem ser úteis para comparaçöes entre os genomas mitocondriais de vertebrados.

DNA fingerprinting in the rare black-fronted piping guan Pipile jacutinga (Cracidae, Aves)

Brazilian Cracidae are threatened by heavy environmental degradation and hunting. The Black-fronted piping-guan (Pipile jacutinga) used to inhabit the Atlantic coastal highland forests. Now it occurs in limited forest areas where it is rarely seen. Interative management, including captive breeding, might be an important action for its survival. We present data on DNA fingerprinting using Jeffreys' human minisatlelite probes 33.6 and 33.15. Our results show that this technique is useful for estimating the genetic variability of natural populations and may help to maintain the genetic variability of captive bred individuals of this species. A linkage analysis of the fingerprint profiles in a family with 7 chicks was performed (to estimate the number of independently segregating loci detected in this species) and at least 16 highly polymorphic independent loci were identified for each probe.