Resolution of the early placental mammal radiation using Bayesian phylogenetics.

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).

A molecular phylogeny for aplocheiloid fishes (Atherinomorpha, Cyprinodontiformes): the role of vicariance and the origins of annualism.

Annual aplocheiloid killifish embryos possess a rare ability among vertebrates to enter stages of developmental arrest (diapause) when subjected to adverse environmental conditions. Previous morphological analyses have presented disparate hypotheses regarding the evolution of the intriguing life history associated with this phenomenon. We present a novel hypothesis of aplocheiloid relationships based on 1,009 bp of sequence data from three mitochondrial genes (cytochrome b, 12S rRNA, and 16S rRNA). Phylogenetic analysis using maximum parsimony, neighbor-joining, and maximum likelihood produce strongly congruent topologies. Our data confirm the monophyly of the Neotropical family Rivulidae, while demonstrating a paraphyletic Old World assemblage. The basal sister group position of Indo-Malaysian and Madagascaran taxa relative to a monophyletic South American/African dichotomy strongly indicates the role of vicariance in the diversification of these fishes in spite of their definition as secondary freshwater fish. The distribution of annualism onto this topology implies a single early origin for this suite of characters, prior to the divergence of South American and African taxa. If so, then annualism has since been lost several times during the evolution of genera now residing in permanent aquatic habitats. Paleoclimatic knowledge complements this scenario based on molecular characters.

Phylogenetic relationships within the aplocheiloid fish genus Rivulus (Cyprinodontiformes, Rivulidae): implications for Caribbean and Central American biogeography.

We examined the phylogenetic relationships of 16 northern species of the aplocheiloid genus Rivulus inhabiting the Caribbean, Central America, and South America. A total of 714 base pairs per taxon were sequenced from two segments of the mitochondrial genome, 12S rRNA and cytochrome b. Both parsimony and neighbor-joining analyses suggest an ancient vicariant origin of the Greater Antillean taxa, in addition to a quite recent dispersal of species into the Lesser Antilles from the South American mainland. Combined analyses support the monophyly of the northern South American assemblage as the sister group of a Central American/Columbian biota. However, the monophyly of the Central American biota remains uncertain. Divergence estimates for the Central American taxa are calibrated from the Last Cretaceous separation of the proto-Antilles from the Americas. These data suggest that the extant Central American taxa represent the descendants of at least two separate invasions during the Cenozoic, prior to the closing of the Panamanian isthmus. Times are consistent with the extensive evidence for reptilian and mammalian exchange throughout the Cenozoic.

Poststreptococcal crescenteric glomerulonephritis in children: comparison of quintuple therapy versus supportive care.

Crescenteric glomerulonephritis preceded by a streptococcal infection with creatinine clearance CCr of less than 30 ml/minute/1.73 m2 was treated by supportive care plus three months of quintuple therapy (prednisone, azathioprine, cyclophosphamide, dipyridamole, and heparin followed by warfarin) in five children (Group A) or by supportive care alone in five others (Group B). Of the glomeruli examined, 69.8 +/- 11.7% (mean +/- SE) in Group A and 64.4 +/- 10.6% in Group B had crescents which involved 54.0 +/- 10.8% and 60.0 +/- 10.5% of glomerular circumference, respectively. Clinical and histologic findings supported a recent streptococcal infection in every patient. Two patients from Group A had mild proteinuria and normal CCr at 12 months; one died abruptly of pulmonary hemorrhage after maintaining a normal CCr for 25 months. Following a second episode of poststreptococcal acute glomerulonephritis seven months after the first, one patient from Group B had persistent mild proteinuria for 41 months and hypertension through 56 months of follow-up. Nine surviving patients have maintained normal CCr for eight to 60 months (mean 29.5 months). The findings of this study suggest that this quintuple therapy offers no advantage over supportive care in the clinical management and outcome of children with severe crescenteric glomerulonephritis when an antecedent streptococcal infection is confirmed by serologic and histopathologic criteria.