A hitchhikers guide to the Galápagos: co-phylogeography of Galápagos mockingbirds and their parasites.

BACKGROUND: Parasites are evolutionary hitchhikers whose phylogenies often track the evolutionary history of their hosts. Incongruence in the evolutionary history of closely associated lineages can be explained through a variety of possible events including host switching and host independent speciation. However, in recently diverged lineages stochastic population processes, such as retention of ancestral polymorphism or secondary contact, can also explain discordant genealogies, even in fully co-speciating taxa. The relatively simple biogeographic arrangement of the Galápagos archipelago, compared with mainland biomes, provides a framework to identify stochastic and evolutionary informative components of genealogic data in these recently diverged organisms. RESULTS: Mitochondrial DNA sequences were obtained for four species of Galápagos mockingbirds and three sympatric species of ectoparasites--two louse and one mite species. These data were complemented with nuclear EF1α sequences in selected samples of parasites and with information from microsatellite loci in the mockingbirds. Mitochondrial sequence data revealed differences in population genetic diversity between all taxa and varying degrees of topological congruence between host and parasite lineages. A very low level of genetic variability and lack of congruence was found in one of the louse parasites, which was excluded from subsequent joint analysis of mitochondrial data. The reconciled multi-species tree obtained from the analysis is congruent with both the nuclear data and the geological history of the islands. CONCLUSIONS: The gene genealogies of Galápagos mockingbirds and two of their ectoparasites show strong phylogeographic correlations, with instances of incongruence mostly explained by ancestral genetic polymorphism. A third parasite genealogy shows low levels of genetic diversity and little evidence of co-phylogeny with their hosts. These differences can mostly be explained by variation in life-history characteristics, primarily host specificity and dispersal capabilities. We show that pooling genetic data from organisms living in close ecological association reveals a more accurate phylogeographic history for these taxa. Our results have implications for the conservation and taxonomy of Galápagos mockingbirds and their parasites.

Hypothyroidism in a breast-fed preterm infant resulting from maternal topical iodine exposure.

Hypothyroidism developed in a preterm infant, whose initial screening thyroid function test results were normal, at 2 weeks of life. The infant's mother was packing her Caesarian incision with iodine soaked gauze, resulting in a markedly increased breast milk iodine concentration. Treatment with oral L-thyroxine normalized thyroid function tests.

Trends in severe bronchopulmonary dysplasia rates between 1994 and 2002.

OBJECTIVE: To examine temporal trends in the rates of severe bronchopulmonary dysplasia (BPD) between 1994 and 2002. STUDY DESIGN: In a retrospective cohort study, all infants with a gestational age (GA) <33 weeks in a large managed care organization were identified. Annual rates of BPD (defined as an oxygen requirement at 36 weeks corrected GA), severe BPD (defined as respiratory support at 36 weeks corrected GA), and death before 36 weeks corrected GA were examined. RESULTS: Of the 5115 infants in the study cohort, 603 (12%) had BPD, including 246 (4.9%) who had severe BPD. There were 481 (9.5%) deaths before 36 weeks corrected GA. Although the decline in BPD in this period was not significant, the rates of severe BPD declined from 9.7% in 1994 to 3.7% in 2002. Controlling for gestational age, the odds ratio (95% CI) for annual rate of decline in severe BPD was 0.890 (0.841-0.941). Controlling for gestational age, deaths before 36 weeks corrected GA also declined, with the odds ratio (CI) for the annual decline being 0.944 (0.896-0.996). CONCLUSIONS: In this study population, the odds of having of BPD remained constant after controlling for GA. However, the odds of having severe BPD declined on average 11% per year between 1994 and 2002.

Rehospitalization in the first year of life among infants with bronchopulmonary dysplasia.

OBJECTIVE: To describe rates and identify risk factors for rehospitalization during the first year of life among infants with bronchopulmonary dysplasia (BPD). STUDY DESIGN: This was a retrospective cohort study of infants born at a gestational age (GA) <33 weeks, between 1995 and 1999. BPD was defined as requirement of supplemental oxygen and/or mechanical ventilation at 36 weeks' corrected GA. The outcome was rehospitalization for any reason before first birthday. RESULTS: In the first year of life, 118 of 238 (49%) infants with BPD were rehospitalized, more than twice the rate of rehospitalization of the non-BPD population, which was 309 of 1359 (23%) (P=<.0001). No measured factor discriminated between those infants with BPD who were and were not rehospitalized, even when only rehospitalizations for respiratory diagnoses were considered. CONCLUSIONS: Among premature infants, BPD substantially increases the risk of rehospitalization during the first year of life. Neither demographic nor physiologic factors predicted rehospitalization among the infants with BPD. Other factors, such as air quality of home environment, passive smoking exposure, respiratory syncytial virus prophylaxis, breast-feeding status, and/or parenting and primary care management styles, should be examined in future studies.