The changing picture in surgery of pulmonary tuberculosis

In a review of the operative treatment of 1,271 patients with pulmonary tuberculosis in an 11-year period, it was noted that, beginning with 1947, there was a great increase, relatively, in the number of cases in which pulmonary resection was carried out. In 1943, the first year of the period of study, there were six minor operative procedures to every four major operations; in 1953 the ratio was one minor to nine major. This reversal reflects the discoveries of antibiotics for conservative therapy on the one hand and the advances in surgical techniques for major operative treatment on the other. Now that it is safer, resection will probably be used more and more-including bilateral resection in "salvage" cases. On the other hand, with specific antibiotics available, there is a tendency at present to treat conservatively for longer periods in cases in which, formerly, minor operative procedures would have been carried out early.     

Assortative mating among rock-dwelling cichlid fishes supports high estimates of species richness from Lake Malawi

It has been estimated that Lake Malawi, Africa, contains 500–650 endemic species of cichlid fishes, the largest number of vertebrate species endemic to any comparable sized area on the planet. As many of these putative species cannot be distinguished anatomically, these estimates of species richness depend to a great extent on the assumption that sympatrically occurring male colour morphs represent biological species. We have tested this assumption using a combination of behavioural observations of courtship and microsatellite DNA analysis for six putative species of the Pseudotropheus ( Tropheops ) complex and three of the Pseudotropheus ( Maylandia ) complex occurring sympatrically at Nkhata Bay. We were unable to demonstrate assortative courtship for the species pairs Pseudotropheus ( Maylandia ) zebra / P . 'gold zebra' or P. ( Tropheops ) 'band'/ P. ( T .) 'rust' because we were unable to distinguish between the females of these taxa. All other taxa showed clear assortative courtship, except for P. ( T .) 'deep', a deep-water species which was rarely observed. Fixation indices (θ_ST for the infinite allele model, and R _ST for the stepwise mutation model) calculated from six microsatellite DNA loci demonstrated significant deviations from panmixia in all pairwise comparisons of putative species, indicating little or no gene flow between populations. All taxa showed high levels of allelic diversity providing evidence that genetic bottlenecking may have been of limited importance in the speciation process. Assortative mating among taxa differing only in male colouration is supportive of theories that speciation in these fishes has been driven by sexual selection by female choice.     

The role of forest maturation in causing the decline of Black Grouse Tetrao tetrix

Black Grouse Tetrao tetrix in Britain have declined through the 20th century, and most birds are now in Scotland. Many causes for this decline have been suggested, notably agricultural intensification, increased grazing levels and moorland afforestation. We examine habitat correlates of Black Grouse distribution and population change from a 700-km² area in the core of the Scottish range, where the numbers of lekking male Black Grouse declined by an estimated 70% to 270 between 1990 and 2002. Habitat data were derived from satellite imagery, in combination with map and field-collected data. Lek occurrence, lek size and changes in lek size were all correlated with forest structure, either positively with the amount of pre-thicket forest cover, or negatively with closed canopy cover. Additional effects of the cover of grass moor and dry heath suggest that Black Grouse are most likely to occur where moorland comprises Heather Calluna vulgaris and grass mosaics. Analysis of the change in Black Grouse abundance within 1.5 km of discrete forest blocks suggests that forest maturation, which has been the dominant habitat change during the course of the study, alone accounts for 58–78% of the decline. Given the close association of Black Grouse and the occurrence of woodland (and particularly conifer plantation) throughout much of their British range, these findings can be used to inform the design of management schemes for the recovery of Black Grouse.