Phylogeny and biogeography of ratite birds inferred from DNA sequences of the mitochondrial ribosomal genes

The origin of the flightless ratite birds of the southern continents has been debated for over a century. Whether dispersal or vicariance (continental breakup) best explains their origin depends largely on their phylogenetic relationships. No consensus has been reached on this issue despite many morphological and molecular studies. To address this question further we sequenced a 2.8-kb region of mitochondrial DNA containing the ribosomal genes in representative ratites and a tinamou. Phylogenetic analyses indicate that Struthio (Africa) is basal and Rhea (South America) clusters with living Australasian ratites. This phylogeny agrees with transferrin and DNA hybridization studies but not with sequence analyses of some protein-coding genes. These results also require reevaluation of the phylogenetic position of the extinct moas of New Zealand. We propose a new hypothesis for the origin of ratites that combines elements of dispersal and vicariance.      

Moth sex chromatin probed by comparative genomic hybridization (CGH).

Abstract: Comparative genomic hybridization (CGH) with a probe mixture of differently labeled genomic DNA from females and males highlighted the W chromosomes in mitotic plates and the W chromatin in polyploid interphase nuclei of the silkworm Bombyx mori, the flour moth Ephestia kuehniella, and the wax moth Galleria mellonella. The overproportionate fluorescence signal indicated an accumulation of repetitive sequences in the respective W chromosomes. Measurements of the fluorescence signals revealed two components, one that is present also in male DNA (non-W chromosomes) and another one that is present only in or preponderantly in female DNA (W chromosomes). While the W chromosomes of E. kuehniella and G. mellonella had both components, that of B. mori appeared to lack the latter component. Our results show that CGH can be applied to obtain a first estimate of the sequence composition of sex chromosomes in species from which otherwise little is known on the molecular level.