A survey of cardinalfish (Apogonidae) of Antsiranana Bay, northern Madagascar

The cardinalfish of Antsiranana Bay, northern Madagascar, were surveyed over an 11 month period by underwater census employing a simple search pattern using self-contained underwater breathing apparatus. Over this period 15 species were observed including one species not previously recorded in Madagascar, Siphamia versicolor. Whilst some species were ubiquitous across sites within the bay others appeared only as single records. Cardinalfish communities were compared between sites within the bay using PRIMER 6 (Plymouth Routines In Multivariate Ecological Research) and on a national scale against existing records. Overall the species richness of cardinalfish in Antsiranana Bay is less than that observed in other regions of Madagascar. The reasons behind these regional variations include oceanic currents, temperature, depth, disturbance and sedimentation, a recognised threat to Madagascar’s marine communities. This final point was reaffirmed by comparison of cardinalfish communities between sites within the bay which revealed little variation in species composition between sites, with the exception of highly-sedimented sites in the north - east of the bay that had a significantly different cardinalfish fauna to the rest. As a family that rely on the complexity of the coral reef for shelter, and exhibit high site fidelity, examination of cardinalfish communities may provide a measure of the health of a region’s reef

The decline of isochores in mammals: an assessment of the GC content variation along the mammalian phylogeny.

Whether isochores, the large-scale variation of the GC content in mammalian genomes, are being maintained has recently been questioned. It has been suggested that GC-rich isochores originated in the ancestral amniote genome but that whatever force gave rise to them is no longer effective and that isochores are now disappearing from mammalian genomes. Here we investigated the evolution of the GC content of 41 coding genes in 6 to 66 species of mammals by estimating the ancestral GC content using a method which allows for different rates of substitution between sites. We found a highly significant decrease in the GC content during early mammalian evolution, as well as a weaker but still significant decrease in the GC content of GC-rich genes later in at least three groups of mammals: primates, rodents, and carnivores. These results are of interest because they confirm the recently suggested disappearance of GC-rich isochores in some mammalian genomes, and more importantly, they suggest that this disappearance started very early in mammalian evolution

In the heartland of Eurasia: the multilocus genetic landscape of Central Asian populations

Located in the Eurasian heartland, Central Asia has played a major role in both the early spread of modern humans out of Africa and the more recent settlements of differentiated populations across Eurasia. A detailed knowledge of the peopling in this vast region would therefore greatly improve our understanding of range expansions, colonizations and recurrent migrations, including the impact of the historical expansion of eastern nomadic groups that occurred in Central Asia. However, despite its presumable importance, little is known about the level and the distribution of genetic variation in this region. We genotyped 26 Indo-Iranian- and Turkic-speaking populations, belonging to six different ethnic groups, at 27 autosomal microsatellite loci. The analysis of genetic variation reveals that Central Asian diversity is mainly shaped by linguistic affiliation, with Turkic-speaking populations forming a cluster more closely related to East-Asian populations and Indo-Iranian speakers forming a cluster closer to Western Eurasians. The scattered position of Uzbeks across Turkic- and Indo-Iranian-speaking populations may reflect their origins from the union of different tribes. We propose that the complex genetic landscape of Central Asian populations results from the movements of eastern, Turkic-speaking groups during historical times, into a long-lasting group of settled populations, which may be represented nowadays by Tajiks and Turkmen. Contrary to what is generally thought, our results suggest that the recurrent expansions of eastern nomadic groups did not result in the complete replacement of local populations, but rather into partial admixture