Species-specific population structure in rock-specialized sympatric cichlid species in Lake Tanganyika, East Africa.

Species richness and geographical phenotypic variation in East African lacustrine cichlids are often correlated with ecological specializations and limited dispersal. This study compares mitochondrial and microsatellite genetic diversity and structure among three sympatric rock-dwelling cichlids of Lake Tanganyika, Eretmodus cyanostictus, Tropheus moorii, and Ophthalmotilapia ventralis. The species represent three endemic, phylogenetically distinct tribes (Eretmodini, Tropheini, and Ectodini), and display divergent ecomorphological and behavioral specialization. Sample locations span both continuous, rocky shoreline and a potential dispersal barrier in the form of a muddy bay. High genetic diversity and population differentiation were detected in T. moorii and E. cyanostictus, whereas much lower variation and structure were found in O. ventralis. In particular, while a 7-km-wide muddy bay curtails dispersal in all three species to a similar extent, gene flow along mostly continuous habitat appeared to be controlled by distance in E. cyanostictus, further restricted by site philopatry and/or minor habitat discontinuities in T. moorii, and unrestrained in O. ventralis. In contrast to the general pattern of high gene flow along continuous shorelines in rock-dwelling cichlids of Lake Malawi, our study identifies differences in population structure among stenotopic Lake Tanganyika species. The amount of genetic differentiation among populations was not related to the degree of geographical variation of body color, especially since more phenotypic variation is observed in O. ventralis than in the genetically highly structured E. cyanostictus

Risk Factors of γ-Hydroxybutyrate Overdosing

The aim of this study was to identify in recreational drug users the factors which increase the risk of overdosing (OD) with γ-hydroxybutyrate (GHB). A purposive sample of 45 experienced GHB users was interviewed, equally divided into three groups (never OD, occasional OD, and repeat OD). The repeat OD group scored highest on many risk factors regarding GHB use, the occasional OD group scored intermediate, and the never OD group scored lowest. Participants, whether or not they had overdosed on GHB, most often perceived GHB use (e.g. using more GHB than usual, using GHB doses too closely together) as the main reason for GHB OD, and many participants who had overdosed on GHB reported that they had taken more GHB than usual at their most recent occasion of GHB OD. No significant differences in co-use of GHB with other substances were found between the three groups. Our findings indicate that using GHB in the company of groups of friends probably reduces, but does not eliminate, the risk of OD

A comparison of adaptive radiations of Antarctic fish with those of nonAntarctic fish

Antarctic biologists frequently emphasize the differences between the modern Antarctic environment and its fauna, and aquatic habitats and faunas elsewhere in the world. While it is valid to portray Antarctica as remote and its fauna as endemic and cold adapted, this approach tends to obscure broad scale similarities between Antarctic and non-Antarctic faunas. For example, the Antarctic fish fauna shares an evolutionary response to its habitat with fish in some tropical, temperate and boreal lakes. In this review we compare some well studied lacustrine radiations of fish with the two radiations of marine fish in the Antarctic Region of the Southern Ocean, notothenioids and liparids. We shall first make the case that, unlike other marine habitats, the Antarctic Region fulfills most of the essential parameters of lakes containing radiations of fish and that this large component of the world ocean is equivalent to a closed basin. Therefore in spite of its vastness, the Antarctic Region provides a comparable opportunity for studying evolutionary biology within a confined area. It is likely that notothenioids, and possibly liparids, are the first known examples of species flocks or radiations of marine fish. Thus the high Antarctic shelf and upper slope is an insular evolutionary site, with endemic faunas equally as interesting, but less well known, as those in ancient lakes throughout the world