Sex-biased gene expression and recent sex chromosome turnover

Cichlids are well known for their propensity to radiate generating arrays of morphologically and ecologically diverse species in short evolutionary time. Following this rapid evolutionary pace, cichlids show high rates of sex chromosome turnover. We here studied the evolution of sex-biased gene (SBG) expression in 14 recently diverged taxa of the Lake Tanganyika Tropheini cichlids, which show different XY sex chromosomes. Across species, sex chromosome sequence divergence predates divergence in expression between the sexes. Only one sex chromosome, the oldest, showed signs of demasculinization in gene expression and potentially contribution to the resolution of sexual conflict. SBGs in general showed high rates of turnovers and evolved mostly under drift. Sexual selection did not shape the rapid evolutionary changes of SBGs. Male-biased genes evolved faster than female-biased genes, which seem to be under more phylogenetic constraint. We found a relationship between the degree of sex bias and sequence evolution driven by sequence differences among the sexes. Consistent with other species, strong sex bias towards sex-limited expression contributes to resolving sexual conflict in cichlids. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)’.

Nosy Be (Madagascar) and the neighbouring islands versus tourism development

Madagascar is one of the trendiest holiday destinations. One of two key destinations is Nosy Be and surrounding smaller islands. It can be considered a local tourist hub. This work aims to illustrate the variability of the region’s tourism evolution in reference to Butler’s concept, and to specify circumstances characteristic of tropical islands, especially in less developed countries. Typology of islands has been performed according to level of tourism development; moreover, the brief evolution of post-1960s tourism development was assessed. The archipelago’s evolutionary stages of tourism development are significantly diversified, evolution has been non-linear and not always unidirectional. It is difficult to observe all stages of the cycle. The stage tends to be hard to determine, evolutionary pace tends to vary, and some stages are absent. Regional under-development and external factors may cause a regression in development. No stage changes were observed on most islands where enclave tourism developed.

A Simple Model of Unbounded Evolutionary Versatility as a Largest-Scale Trend in Organismal Evolution

The idea that there are any large-scale trends in the evolution of biological organisms is highly controversial. It is commonly believed, for example, that there is a large-scale trend in evolution towards increasing complexity, but empirical and theoretical arguments undermine this belief. Natural selection results in organisms that are well adapted to their local environments, but it is not clear how local adaptation can produce a global trend. In this paper, I present a simple computational model, in which local adaptation to a randomly changing environment results in a global trend towards increasing evolutionary versatility. In this model, for evolutionary versatility to increase without bound, the environment must be highly dynamic. The model also shows that unbounded evolutionary versatility implies an accelerating evolutionary pace. I believe that unbounded increase in evolutionary versatility is a large-scale trend in evolution. I discuss some of the testable predictions about organismal evolution that are suggested by the model.

Community Policing: Where are We Now?

Data from a national survey of police departments are presented to explore the progression of American policing from a traditional orientation to a community policing model. Despite widespread support for the idea of community policing and its service-centered orientation, the authors' findings suggest that crime control remains the primary mission of most police agencies. We infer from these data that the demonstrable transition of police agencies from a professional model to a community policing one typically is moving at an evolutionary pace rather than a revolutionary one in most places.

Carotid Angioplasty: Is it Safe?

For 15 years, balloon angioplasty has been cautiously applied to carotid artery occlusive lesions. Procedural results have, by and large, been satisfactory, but the potential for significant neurologic complications and a dearth of controlled studies with long-term follow-up have impeded the development of carotid angioplasty until recently. This review of the literature chronicles the slow but steady evolutionary pace of carotid angioplasty from its beginnings in 1980 to today's shifting focus to the use of stents. Based on these existing reports and significant personal experience, the advantages and risks of endoluminal carotid interventions are enumerated, along with suggested criteria for the application of carotid angioplasty.