Evolution of early male-killing in horizontally transmitted parasites

Modelling lifestyle changes in Insect endosymbionts, from insect mutualist to plant pathogen

Several insect endosymbionts have evolved to become plant pathogens, but the causes of this transition are currently unknown. In this paper, we use adaptive dynamics to develop hypotheses to explain why an insect endosymbiont would evolve to become a plant pathogen. We develop a model of facultative insect endosymbionts, capable of both vertical transmission within the insect population and horizontal transmission between insect and plant populations. We assume that an evolutionary trade-off between vertical and horizontal transmission exists. The transmission method of an endosymbiont is correlated with the nature of the symbiotic relationship between host and symbiont. We assume that vertical transmission represents an insect endosymbiont lifestyle and horizontal transmission represents a plant pathogen lifestyle. Our results suggest that temperature increases, increased agricultural intensification, disease dynamics within the plant host, insect mating system and change in the host plant of the insect may influence an evolutionary transition from an insect endosymbiont to a plant pathogen.

Micropathogen Community Analysis in Hyalomma rufipes via High-Throughput Sequencing of Small RNAs

Ticks are important vectors in the transmission of a broad range of micropathogens to vertebrates, including humans. Because of the role of ticks in disease transmission, identifying and characterizing the micropathogen profiles of tick populations have become increasingly important. The objective of this study was to survey the micropathogens of Hyalomma rufipes ticks. Illumina HiSeq2000 technology was utilized to perform deep sequencing of small RNAs (sRNAs) extracted from field-collected H. rufipes ticks in Gansu Province, China. The resultant sRNA library data revealed that the surveyed tick populations produced reads that were homologous to St. Croix River Virus (SCRV) sequences. We also observed many reads that were homologous to microbial and/or pathogenic isolates, including bacteria, protozoa, and fungi. As part of this analysis, a phylogenetic tree was constructed to display the relationships among the homologous sequences that were identified. The study offered a unique opportunity to gain insight into the micropathogens of H. rufipes ticks. The effective control of arthropod vectors in the future will require knowledge of the micropathogen composition of vectors harboring infectious agents. Understanding the ecological factors that regulate vector propagation in association with the prevalence and persistence of micropathogen lineages is also imperative. These interactions may affect the evolution of micropathogen lineages, especially if the micropathogens rely on the vector or host for dispersal. The sRNA deep-sequencing approach used in this analysis provides an intuitive method to survey micropathogen prevalence in ticks and other vector species.