Background: Within-host competition between strains of a vector-borne pathogen can affect strain frequencies in both the host and vector, thereby affecting viral population dynamics. However little is known about inter-strain competition in one of the most genetically diverse and epidemiologically important mosquito-borne RNA virus: dengue virus (DENV). To assess the strength and symmetry of intra-host competition among different strains of DENV, the effect of mixed infection of two DENV serotypes, DENV2 and DENV4, on the replication of each in cultured mosquito cells was tested. The number of infectious particles produced by each DENV strain in mixed infections was compared to that in single infections to determine whether replication of each strain was decreased in the presence of the other strain (i.e., competition). The two DENV strains were added to cells either simultaneously (coinfection) or with a 1 or 6-hour time lag between first and second serotype (superinfection).

The structure of the hybrid zone between the ground crickets, Allonemobius socius and Allonemobius fasciatus, approximates an environmental mosaic based on temperature/moisture at regional spatial scales. In the present study, we show that the micro‐geographic spatial structure (i.e. single fields) of this hybrid zone is governed by the same criteria. Thus, the criteria that structure this hybrid zone are scale independent, even though the agents that implement these criteria may differ at various scales (climate, latitude, and elevation at regional scales; grass height, slope aspect, and field use at micro‐geographic scales). Additionally, the study demonstrates a previously unknown barrier to genetic exchange in this system that acts before conspecific sperm precedence. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 777–796.