The 'dilution effect' (DE) hypothesis predicts that diverse host communities will show reduced disease. The underlying causes of pathogen dilution are complex, because they involve non-additive (driven by host interactions and differential habitat use) and additive (controlled by host species composition) mechanisms. Here, we used measures of complementarity and selection traditionally employed...

We have studied the effect of different light gradient regimes on host-plant selection of the carrot psyllid, Trioza apicalis Förster. In both a strong and a weak light gradient, carrot psyllids preferred a carrot leaf placed in higher light intensity. When the choice was between the host (carrot Daucus carota L.) and a non-host (barley Hordeum vulgare L.) virgin adults settled significantly mo...

The evolution of complex organismal traits is obvious as a historical fact, but the underlying causes--including the role of natural selection--are contested. Gould argued that a random walk from a necessarily simple beginning would produce the appearance of increasing complexity over time. Others contend that selection, including coevolutionary arms races, can systematically push organisms tow...

Traditionally, evolutionary biologists have viewed mutations within individual genes as the major source of phenotypic variation leading to adaptation through natural selection, and ultimately generating diversity among species. Although such processes must contribute to the initial development of gene functions and their subsequent fine-tuning, changes in genome repertoire, occurring through g...

With the increasing appreciation for the crucial roles that microbial symbionts play in the development and fitness of plant and animal hosts, there has been a recent push to interpret evolution through the lens of the "hologenome"--the collective genomic content of a host and its microbiome. But how symbionts evolve and, particularly, whether they undergo natural selection to benefit hosts are...

Organisms and the symbionts they harbor may experience opposing forces of selection. In particular, the contrasting inheritance patterns of maternally transmitted symbionts and their host's nuclear genes can engender conflict among organizational levels over the optimal host offspring sex ratio. This study uses a male-killing Wolbachia endosymbiont and its host Drosophila innubila to experiment...

Parasites and hosts are involved in a continuous coevolutionary process leading to genetic changes in both counterparts. To understand this process, it is necessary to track host responses, one of which could be an increase in sex and recombination, such as is proposed by the Red Queen hypothesis. In this theoretical framework, the inducible recombination hypothesis states that B-chromosomes (g...

We model the genealogies of coupled haploid host-virus populations. Hosts reproduce and replace other hosts as in the Moran model. The virus can be transmitted between individuals of the same and succeeding generations. The epidemic model allows a selective advantage for susceptible over infected hosts. The coupled host-virus ancestry of a sample of hosts is embedded in a branching and coalesci...

Genetic selection for resistance to pesticides has been proposed as a method for enhancing the use of parasites in integrated pest management (IPM)programs. Genetic improvementof parasites is an experimental tactic in biologicalcontrol, and a series of questions need to be resolved. First, is it possible to select parasites for resistance to pesticides? The JulyAugust 1988 issue of California A...