Inconsistent dilution: experimental but not field evidence for a dilution effect in Daphnia-bacteria interactions.

The dilution effect hypothesis, which suggests greater host biodiversity can reduce infectious disease transmission, occurs in many systems but is not universal. Most studies only investigate the dilution of a single parasite in a community, but many host communities have multiple parasites circulating. We studied a zooplankton host community with prior support for a dilution effect in laboratory- and field-based studies of a fungal parasite, Metschnikowia bicuspidata.

Pathways linking nutrient enrichment, habitat structure, and parasitism to host-resource interactions.

Human activities simultaneously alter nutrient levels, habitat structure, and levels of parasitism. These activities likely have individual and joint impacts on food webs. Furthermore, there is particular concern that nutrient additions and changes to habitat structure might exacerbate the size of epidemics and impacts on host density.

Honeybee visitation to shared flowers increases prevalence in bumblebees.

is a widespread pollinator parasite that commonly infects honeybees and wild pollinators, including bumblebees. Honeybees are highly competent hosts and previous work in experimental flight cages suggests can be transmitted during visitation to shared flowers. However, the relationship between floral visitation in the natural environment and the prevalence of among multiple bee species has not been explored.

Habitat quality influences pollinator pathogen prevalence through both habitat-disease and biodiversity-disease pathways.

The dilution effect hypothesis posits that increasing biodiversity reduces infectious disease transmission. Here, we propose that habitat quality might modulate this negative biodiversity-disease relationship. Habitat may influence pathogen prevalence directly by affecting host traits like nutrition and immune response (we coined the term "habitat-disease relationship" to describe this phenomenon) or indirectly by changing host biodiversity (biodiversity-disease relationship).

Pollinator community species richness dilutes prevalence of multiple viruses within multiple host species.

Most pathogens are embedded in complex communities composed of multiple interacting hosts, but we are still learning how community-level factors, such as host diversity, abundance, and composition, contribute to pathogen spread for many host-pathogen systems. Evaluating relationships among multiple pathogens and hosts may clarify whether particular host or pathogen traits consistently drive links between community factors and pathogen prevalence. Pollinators are a good system to test how community composition influences pathogen spread because pollinator communities are extremely variable and contain several multi-host pathogens transmitted on shared floral resources.

Rapid juvenile hormone downregulation in subordinate wasp queens facilitates stable cooperation.

In many cooperatively breeding animals, subordinate group members have lower reproductive capacity than dominant group members. Theory suggests subordinates may downregulate their reproductive capacity because dominants punish subordinates who maintain high fertility. However, there is little direct experimental evidence that dominants cause physiological suppression in subordinates.