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Given the difficulty of testing evolutionary and ecological theory in situ, in vitro model systems are attractive alternatives (1); however, can we appraise whether an experimental result is particular to [...]

Author(s): Samantha E. Forde (corresponding author) [1, 3]; John N. Thompson [2]; Brendan J. M. Bohannan [1] One of the central challenges of evolutionary biology is to understand how coevolution [...]

Objectives: Caring for community-residing patients with heart failure can affect caregivers’ emotional wellbeing. However, few studies have examined caregivers’ well-being longitudinally, or identified factors associated with positive and negative outcomes. The objective of this longitudinal cohort study was to examine changes in caregivers’ well-being over time, and to identify patient and caregiver factors associated with positive and negative outcomes. Method:Fifty caregiver/heart failure patient dyads were recruited from an acute care facility and followed in the community. All participants completed surveys at hospital admission and 3, 6 and 12 months later. Caregivers completed assessments of depression symptoms and positive affect and standardized measures to capture assistance provided, mastery, personal gain, social support, participation restriction, and patients’ behavioral and psychological symptoms. From patients, we collected demographic characteristics and health-related quality of life. Individual Growth Curve modelling was used to analyze the data. Results: Caregivers’ negative and positive emotions remained stable over time. Depression symptoms were associated with higher participation restriction in caregivers. Positive affect was associated with more personal gain and more social support. Patients’ health-related quality of life and their behavioral and psychological symptoms were not significantly associated with caregivers’ emotional outcomes. Conclusion:Interventions should be offered based on caregivers’ needs rather than patients’ health outcomes, and should focus on fostering caregivers’ feelings of personal gain, assisting them with securing social support, and engaging in valued activities. [ABSTRACT FROM AUTHOR]

Resource availability, dispersal and infection genetics all have the potential to fundamentally alter the coevolutionary dynamics of bacteria-bacteriophage interactions. However, it remains unclear how these factors synergise to shape diversity within bacterial populations. We used a combination of laboratory experiments and mathematical modeling to test how the structure of a dispersal network affects host phenotypic diversity in a coevolving bacteria-phage system in communities of differential resource input. Unidirectional dispersal of bacteria and phage from high to low resources consistently increased host diversity compared with a no dispersal regime. Bidirectional dispersal, on the other hand, led to a marked decrease in host diversity. Our mathematical model predicted these opposing outcomes when we incorporated modified gene-for-gene infection genetics. To further test how host diversity depended on the genetic underpinnings of the bacteria-phage interaction, we expanded our mathematical model to include different infection mechanisms. We found that the direction of dispersal had very little impact on bacterial diversity when the bacteria-phage interaction was mediated by matching alleles, gene-for-gene or related infection mechanisms. Our experimental and theoretical results demonstrate that the effects of dispersal on diversity in coevolving host-parasite systems depend on an intricate interplay of the structure of the underlying dispersal network and the specifics of the host-parasite interaction. [ABSTRACT FROM AUTHOR]

1. Emerging infectious diseases may decimate populations or become endemic, but such worst-case scenarios do not occur as frequently as might be expected, even for virulent parasites. 2. One explanation for this apparent paradox is that rapid evolution of host resistance may diminish or terminate epidemics. Theoretical and empirical studies have shown that evolution in host-parasite systems can dramatically alter the prevalence and intensity of infection. 3. The potential for rapid evolution to protect host populations from negative effects of virulent parasites depends on the type of parasite-driven evolution that occurs. In some host-parasite systems, evolution of increased host resistance can terminate epidemics. However, evolution resulting from parasite-mediated disruptive selection might actually allow a disease to persist in the host population. Epidemics may also be sustained through coevolution of the parasite. 4. The rate of evolution and subsequent disease dynamics will be affected by both the diversity of the host population and the community context in which the host-parasite interaction is embedded. Predators, competitors and food resources can all affect the rates of evolution of hosts and parasites and interact with evolution to determine the outcome of epidemics. 5. Freshwater organisms have played an important role in the studies of eco-evolutionary dynamics. Rapid evolution in response to parasitism has been demonstrated in multiple freshwater host species, which appears to have protected some of these populations from the virulent effects of infectious diseases. 6. Studies of emerging infectious diseases in freshwater ecosystems should consider the possibility of evolution of hosts and/or parasites on ecological timescales, since this phenomenon can profoundly affect disease dynamics. [ABSTRACT FROM AUTHOR]