The Effects of Mating System and Genetic Variability on Susceptibility to Trematode Parasites in a Freshwater Snail, Lymnaea Stagnalis

Puurtinen, Mikael; Hytönen, Mirjami; Knott, K. Emily; Taskinen, Jouni; Nissinen, Kari; Kaitala, Veijo

doi:10.1554/04-465

Cited by 10 publications

(15 citation statements)

References 51 publications

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“…This relationship has not been so commonly studied in invertebrates but experimental work has shown that a lower genetic diversity increases the probability of parasitic infection in Daphnia magna and the freshwater snail Lymnaea stagnalis [18,19]. Thus parasitism may be a mechanism that increases the risk of extinction in small, isolated and inbred populations [7].…”

Section: Discussionmentioning

confidence: 99%

Genetic diversity, parasite prevalence and immunity in wild bumblebees

et al. 2010

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Inbreeding and a consequent loss of genetic diversity threaten small, isolated populations. One mechanism by which genetically impoverished populations may become extinct is through decreased immunocompetence and higher susceptibility to parasites. Here, we investigate the relationship between immunity and inbreeding in bumblebees, using Hebridean island populations of Bombus muscorum. We sampled nine populations and recorded parasite prevalence and measured two aspects of immunity: the encapsulation response and levels of phenoloxidase (PO). We found that prevalence of the gut parasite Crithidia bombi was higher in populations with lower genetic diversity. Neither measure of immune activity was correlated with genetic diversity. However, levels of PO declined with age and were also negatively correlated with parasite abundance. Our results suggest that as insect populations lose heterozygosity, the impact of parasitism will increase, pushing threatened populations closer to extinction.

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Section: Discussionmentioning

confidence: 99%

Genetic diversity, parasite prevalence and immunity in wild bumblebees

et al. 2010

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“…Contrary to theoretical predictions, empirical studies suggest mainly positive directional selection on quantitative immune defence traits in the wild. Birds are the most comprehensively studied group of organisms, and several studies report positive selection gradients on immune traits due to increased survival (Saino et al, 1997;Christe et al, 1998Christe et al, , 2001Gonzalez et al, 1999;Hõrak et al, 1999;Merino et al, 2000;R aberg & Stjernman, 2003;Parejo & Silva, 2009;Wilcoxen et al, 2010). For instance, male barn swallows (Hirundo rustica) that show the strongest responses in their gamma globulin levels to immune activation by sheep red blood cells are most likely to survive from one breeding season to the next (Saino et al, 1997).…”

Section: Empirical Evidencementioning

confidence: 99%

Natural selection on quantitative immune defence traits: a comparison between theory and data

Seppälä

2014

J of Evolutionary Biology

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Parasites present a threat for free-living species and affect several ecological and evolutionary processes. Immune defence is the main physiological barrier against infections, and understanding its evolution is central for predicting disease dynamics. I review theoretical predictions and empirical data on natural selection on quantitative immune defence traits in the wild. Evolutionary theory predicts immune traits to be under stabilizing selection owing to trade-offs between immune function and life-history traits. Empirical data, however, support mainly positive directional selection, but also show variation in the form of selection among study systems, immune traits and fitness components. I argue that the differences between theory and empirical data may at least partly arise from methodological difficulties in testing stabilizing selection as well as measuring fitness. I also argue that the commonness of positive directional selection and the variation in selection may be caused by several biological factors. First, selection on immune function may show spatial and temporal variation as epidemics are often local/seasonal. Second, factors affecting the range of phenotypic variation in immune traits could alter potential for selection. Third, different parasites may impose different selective pressures depending on their characteristics. Fourth, condition dependence of immune defence can obscure trade-offs related to it, thus possibly modifying observed selection gradients. Fifth, nonimmunological defences could affect the form of selection by reducing the benefits of strong immune function. To comprehensively understand the evolution of immune defence, the role of above factors should be considered in future studies.

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“…The majority of populations (17/27) show no significant relationship between victim inbreeding and infection, 26% of populations (7/27) demonstrate the predicted positive relationship between victim selfing rate and enemy abundance or intensity of infection, and 11% of populations (3/27) show the reverse pattern (Table 2). Two studies to date have also examined the relationship between infection rate and inbreeding among populations (Trouvé et al 2003;Puurtinen et al 2004;Table 2, panel B). In both cases there was a trend for infection rate to increase with population selfing rate; however, this relationship was only statistically significant in the Puurtinen et al (2004) study.…”

Section: Enemies Intensify Inbreeding Depressionmentioning

confidence: 99%

“…Two studies to date have also examined the relationship between infection rate and inbreeding among populations (Trouvé et al 2003;Puurtinen et al 2004;Table 2, panel B). In both cases there was a trend for infection rate to increase with population selfing rate; however, this relationship was only statistically significant in the Puurtinen et al (2004) study. Greater understanding of the genetics underlying the victim-enemy interaction may help to explain the neutral and negative responses; theory finds that when victim-enemy interactions are controlled by interactions between specific resistance and virulence genes (e.g.…”

Section: Enemies Intensify Inbreeding Depressionmentioning

confidence: 99%

The Role of Natural Enemies in the Expression and Evolution of Mixed Mating in Hermaphroditic Plants and Animals

et al. 2007

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Although a large portion of plant and animal species exhibit intermediate levels of outcrossing, the factors that maintain this wealth of variation are not well understood. Natural enemies are one relatively understudied ecological factor that may influence the evolutionary stability of mixed mating. In this paper, we aim for a conceptual unification of the role of enemies in mating system expression and evolution in both hermaphroditic animals and plants. We review current theory and detail the potential effects of enemies on fundamental mating system parameters. In doing so, we identify situations in which consideration of enemies alters expectations about the stability of mixed mating. Generally, we find that inclusion of the enemy dimension may broaden conditions in which mixed mating systems are evolutionarily stable. Finally, we highlight avenues ripe for future theoretical and empirical work that will advance our understanding of enemies in the expression and evolution of mixed mating in their hosts/victims, including examination of feedback cycles between victims and enemies and quantification of mating system-related parameters in victim populations in the presence and absence of enemies.

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The Effects of Mating System and Genetic Variability on Susceptibility to Trematode Parasites in a Freshwater Snail, Lymnaea Stagnalis

Cited by 10 publications

References 51 publications

Genetic diversity, parasite prevalence and immunity in wild bumblebees

Genetic diversity, parasite prevalence and immunity in wild bumblebees

Natural selection on quantitative immune defence traits: a comparison between theory and data

The Role of Natural Enemies in the Expression and Evolution of Mixed Mating in Hermaphroditic Plants and Animals

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