Seasonal stress drives predictable changes in inbreeding depression in field-tested captive populations of
            <i>Drosophila melanogaster</i>

Enders, Laramy; Nunney, Leonard

doi:10.1098/rspb.2012.1018

Cited by 25 publications

(26 citation statements)

References 53 publications

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“…These results suggest that the effects of stress on inbreeding depression are more homogeneous than formerly thought, and not so idiosyncratic regarding the genetic architecture of the population or the type of environmental variable causing stressful conditions, with greater levels of stress consistently leading to more inbreeding depression. This result has been confirmed by an independent meta‐analysis using Drosophila and experiments in both the laboratory and field 37 . Just as was found by Fox and Reed, 6 Enders and Nunney 37 found a strong linear relationship between inbreeding depression and the magnitude of multiple stressors, with inbreeding depression increasing linearly as the level of stress increases (Fig.…”

Section: Introductionsupporting

confidence: 71%

Inbreeding–stress interactions: evolutionary and conservation consequences

Reed

Fox

Enders

et al. 2012

Annals of the New York Academy of Sciences

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149

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The effect of environmental stress on the magnitude of inbreeding depression has a long history of intensive study. Inbreeding-stress interactions are of great importance to the viability of populations of conservation concern and have numerous evolutionary ramifications. However, such interactions are controversial. Several meta-analyses over the last decade, combined with omic studies, have provided considerable insight into the generality of inbreeding-stress interactions, its physiological basis, and have provided the foundation for future studies. In this review, we examine the genetic and physiological mechanisms proposed to explain why inbreeding-stress interactions occur. We specifically examine whether the increase in inbreeding depression with increasing stress could be due to a concomitant increase in phenotypic variation, using a larger data set than any previous study. Phenotypic variation does usually increase with stress, and this increase can explain some of the inbreeding-stress interaction, but it cannot explain all of it. Overall, research suggests that inbreeding-stress interactions can occur via multiple independent channels, though the relative contribution of each of the mechanisms is unknown. To better understand the causes and consequences of inbreeding-2 stress interactions in natural populations, future research should focus on elucidating the genetic architecture of such interactions and quantifying naturally occurring levels of stress in the wild.

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Section: Introductionsupporting

confidence: 71%

Inbreeding–stress interactions: evolutionary and conservation consequences

Reed

Fox

Enders

et al. 2012

Annals of the New York Academy of Sciences

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149

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“…Predicting the outcome of inbreeding-stress interactions centers on the concept that stress alters the strength of selection against deleterious alleles that cause ID (Agrawal and Whitlock, 2010;Yun and Agrawal, 2014). The finding that the intensity of stress scales positively with ID in a variety of taxa (Fox and Reed, 2011;Enders and Nunney, 2012;Schou et al, 2015) supports the general prediction that selection is greater in stressful environments. However, different stress types have been shown to vary in their ability to increase selection against mutations (Agrawal and Whitlock, 2010).…”

Section: Introductionsupporting

confidence: 50%

Reduction in the cumulative effect of stress-induced inbreeding depression due to intragenerational purging in Drosophila melanogaster

Enders

Nunney

2015

Heredity

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Environmental stress generally exacerbates the harmful effects of inbreeding and it has been proposed that this could be exploited in purging deleterious alleles from threatened inbred populations. However, understanding what factors contribute to variability in the strength of inbreeding depression (ID) observed across adverse environmental conditions remains a challenge. Here, we examined how the nature and timing of stress affects ID and the potential for purging using inbred and outbred Drosophila melanogaster larvae exposed to biotic (larval competition, bacteria infection) and abiotic (ethanol, heat) stressors compared with unstressed controls. ID was measured during (larval survival) and after (male mating success) stress exposure. The level of stress imposed by each stressor was approximately equal, averaging a 42% reduction in outbred larval survival relative to controls. All stressors induced on average the same ID, causing a threefold increase in lethal equivalents for larval survival relative to controls. However, stress-induced ID in larval success was followed by a 30% reduction in ID in mating success of surviving males. We propose that this fitness recovery is due to 'intragenerational purging' whereby fitness correlations facilitate stress-induced purging that increases the average fitness of survivors in later life history stages. For biotic stressors, post-stress reductions in ID are consistent with intragenerational purging, whereas for abiotic stressors, there appeared to be an interaction between purging and stress-induced physiological damage. For all stressors, there was no net effect of stress on lifetime ID compared with unstressed controls, undermining the prediction that stress enhances the effectiveness of populationlevel purging across generations.

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“…This possibility is to some extent in contrast to studies suggesting that purging is an environment-specific process. Comparing the rate of change in lethal equivalents with increasing stress in this study (slope N10 = 4.38 ± 0.63; slope N50 = 1.52 ± 1.12) with that of the meta-analysis by Reed et al (2012) (slope = 3.35 ± 0.53) and with Enders and Nunney (2012) (slope = 1.56 ± 0.39) reveals large discrepancies in the slope estimates. A part of the discrepancy between studies may stem from the use of replicate inbred populations with different demographic histories, such as different rates of inbreeding or violations of the assumptions behind LE.…”

Section: Figurementioning

confidence: 99%

“…Conversely, population sizes at an intermediate level (N = 50) may avoid I-E interactions up until stress levels of 0.25 (Figure 2). Stress levels in nature may in general be lower, but seasonal events such as cold winter, summer heat waves or food shortage can increase stress levels beyond 0.25 (see, for example, Enders and Nunney, 2012). The evolutionary dynamics and extinction risks of small populations will thus be highly dependent on the specific demographic history and the frequency of different stress levels in their environment.…”

Section: Figurementioning

confidence: 99%

Inbreeding depression across a nutritional stress continuum

2015

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Many natural populations experience inbreeding and genetic drift as a consequence of nonrandom mating or low population size. Furthermore, they face environmental challenges that may interact synergistically with deleterious consequences of increased homozygosity and further decrease fitness. Most studies on inbreeding-environment (I-E) interactions use one or two stress levels, whereby the resolution of the possible stress and inbreeding depression interaction is low. Here we produced Drosophila melanogaster replicate populations, maintained at three different population sizes (10, 50 and a control size of 500) for 25 generations. A nutritional stress gradient was imposed on the replicate populations by exposing them to 11 different concentrations of yeast in the developmental medium. We assessed the consequences of nutritional stress by scoring egg-toadult viability and body mass of emerged flies. We found: (1) unequivocal evidence for I-E interactions in egg-to-adult viability and to a lesser extent in dry body mass, with inbreeding depression being more severe under higher levels of nutritional stress; (2) a steeper increase in inbreeding depression for replicate populations of size 10 with increasing nutritional stress than for replicate populations of size 50; (3) a nonlinear norm of reaction between inbreeding depression and nutritional stress; and (4) a faster increase in number of lethal equivalents in replicate populations of size 10 compared with replicate populations of size 50 with increasing nutritional stress levels. Our data provide novel and strong evidence that deleterious fitness consequences of I-E interactions are more pronounced at higher nutritional stress and at higher inbreeding levels.

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Seasonal stress drives predictable changes in inbreeding depression in field-tested captive populations of Drosophila melanogaster

Cited by 25 publications

References 53 publications

Inbreeding–stress interactions: evolutionary and conservation consequences

Inbreeding–stress interactions: evolutionary and conservation consequences

Reduction in the cumulative effect of stress-induced inbreeding depression due to intragenerational purging in Drosophila melanogaster

Inbreeding depression across a nutritional stress continuum

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