Correlative Changes in Life-History Variables in Response to Environmental Change in a Model Organism

Global change alters the environment, including increases in the frequency of (un)favorable events and shifts in environmental noise color. However, how these changes impact the dynamics of populations, and whether these can be predicted accurately has been largely unexamined. Here we combine recently developed population modeling approaches and theory in stochastic demography to explore how life history, morphology, and average fitness respond to changes in the frequency of favorable environmental conditions and in the color of environmental noise in a model organism (an acarid mite). We predict that different life-history variables respond correlatively to changes in the environment, and we identify different life-history variables, including lifetime reproductive success, as indicators of average fitness and life-history speed across stochastic environments. Depending on the shape of adult survival rate, generation time can be used as an indicator of the response of populations to stochastic change, as in the deterministic case. This work is a useful step toward understanding population dynamics in stochastic environments, including how stochastic change may shape the evolution of life histories

The role of dispersal in life history and population dynamics: an experimental and theoretical approach

Understanding the evolution and maintenance of phenotypic and genetic variation within populations is a key challenge in population biology. Discrete phenotypic variation such as alternative reproductive strategies and dispersal strategies are extreme forms of this. To understand phenotypic variations, such as male dimorphisms and dispersal expression, requires investigating the costs and benefits of these different phenotypes. In this thesis I do so. First, at the individual level, I determine trade-offs between life-history traits and phenotypic expression. The influence of male morph expression is assessed by determining whether male morph survival is frequency dependent. Costs of dispersal expression were assessed by comparing individuals that expressed the dispersal phenotype during their ontogeny with individuals that did not. Second, at the population level, I specifically investigate costs of phenotype expression to the natal population when dispersers fail to disperse. To determine any demographic costs to natal populations, I used structured integral population models to calculate population biology quantities, which I compared between populations that produced dispersers that fail to disperse and populations that produced no dispersers. I show that expressing a dispersal morph is costly to life-history traits and skews the male morph ratio, indicating that these two conditional strategies interact during ontogeny. This questions whether current models explaining single conditional strategies, such as the environmental threshold model, should consider interactions between different conditional strategies. In natal populations where dispersal is expressed, but dispersers fail to disperse, populations suffer reduced fitness and this demographic cost is enhanced in stochastic environments. These results do not include benefits of successful dispersal or other costs such as inbreeding. However, they do provide a cost of dispersal expression which indicates what the benefits of dispersal would need to be for dispersal to evolve. One aspect that the results do not inform on is possible eco-evolutionary dynamics in populations. Future work should look to incorporate eco-evolutionary feedback, within a metapopulation structure, to identify the maintenance and evolution of male dimorphism and dispersal

The role of dispersal in life history and population dynamics: an experimental and theoretical approach

Understanding the evolution and maintenance of phenotypic and genetic variation within populations is a key challenge in population biology. Discrete phenotypic variation such as alternative reproductive strategies and dispersal strategies are extreme forms of this. To understand phenotypic variations, such as male dimorphisms and dispersal expression, requires investigating the costs and benefits of these different phenotypes. In this thesis I do so. First, at the individual level, I determine trade-offs between life-history traits and phenotypic expression. The influence of male morph expression is assessed by determining whether male morph survival is frequency dependent. Costs of dispersal expression were assessed by comparing individuals that expressed the dispersal phenotype during their ontogeny with individuals that did not. Second, at the population level, I specifically investigate costs of phenotype expression to the natal population when dispersers fail to disperse. To determine any demographic costs to natal populations, I used structured integral population models to calculate population biology quantities, which I compared between populations that produced dispersers that fail to disperse and populations that produced no dispersers. I show that expressing a dispersal morph is costly to life-history traits and skews the male morph ratio, indicating that these two conditional strategies interact during ontogeny. This questions whether current models explaining single conditional strategies, such as the environmental threshold model, should consider interactions between different conditional strategies. In natal populations where dispersal is expressed, but dispersers fail to disperse, populations suffer reduced fitness and this demographic cost is enhanced in stochastic environments. These results do not include benefits of successful dispersal or other costs such as inbreeding. However, they do provide a cost of dispersal expression which indicates what the benefits of dispersal would need to be for dispersal to evolve. One aspect that the results do not inform on is possible eco-evolutionary dynamics in populations. Future work should look to incorporate eco-evolutionary feedback, within a metapopulation structure, to identify the maintenance and evolution of male dimorphism and dispersal

Data from: Correlative changes in life history variables in response to environmental change in a model organism

Global change alters the environment, including increases in the frequency of (un)favorable events and shifts in environmental noise color. However, how these changes impact the dynamics of populations, and whether these can be predicted accurately has been largely unexamined. Here we combine recently developed population modeling approaches and theory in stochastic demography to explore how life history, morphology, and average fitness respond to changes in the frequency of favorable environmental conditions and in the color of environmental noise in a model organism (an acarid mite). We predict that different life-history variables respond correlatively to changes in the environment, and we identify different life-history variables, including lifetime reproductive success, as indicators of average fitness and life-history speed across stochastic environments. Depending on the shape of adult survival rate, generation time can be used as an indicator of the response of populations to stochastic change, as in the deterministic case. This work is a useful step toward understanding population dynamics in stochastic environments, including how stochastic change may shape the evolution of life histories

Growth and survival data of R. robini

Data on growth and survival of Rhizoglyphus robini females raised in a good (yeast) or a bad (filter paper) environment. Mites were reared individually and always had ad lib access to their food. These data were used to estimate the Gompertz functions (see Methods) and character-demography functions of the Integral Projection Model (see Methods)

Life cycle of the bulb mite.

<p>The life cycle has six life stages; the deutonymph stage is the facultative dispersal stage that develops under unfavourable conditions. Male morph determination is dependent on the size of the tritonymph stage. Here, we found that adult males that had expressed the dispersal stage all matured as fighters (see <i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#sec011" target="_blank">Results</a></i>).</p

Thermal tolerance in a south-east African population of the tsetse fly Glossina pallidipes (Diptera, Glossinidae) : implications for forecasting climate change impacts

The original publication is available at http://www.journals.elsevier.com/journal-of-insect-physiology/For tsetse (Glossina spp.), the vectors of human and animal trypanosomiases, the physiological mechanisms linking variation in population dynamics with changing weather conditions have not been well established. Here, we investigate high- and low-temperature tolerance in terms of activity limits and survival in a natural population of adult Glossina pallidipes from eastern Zambia. Due to increased interest in chilling flies for handling and aerial dispersal in sterile insect technique control and eradication programmes, we also provide further detailed investigation of low-temperature responses. In wild-caught G. pallidipes, the probability of survival for 50% of the population at low-temperatures was at 3.7, 8.9 and 9.6 °C (95% CIs: ±1.5 °C) for 1, 2 and 3 h treatments, respectively. At high temperatures, it was estimated that treatments at 37.9, 36.2 and 35.6 °C (95% CIs: ±0.5 °C) would yield 50% population survival for 1, 2 and 3 h, respectively. Significant effects of time and temperature were detected at both temperature extremes (GLZ, p0.5 in all cases). However, flies with low chill coma values had the highest body water and fat content, indicating that when energy reserves are depleted, low-temperature tolerance may be compromised. Overall, these results suggest that physiological mechanisms may provide insight into tsetse population dynamics, hence distribution and abundance, and support a general prediction for reduced geographic distribution under future climate warming scenarios. © 2007 Elsevier Ltd. All rights reserved.Publishers' Versio

Summary of the comparison between the effects of deutonymph expression (dispersal by phoresy) and dispersal via flight on life-history traits and sex ratio.

<p>¹Roff [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref044" target="_blank">44</a>]</p><p>² Dixon et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref045" target="_blank">45</a>]</p><p>³Roff & Fairbairn [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref046" target="_blank">46</a>]</p><p>⁴Zera and Denno [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref011" target="_blank">11</a>]</p><p>⁵Bonte et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref014" target="_blank">14</a>]</p><p>⁶Rankin & Burchsted [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref010" target="_blank">10</a>]</p><p>⁷Min et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref012" target="_blank">12</a>]</p><p>⁸Hanski et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref013" target="_blank">13</a>]</p><p>⁹Fadamiro et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref047" target="_blank">47</a>]</p><p>¹⁰Perez-Mendoza et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref048" target="_blank">48</a>]</p><p>¹¹Gäde [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref049" target="_blank">49</a>]</p><p>¹²Nishigaki & Ohtaki [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0136872#pone.0136872.ref050" target="_blank">50</a>]; NA–not applicable</p><p>^§This study</p><p>^#Sexes were not separated in this study</p><p>*Measurement was lipid content.</p><p>Summary of the comparison between the effects of deutonymph expression (dispersal by phoresy) and dispersal via flight on life-history traits and sex ratio.</p

Compensatory growth.

<p>Total growth (mm) and standardised growth (mm per day per tritonymph length) during the tritonymph stage, as a function of deutonymph presence (Deuto) or deutonymph absence (No Deuto) during development in females (A) and fighter males (B). Boxes represent upper and lower quartile ranges, middle bands are medians and whiskers represent the extremes. Outliers are shown as points.</p