scholarly journals Plasticity as panacea? Nerves, hormones, and the currencies of trade-offs

2015 ◽  
Vol 61 (2) ◽  
pp. 251-264 ◽  
Author(s):  
Elizabeth Bastiaans ◽  
Elizabeth Bastiaans

Abstract Phenotypic plasticity is nearly universal among organisms, and evidence indicates that plasticity can exhibit additive genetic variation and respond to selection. These findings have important implications for our understanding of how plasticity may be constrained and how its mechanistic structure may affect its evolution. Many life history trade-offs may be conceptualized as plastic traits, with individuals varying in their position along trade-off axes due to genetic differences, developmental plasticity, or short-term plasticity occurring throughout an individual’s lifetime. Behavioral plasticity is key to understanding when organisms are likely to encounter trade-offs, whether those trade-offs can be mitigated, and how the trade-offs affect the ecology and evolution of populations. In this review, we discuss hormonal and neural mechanisms that may influence how plastic behavioral traits are expressed and evolve. We also outline a classification of life history trade-offs and their mechanistic bases and discuss the currencies most likely to mediate each category of trade-off and how they are tied to the mechanisms by which animals express their behaviors.

Author(s):  
Maren N. Vitousek ◽  
Laura A. Schoenle

Hormones mediate the expression of life history traits—phenotypic traits that contribute to lifetime fitness (i.e., reproductive timing, growth rate, number and size of offspring). The endocrine system shapes phenotype by organizing tissues during developmental periods and by activating changes in behavior, physiology, and morphology in response to varying physical and social environments. Because hormones can simultaneously regulate many traits (hormonal pleiotropy), they are important mediators of life history trade-offs among growth, reproduction, and survival. This chapter reviews the role of hormones in shaping life histories with an emphasis on developmental plasticity and reversible flexibility in endocrine and life history traits. It also discusses the advantages of studying hormone–behavior interactions from an evolutionary perspective. Recent research in evolutionary endocrinology has provided insight into the heritability of endocrine traits, how selection on hormone systems may influence the evolution of life histories, and the role of hormonal pleiotropy in driving or constraining evolution.


2018 ◽  
Vol 285 (1892) ◽  
pp. 20182141 ◽  
Author(s):  
Stefania Casagrande ◽  
Michaela Hau

The trade-off between reproductive investment and survival is central to life-history theory, but the relative importance and the complex interactions among the physiological mechanisms mediating it are still debated. Here we experimentally tested whether baseline glucocorticoid hormones, the redox system or their interaction mediate reproductive investment–survival trade-offs in wild great tits ( Parus major ). We increased the workload of parental males by clipping three feathers on each wing, and 5 days later determined effects on baseline corticosterone concentrations (Cort), redox state (reactive oxygen metabolites, protein carbonyls, glutathione peroxidase [GPx], total non-enzymatic antioxidants), body mass, body condition, reproductive success and survival. Feather-clipping did not affect fledgling numbers, chick body condition, nest provisioning rates or survival compared with controls. However, feather-clipped males lost mass and increased both Cort and GPx concentrations. Within feather-clipped individuals, GPx increases were positively associated with reproductive investment (i.e. male nest provisioning). Furthermore, within all individuals, males that increased GPx suffered reduced survival rates. Baseline Cort increases were related to mass loss but not to redox state, nest provisioning or male survival. Our findings provide experimental evidence that changes in the redox system are associated with the trade-off between reproductive investment and survival, while baseline Cort may support this trade-off indirectly through a link with body condition. These results also emphasize that plastic changes in individuals, rather than static levels of physiological signals, may mediate life-history trade-offs.


2020 ◽  
Vol 7 ◽  
Author(s):  
Qihang Liang ◽  
Xianpeng Su ◽  
Fang Wang ◽  
Baishan Zhu ◽  
Mingdi He

Boldness and aggressiveness are crucial behavioral traits in the field of animal personality, and both have important ecological and evolutionary significance. As swimming crabs (Portunus trituberculatus) are aggressive, their production is affected; thus, it is important to study their behavior. To assess the relationship between boldness and aggressiveness of male P. trituberculatus and the differences between their different life stages, we determined the individual differences in these two traits in juvenile and adult crabs under laboratory conditions. Based on the k-means cluster analysis, boldness of crabs is classified according to their rush to adventure, and aggressiveness of crabs is classified according to their aggressive behavior toward conspecifics. The results show that the personality classification of juvenile and adult crabs was consistent. Boldness was divided into three levels: bold, middle, and shy. Aggressiveness was divided into two levels: aggressiveness and non-aggressiveness. The personality of juveniles and adults P. trituberculatus males was significantly different; juveniles presented higher aggressiveness and lower boldness than adults. Additionally, a significant positive correlation between boldness and aggressiveness of adult crabs was verified (P = 0.001, ρ = 0.271). However, this correlation in juvenile crabs was not significant (P = 0.702, ρ = 0.042). These preliminary results indicate that the personality of P. trituberculatus males has developmental plasticity and adults have the boldness-aggressiveness behavioral syndrome.


2019 ◽  
Vol 128 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Jordan R Glass ◽  
Zachary R Stahlschmidt

Abstract Complex environments, characterized by co-varying factors (e.g. temperature and food availability) may cause animals to invest resources differentially into fitness-related traits. Thus, experiments manipulating multiple environmental factors concurrently provide valuable insight into the role of the environment in shaping not only important traits (e.g. dispersal capacity or reproduction), but also trait–trait interactions (e.g. trade-offs between traits). We used a multi-factorial design to manipulate variation in temperature (constant 28 °C vs. 28 ± 5 °C daily cycle) and food availability (unlimited vs. intermittent access) throughout development in the sand field cricket (Gryllus firmus). Using a univariate approach, we found that temperature variability and unlimited food availability promoted survival, development, growth, body size and/or reproductive investment. Using principal components as indices of resource allocation strategy, we found that temperature variability and unlimited food reduced investment into flight capacity in females. Thus, we detected a sex-specific trade-off between flight and other life-history traits that was developmentally plastic in response to variation in temperature and food availability. We develop an experimental and statistical framework to reveal shifts in correlative patterns of investment into different life-history traits. This approach can be applied to a range of biological systems to investigate how environmental complexity influences traits and trait trade-offs.


2016 ◽  
Vol 12 (6) ◽  
pp. 20160101 ◽  
Author(s):  
Alexis Rutschmann ◽  
Donald B. Miles ◽  
Jean Clobert ◽  
Murielle Richard

Life-history traits involved in trade-offs are known to vary with environmental conditions. Here, we evaluate the response of the trade-off between ‘offspring number’ versus ‘energy invested per offspring’ to ambient temperature in 11 natural populations of the common lizard, Zootoca vivipara . We provide evidence at both the intra- and interpopulation levels that the trade-off is reduced with an increase in air temperature. If this effect enhances current individual fitness, it may lead to an accelerated pace of life in warmer environments and could ultimately increase adult mortality. In the context of global warming, our results advocate the need for more studies in natural populations to explore interactions between life-history traits' trade-offs and environmental conditions.


2009 ◽  
Vol 5 (3) ◽  
pp. 339-342 ◽  
Author(s):  
Gregory E. Blomquist

Trade-offs are central to life-history theory but difficult to document. Patterns of phenotypic and genetic correlations in rhesus macaques, Macaca mulatta —a long-lived, slow-reproducing primate—are used to test for a trade-off between female age of first reproduction and adult survival. A strong positive genetic correlation indicates that female macaques suffer reduced adult survival when they mature relatively early and implies primate senescence can be explained, in part, by antagonistic pleiotropy. Contrasts with a similar human study implicate the extension of parental effects to later ages as a potential mechanism for circumventing female life-history trade-offs in human evolution.


PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5454 ◽  
Author(s):  
Julie Gibelli ◽  
Nadia Aubin-Horth ◽  
Frédérique Dubois

Individuals within the same population generally differ among each other not only in their behavioral traits but also in their level of behavioral plasticity (i.e., in their propensity to modify their behavior in response to changing conditions). If the proximate factors underlying individual differences in behavioral plasticity were the same for any measure of plasticity, as commonly assumed, one would expect plasticity to be repeatable across behaviors and contexts. However, this assumption remains largely untested. Here, we conducted an experiment with sailfin mollies (Poecilia latipinna) whose behavioral plasticity was estimated both as the change in their personality traits or mating behavior across a social gradient and using their performance on a reversal-learning task. We found that the correlations between pairwise measures of plasticity were weak and non-significant, thus indicating that the most plastic individuals were not the same in all the tests. This finding might arise because either individuals adjust the magnitude of their behavioral responses depending on the benefits of plasticity, and/or individuals expressing high behavioral plasticity in one context are limited by neural and/or physiological constraints in the amount of plasticity they can express in other contexts. Because the repeatability of behavioral plasticity may have important evolutionary consequences, additional studies are needed to assess the importance of trade-offs between conflicting selection pressures on the maintenance of intra-individual variation in behavioral plasticity.


2020 ◽  
Vol 49 (5) ◽  
pp. 1032-1040
Author(s):  
Karthikeyan Chandrasegaran ◽  
Rasikapriyaa Sriramamurthy ◽  
Avehi Singh ◽  
Pooja Ravichandran ◽  
Suhel Quader

Abstract Antipredatory behavioral responses tend to be energetically expensive, and prey species thus need to resolve trade-offs between these behaviors and other activities such as foraging and mating. While these trade-offs have been well-studied across taxa, less is known about how costs and benefits vary in different life-history contexts, and associated consequences. To address this question, we compared responses of the yellow fever mosquito (Aedes aegypti [Diptera: Culicidae]) to predation threat from guppy (Poecilia reticulata [Cyprinodontiformes: Poeciliidae]) across two life-history stages—larvae (data from previous study) and pupae (from this study). Pupae are motile but do not feed and are comparable to larvae in terms of behavior. To understand how physiological costs affect the threat sensitivity of pupae, we used sex (with size as a covariate) as a proxy for stored energy reserves, and quantified movement and space use patterns of male (small-sized) and female (large-sized) pupae when exposed to predation threat. We found that pupae did not alter movement when exposed to predator cues but instead altered spatial use by spending more time at the bottom of the water column. We found no effect of pupa sex (or size) on the behavioral responses we measured. We conclude that pupa behavior, both antipredatory and otherwise, is primarily targeted at minimizing energy expenditure, as compared with larval behavior, which appears to balance energy expenditure between the opposing pressures of foraging and of avoiding predation. We suggest that antipredatory defenses in metamorphosing prey are modulated by varying energetic trade-offs associated with different life-history stages.


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