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Behavioral Ecology Advance Access

Published: Fri, 17 Nov 2017 00:00:00 GMT

Last Build Date: Fri, 17 Nov 2017 02:43:37 GMT


The price of insurance: costs and benefits of worker production in a facultatively social bee


Kin selection theory is foundational in helping to explain the evolution of sociality; however, the degree to which indirect fitness benefits may underlie helping behavior in species of early stage sociality has received relatively little empirical attention. Facultatively social bees, which demonstrate multiple forms of social organization, provide prime systems in which to empirically test hypotheses regarding the evolutionary origins of sociality. The subsocial small carpenter bee, Ceratina calcarata, may establish a social nest by manipulating brood provisions to rear a worker daughter, which then assists in critical late-season alloparental care. Here, we combine nest demographic and behavioral data with genetic relatedness estimates to calculate the relative inclusive fitness of both subsocial and social reproductive strategies in C. calcarata. Social mothers benefit from improved likelihood of brood survivorship and have higher fitness than subsocial mothers. Worker daughters have low indirect fitness on average, and will not produce their own offspring. Among-sibling relatedness is significantly higher in social nests than subsocial nests, though mothers of either reproductive strategy may mate multiply. Though this study corroborates the ultimate role of indirect fitness and assured fitness returns in the evolution of social traits, it also offers additional support for maternal manipulation as the proximate mechanism underlying evolutionary transitions in early stage insect societies.

Rate maximization and hyperbolic discounting in human experiential intertemporal decision making


Decisions between differently timed outcomes are a well-studied topic in as diverse academic disciplines as economics, psychology, and behavioral ecology. Humans and other animals have been shown to make these intertemporal choices by hyperbolically devaluing rewards as a function of their delays (“delay discounting”), thus often deemed to behave myopically. In behavioral ecology, however, intertemporal choices are assumed to meet optimization principles, that is, the maximization of energy or reward rate. Thus far, it is unclear how different approaches assuming these 2 currencies, reward devaluation and reward rate maximization, could be reconciled. Here, we investigated the degree at which humans (N = 81) discount reward value and maximize reward rate when making intertemporal decisions. We found that both hyperbolic discounting and rate maximization well approximated the choices made in a range of different intertemporal choice design conditions. Notably, rate maximization rules provided even better fits to the choice data than hyperbolic discounting models in all conditions. Interestingly, in contrast to previous findings, rate maximization was universally observed in all choice frames, and not confined to foraging settings. Moreover, rate maximization correlated with the degree of hyperbolic discounting in all conditions. This finding is in line with the possibility that evolution has favored hyperbolic discounting because it subserves reward rate maximization by allowing for flexible adjustment of preference for smaller, sooner or larger, later rewards. Thus, rate maximization may be a universal principle that has shaped intertemporal decision making in general and across a wide range of choice problems.

Do wild ungulates experience higher stress with humans than with large carnivores?


Predation is a major selective pressure for prey; however, the stress response to predation risk and the relative importance of natural versus anthropogenic stress factors in wild populations of animals have rarely been studied. We investigated the level of fecal glucocorticoid metabolites (FGMs) in 6 populations of red deer and roe deer exposed to potentially different levels of stress, resulting from both natural (predator presence, forest cover, undergrowth, ungulate density, and temperature) and anthropogenic (hunting harvest, percentage of build-up areas, and road density) factors. We found the highest and most variable FGM concentrations in both ungulates in areas without large carnivores, and the lowest and least variable FGM levels in areas with wolf and lynx. Anthropogenic factors (hunting harvest, roads, and built-up area) positively correlated with the gradient of FGM levels in both species. Both the mean and the variance of the FGM concentrations measured within populations of both red deer and roe deer were affected positively by variation in hunting harvest and negatively by the minimum temperature. The variance in the roe deer FGM was also positively influenced by the percentage of built-up areas. The results indicate that stress in wild ungulate populations is lower and less variable in areas utilized by large carnivores than in carnivore-free areas where human-related factors predominate. This may be explained by evolutionary adaptations of prey animals constantly exposed to the risk of natural predation and their inability of adapting to the risk from humans probably due to its high intensity and erratic occurrence.

Indirect genetic effects—everything is special, everything is important: a comment on Bailey et al


Bailey et al. (2017) bring us improved understanding of the relevance of indirect genetic effects (IGEs) for behavioral ecology. In addition to reviewing the evidence for IGEs and outlining the theoretical framework underlying the action of IGEs on behavioral phenotypes, they propose a methodological approach that will purportedly inform on whether behavior has a unique role in evolution. Before addressing this notable aspect of Bailey et al.’s (2017) contribution, I will comment on issues dealing with semantics and bias.