Association of social group with both life-history traits and brain size in cooperatively breeding birds

2021 ◽  
Vol 71 (3) ◽  
pp. 261-278
Author(s):  
Ying Jiang ◽  
Long Jin ◽  
Yi Qiang Fu ◽  
Wen Bo Liao
Keyword(s):  
Life History ◽  
Group Size ◽  
Social Group ◽  
Life History Traits ◽  
Brain Size ◽  
Size Variation ◽  
Breeding Birds ◽  
Alloparental Care ◽  
Cooperatively Breeding ◽  
Relative Brain Size

Abstract Social group is associated with life-history traits and can predict brain size variation in cooperative primates and some other mammal groups, but such explicit relationships remain enigmatic in cooperatively breeding birds. Indeed, some compositions of social group in cooperative species (e.g., helper number and group size) would affect the fitness of breeders by providing alloparental care. Here, we conducted comparative tests of the relationship between the social group and both life-history traits and brain size across 197 species of cooperatively breeding birds using phylogenetically controlled comparative analyses. We did not find any correlations between helper numbers and both life-history traits and brain size. However, we found that maximum group size was positively associated with clutch size. Moreover, average group size has positive associations with body mass and relative brain size. Our findings suggest that helper numbers cannot promote variation in relative brain size, while larger groups may predict bigger brains in cooperatively breeding birds.

scholarly journals Coevolution of cultural intelligence, extended life history, sociality, and brain size in primates

2017 ◽  
Vol 114 (30) ◽  
pp. 7908-7914 ◽  
Author(s):  
Sally E. Street ◽  
Ana F. Navarrete ◽  
Simon M. Reader ◽  
Kevin N. Laland
Keyword(s):  
Life History ◽  
Social Learning ◽  
Group Size ◽  
Social Group ◽  
Brain Volume ◽  
Brain Size ◽  
Research Effort ◽  
Human Cognition ◽  
Primate Species ◽  
Brain Expansion

Explanations for primate brain expansion and the evolution of human cognition and culture remain contentious despite extensive research. While multiple comparative analyses have investigated variation in brain size across primate species, very few have addressed why primates vary in how much they use social learning. Here, we evaluate the hypothesis that the enhanced reliance on socially transmitted behavior observed in some primates has coevolved with enlarged brains, complex sociality, and extended lifespans. Using recently developed phylogenetic comparative methods we show that, across primate species, a measure of social learning proclivity increases with absolute and relative brain volume, longevity (specifically reproductive lifespan), and social group size, correcting for research effort. We also confirm relationships of absolute and relative brain volume with longevity (both juvenile period and reproductive lifespan) and social group size, although longevity is generally the stronger predictor. Relationships between social learning, brain volume, and longevity remain when controlling for maternal investment and are therefore not simply explained as a by-product of the generally slower life history expected for larger brained species. Our findings suggest that both brain expansion and high reliance on culturally transmitted behavior coevolved with sociality and extended lifespan in primates. This coevolution is consistent with the hypothesis that the evolution of large brains, sociality, and long lifespans has promoted reliance on culture, with reliance on culture in turn driving further increases in brain volume, cognitive abilities, and lifespans in some primate lineages.

scholarly journals Evolutionary pressures on primate intertemporal choice

2014 ◽  
Vol 281 (1786) ◽  
pp. 20140499 ◽  
Author(s):  
Jeffrey R. Stevens
Keyword(s):  
Group Size ◽  
Social Group ◽  
Intertemporal Choice ◽  
Brain Size ◽  
Waiting Times ◽  
Home Range Size ◽  
Primate Species ◽  
Relative Brain Size ◽  
Phylogenetic Regression ◽  
Intertemporal Choices

From finding food to choosing mates, animals must make intertemporal choices that involve fitness benefits available at different times. Species vary dramatically in their willingness to wait for delayed rewards. Why does this variation across species exist? An adaptive approach to intertemporal choice suggests that time preferences should reflect the temporal problems faced in a species's environment. Here, I use phylogenetic regression to test whether allometric factors relating to body size, relative brain size and social group size predict how long 13 primate species will wait in laboratory intertemporal choice tasks. Controlling for phylogeny, a composite allometric factor that includes body mass, absolute brain size, lifespan and home range size predicted waiting times, but relative brain size and social group size did not. These findings support the notion that selective pressures have sculpted intertemporal choices to solve adaptive problems faced by animals. Collecting these types of data across a large number of species can provide key insights into the evolution of decision making and cognition.

The Central Nervous System of Jawless Vertebrates: Encephalization in Lampreys and Hagfishes

2017 ◽  
Vol 89 (1) ◽  
pp. 33-47
Author(s):  
Carlos A. Salas ◽  
Kara E. Yopak ◽  
Thomas J. Lisney ◽  
Ian C. Potter ◽  
Shaun P. Collin
Keyword(s):  
Life History ◽  
Life History Traits ◽  
Brain Size ◽  
Interspecific Variation ◽  
Feeding Behaviors ◽  
Larval Phase ◽  
Parasitic Species ◽  
Anadromous Migration ◽  
The Central Nervous System ◽  
Relative Brain Size

Lampreys and hagfishes are the sole surviving representatives of the early agnathan (jawless) stage in vertebrate evolution, which has previously been regarded as the least encephalized group of all vertebrates. Very little is known, however, about the extent of interspecific variation in relative brain size in these fishes, as previous studies have focused on only a few species, even though lampreys exhibit a variety of life history traits. While some species are parasitic as adults, with varying feeding behaviors, others (nonparasitic species) do not feed after completing their macrophagous freshwater larval phase. In addition, some parasitic species remain in freshwater, while others undergo an anadromous migration. On the basis of data for postmetamorphic individuals representing approximately 40% of all lamprey species, with representatives from each of the three families, the aforementioned differences in life history traits are reflected in variations in relative brain size. Across all lampreys, brain mass increases with body mass with a scaling factor or slope (α) of 0.35, which is less than those calculated for different groups of gnathostomatous (jawed) vertebrates (α = 0.43-0.62). When parasitic and nonparasitic species are analyzed separately, with phylogeny taken into account, the scaling factors of both groups (parasitic α = 0.43, nonparasitic α = 0.45) approach those of gnathostomes. The relative brain size in fully grown adults of parasitic species is, however, less than that of the adults of nonparasitic species, paralleling differences between fully grown adults and recently metamorphosed individuals of anadromous species. The average degree of encephalization is found in anadromous parasitic lampreys and might thus represent the ancestral condition for extant lampreys. These results suggest that the degree of encephalization in lampreys varies according to both life history traits and phylogenetic relationships.

scholarly journals The energy allocation trade-offs underlying life history traits in hypometabolic strepsirhines and other primates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bruno Simmen ◽  
Luca Morino ◽  
Stéphane Blanc ◽  
Cécile Garcia
Keyword(s):  
Life History ◽  
Energy Expenditure ◽  
Body Mass ◽  
Life History Traits ◽  
Brain Size ◽  
Energy Allocation ◽  
Interbirth Interval ◽  
Energy Investment ◽  
Litter Mass ◽  
Trade Offs

AbstractLife history, brain size and energy expenditure scale with body mass in mammals but there is little conclusive evidence for a correlated evolution between life history and energy expenditure (either basal/resting or daily) independent of body mass. We addressed this question by examining the relationship between primate free-living daily energy expenditure (DEE) measured by doubly labeled water method (n = 18 species), life history variables (maximum lifespan, gestation and lactation duration, interbirth interval, litter mass, age at first reproduction), resting metabolic rate (RMR) and brain size. We also analyzed whether the hypometabolic primates of Madagascar (lemurs) make distinct energy allocation tradeoffs compared to other primates (monkeys and apes) with different life history traits and ecological constraints. None of the life-history traits correlated with DEE after controlling for body mass and phylogeny. In contrast, a regression model showed that DEE increased with increasing RMR and decreasing reproductive output (i.e., litter mass/interbirth interval) independent of body mass. Despite their low RMR and smaller brains, lemurs had an average DEE remarkably similar to that of haplorhines. The data suggest that lemurs have evolved energy strategies that maximize energy investment to survive in the unusually harsh and unpredictable environments of Madagascar at the expense of reproduction.

Brain size evolution in anurans: a review

2019 ◽  
Vol 69 (3) ◽  
pp. 265-279 ◽  
Author(s):  
Chun Lan Mai ◽  
Wen Bo Liao
Keyword(s):  
Sexual Selection ◽  
Life History ◽  
Life History Traits ◽  
Developmental Stages ◽  
Brain Size ◽  
Ecological Factors ◽  
Brain Regions ◽  
Sperm Length ◽  
Testis Size ◽  
Size Evolution

Abstract Selection pressure is an important force in shaping the evolution of vertebrate brain size among populations within species as well as between species. The evolution of brain size is tightly linked to natural and sexual selection, and life-history traits. In particular, increased environmental stress, intensity of sexual selection, and slower life history usually result in enlarged brains. However, although previous studies have addressed the causes of brain size evolution, no systematic reviews have been conducted to explain brain size in anurans. Here, we review whether brain size evolution supports the cognitive buffer hypothesis (CBH), the expensive tissue hypothesis (ETH), or the developmental cost hypothesis (DCH) by analyzing the intraspecific and/or interspecific patterns in brain size and brain regions (i.e., olfactory nerves, olfactory bulbs, telencephalon, optic tectum, and cerebellum) associated with ecological factors (habitat, diet and predator risk), sexual selection intensity, life-history traits (age at sexual maturity, mean age, longevity, clutch size and egg size, testis size and sperm length), and other energetic organs. Our findings suggest that brain size evolution in anurans supports the CBH, ETH or DCH. We also suggest future directions for studying the relationships between brain size evolution and crypsis (i.e., ordinary mucous glands in the skin), and food alteration in different developmental stages.

scholarly journals Rethinking the Effects of Body Size on the Study of Brain Size Evolution

2019 ◽  
Vol 93 (4) ◽  
pp. 182-195 ◽  
Author(s):  
Enrique Font ◽  
Roberto García-Roa ◽  
Daniel Pincheira-Donoso ◽  
Pau Carazo
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Scaling Effects ◽  
Selection Pressures ◽  
Body Tissues ◽  
Relative Brain Size ◽  
Functional Components ◽  
The Brain

Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g., presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.

scholarly journals Why are there so few smart mammals (but so many smart birds)?

2008 ◽  
Vol 5 (1) ◽  
pp. 125-129 ◽  
Author(s):  
Karin Isler ◽  
Carel P Van Schaik
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Population Increase ◽  
Large Brain ◽  
Cooperatively Breeding ◽  
Steep Decline ◽  
Relative Brain Size ◽  
Altricial Birds ◽  
Rates Of Growth ◽  
Very High

The expensive brain hypothesis predicts an interspecific link between relative brain size and life-history pace. Indeed, animals with relatively large brains have reduced rates of growth and reproduction. However, they also have increased total lifespan. Here we show that the reduction in production with increasing brain size is not fully compensated by the increase in lifespan. Consequently, the maximum rate of population increase ( r max ) is negatively correlated with brain mass. This result is not due to a confounding effect of body size, indicating that the well-known correlation between r max and body size is driven by brain size, at least among homeothermic vertebrates. Thus, each lineage faces a ‘grey ceiling’, i.e. a maximum viable brain size, beyond which r max is so low that the risk of local or species extinction is very high. We found that the steep decline in r max with brain size is absent in taxa with allomaternal offspring provisioning, such as cooperatively breeding mammals and most altricial birds. These taxa thus do not face a lineage-specific grey ceiling, which explains the far greater number of independent origins of large brain size in birds than mammals. We also predict that (absolute and relative) brain size is an important predictor of macroevolutionary extinction patterns.

scholarly journals Testing hypotheses of marsupial brain size variation using phylogenetic multiple imputations and a Bayesian comparative framework

2021 ◽  
Vol 288 (1947) ◽  
Author(s):  
Orlin S. Todorov ◽  
Simone P. Blomberg ◽  
Anjali Goswami ◽  
Karen Sears ◽  
Patrik Drhlík ◽  
...  
Keyword(s):  
Litter Size ◽  
Brain Size ◽  
Size Variation ◽  
Reproductive Traits ◽  
Mammalian Brain ◽  
Gestation Length ◽  
High Coverage ◽  
Ecological Predictors ◽  
Size Evolution ◽  
Relative Brain Size

Considerable controversy exists about which hypotheses and variables best explain mammalian brain size variation. We use a new, high-coverage dataset of marsupial brain and body sizes, and the first phylogenetically imputed full datasets of 16 predictor variables, to model the prevalent hypotheses explaining brain size evolution using phylogenetically corrected Bayesian generalized linear mixed-effects modelling. Despite this comprehensive analysis, litter size emerges as the only significant predictor. Marsupials differ from the more frequently studied placentals in displaying a much lower diversity of reproductive traits, which are known to interact extensively with many behavioural and ecological predictors of brain size. Our results therefore suggest that studies of relative brain size evolution in placental mammals may require targeted co-analysis or adjustment of reproductive parameters like litter size, weaning age or gestation length. This supports suggestions that significant associations between behavioural or ecological variables with relative brain size may be due to a confounding influence of the extensive reproductive diversity of placental mammals.

scholarly journals The relationship between egg size and helper number in cooperative breeders: a meta-analysis across species

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4028 ◽  
Author(s):  
Tanmay Dixit ◽  
Sinead English ◽  
Dieter Lukas
Keyword(s):  
Life History ◽  
Social Environment ◽  
Group Size ◽  
Egg Size ◽  
Reproductive Investment ◽  
Maternal Investment ◽  
Differential Allocation ◽  
The Social ◽  
Cooperatively Breeding ◽  
The Relationship

BackgroundLife history theory predicts that mothers should adjust reproductive investment depending on benefits of current reproduction and costs of reduced future reproductive success. These costs and benefits may in turn depend on the breeding female’s social environment. Cooperative breeders provide an ideal system to test whether changes in maternal investment are associated with the social conditions mothers experience. As alloparental helpers assist in offspring care, larger groups might reduce reproductive costs for mothers or alternatively indicate attractive conditions for reproduction. Thus, mothers may show reduced (load-lightening) or increased (differential allocation) reproductive investment in relation to group size. A growing number of studies have investigated how cooperatively breeding mothers adjust pre-natal investment depending on group size. Our aim was to survey these studies to assess, first, whether mothers consistently reduce or increase pre-natal investment when in larger groups and, second, whether these changes relate to variation in post-natal investment.MethodsWe extracted data on the relationship between helper number and maternal pre-natal investment (egg size) from 12 studies on 10 species of cooperatively breeding vertebrates. We performed meta-analyses to calculate the overall estimated relationship between egg size and helper number, and to quantify variation among species. We also tested whether these relationships are stronger in species in which the addition of helpers is associated with significant changes in maternal and helper post-natal investment.ResultsAcross studies, there is a significant negative relationship between helper number and egg size, suggesting that in most instances mothers show reduced reproductive investment in larger groups, in particular in species in which mothers also show a significant reduction in post-natal investment. However, even in this limited sample, substantial variation exists in the relationship between helper number and egg size, and the overall effect appears to be driven by a few well-studied species.DiscussionOur results, albeit based on a small sample of studies and species, indicate that cooperatively breeding females tend to produce smaller eggs in larger groups. These findings on prenatal investment accord with previous studies showing similar load-lightening reductions in postnatal parental effort (leading to concealed helper effects), but do not provide empirical support for differential allocation. However, the considerable variation in effect size across studies suggests that maternal investment is mitigated by additional factors. Our findings indicate that variation in the social environment may influence life-history strategies and suggest that future studies investigating within-individual changes in maternal investment in cooperative breeders offer a fruitful avenue to study the role of adaptive plasticity.

scholarly journals Understanding primate brain evolution

2007 ◽  
Vol 362 (1480) ◽  
pp. 649-658 ◽  
Author(s):  
R.I.M Dunbar ◽  
Susanne Shultz
Keyword(s):  
Life History ◽  
Path Analysis ◽  
Group Size ◽  
Brain Size ◽  
Brain Evolution ◽  
Primate Brain ◽  
The Social ◽  
Large Brain ◽  
Brain Data ◽  
The Relationship

We present a detailed reanalysis of the comparative brain data for primates, and develop a model using path analysis that seeks to present the coevolution of primate brain (neocortex) and sociality within a broader ecological and life-history framework. We show that body size, basal metabolic rate and life history act as constraints on brain evolution and through this influence the coevolution of neocortex size and group size. However, they do not determine either of these variables, which appear to be locked in a tight coevolutionary system. We show that, within primates, this relationship is specific to the neocortex. Nonetheless, there are important constraints on brain evolution; we use path analysis to show that, in order to evolve a large neocortex, a species must first evolve a large brain to support that neocortex and this in turn requires adjustments in diet (to provide the energy needed) and life history (to allow sufficient time both for brain growth and for ‘software’ programming). We review a wider literature demonstrating a tight coevolutionary relationship between brain size and sociality in a range of mammalian taxa, but emphasize that the social brain hypothesis is not about the relationship between brain/neocortex size and group size per se ; rather, it is about social complexity and we adduce evidence to support this. Finally, we consider the wider issue of how mammalian (and primate) brains evolve in order to localize the social effects.

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