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

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.

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

10.1101/2021.02.17.431536 ◽

2021 ◽

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

AbstractConsiderable 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 generalised 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 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.

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The Evolution of Relative Brain Size in Marsupials Is Energetically Constrained but Not Driven by Behavioral Complexity

Brain Behavior and Evolution ◽

10.1159/000377666 ◽

2015 ◽

Vol 85 (2) ◽

pp. 125-135 ◽

Cited By ~ 21

Author(s):

Vera Weisbecker ◽

Simon Blomberg ◽

Anne W. Goldizen ◽

Meredeth Brown ◽

Diana Fisher

Keyword(s):

Social Complexity ◽

Brain Size ◽

Maternal Investment ◽

Generalized Least Squares ◽

Brain Morphology ◽

Mammalian Brain ◽

Data Set ◽

Behavioral Complexity ◽

Size Evolution ◽

Relative Brain Size

Evolutionary increases in mammalian brain size relative to body size are energetically costly but are also thought to confer selective advantages by permitting the evolution of cognitively complex behaviors. However, many suggested associations between brain size and specific behaviors - particularly related to social complexity - are possibly confounded by the reproductive diversity of placental mammals, whose brain size evolution is the most frequently studied. Based on a phylogenetic generalized least squares analysis of a data set on the reproductively homogenous clade of marsupials, we provide the first quantitative comparison of two hypotheses based on energetic constraints (maternal investment and seasonality) with two hypotheses that posit behavioral selection on relative brain size (social complexity and environmental interactions). We show that the two behavioral hypotheses have far less support than the constraint hypotheses. The only unambiguous associates of brain size are the constraint variables of litter size and seasonality. We also found no association between brain size and specific behavioral complexity categories within kangaroos, dasyurids, and possums. The largest-brained marsupials after phylogenetic correction are from low-seasonality New Guinea, supporting the notion that low seasonality represents greater nutrition safety for brain maintenance. Alternatively, low seasonality might improve the maternal support of offspring brain growth. The lack of behavioral brain size associates, found here and elsewhere, supports the general ‘cognitive buffer hypothesis' as the best explanatory framework of mammalian brain size evolution. However, it is possible that brain size alone simply does not provide sufficient resolution on the question of how brain morphology and cognitive capacities coevolve.

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Different environmental variables predict body and brain size evolution in Homo

Nature Communications ◽

10.1038/s41467-021-24290-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Manuel Will ◽

Mario Krapp ◽

Jay T. Stock ◽

Andrea Manica

Keyword(s):

Environmental Factors ◽

Cognitive Abilities ◽

Net Primary Productivity ◽

Brain Size ◽

Environmental Influence ◽

Size Variation ◽

Evolutionary Pattern ◽

Statistical Framework ◽

Size Evolution ◽

Major Predictor

AbstractIncreasing body and brain size constitutes a key macro-evolutionary pattern in the hominin lineage, yet the mechanisms behind these changes remain debated. Hypothesized drivers include environmental, demographic, social, dietary, and technological factors. Here we test the influence of environmental factors on the evolution of body and brain size in the genus Homo over the last one million years using a large fossil dataset combined with global paleoclimatic reconstructions and formalized hypotheses tested in a quantitative statistical framework. We identify temperature as a major predictor of body size variation within Homo, in accordance with Bergmann’s rule. In contrast, net primary productivity of environments and long-term variability in precipitation correlate with brain size but explain low amounts of the observed variation. These associations are likely due to an indirect environmental influence on cognitive abilities and extinction probabilities. Most environmental factors that we test do not correspond with body and brain size evolution, pointing towards complex scenarios which underlie the evolution of key biological characteristics in later Homo.

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The impact of maternal genetic merit and country of origin on ewe reproductive performance, lambing performance and ewe survival

Translational Animal Science ◽

10.1093/tas/txab070 ◽

2021 ◽

Author(s):

N Fetherstone ◽

N McHugh ◽

T M Boland ◽

F M McGovern

Keyword(s):

New Zealand ◽

Birth Weight ◽

Litter Size ◽

Country Of Origin ◽

Reproductive Traits ◽

Gestation Length ◽

Genetic Merit ◽

Genetic Groups ◽

One Year ◽

The Impact

Abstract The objective of this study was to investigate the impact of the ewe’s maternal genetic merit and country of origin (New Zealand or Ireland) on ewe reproductive, lambing and productivity traits. The study was performed over a four year period (2016 to 2019) and consisted of three genetic groups: high maternal genetic merit New Zealand (NZ), high maternal genetic merit Irish (High Irish) and low maternal genetic merit Irish (Low Irish) ewes. Each group contained 30 Suffolk and 30 Texel ewes, selected based on the respective national maternal genetic indexes; i.e. either the New Zealand Maternal Worth (New Zealand group) or the €uro-star Replacement index (Irish groups). The impact of maternal genetic merit on reproductive traits such as litter size; lambing traits such as gestation length, birth weight, lambing difficulty, mothering ability, and productivity traits such as the number of lambs born and weaned were analyzed using linear mixed models. For binary traits, the impact of maternal genetic merit on reproductive traits such as conception to first AI service; lambing traits such as dystocia, perinatal lamb mortality and productivity traits such as ewe survival were analyzed using logistic regression. New Zealand ewes outperformed Low Irish ewes for conception to first AI (P<0.05) and litter size (P=0.05). Irish ewes were more likely to suffer from dystocia (6.84 (High Irish) and 8.25 (Low Irish) times) compared to NZ ewes (P<0.001); birth weight and perinatal mortality did not differ between groups (P>0.05). Lambs born from NZ ewes were 4.67 (95% CI: 1.89 to 11.55; P<0.001) and 6.54 (95% CI: 2.56 to 16.71; P<0.001) times more likely to stand up and suckle unassisted relative to lambs born from High or Low Irish ewes, respectively. New Zealand and High Irish ewes had a greater number of lambs born and weaned throughout the duration of the study compared to their Low Irish counterparts (P<0.001). New Zealand ewes tended to be more likely to survive from one year to the next compared to Low Irish ewes (P=0.07). Irish ewes of high maternal genetic merit outperformed their Low counterparts in total number of lambs born and weaned per ewe, but performance did not differ across other traits investigated. This highlights the importance of continuous development of the Irish maternal sheep index to ensure favourable improvements in reproductive, lambing and productivity traits at farm level. Overall, results demonstrate the suitability of NZ genetics in an Irish production system.

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

Brain Behavior and Evolution ◽

10.1159/000501161 ◽

2019 ◽

Vol 93 (4) ◽

pp. 182-195 ◽

Cited By ~ 4

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.

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INTERRELATIONS BETWEEN SOME REPRODUCTIVE TRAITS IN SWINE

Canadian Journal of Animal Science ◽

10.4141/cjas72-004 ◽

1972 ◽

Vol 52 (1) ◽

pp. 39-45 ◽

Cited By ~ 4

Author(s):

M. H. FAHMY ◽

C. S. BERNARD

Keyword(s):

Litter Size ◽

Survival Rates ◽

Reproductive Traits ◽

The Other ◽

Gestation Length ◽

Percentage Survival ◽

Weaning Pig ◽

Highly Correlated ◽

Daily Gain ◽

Size At Birth

The associations between 15 preweaning traits in pigs were studied to determine which had the most important effects on litter weights at birth and weaning. The traits were litter size at birth and weaning, number born alive, percentage survival to birth and weaning, pig and litter weights at birth and weaning, daily gain from birth to weaning, gestation length, number of teats, weights of dam at farrowing and at weaning, and the change in dam weight during lactation. Of the 105 correlations, 66 were statistically significant, though many were markedly low. Litter weights at birth and weaning were significantly and relatively highly correlated with most of the other traits, whereas number of teats was correlated only with survival rates at birth and weaning and pig birth weight. The results showed that the importance of litter size was almost twice that of pig weight in determining litter weights at birth and weaning. The results in general indicated that most of the economically important traits related to swine reproductivity are favorably associated.

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Genes underlying the evolution of tetrapod testes size

BMC Biology ◽

10.1186/s12915-021-01107-z ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Joanna Baker ◽

Andrew Meade ◽

Chris Venditti

Keyword(s):

Candidate Genes ◽

Biological Diversity ◽

Brain Size ◽

Size Variation ◽

Phenotypic Change ◽

Testis Size ◽

Protein Coding ◽

Size Evolution ◽

Size Diversity ◽

To Come

Abstract Background Testes vary widely in mass relative to body mass across species, but we know very little about which genes underlie and contribute to such variation. This is partly because evidence for which genes are implicated in testis size variation tends to come from investigations involving just one or a few species. Contemporary comparative phylogenetic methods provide an opportunity to test candidate genes for their role in phenotypic change at a macro-evolutionary scale—across species and over millions of years. Previous attempts to detect genotype-phenotype associations across species have been limited in that they can only detect where genes have driven directional selection (e.g. brain size increase). Results Here, we introduce an approach that uses rates of evolutionary change to overcome this limitation to test whether any of twelve candidate genes have driven testis size evolution across tetrapod vertebrates—regardless of directionality. We do this by seeking a relationship between the rates of genetic and phenotypic evolution. Our results reveal five genes (Alkbh5, Dmrtb1, Pld6, Nlrp3, Sp4) that each have played unique and complex roles in tetrapod testis size diversity. In all five genes, we find strong significant associations between the rate of protein-coding substitutions and the rate of testis size evolution. Such an association has never, to our knowledge, been tested before for any gene or phenotype. Conclusions We describe a new approach to tackle one of the most fundamental questions in biology: how do individual genes give rise to biological diversity? The ability to detect genotype-phenotype associations that have acted across species has the potential to build a picture of how natural selection has sculpted phenotypic change over millions of years.

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Predator-driven brain size evolution in natural populations of Trinidadian killifish ( Rivulus hartii )

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.1075 ◽

2016 ◽

Vol 283 (1834) ◽

pp. 20161075 ◽

Cited By ~ 17

Author(s):

Matthew R. Walsh ◽

Whitnee Broyles ◽

Shannon M. Beston ◽

Stephan B. Munch

Keyword(s):

Brain Size ◽

Natural Populations ◽

Size Variation ◽

Laboratory Selection ◽

Trade Offs ◽

Female Brain ◽

Size Evolution ◽

Selection Experiments ◽

Fitness Benefits ◽

Recent Laboratory

Vertebrates exhibit extensive variation in relative brain size. It has long been assumed that this variation is the product of ecologically driven natural selection. Yet, despite more than 100 years of research, the ecological conditions that select for changes in brain size are unclear. Recent laboratory selection experiments showed that selection for larger brains is associated with increased survival in risky environments. Such results lead to the prediction that increased predation should favour increased brain size. Work on natural populations, however, foreshadows the opposite trajectory of evolution; increased predation favours increased boldness, slower learning, and may thereby select for a smaller brain. We tested the influence of predator-induced mortality on brain size evolution by quantifying brain size variation in a Trinidadian killifish, Rivulus hartii , from communities that differ in predation intensity. We observed strong genetic differences in male (but not female) brain size between fish communities; second generation laboratory-reared males from sites with predators exhibited smaller brains than Rivulus from sites in which they are the only fish present. Such trends oppose the results of recent laboratory selection experiments and are not explained by trade-offs with other components of fitness. Our results suggest that increased male brain size is favoured in less risky environments because of the fitness benefits associated with faster rates of learning and problem-solving behaviour.

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EVALUATION OF PRODUCTIVE AND REPRODUCTIVE PERFORMANCES OF BLACK BENGAL GOATS IN RAJSHAHI GOVERNMENT GOAT DEVELOPMENT FARM IN BANGLADESH

Journal of Veterinary Medical and One Health Research ◽

10.36111/jvmohr.2019.1(2).0012 ◽

2019 ◽

Vol 1 (2) ◽

pp. 201-210

Author(s):

M. I. Z. Moni ◽

M. A. Samad

Keyword(s):

Birth Weight ◽

Litter Size ◽

Post Partum ◽

Economic Status ◽

Reproductive Traits ◽

Young Female ◽

Conception Rate ◽

Morbidity And Mortality ◽

Gestation Length ◽

Intensive System

Background: The Black Bengal goat (BBG) is well adapted food animals with profitable productive and reproductive traits being naturally reared to enhance economic status and food security in rural people. Bangladesh government has taken program through establishment of ‘Government Goat Development Farms’ (GGDF) to enhance the goat rearing activities of the smallholders at rural level but the research reports on the productive and reproductive performances of goats in these GGDF are very limited. Objective: The main objective of this study was to evaluate the productive and reproductive performances of the BBG reared in semi-intensive system at the Rajshahi GGDF Materials and Methods: The Rajshahi GGDF had 398 goat populations of which 121 does were selected to study the productive and reproductive performances during the period from July 2010 to June 2011. The age of first estrus, conception rate by natural service, gestation length, post-partum heat, kidding interval, litter size, survivability of kids, morbidity and mortality of kids and their seasonal influence were studied. Results: The age of young female BBG showed 1st estrus varied from 180 to 270 with an average of 204  27 days. The conception rate varied from 88 to 100 with an average of 97% with natural services. The gestation length varied from 145 to 182 with an average of 150  5 days. The post-partum heat period varied from 60 to 90 days with an average of 69  7 days. The kidding interval varied from 199 to 268 with an average of 219  13 days. The litter size varied from 1 to 3 with an average of 2. Out of 234 kids borne, 47.44% were male and 52.56% female with higher mortality in male (10.81%) than female (5.69%) with an overall average mortality of 8.12%. There was no significant influence of season and parity on the birth weight of kids. However, the heavier birth weight of kids was recorded in male (1.38 kg) than female (1.17kg) kids. The birth of twin kids (56.41%) was found significantly (p < 0.0001) highest in comparison to triplets (26.92%), single (11.54%) and quadruplet (5.13%). Conclusions: The results support promising breeding and reproductive efficiency of BBG under local environmental conditions and therefore, there is a need to be improved milk yield of dam and control of morbidity and mortality in BBG kids. It may be concluded that the productive and reproductive performances of the BBG reared by using semi-intensive system of management appears to be encouraging at the Rajshahi GGDF which could be extended and compared to research findings with other four GGDF in Bangladesh.

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Genome wide association analysis identifies genetic variants associated with reproductive variation across domestic dog breeds and uncovers links to domestication

10.1101/285791 ◽

2018 ◽

Cited By ~ 1

Author(s):

Julie Baker Phillips ◽

Samuel A. Smith ◽

Maddison L. Johnson ◽

Patrick Abbot ◽

John A. Capra ◽

...

Keyword(s):

Cesarean Section ◽

Litter Size ◽

Reproductive Traits ◽

Genome Wide Association ◽

Domestic Dog ◽

Cesarean Section Rate ◽

Gestation Length ◽

Stillbirth Rate ◽

Phenotypic Data ◽

Genome Wide

AbstractThe diversity of eutherian reproductive strategies has led to variation in many traits, such as number of offspring, age of reproductive maturity, and gestation length. While reproductive trait variation has been extensively investigated and is well established in mammals, the genetic loci contributing to this variation remain largely unknown. The domestic dog, Canis lupus familiaris is a powerful model for studies of the genetics of inherited disease due to its unique history of domestication. To gain insight into the genetic basis of reproductive traits across domestic dog breeds, we collected phenotypic data for four traits – cesarean section rate (n = 97 breeds), litter size (n = 60), stillbirth rate (n = 57), and gestation length (n = 23) – from primary literature and breeders’ handbooks. By matching our phenotypic data to genomic data from the Cornell Veterinary Biobank, we performed genome wide association analyses for these four reproductive traits, using body mass and kinship among breeds as co-variates. We identified 14 genome-wide significant associations between these traits and genetic loci, including variants near CACNA2D3 with gestation length, MSRB3 with litter size, SMOC2 with cesarean section rate, MITF with litter size and still birth rate, KRT71 with cesarean section rate, litter size, and stillbirth rate, and HTR2C with stillbirth rate. Some of these loci, such as CACNA2D3 and MSRB3, have been previously implicated in human reproductive pathologies. Many of the variants that we identified have been previously associated with domestication-related traits, including brachycephaly (SMOC2), coat color (MITF), coat curl (KRT71), and tameness (HTR2C). These results raise the hypothesis that the artificial selection that gave rise to dog breeds also shaped the observed variation in their reproductive traits. Overall, our work establishes the domestic dog as a system for studying the genetics of reproductive biology and disease.

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