scholarly journals Rapid mosaic brain evolution under artificial selection for relative telencephalon size in the guppy (Poecilia reticulata)

2021 ◽  
Author(s):  
Stephanie Fong ◽  
Björn Rogell ◽  
Mirjam Amcoff ◽  
Alexander Kotrschal ◽  
Wouter van der Bijl ◽  
...  
Keyword(s):  
Artificial Selection ◽  
Poecilia Reticulata ◽  
Brain Size ◽  
Brain Evolution ◽  
Brain Regions ◽  
Research Field ◽  
Selected Lines ◽  
Vertebrate Brain ◽  
Offspring Production ◽  
Mosaic Brain Evolution

The vertebrate brain displays enormous morphological variation and the quest to understand the evolutionary causes and consequences of this variation has spurred much research. The mosaic brain evolution hypothesis, stating that brain regions can evolve relatively independently, is an important idea in this research field. Here we provide experimental support for this hypothesis through an artificial selection experiment in the guppy (Poecilia reticulata). After four generations of selection on relative telencephalon volume (relative to brain size) in replicated up-selected, down-selected and control-lines, we found substantial changes in telencephalon size, but no changes in other regions. Comparisons revealed that up-selected lines had larger telencephalon while down-selected lines had smaller telencephalon than wild Trinidadian populations. No cost of increasing telencephalon size was detected in offspring production. Our results support that independent evolutionary changes in specific brain regions through mosaic brain evolution can be important facilitators of cognitive evolution.

scholarly journals Rapid mosaic brain evolution under artificial selection for relative telencephalon size in the guppy ( Poecilia reticulata )

2021 ◽  
Vol 7 (46) ◽  
Author(s):  
Stephanie Fong ◽  
Björn Rogell ◽  
Mirjam Amcoff ◽  
Alexander Kotrschal ◽  
Wouter van der Bijl ◽  
...  
Keyword(s):  
Artificial Selection ◽  
Poecilia Reticulata ◽  
Brain Evolution ◽  
Selection For ◽  
Mosaic Brain Evolution

Predation impacts brain allometry and offspring production in female guppies (Poecilia reticulata)

2021 ◽  
Author(s):  
Regina Vega-Trejo ◽  
David Joseph Mitchell ◽  
Catarina Vila Pouca ◽  
Alexander Kotrschal
Keyword(s):  
Poecilia Reticulata ◽  
Brain Size ◽  
Relative Size ◽  
Reproductive Traits ◽  
Brain Evolution ◽  
Predation Pressure ◽  
Control Fish ◽  
Brain Anatomy ◽  
Offspring Production ◽  
The Impact

Survivorship under predation exerts strong selection on reproductive traits as well as on brain anatomy of prey. However, how exactly predation and brain evolution are linked has not been resolved as current empirical evidence is inconclusive. This may be due to predation pressure having different effects across life stages and/or due to confounding factors in ecological comparisons of predation pressure. Here, we used adult guppies (Poecilia reticulata) to experimentally test the impact of a period of strong predation on brain anatomy and reproduction of surviving individuals. We compared the survivors to control fish, which were exposed to visual and olfactory predator cues but could not be predated on, and found that predation impacted the relative size of female brains. This effect was dependent on body size as larger female survivors showed relatively larger brains, while smaller survivors showed relatively smaller brains when compared to control animals. There were no differences in male relative brain size between the treatments, nor for any specific relative brain region sizes for either sex. Moreover, survivors produced more offspring, but did not show shorter interbrood intervals than controls. Our results corroborate the important, yet complex, role of predation as an important factor behind variation in brain anatomy.

scholarly journals Convergent mosaic brain evolution is associated with the evolution of novel electrosensory systems in teleost fishes

2021 ◽  
Author(s):  
Erika L. Schumacher ◽  
Bruce A. Carlson
Keyword(s):  
Brain Region ◽  
Brain Size ◽  
Brain Evolution ◽  
Brain Regions ◽  
Torus Semicircularis ◽  
Micro Computed Tomography ◽  
Electrosensory System ◽  
Electric Fishes ◽  
Weakly Electric ◽  
Region Size

AbstractBrain region size generally scales allometrically with total brain size, but mosaic shifts in brain region size independent of brain size have been found in several lineages and may be related to the evolution of behavioral novelty. African weakly electric fishes (Mormyroidea) evolved a mosaically enlarged cerebellum and hindbrain, yet the relationship to their behaviorally novel electrosensory system remains unclear. We addressed this by studying South American weakly electric fishes (Gymnotiformes) and weakly electric catfishes (Synodontis spp.), which evolved varying aspects of electrosensory systems, independent of mormyroids. If the mormyroid mosaic increases are related to evolving an electrosensory system, we should find similar mosaic shifts in gymnotiforms and Synodontis. Using micro-computed tomography scans, we quantified brain region scaling for multiple electrogenic, electroreceptive, and non-electrosensing species. We found mosaic increases in cerebellum in all three electrogenic lineages relative to non-electric lineages and mosaic increases in torus semicircularis and hindbrain associated with the evolution of electrogenesis and electroreceptor type. These results show that evolving novel electrosensory systems is repeatedly and independently associated with changes in the sizes of individual brain regions independent of brain size, which suggests that selection can impact structural brain composition to favor specific regions involved in novel behaviors.

scholarly journals Quantitative genetic analysis of brain size variation in sticklebacks: support for the mosaic model of brain evolution

2015 ◽  
Vol 282 (1810) ◽  
pp. 20151008 ◽  
Author(s):  
Kristina Noreikiene ◽  
Gábor Herczeg ◽  
Abigél Gonda ◽  
Gergely Balázs ◽  
Arild Husby ◽  
...  
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Additive Genetic Variance ◽  
Genetic Correlations ◽  
Relative Size ◽  
Strong Support ◽  
Brain Evolution ◽  
Brain Regions ◽  
Independent Evolution ◽  
Mosaic Model

The mosaic model of brain evolution postulates that different brain regions are relatively free to evolve independently from each other. Such independent evolution is possible only if genetic correlations among the different brain regions are less than unity. We estimated heritabilities, evolvabilities and genetic correlations of relative size of the brain, and its different regions in the three-spined stickleback ( Gasterosteus aculeatus ). We found that heritabilities were low (average h 2 = 0.24), suggesting a large plastic component to brain architecture. However, evolvabilities of different brain parts were moderate, suggesting the presence of additive genetic variance to sustain a response to selection in the long term. Genetic correlations among different brain regions were low (average r G = 0.40) and significantly less than unity. These results, along with those from analyses of phenotypic and genetic integration, indicate a high degree of independence between different brain regions, suggesting that responses to selection are unlikely to be severely constrained by genetic and phenotypic correlations. Hence, the results give strong support for the mosaic model of brain evolution. However, the genetic correlation between brain and body size was high ( r G = 0.89), suggesting a constraint for independent evolution of brain and body size in sticklebacks.

Synthesis

2019 ◽  
pp. 423-472
Author(s):  
Georg F. Striedter ◽  
R. Glenn Northcutt
Keyword(s):  
Functional Organization ◽  
Brain Size ◽  
Brain Regions ◽  
Brain Areas ◽  
Nervous Systems ◽  
Internal Organization ◽  
Vertebrate Brain ◽  
Relative Brain Size

After summarizing the earlier chapters, which focused on the evolution of specific lineages, this chapter examines general patterns in the evolution of vertebrate nervous systems. Most conspicuous is that relative brain size and complexity increased independently in many lineages. The proportional size of individual brain regions tends to change predictably with absolute brain size (and neurogenesis timing), but the scaling rules vary across lineages. Attempts to link variation in the size of individual brain areas (or entire brains) to behavior are complicated in part because the connections, internal organization, and functions of individual brain regions also vary across phylogeny. In addition, major changes in the functional organization of vertebrate brains were caused by the emergence of novel brain regions (e.g., neocortex in mammals and area dorsalis centralis in teleosts) and novel circuits. These innovations significantly modified the “vertebrate brain Bauplan,” but their mechanistic origins and implications require further investigation.

scholarly journals Artificial selection on male genitalia length alters female brain size

2016 ◽  
Vol 283 (1843) ◽  
pp. 20161796 ◽  
Author(s):  
Séverine D. Buechel ◽  
Isobel Booksmythe ◽  
Alexander Kotrschal ◽  
Michael D. Jennions ◽  
Niclas Kolm
Keyword(s):  
Cognitive Ability ◽  
Sexual Conflict ◽  
Artificial Selection ◽  
Brain Size ◽  
Brain Evolution ◽  
Brain Anatomy ◽  
Male Harassment ◽  
Female Brain ◽  
Eastern Mosquitofish ◽  
Specific Interests

Male harassment is a classic example of how sexual conflict over mating leads to sex-specific behavioural adaptations. Females often suffer significant costs from males attempting forced copulations, and the sexes can be in an arms race over male coercion. Yet, despite recent recognition that divergent sex-specific interests in reproduction can affect brain evolution, sexual conflict has not been addressed in this context. Here, we investigate whether artificial selection on a correlate of male success at coercion, genital length, affects brain anatomy in males and females. We analysed the brains of eastern mosquitofish ( Gambusia holbrooki ), which had been artificially selected for long or short gonopodium, thereby mimicking selection arising from differing levels of male harassment. By analogy to how prey species often have relatively larger brains than their predators, we found that female, but not male, brain size was greater following selection for a longer gonopodium. Brain subregion volumes remained unchanged. These results suggest that there is a positive genetic correlation between male gonopodium length and female brain size, which is possibly linked to increased female cognitive ability to avoid male coercion. We propose that sexual conflict is an important factor in the evolution of brain anatomy and cognitive ability.

Précis of Principles of Brain Evolution

2006 ◽  
Vol 29 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Georg F. Striedter
Keyword(s):  
Brain Structure ◽  
Homo Sapiens ◽  
Brain Size ◽  
Brain Evolution ◽  
Detailed Examination ◽  
Brain Regions ◽  
Impact Function ◽  
Neuronal Connections ◽  
Rules And Principles ◽  
Using Data

Brain evolution is a complex weave of species similarities and differences, bound by diverse rules and principles. This book is a detailed examination of these principles, using data from a wide array of vertebrates but minimizing technical details and terminology. It is written for advanced undergraduates, graduate students, and more senior scientists who already know something about “the brain,” but want a deeper understanding of how diverse brains evolved. The book's central theme is that evolutionary changes in absolute brain size tend to correlate with many other aspects of brain structure and function, including the proportional size of individual brain regions, their complexity, and their neuronal connections. To explain these correlations, the book delves into rules of brain development and asks how changes in brain structure impact function and behavior. Two chapters focus specifically on how mammal brains diverged from other brains and how Homo sapiens evolved a very large and “special” brain.

scholarly journals Why big brains? A comparison of models for both primate and carnivore brain size evolution

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0261185
Author(s):  
Helen Rebecca Chambers ◽  
Sandra Andrea Heldstab ◽  
Sean J. O’Hara
Keyword(s):  
Life History ◽  
Brain Size ◽  
Size Variation ◽  
Ecological Factors ◽  
Brain Evolution ◽  
Brain Regions ◽  
Home Range Size ◽  
Careful Consideration ◽  
Social Brain ◽  
Multiple Variables

Despite decades of research, much uncertainty remains regarding the selection pressures responsible for brain size variation. Whilst the influential social brain hypothesis once garnered extensive support, more recent studies have failed to find support for a link between brain size and sociality. Instead, it appears there is now substantial evidence suggesting ecology better predicts brain size in both primates and carnivores. Here, different models of brain evolution were tested, and the relative importance of social, ecological, and life-history traits were assessed on both overall encephalisation and specific brain regions. In primates, evidence is found for consistent associations between brain size and ecological factors, particularly diet; however, evidence was also found advocating sociality as a selection pressure driving brain size. In carnivores, evidence suggests ecological variables, most notably home range size, are influencing brain size; whereas, no support is found for the social brain hypothesis, perhaps reflecting the fact sociality appears to be limited to a select few taxa. Life-history associations reveal complex selection mechanisms to be counterbalancing the costs associated with expensive brain tissue through extended developmental periods, reduced fertility, and extended maximum lifespan. Future studies should give careful consideration of the methods chosen for measuring brain size, investigate both whole brain and specific brain regions where possible, and look to integrate multiple variables, thus fully capturing all of the potential factors influencing brain size.

scholarly journals Experimental translocations to low predation lead to non-parallel increases in relative brain size

2020 ◽  
Vol 16 (1) ◽  
pp. 20190654 ◽  
Author(s):  
David J. Mitchell ◽  
Regina Vega-Trejo ◽  
Alexander Kotrschal
Keyword(s):  
Poecilia Reticulata ◽  
Brain Size ◽  
Parallel Evolution ◽  
Brain Evolution ◽  
Common Garden ◽  
Brain Anatomy ◽  
In The Wild ◽  
High Predation ◽  
Relative Brain Size ◽  
Introduction Experiment

Predation is a near ubiquitous factor of nature and a powerful selective force on prey. Moreover, it has recently emerged as an important driver in the evolution of brain anatomy, though population comparisons show ambiguous results with considerable unexplained variation. Here, we test the reproducibility of reduced predation on evolutionary trajectories of brain evolution. We make use of an introduction experiment, whereby guppies ( Poecilia reticulata ) from a single high predation stream were introduced to four low predation streams. After 8–9 years of natural selection in the wild and two generations of common garden conditions in the laboratory, we quantified brain anatomy. Relative brain region sizes did not differ between populations. However, we found a general increase and striking variation in relative brain size of introduced populations, which varied from no change to a 12.5% increase in relative brain weight, relative to the ancestral high predation population. We interpret this as evidence for non-parallel evolution, which implies a weak or inconsistent association of relative brain size with fitness in low predation sites. The evolution of brain anatomy appears sensitive to unknown environmental factors, or contingent on either chance events or historical legacies of environmental change.

scholarly journals Peeking Inside the Lizard Brain: Neuron Numbers in Anolis and Its Implications for Cognitive Performance and Vertebrate Brain Evolution

2020 ◽  
Author(s):  
Levi Storks ◽  
Brian J Powell ◽  
Manuel Leal
Keyword(s):  
Cognitive Performance ◽  
Brain Size ◽  
Motor Task ◽  
Behavioral Flexibility ◽  
Brain Evolution ◽  
Relative Mass ◽  
Published Data ◽  
Vertebrate Brain ◽  
Isotropic Fractionator ◽  
The Brain

Abstract Studies of vertebrate brain evolution have mainly focused on measures of brain size, particularly relative mass and its allometric scaling across lineages, commonly with the goal of identifying the substrates that underly differences in cognition. However, recent studies on birds and mammals have demonstrated that brain size is an imperfect proxy for neuronal parameters that underly function, such as the number of neurons that make up a given brain region. Here we present estimates of neuron numbers and density in two species of lizard, Anolis cristatellus and A. evermanni, representing the first such data from squamate species, and explore its implications for differences in cognitive performance and vertebrate brain evolution. The isotropic fractionator protocol outlined in this article is optimized for the unique challenges that arise when using this technique with lineages having nucleated erythrocytes and relatively small brains. The number and density of neurons and other cells we find in Anolis for the telencephalon, cerebellum, and the rest of the brain (ROB) follow similar patterns as published data from other vertebrate species. Anolis cristatellus and A. evermanni exhibited differences in their performance in a motor task frequently used to evaluate behavioral flexibility, which was not mirrored by differences in the number, density, or proportion of neurons in either the cerebellum, telencephalon, or ROB. However, the brain of A. evermanni had a significantly higher number of nonneurons and a higher nonneuron to neuron ratio across the whole brain, which could contribute to the observed differences in problem solving between A. cristatellus and A. evermanni. Although limited to two species, our findings suggest that neuron number and density in lizard brains scale similarly to endothermic vertebrates in contrast to the differences observed in brain to body mass relationships. Data from a wider range of species are necessary before we can fully understand vertebrate brain evolution at the neuronal level.

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