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Dieter C.t. Kruska - One of the best experts on this subject based on the ideXlab platform.

  • Encephalization of Bathyergidae and comparison of brain structure volumes between the Zambian mole-rat Fukomys anselli and the giant mole-rat Fukomys mechowii
    Mammalian Biology, 2009
    Co-Authors: Dieter C.t. Kruska, Katja Steffen
    Abstract:

    Encephalization indices were calculated for Fukomys anselli and Fukomys mechowii by using interspecific allometric lines of Tenrecinae (recent Eutheria with the smallest brains) and average Rodentia to compare brain sizes independent of body size influence. These were contrasted with corresponding indices of other Bathyergidae and additionally with other rodents. The Bathyergidae species had indices within the variation of some Cricetidae and Muridae and thus do not differ in Encephalization. F. anselli, however, had a clearly higher Encephalization index than the sister species F. mechowii. The sizes of diverse structures were measured in the brains of these two species by help of the serial section method. No differences were found in relative composition. The lower Encephalization of F. mechowii is discussed as a special phenomenon of gigantism during phylogenetic radiation which similarly was documented for other forms.

  • on the evolutionary significance of Encephalization in some eutherian mammals effects of adaptive radiation domestication and feralization
    Brain Behavior and Evolution, 2005
    Co-Authors: Dieter C.t. Kruska
    Abstract:

    Allometries of the brain to body size relationship in eutherian mammals are examined in this study as they can be used for comparative analyses concerning Encephalization. In contrast with some modern presentations of this issue, an older concept is revived and expanded through this author's current study. Three allometries with clearly different slopes are valid and lead to reliable results: interspecific, intraspecific, and ontogenetic allometries. Interspecific allometries follow lines with slope values of 0.56 or 0.63 for larger and smaller species, respectively, and characterize different average Encephalization plateaus with rodents and lagomorphs generally more strongly encephalized compared to basal insectivores. Artiodactyls, perissodactyls and carnivores as a whole are again on a higher but rather similar plateau. Several species of carnivores have reached different Encephalization levels with respect to their average plateau indicating diverse radiations. A phylogenetic brain size increase from fossil to recent radiations is also evident. Intraspecific allometries have slope values of about 0.25. These are of help in comparing brain sizes of ancestral species with their domesticated relatives. Domestication has generally led to a brain size decrease, but species on higher Encephalization plateaus show this trend more strongly than species on a lower level of Encephalization. Several brain parts and the sense organs also decrease in size during the domestication process, but vary arbitrarily and to different degrees. Ontogenetic growth allometries are species-specific, but are especially different between altricial and precocial mammals. A very steep 1st phase slope of highly encephalized species is particularly useful for understanding evolutionary and adaptive phenomena. Domesticated mammals that have become feral do not show an increase in brain size despite living many generations in wild habitats.

  • on the evolutionary significance of Encephalization in some eutherian mammals effects of adaptive radiation domestication and feralization
    Brain Behavior and Evolution, 2005
    Co-Authors: Dieter C.t. Kruska
    Abstract:

    Allometries of the brain to body size relationship in eutherian mammals are examined in this study as they can be used for comparative analyses concerning Encephalization. In contrast with some modern

Bruce A. Carlson - One of the best experts on this subject based on the ideXlab platform.

  • Intraspecific Energetic Trade-Offs and Costs of Encephalization Vary from Interspecific Relationships in Three Species of Mormyrid Electric Fishes.
    Brain behavior and evolution, 2019
    Co-Authors: Kimberley V. Sukhum, Megan K. Freiler, Bruce A. Carlson
    Abstract:

    The evolution of increased Encephalization comes with an energetic cost. Across species, this cost may be paid for by an increase in metabolic rate or by energetic trade-offs between the brain and other energy-expensive tissues. However, it remains unclear whether these solutions to deal with the energetic requirements of an enlarged brain are related to direct physiological constraints or other evolved co-adaptations. We studied the highly encephalized mormyrid fishes, which have extensive species diversity in relative brain size. We previously found a correlation between resting metabolic rate and relative brain size across species; however, it is unknown how this interspecific relationship evolved. To address this issue, we measured intraspecific variation in relative brain size, the sizes of other organs, metabolic rate, and hypoxia tolerance to determine if intraspecific relationships between brain size and organismal energetics are similar to interspecific relationships. We found that 3 species of mormyrids with varying degrees of Encephalization had no intraspecific relationships between relative brain size and relative metabolic rate or relative sizes of other organs, and only 1 species had a relationship between relative brain size and hypoxia tolerance. These species-specific differences suggest that the interspecific relationship between metabolic rate and relative brain size is not the result of direct physiological constraints or strong stabilizing selection, but is instead due to other species level co-adaptations. We conclude that variation within species must be considered when determining the energetic costs and trade-offs underlying the evolution of extreme Encephalization.

  • The costs of a big brain: extreme Encephalization results in higher energetic demand and reduced hypoxia tolerance in weakly electric African fishes.
    Proceedings. Biological sciences, 2016
    Co-Authors: Kimberley V. Sukhum, Megan K. Freiler, Robert Wang, Bruce A. Carlson
    Abstract:

    A large brain can offer several cognitive advantages. However, brain tissue has an especially high metabolic rate. Thus, evolving an enlarged brain requires either a decrease in other energetic requirements, or an increase in overall energy consumption. Previous studies have found conflicting evidence for these hypotheses, leaving the metabolic costs and constraints in the evolution of increased Encephalization unclear. Mormyrid electric fishes have extreme Encephalization comparable to that of primates. Here, we show that brain size varies widely among mormyrid species, and that there is little evidence for a trade-off with organ size, but instead a correlation between brain size and resting oxygen consumption rate. Additionally, we show that increased brain size correlates with decreased hypoxia tolerance. Our data thus provide a non-mammalian example of extreme Encephalization that is accommodated by an increase in overall energy consumption. Previous studies have found energetic trade-offs with variation in brain size in taxa that have not experienced extreme Encephalization comparable with that of primates and mormyrids. Therefore, we suggest that energetic trade-offs can only explain the evolution of moderate increases in brain size, and that the energetic requirements of extreme Encephalization may necessitate increased overall energy investment.

John A Finarelli - One of the best experts on this subject based on the ideXlab platform.

  • © 2009 The Authors Journal compilation © 2009 Anatomical Society of Great Britain and Ireland Blackwell Publishing Ltd The evolution of orbit orientation and Encephalization in the Carnivora (Mammalia)
    2016
    Co-Authors: John A Finarelli, Anjali Goswami
    Abstract:

    Evolutionary change in Encephalization within and across mammalian clades is well-studied, yet relatively few comparative analyses attempt to quantify the impact of evolutionary change in relative brain size on cranial morphology. Because of the proximity of the braincase to the orbits, and the inter-relationships among ecology, sensory systems and neuroanatomy, a relationship has been hypothesized between orbit orientation and Encephalization for mammals. Here, we tested this hypothesis in 68 fossil and living species of the mammalian order Carnivora, comparing orbit orientation angles (convergence and frontation) to skull length and Encephalization. No significant correlations were observed between skull length and orbit orientation when all taxa were analysed. Significant correlations were observed between Encephalization and orbit orientation; however, these were restricted to the families Felidae and Canidae. Encephalization is positively correlated with frontation in both families and negatively correlated with convergence in canids. These results indicate that no universal relationship exists between Encephalization and orbit orientation for Carnivora. Braincase expansion impacts orbit orientation in specific carnivoran clades, the nature of which is idiosyncratic to the clade itself. Key word

  • Does Encephalization correlate with life history or metabolic rate in Carnivora
    Biology letters, 2009
    Co-Authors: John A Finarelli
    Abstract:

    A recent analysis of brain size evolution reconstructed the plesiomorphic brain–body size allometry for the mammalian order Carnivora, providing an important reference frame for comparative analyses of Encephalization (brain volume scaled to body mass). I performed phylogenetically corrected regressions to remove the effects of body mass, calculating correlations between residual values of Encephalization with basal metabolic rate (BMR) and six life-history variables (gestation time, neonatal mass, weaning time, weaning mass, litter size, litters per year). No significant correlations were recovered between Encephalization and any life-history variable or BMR, arguing against hypotheses relating Encephalization to maternal energetic investment. However, after correcting for clade-specific adaptations, I recovered significant correlations for several variables, and further analysis revealed a conserved carnivoran reproductive strategy, linking degree of Encephalization to the well-documented mammalian life-history trade-off between neonatal mass and litter size. This strategy of fewer, larger offspring correlating with increased Encephalization remains intact even after independent changes in Encephalization allometries in the evolutionary history of this clade.

  • Brain-size evolution and sociality in Carnivora
    Proceedings of the National Academy of Sciences of the United States of America, 2009
    Co-Authors: John A Finarelli, John J. Flynn
    Abstract:

    Increased Encephalization, or larger brain volume relative to body mass, is a repeated theme in vertebrate evolution. Here we present an extensive sampling of relative brain sizes in fossil and extant taxa in the mammalian order Carnivora (cats, dogs, bears, weasels, and their relatives). By using Akaike Information Criterion model selection and endocranial volume and body mass data for 289 species (including 125 fossil taxa), we document clade-specific evolutionary transformations in Encephalization allometries. These evolutionary transformations include multiple independent Encephalization increases and decreases in addition to a remarkably static basal Carnivora allometry that characterizes much of the suborder Feliformia and some taxa in the suborder Caniformia across much of their evolutionary history, emphasizing that complex processes shaped the modern distribution of Encephalization across Carnivora. This analysis also permits critical evaluation of the social brain hypothesis (SBH), which predicts a close association between sociality and increased Encephalization. Previous analyses based on living species alone appeared to support the SBH with respect to Carnivora, but those results are entirely dependent on data from modern Canidae (dogs). Incorporation of fossil data further reveals that no association exists between sociality and Encephalization across Carnivora and that support for sociality as a causal agent of Encephalization increase disappears for this clade.

  • The evolution of orbit orientation and Encephalization in the Carnivora (Mammalia)
    Journal of anatomy, 2009
    Co-Authors: John A Finarelli, Anjali Goswami
    Abstract:

    Evolutionary change in Encephalization within and across mammalian clades is well-studied, yet relatively few comparative analyses attempt to quantify the impact of evolutionary change in relative brain size on cranial morphology. Because of the proximity of the braincase to the orbits, and the inter-relationships among ecology, sensory systems and neuroanatomy, a relationship has been hypothesized between orbit orientation and Encephalization for mammals. Here, we tested this hypothesis in 68 fossil and living species of the mammalian order Carnivora, comparing orbit orientation angles (convergence and frontation) to skull length and Encephalization. No significant correlations were observed between skull length and orbit orientation when all taxa were analysed. Significant correlations were observed between Encephalization and orbit orientation; however, these were restricted to the families Felidae and Canidae. Encephalization is positively correlated with frontation in both families and negatively correlated with convergence in canids. These results indicate that no universal relationship exists between Encephalization and orbit orientation for Carnivora. Braincase expansion impacts orbit orientation in specific carnivoran clades, the nature of which is idiosyncratic to the clade itself.

  • testing hypotheses of the evolution of Encephalization in the canidae carnivora mammalia
    Paleobiology, 2008
    Co-Authors: John A Finarelli
    Abstract:

    Evolutionary trends observed over large clades have the potential to mask underlying trends that occur within their constituent subclades. A recent study of Encephalization in the Caniformia (Carnivora, Mammalia) found evidence for an abrupt increase in median log-Encephalization quotients (logEQs), indicating higher brain volume relative to body mass, at the end-Miocene, but gradual increase in the variance of logEQs. In this study, new endocranial volume estimates for fossil taxa in the well-sampled caniform subclade Canidae are reported. Using the Encephalization data for the Canidae, hypotheses of evolution in Encephalization allometries were tested with respect to canid phylogeny. The Akaike Information Criterion and likelihood ratios recovered support for a preferred hypothesis of the evolution of canid Encephalization, which proposed two distinct allometric relationships: (1) a plesiomorphic grade of Encephalization in the subfamilies Hesperocyoninae and Borophaginae and the paraphyletic canine genus Leptocyon , and (2) an apomorphic grade in the crown radiation of Caninae. This defines a shift in to higher Encephalization, but without an associated change in the variance around the allometry. Increased canid Encephalization coincides with a reorganization of the brain and the observed trend may reflect the evolution of complex social behavior in this clade.

Masahito Tsuboi - One of the best experts on this subject based on the ideXlab platform.

  • breakdown of brain body allometry and the Encephalization of birds and mammals
    Nature Ecology and Evolution, 2018
    Co-Authors: Masahito Tsuboi, Wouter Van Der Bijl, Bjorn Tore Kopperud, Johannes Erritzoe, Kjetil L Voje, Alexander Kotrschal, Kara E Yopak, Shaun P Collin
    Abstract:

    The allometric relationship between brain and body size among vertebrates is often considered a manifestation of evolutionary constraints. However, birds and mammals have undergone remarkable Encephalization, in which brain size has increased without corresponding changes in body size. Here, we explore the hypothesis that a reduction of phenotypic integration between brain and body size has facilitated Encephalization in birds and mammals. Using a large dataset comprising 20,213 specimens across 4,587 species of jawed vertebrates, we show that the among-species (evolutionary) brain–body allometries are remarkably constant, both across vertebrate classes and across taxonomic levels. Birds and mammals, however, are exceptional in that their within-species (static) allometries are shallower and more variable than in other vertebrates. These patterns are consistent with the idea that birds and mammals have reduced allometric constraints that are otherwise ubiquitous across jawed vertebrates. Further exploration of ontogenetic allometries in selected taxa of birds, fishes and mammals reveals that birds and mammals have extended the period of fetal brain growth compared to fishes. Based on these findings, we propose that avian and mammalian Encephalization has been contingent on increased variability in brain growth patterns.

  • comparative support for the expensive tissue hypothesis big brains are correlated with smaller gut and greater parental investment in lake tanganyika cichlids
    Evolution, 2015
    Co-Authors: Masahito Tsuboi, Alexander Kotrschal, Arild Husby, Alexander Hayward, Severine D Buechel, Josefina Zidar, Hanne Lovlie, Niclas Kolm
    Abstract:

    The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the energetic requirements of Encephalization are suggested to impose considerable constraints on brain size evolution. Three main hypotheses concerning how energetic constraints might affect brain evolution predict covariation between brain investment and (1) investment into other costly tissues, (2) overall metabolic rate, and (3) reproductive investment. To date, these hypotheses have mainly been tested in homeothermic animals and the existing data are inconclusive. However, there are good reasons to believe that energetic limitations might play a role in large-scale patterns of brain size evolution also in ectothermic vertebrates. Here, we test these hypotheses in a group of ectothermic vertebrates, the Lake Tanganyika cichlid fishes. After controlling for the effect of shared ancestry and confounding ecological variables, we find a negative association between brain size and gut size. Furthermore, we find that the evolution of a larger brain is accompanied by increased reproductive investment into egg size and parental care. Our results indicate that the energetic costs of Encephalization may be an important general factor involved in the evolution of brain size also in ectothermic vertebrates.

Carmela Serio - One of the best experts on this subject based on the ideXlab platform.

  • Macroevolution of Toothed Whales Exceptional Relative Brain Size
    Evolutionary Biology, 2019
    Co-Authors: Carmela Serio, Marina Melchionna, Alessandro Mondanaro, Silvia Castiglione, Gianmarco Tesone, Martina Piccolo, Mirko Febbraro, Pasquale Raia
    Abstract:

    Toothed whales (Odontoceti, Cetacea) are well-known for their ability to produce complex vocalizations, to use tools, to possess self-recognition, and for their extreme behavioural plasticity. The toothed whale intelligence is said to compete with that of primates, so does their extremely large brain to body size ratio. Common explanations for the acquisition of such large brains over the evolutionary time (Encephalization) in toothed whales range from their demanding, complex social lives, to their feeding habits, to echolocation. Yet, several studies found no macroevolutionary trend in Odontoceti Encephalization, which casts doubts on its selective advantage. We applied a recently developed phylogenetic comparative method to study macroevolutionary trends in relative brain size (RBS) and brain size evolutionary rates in cetaceans, comparing toothed whales to the other cetaceans and contrasting groups of species as ascribed to different feeding categories. We found that cetaceans as a whole followed a trend for increased Encephalization over time, starting from small-brained archaeocete ancestors. Toothed whales do not show this same trend in RBS but have possessed larger RBS than any other cetacean ever since the beginning of their existence. The rate of RBS evolution in Odontoceti is significantly slower than in other Cetacea and slower than the rate of Odontoceti body size evolution. These results suggest that toothed whales’ history is characterized by high and conservative relative Encephalization. Feeding lifestyle does not explain these patterns, while the appearance of echolocation within stem group Odontoceti remains a viable candidate for them.

  • Macroevolutionary trends of brain mass in Primates
    Biological Journal of the Linnean Society, 2019
    Co-Authors: Marina Melchionna, Alessandro Mondanaro, Carmela Serio, Silvia Castiglione, M. Di Febbraro, Lorenzo Rook, José Alexandre Felizola Diniz-filho, Giorgio Manzi, Antonio Profico, Gabriele Sansalone
    Abstract:

    Abstract A distinctive trait in primate evolution is the expansion in brain mass. The potential drivers of this trend and how and whether Encephalization influenced diversification dynamics in this group are hotly debated. We assembled a phylogeny accounting for 317 primate species, including both extant and extinct taxa, to identify macroevolutionary trends in brain mass evolution. Our findings show that Primates as a whole follow a macroevolutionary trend for an increase in body mass, relative brain mass and speciation rate over time. Although the trend for increased Encephalization (brain mass) applies to all Primates, hominins stand out for their distinctly higher rates. Within hominins, this unique trend applies linearly over time and starts with Australopithecus africanus. The increases in both speciation rate and Encephalization begin in the Oligocene, suggesting the two variables are causally associated. The substitution of early, stem Primates belonging to plesiadapiforms with crown Primates seems to be responsible for these macroevolutionary trends. However, our findings also suggest that cognitive capacities favoured speciation in hominins.