Brain size variation along altitudinal gradients in the Asiatic Toad (<i>Bufo gargarizans</i>)

Yao, Zhongyi; Qi, Yin; Yue, Bisong; Fu, Jinzhong

doi:10.1002/ece3.7192

Cited by 6 publications

(4 citation statements)

References 81 publications

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“…Studies in birds suggest that those inhabiting higher altitudes tend to have relatively larger brains 56 or hippocampal volumes 57 compared to birds living at lower altitudes, but birds are more tolerant of highaltitude hypoxia than mammals and are not believed to experience increased intracranial pressure or mountain sickness 58 . On the other hand, in accordance with the expensive tissue (brain) hypothesis, Asiatic toads from high altitudes had smaller brains than lower-altitude populations 59 . Environmental harshness linked to colder climates was shown to be positively correlated with brain size in birds 60 and humans 61,62 .…”

supporting

confidence: 65%

Counter-gradient variation and the expensive tissue hypothesis explain parallel brain size reductions at high elevation in cricetid and murid rodents

Nengovhela

Ivy

Scott

et al. 2023

Sci Rep

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To better understand functional morphological adaptations to high elevation (> 3000 m above sea level) life in both North American and African mountain-associated rodents, we used microCT scanning to acquire 3D images and a 3D morphometric approach to calculate endocranial volumes and skull lengths. This was done on 113 crania of low-elevation and high-elevation populations in species of North American cricetid mice (two Peromyscus species, n = 53), and African murid rodents of two tribes, Otomyini (five species, n = 49) and Praomyini (four species, n = 11). We tested two distinct hypotheses for how endocranial volume might vary in high-elevation populations: the expensive tissue hypothesis, which predicts that brain and endocranial volumes will be reduced to lessen the costs of growing and maintaining a large brain; and the brain-swelling hypothesis, which predicts that endocranial volumes will be increased either as a direct phenotypic effect or as an adaptation to accommodate brain swelling and thus minimize pathological symptoms of altitude sickness. After correcting for general allometric variation in cranial size, we found that in both North American Peromyscus mice and African laminate-toothed (Otomys) rats, highland rodents had smaller endocranial volumes than lower-elevation rodents, consistent with the expensive tissue hypothesis. In the former group, Peromyscus mice, crania were obtained not just from wild-caught mice from high and low elevations but also from those bred in common-garden laboratory conditions from parents caught from either high or low elevations. Our results in these mice showed that brain size responses to elevation might have a strong genetic basis, which counters an opposite but weaker environmental effect on brain volume. These results potentially suggest that selection may act to reduce brain volume across small mammals at high elevations but further experiments are needed to assess the generality of this conclusion and the nature of underlying mechanisms.

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supporting

confidence: 65%

Counter-gradient variation and the expensive tissue hypothesis explain parallel brain size reductions at high elevation in cricetid and murid rodents

Nengovhela

Ivy

Scott

et al. 2023

Sci Rep

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“…High-altitude environments are characterized by hypoxia, low temperature, high ultraviolet radiation, high climatic diurnal, and seasonal variability (Storz et al, 2010). Therefore, high altitude represents strong directional selection (Yao et al, 2021). Altitude, temperature, and rainfall are closely related to environmental factors.…”

Section: Discussionmentioning

confidence: 99%

“…In recent years, the adaptive evolution of brain size in amphibians and other poikilotherms has also received more attention (Liao et al, 2015(Liao et al, , 2016(Liao et al, , 2018Luo et al, 2017;Yu et al, 2018;Huang et al, 2020). Research uncovered that amphibians' brain size evolution is closely related to environmental factors; 10.3389/fevo.2022.982590 for instance, the seasonal variation in temperature could explain the variabilities of the relative brain size and the size of the optic tectum (TEC) in 30 amphibian species (Luo et al, 2017), and the toad's relative brain size decreased with the increase in altitude (Yao et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Relationship between brain size and digestive tract length support the expensive-tissue hypothesis in Feirana quadranus

Song

Liu

et al. 2022

Front. Ecol. Evol.

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The brain is among the most energetically costly organs in the vertebrate body, while the size of the brain varies within species. The expensive-tissue hypothesis (ETH) predicts that increasing the size of another costly organ, such as the gut, should compensate for the cost of a small brain. Here, the ETH was tested by analyzing the relationship between brain size variation and digestive tract length in a Swelled-vented frog (Feirana quadranus). A total of 125 individuals across 10 populations ranging from 586 to 1,702 m a.s.l. from the Qinling-Daba Mountains were sampled. With the increase in altitude, the brain size decreases and the digestive tract length increases. Different brain regions do not change their relative size in a consistent manner. The sizes of telencephalon and cerebellum decrease with the increase in altitude, while the olfactory nerve increases its size at high altitudes. However, the olfactory bulb and optic tectum have no significant relationship with altitude. After controlling for snout-vent length (SVL), a significant negative correlation could be found between brain size and digestive tract length in F. quadranus. Therefore, the intraspecific variation of brain size follows the general patterns of ETH in this species. The results suggest that annual mean temperature and annual precipitation are environmental factors influencing the adaptive evolution of brain size and digestive tract length. This study also suggests that food composition, activity times, and habitat complexity are the potential reasons driving the adaptive evolution of brain size and digestive tract length.

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“…The Asiatic toad is an explosive breeder, and reproduction takes place in December–January or January–February with a breeding period of 25–30 days in Nanchong City, China [ 25 ]. In addition, some information on the morphological anatomy, larval development, habitat selection, diet, mating behavior, age structure, brain size evolution, muscular metabolism, and secondary sexual dimorphism of the B. gargarizans has been reported in recent years [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. This study aims to document the traits of sexual dimorphism in the size and shape of the limb bones of the species and explore implications of observed differences for the evolutionary ecology of the B. gargarizans .…”

Section: Introductionmentioning

confidence: 99%

Sexual Dimorphism in the Limb Bones of Asiatic Toad (Bufo gargarizans) in Relation to Sexual Selection

Yan

Yang

et al. 2023

Animals

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Sexual dimorphism is often considered to be the result of differences in the intensity of sexual selection between sexes. From this point of view, the sexual dimorphism of the limb bones of the Bufo gargarizans in southwest China was studied. Results showed that the fore- and hindlimb skeletons of this species were sexually dimorphic in anatomy. The humerus, radioulna, and total lengths of the forelimb skeleton of males were substantially longer than those of females, but the hand length of males was smaller than that of females. Several other features of males, such as deltoid and medial crest areas and humerus and radioulnar weights, were also significantly larger than those of females. The femoris, tibiofibula, talus–calcaneus, and foot lengths; total hindlimb skeleton length; and femoral upper crest areas of males were significantly greater than those of females. However, no significant intersexual difference in femoris and tibiofibular weights was observed. These findings suggested that robust forelimb bones and long hindlimb bones could contribute to the mating success of males; if so, sexual selection promotes the evolution of sexual size and shape dimorphism in the limb bones of the B. gargarizans.

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Brain size variation along altitudinal gradients in the Asiatic Toad (Bufo gargarizans)

Cited by 6 publications

References 81 publications

Counter-gradient variation and the expensive tissue hypothesis explain parallel brain size reductions at high elevation in cricetid and murid rodents

Counter-gradient variation and the expensive tissue hypothesis explain parallel brain size reductions at high elevation in cricetid and murid rodents

Relationship between brain size and digestive tract length support the expensive-tissue hypothesis in Feirana quadranus

Sexual Dimorphism in the Limb Bones of Asiatic Toad (Bufo gargarizans) in Relation to Sexual Selection

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