The impact of environmental factors on the evolution of brain size in carnivorans

Abstract

The reasons why some animals have developed larger brains has long been a subject of debate. Yet, it remains unclear which selective pressures may favour the encephalization and how it may act during evolution at different taxonomic scales. Here we studied the patterns and tempo of brain evolution within the order Carnivora and present large-scale comparative analysis of the effect of ecological, environmental, social, and physiological variables on relative brain size in a sample of 174 extant carnivoran species. We found a complex pattern of brain size change between carnivoran families with differences in both the rate and diversity of encephalization. Our findings suggest that during carnivorans’ evolution, a trade-off have occurred between the cognitive advantages of acquiring a relatively large brain allowing to adapt to specific environments, and the metabolic costs of the brain which may constitute a disadvantage when facing the need to colonize new environments.

Neuropil Variation in the Prefrontal, Motor, and Visual Cortex of Six Felids

“…In addition to exploring the bivariate relationships between NF and morphological characteristics, we also explored the relationship between NF and published average species behavioral and ecological characteristics. Species behavioral and ecological data (i.e., social complexity, behavioral complexity, dexterity score, species average group size, home range, geographic range) were sourced from species averages [4,39]. The relationship between NF and continuous data (obtained from published sources) was compared using correlation coefficients (Pearson).…”

“…Species were split into two groups (social and solitary) as defined by Benson-Amram et al [4] before testing for significant differences in group means. Similarly, species were split into diel groups (diurnal, nocturnal, and cathemeral-crepuscular) as coded by Michaud, Toussaint, and Gilissen [39] before significance testing. Based on the functions of the prefrontal cortex in planning, reasoning, and long-term memory in mammals [40], we predicted that prefrontal cortex NF would be correlated with social complexity, behavioral diversity, and species average group size.…”

“…To investigate the relationship between NF and published species behavioral and ecological characteristics [4,39], we used correlational analysis (Pearson) as well as analysis of variance (Table 6). Our analyses revealed that NF primary motor cortex was strongly and significantly correlated with species home range (R 2 = 0.81, p = 0.01).…”

“…NF, neuropil fraction; Asvol, aspiny volume (μm 3 ); ASomaS, AAspiny Somal Size (μm 2 ); ASTDL, aspiny total dendritic length (μm); ASMSL, aspiny mean segment length (μm); ASDSC, aspiny-number of dendritic segments; Pvol, pyramidal volume (μm 3 ); PSomaS, pyramidal somal size (μm 2 ); PTDL, pyramidal total dendritic length (μm); PMSL, pyramidal mean segment length (μm); PDSC, pyramidal number of dendritic segments; PDSN, pyramidal total number of spines on dendritic Segments; PDSD, pyramidal average mumber of spines on dendritic length; r 2 , coefficient of determination. Behavioral and ecological data were sourced from [4,39].…”

Evolutionary ecomorphology for the twenty-first century: examples from mammalian carnivores

“…for the individual when adapting to new environments [72]. An increasing number of studies have come to focus on the relative volumes of different regions of the brain [61,62,65,[73][74][75][76][77] and have found correlations that were missed when looking at whole brain size.…”