Abstract
There is remarkable diversity in brain anatomy among vertebrates and evidence is accumulating that predatory interactions are crucially important for this diversity. To test this hypothesis, we collected female guppies (Poecilia reticulata) from 16 wild populations and related their brain anatomy to several aspects of predation pressure in this ecosystem, such as the biomass of the four major predators of guppies (one prawn and three fish species), and predator diversity (number of predatory fish species in each site). We found that populations from localities with higher prawn biomass had relatively larger telencephalon size as well as larger brains. Optic tectum size was positively associated with one of the fish predator’s biomass and with overall predator diversity. However, both olfactory bulb and hypothalamus size were negatively associated with the biomass of another of the fish predators. Hence, while fish predator occurrence is associated with variation in brain anatomy, prawn occurrence is associated with variation in brain size. Our results suggest that cognitive challenges posed by local differences in predator communities may lead to changes in prey brain anatomy in the wild.
Highlights
Predation is a major force of natural selection
This was true for a model with only prawns as factor (LMMbrain: body size: DF = 160.2, t = 45.4, p \ 0.001; prawns: DF = 160.5, t = 2.81, p = 0.0125, AIC = -735.6), but glmulti revealed that brain size was best explained if the effects of blue acara and pike cichlid were accounted for
In line with our predictions, one of our most salient findings was that specific aspects of predation pressure and larger brains are positively associated in the wild
Summary
Predation is a major force of natural selection. After all, most species are subject to the risk of being eaten during at least some part of their life. A recent analysis of 623 predator–prey pairs revealed that brains of prey species were relatively larger than those of non-prey species. In these predator–prey pairs, the size of prey and predators’ brains were correlated, suggesting a cognitive arms race (Kondoh 2010). The cognitive advantage of a larger brain can lead to increased survival This was recently shown in guppies (Poecilia reticulata) that were artificially selected for large and small brain size where large-brained females survived better under predation in a seminatural setting (Kotrschal et al 2015a). Such studies should be conducted on wild populations, include detailed data on all key predator species, and use well-replicated designs
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