Selection for relative brain size affects context-dependent male preferences, but not discrimination, of female body size in guppies

Abstract

Understanding what drives animal decisions is fundamental in evolutionary biology, and mate choice decisions are arguably some of the most important in any individual's life. As cognitive ability can impact decision making, elucidating the link between mate choice and cognitive ability is necessary to fully understand mate choice. To experimentally study this link, we used guppies () artificially selected for divergence in relative brain size and with previously demonstrated differences in cognitive ability. A previous test in our female guppy selection lines demonstrated the impact of brain size and cognitive ability on information processing during female mate choice decisions. Here, we evaluated the effect of brain size and cognitive ability on male mate choice decisions. Specifically, we investigated the preference of large-brained, small-brained and non-selected guppy males for female body size, a key indicator of female fecundity in this species. For this, male preference was quantified in dichotomous choice tests when presented with dyads of females with small, medium and large body size differences. All types of males showed a preference for larger females but no effect of brain size was found in the ability to discriminate between differently sized females. However, we found that non-selected and large-brained males, but not small-brained males, showed a context-dependent preference for larger females depending on the difference in female size. Our results have two important implications. First, they provide further evidence that male mate choice also occurs in a species in which secondary sexual ornamentation is present only in males. Second, they show that brain size and cognitive ability have important effects on individual variation in mating preference and sexually selected traits.

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

“…Recently, the effect of predation on brain evolution has begun to be unveiled [8][9][10]. Larger brains are often associated with better executive function than smaller brains [11,12], which has been experimentally shown in guppies selected for relative brain size [13][14][15][16][17]. These selection lines highlighted the potentially strong selective pressure of predation on brain size, as large-brained guppies exposed to predators survived better than small-brained guppies [18], potentially owing to behavioural advantages [17].…”

Brain size predicts behavioural plasticity in guppies (Poecilia reticulata): An experiment

“…A set of recent studies on these selection lines have shown that brain size affects cognitive abilities in terms of numerical learning ability (Kotrschal et al., ), spatial learning (Kotrschal, Corral‐Lopez, Amcoff, & Kolm, ) and reversal learning (Buechel, Boussard, Kotrschal, van der Bijl, & Kolm, ). Different behaviours with strong fitness effects are also positively affected by brain size such as predator avoidance (van der Bijl, Thyselius, Kotrschal, & Kolm, ; Kotrschal, Buechel, et al., ) and mate choice (Bloch et al., ; Corral‐Lopez et al., ; Corral‐Lopez, Kotrschal, & Kolm, ). In several of these studies (e.g.…”

Social Plasticity in the Fish Brain: Neuroscientific and Ethological Aspects

“…A relationship between social plasticity and brain size was found by Kotrschal et al (2012), who observed that male brains were larger in guppies that interacted with females, while the optic tectum was larger in females in female-only groups, suggesting that, while differences in brain sizes between sexes can be attributed to differences in emotional and foraging behavior, cognitive demands associated with courtship can also be responsible for brain size plasticity. Similar changes are seem after multiple generations of breeding guppies for large and small brain size relative to body size: after only two generations of selection, Corral-López et al (2018) found that non-selected and largebrained males, but not small-brained males, showed context-dependent preferences for larger females that depend on the difference in female size; similarly non-selected and large-brained females show a strong preference for males with color traits that predict attractiveness in P. reticulata (Corral-López et al, 2017). That social complexity changes brain size has also been observed in the cooperatively breeding cichlid N.…”