Background: Hybridization events are relatively common in vascular plants. However, the frequency of these events is unevenly distributed across the plant phylogeny. Plant families in which individual species are pollinated by specific pollinator species are predicted to be less prone to hybridization than other families. However, exceptions may occur within these families, when pollinators shift host-plant species. Indeed, host shifts are expected to increase the rate of hybridization events. Pollinators of Ficus section Galoglychia are suspected to have changed host repeatedly, based on several cases of incongruence between plant phylogeny and taxonomy, and insect phylogeny and taxonomy. We tracked cyto-nuclear discordance across section Galoglychia as evidence for hybridization. To achieve a proper global view, we first clarified the monophyly of section Galoglychia as it had been questioned by recent phylogenetic studies. Moreover, we investigated if fig size could be a factor facilitating host shifts. Results: Phylogenetic chloroplast and nuclear results demonstrated the monophyly of section Galoglychia. Within section Galoglychia, we detected several cases of statistically significant cyto-nuclear discordance. Discordances concern both terminal nodes of the phylogenetic trees and one deep node defining relationships between subsections. Because nuclear phylogeny is congruent with morphological taxonomy, discordances were caused by the chloroplast phylogeny. Introgressive hybridization was the most likely explanation for these discordances. We also detected that subsections pollinated by several wasp genera had smaller figs and were pollinated by smaller wasps than subsections pollinated by a single wasp genus. Conclusion: As hypothesized, we discovered evidences of past hybridization in Ficus section Galoglychia. Further, introgression was only detected in subsections presenting incongruence between plant and pollinator phylogenies and taxonomy. This supports the hypothesis that host shift is the cause for plant-pollinator incongruence. Moreover, small fig size could facilitate host shifts. Eventually, this study demonstrates that non-coding chloroplast markers are valuable to resolve deep nodes in Ficus phylogeny.

Sexual ornaments are often assumed to be indicators of mate quality. Yet it remains poorly known how certain ornaments are chosen before any coevolutionary race makes them indicative. Perceptual biases have been proposed to play this role, but known biases are mostly restricted to a specific taxon, which precludes evaluating their general importance in sexual selection. Here we identify a potentially universal perceptual bias in mate choice. We used an algorithm that models the sparseness of the activity of simple cells in the primary visual cortex (or V1) of humans when coding images of female faces. Sparseness was found positively correlated with attractiveness as rated by men and explained up to 17% of variance in attractiveness. Because V1 is adapted to process signals from natural scenes, in general, not faces specifically, our results indicate that attractiveness for female faces is influenced by a visual bias. Sparseness and more generally efficient neural coding are ubiquitous, occurring in various animals and sensory modalities, suggesting that the influence of efficient coding on mate choice can be widespread in animals.

Communication signals often comprise an array of colours, lines, spots, notes or odours that are arranged in complex patterns, melodies or blends. Receiver perception is assumed to influence preference and thus the evolution of signal design, but evolutionary biologists still struggle to understand how perception, preference and signal design are mechanistically linked. In parallel, the field of empirical aesthetics aims to understand why people like some designs more than others. The model of processing bias discussed here is rooted in empirical aesthetics, which posits that preferences are influenced by the emotional system as it monitors the dynamics of information processing and that attractive signals have effective designs that maximize information transmission, efficient designs that allow information processing at low metabolic cost, or both. We refer to the causal link between preference and the emotionally rewarding experience of effective and efficient information processing as the processing bias, and we apply it to the evolutionary model of sensory drive. A sensory drive model that incorporates processing bias hypothesizes a causal chain of relationships between the environment, perception, pleasure, preference and ultimately the evolution of signal design, both simple and complex.