Biology subjects

Llaurens, V.

Publications and source records attributed to Llaurens, V..

21 records · Page 2Linked to original sources

bioRxiv2019

Evolution of conspicuousness in defended species involved in Mullerian mimicry

Variation in the conspicuousness of colour patterns is observed within and among defended prey species. The evolution of conspicuous colour pattern in defended species can be strongly impaired because of increased detectability by predators. Nevertheless, such evolution of the colour pattern can be favoured if changes in conspicuousness result in Mullerian mimicry with other defended prey. Here, we develop a model describing the population dynamics of a conspicuous defended prey species, and we assess the invasion conditions of derived phenotypes that differ from the ancestral phenotype by their conspicuousness. Such change in conspicuousness may then modify their level of mimicry with the local community of defended species. Derived colour pattern displayed in this focal population can therefore be either exactly similar, partially resembling or completely dissimilar to the local mimicry ring displaying the ancestral colour pattern. We assume that predation risk depends (1) on the number of individuals sharing a given colour pattern within the population, (2) on the occurrence of co-mimetic defended species, and (3) on the availability of alternative edible prey. Using a combination of analytical derivations and numerical simulations, we show that less conspicuous colour patterns are generally favoured within mimicry rings, unless reduced conspicuousness impairs mimicry. By contrast, when a mutation affecting the colour pattern leads to a shift toward a better protected mimicry ring, crypsis is no longer necessarily beneficial and a more conspicuous colour pattern can be favoured. The selected aposematic pattern then depends on the local composition of mimetic communities, as well as on the detectability, memorability and level of mimicry of the colour patterns.

evolutionary biology↗

bioRxiv2019

How heterozygote advantage can promote the evolution of disassortative mating and shape the underlying geneticarchitecture?

The evolution of mate preferences may depend on natural selection acting on the mating cues and on the underlying genetic architecture. While the evolution of assortative mating with respect to locally adapted traits has been well-characterized, the evolution of disassortative mating is poorly characterized. Here we aim at understanding the evolution of disassortative mating for traits under strong balancing selection, by focusing on polymorphic mimicry as an illustrative example. Positive frequency-dependent selection exerted by predators generates local selection on wing patterns acting against rare variants and promoting local monomorphism. This acts across species boundaries, favouring Mullerian mimicry among defended species. In this well-characterized adaptive landscape, polymorphic mimicry is rare but is observed in a butterfly species, associated with polymorphic chromosomal inversions. Because inversions are often associated with recessive deleterious mutations, we hypothesize they may induce heterozygote advantage at the color pattern locus, putatively favoring the evolution of disassortative mating. To explore the conditions underlying the emergence of disassortative mating, we modeled both a trait locus (colour pattern for instance), subject to mutational load, and a preference locus. We confirm that heterozygote advantage favors the evolution of disassortative mating and show that disassortative mating is more likely to emerge if at least one allele at the trait locus is free from any recessive deleterious mutations. We modelled different possible genetic architectures underlying mate choice behaviour, such as self referencing alleles, or specific preference or rejection alleles. Our results showed that self referencing or rejection alleles linked to the color pattern locus can be under positive selection and enable the emergence of disassortative mating. However rejection alleles allow the emergence of disassortative mating only when the color pattern and preference loci are tightly linked. Our results therefore provide relevant predictions on both the selection regimes and the genetic architecture favoring the emergence of disassortative mating and a theoretical framework in which to interprete empirical data on mate preferences in wild populations.

evolutionary biology↗

bioRxiv2018

Generalisation behaviour of predators toward warning signals displayed by harmful prey: answers from a video-game played by humans.

The persistence of several warning signals in sympatry is a puzzling evolutionary question because selection favours convergence of colour patterns among toxic species. Such convergence is shaped by predators reaction to similar but not identical stimulus, i.e. generalisation behaviour. However, studying generalisation behaviour in complex natural communities of predators is challenging, and is thus generally limited to simple variations of prey colour patterns. Here, we used humans as surrogate predators to investigate generalisation behaviours on two prey communities with different level of warning signals complexity. Humans generalisation capacities were estimated using a computer game simulating a simple (4 morphs) and a complex (10 morphs) community of defended (associated with a penalty) and palatable butterflies. Colour patterns used in the game are actually observed in natural populations of the defended butterflies H. numata, and generalisation behaviour of natural predators communities on these colour patterns have previously been investigated in the wild, allowing direct comparison with human behaviour. We investigated human predation behaviour by recording attack rates on the different defended and palatable colour patterns, as well as player survival time (i.e. score). Phenotypic similarity among the different colour patterns was precisely quantified using a custom algorithm accounting for both colour and pattern variations (CPM method). By analysing attack behaviours of 491 game players, we found that learning was more efficient in the simple prey community. Additionally, profitable prey gained protection from sharing key visual features with unprofitable prey in both communities while learning, in accordance with natural predator behaviours. Moreover, other behaviours observed in natural predators, such as colour neophobia, were detected in humans and shaped morph vulnerability during the game. Similarities between our results in humans and the reaction of natural predator communities to the same colour patterns validate our video-game as a useful proxy to study predator behaviour. This experimental set-up can thus be compared to natural systems, enabling further investigations of generalisation on mimicry evolution.

evolutionary biology↗