Hiding among holes: mechanisms underlying the evolution of masquerade in flea beetles (Chrysomelidae)

1. The herbivorous flea beetles (Chrysomelidae: Alticini) have evolved a masquerading strategy by hiding among their own feeding damage. Similarities between beetle bodies and their feeding damage may act as a defence that reduces detection by visual predators. 2. We analyse the evolutionary origin of flea beetles' camouflage using the French fauna (284 species) as a case study. We assess two competing hypotheses: (H1) the type of leaf tissue is the primary determinant of the colour and size of beetle species feeding on them, because each type of leaf tissue may have a tendency to result in a particular type of damage or, (H2) the morphological characteristics of the beetle explain the damage pattern, because beetle species evolve strategies to produce feeding damage that matches its own characteristics. 3. We assessed bipartite networks of feeding interactions (beetle species and host plants). Beetle-host interactions were non-randomly distributed and highly modular, with more than 25% of the network modules showing beetle colour and size distributions significantly different from null expectations. 4. Our results suggest that the evolutionary origin of flea beetles masquerading can be partially explained by both hypotheses. Some host plants seem to restrict feeding damage appearance on their leaves, favouring the survival of specific beetles with matching colour and size (H1). However, in most plant taxa, it is suggested, the existence of beetle-associated constraints exert a selective pressure for the beetle to damage leaves in a particular way, similar to its own colour and size (H2)The authors were supported by the Spanish Ministry of Science and Innovation and the European Regional Development Fund (ERDF) through grant PID2020-112935GB-I00S