O lado escuro do pós-fogo: artrópodes selecionam substratos alterados por correspondência de fundo?

Abstract

Besides the colouration patterns of prey that reduces conspicuity, another important aspect in camouflage is the colour properties of the occupied substrate. Changes on substrate colouration caused by burning can mediate the differential survival of prey by visually oriented predators. In this study, we investigated whether arthropods predominantly use burned or unburned trunks to camouflage themselves out of birds’ sight, if they are more frequents at the best types and height of the substrates to best correspond in colouration, just as the morphs of Ronderosia bergii (Orthoptera), a polymorphic grasshopper’s species, correspond to the type of substrate selected. Only Mantodea presented background matching. The arthropod community preferentially occupied burned trunks. The selected substrates have smaller contrasts than other potential ones. There was a positive relationship between the height of occupation by Orthoptera and its achromatic contrast. Ronderosia bergii preferentially occupied burned substrates, dark morphotypes showed lower contrasts on burned substrates, while browner morphotypes on unburned substrates, although none were camouflaged for predatory birds. We argue that the generalization of habitat and trade-offs may be potential factors that are related to the absence of background matching by these arthropods. We suggest that there are selective predation pressures mediating colour variations in Ronderosia bergii and background matching in Mantodea.