Maternal effects and warning signal honesty in eggs and offspring of an aposematic ladybird beetle

Abstract

1. The eggs of oviparous species are often subject to intense predation pressure. One parentalstrategy to deter predators is to produce eggs that are laced with noxious chemicals and areconspicuo usly coloured (i.e. aposematism). 2. Ladybird eggs are conspicuously coloured and contain alkaloids; these traits are believed tofunction in concert as visual signal and chemical defence, respect ively, to deter predators.However, it remains unclear whether such aposematic signals reveal the strength (rather thansimply the existence) of chemical defences. 3. Furthermore, additional functions of egg pigments and toxins could apply; in particular,mothers might deposit such resources into eggs to aid the development of offspring or toprovide resources that could contribute to aposematic traits in offspring. 4. We bred wild-caught seven-spot ladybird beetles (Coccinella septempunctata) in the labora-tory and then measured relationships between egg colorat ion and toxin concen trations (i.e. thealkaloids precoccinelline and coccinelline). We also measured relationships between egg carote-noids and egg coloration, and between egg coloration and toxin levels, and the elytra colora-tion and toxin concentrations of offspring at eclosio n for a subset of eggs that were allowed todevelop. 5. Egg carotenoids predicted egg colour saturation. In turn, egg colour saturation and huepositively predicted egg concentrations of preco ccinelline. However, there were no significantrelationships between egg coccinelline concentration and any measure of egg coloration. 6. In recently eclosed adults of both sexes, elytra saturation was significantly explained by vari-ation in egg saturation and hue. Finally, body con centrations of coccinelline were significantlyexplained by variation in elytra hue.7. These results suggest that the coloration of C. septempunctata eggs is a reliable signal of thestrength of chemical defences contained therein, but in addition, maternal investment ofpigments and toxins into eggs may serve to influence the reliability of aposematic signalling inresultant offspring.