Maternal effects of carotenoid consumption in guppies (Poecilia reticulata)

1. Carotenoids transferred from mother to offspring may enhance the quality of the offspring. Whether such maternal effects occur in guppies (Poecilia reticulata) has an important bearing on mate preference evolution. 2. By raising female guppies from birth on different dietary carotenoid levels, we examined the pattern of carotenoid allocation to maternal tissue (skin) vs. eggs. Skin carotenoid content was only weakly affected by carotenoid intake while egg carotenoid content was strongly affected. 3. We then tested for effects of maternal carotenoid intake on several measures of offspring quality, including size and condition at birth, juvenile growth rate, and the size, condition, skin carotenoid content and colouration of mature sons. To test for interactions between maternal and offspring carotenoid intake, broods were split and offspring were reared on one of two carotenoid levels. 4. Offspring carotenoid intake had the expected effects on male colouration, but otherwise we found no evidence that maternal or offspring carotenoid intake influences offspring quality. It remains possible that maternal carotenoids affect offspring fitness parameters that we did not measure or that such effects depend on environmental factors that were absent in our laboratory aquaria. 5. Our review of the literature on maternal carotenoid effects in birds and fishes suggests that such effects may be taxon-specific. Thus, it seems unwarranted to assume that an adaptive trade-off necessarily exists between allocation of carotenoids to eggs vs. maternal tissues. Alternative hypotheses, such as the possibility that eggs provide a means of excreting excess carotenoids, also merit consideration. 6. Our results indirectly support the indicator model of mate preference evolution by casting doubt on an alternative hypothesis that requires females to benefit more from consuming carotenoids than males do.