Genetic documentation of filial cannibalism in nature

Cannibalism is widespread in natural populations of fishes, where the stoma chs of adults frequently contain conspecific juveniles. Furthermore, field observations suggest that guardian males routinely eat offspring from their own nests. However, recent genetic paternity analyses have shown that fish nests often contain embryos not sired by the nest-tending male (because of cuckoldry events, egg thievery, or nest piracy). Such findings, coupled wi th the fact that several fish species have known capabilities for distingui shing kin from nonkin. raise the possibility that cannibalism by guardian m ales is directed primarily or exclusively toward unrelated embryos in their nests. Here, we test this hypothesis by collecting freshly cannibalized em bryos from the stomachs of several nest-tending darter and sunfish males in nature and determining their genetic parentage by using polymorphic micros atellite markers. Our molecular results clearly indicate that guardian male s do indeed consume their own genetic offspring, even when unrelated (foste r) embryos are present within the nest. These data provide genetic document ation of filial cannibalism in nature. Furthermore, they suggest that the p henomenon may result, at least in part, from an inability of guardians to d ifferentiate between kin and nonkin within their own nests.