Testing Allsop and West's size at sex change invariant within a fish species: A spurious ratio or a useful group descriptor?

Abstract

Recently, it has been suggested that sequential hermaphrodites, from a variety of taxa and a wide range of sizes, change sex at the same relative size. It is said that there exists an invariant (a constant ratio) for such a life trait. However, recent criticisms point out that these results could be a statistical artefact. It has been argued that the wider the range of x-axis values (from 2 mm to 1.5 m in the case of sex change), the higher the probability of identifying an invariant by chance. Here, the invariance of the size at sex change ratio is analysed within a single fish species for which the size of sex change varies within a range of only 6.5 cm. Our results support the invariant rule that fishes change sex when reaching 79% of their maximum size. © 2008 The Authors.