What does the maintained presence of the stabilimentum across many, though not all, *Argiope* species imply about its evolutionary history?

It evolved relatively early in the genus's diversification and has been maintained due to strong selective pressures favoring its function.

The distribution pattern of the stabilimentum trait—being present across many related species within the *Argiope* genus, although not universally—suggests a deep evolutionary origin. This widespread presence indicates that the structure likely evolved relatively early in the genus's diversification process. Furthermore, its retention across these lines implies that it has been consistently subjected to strong selective pressures that favor whatever its ultimate function may be, whether visual signaling or defense. If the trait only offered marginal utility, it would logically be lost in descendant lines that subsequently specialized in different habitats or web designs.