*4.1. Alga Material*

Thalli from *G. imbricata* were collected along the northeast coast of Gran Canaria in the Canary Islands. Within 2 h of collection, thalli were examined under a stereomicroscope to identify cystocarps. Axes with no visible cystocarps (henceforth, fertilised thalli) and axes with light-red dots that are indicative of cystocarps (henceforth, fertile thalli), both belonging to the same individual (i.e., anchored to the same basal structure), were identified and separated for further use.

Two categories of fertile thalli were also identified; thalli with well-developed cystocarps and those that have fully-developed cystocarps (intense red dot and referred to as mature; Figure 3). Infertile thalli without any cystocarps were used as controls.
