Delimitation of adult and juvenile clusters
For the MOTUs that could not be identified to species level, we used the best match to which the taxonomic assignment algorithm assigned that MOTU, that is, the identifier of the specific sequence in the database which was the most similar to the seed sequence of the MOTU. If the best match of two unidentified MOTUs was the same, they were collapsed and were treated as the same taxon. For comparative purposes, we also analysed the results in two additional alternative ways: using a ”splitter” approach (every unidentified MOTU as a different species) and using a “lumper” approach (all the unidentified MOTUs of the same genus/family considered as the same species). However, using either of those approaches only translated into minor differences in the results with respect to the “best match” approach.