Inclusion, exclusion, and screening
Prior to the search, we established inclusion and exclusion criteria. We retained studies of marine invertebrates that had quantitative data on a fitness measure during the life history—we therefore excluded behavioural studies or qualitative descriptions. We first screened records using the title and abstract, then imported relevant records to EndNote (version X8.2) where full-text articles were assessed for eligibility. In total, after 241 duplicates were removed, all search terms resulted in 17,337 records screened at the title and abstract level, 6,597 full-text articles checked for eligibility, and 1,716 references included in the final map (see summary in Figure S1 and ‘Data Sources’, Supporting Information).