Understanding the ecological and evolutionary links between stages in
complex life histories is an important goal of biology, but studies
differ greatly in their approach. Some studies follow individuals across
their life history (“individual longitudinal”), while others follow
cohorts (“cohort longitudinal”)—each have their strengths and
weaknesses. Our understanding of links among life-history stages
probably depends on the approaches we use, but we have no estimates of
their relative prevalence. Using marine invertebrates as a model, we
used a formal, systematic literature map to screen 17,000+ papers
studying complex life histories. For 3,315 experiments from 1,716
articles, we characterised the study type, (i.e. cohort longitudinal,
individual longitudinal or single stage) as well as other factors.
Individual longitudinal studies are extremely rare, accounting for just
1.7% of studies. Clearly much progress has been made, but to fully
understand the links among life-history stages, more individual
longitudinal studies are necessary.