CONCLUDING REMARKS: ARE ALL SPECIES FAST OR SLOW?
Hypothesis-driven research, rather than exploratory data analyses,
should guide the study of multivariate life history traits and the
eco-evolutionary drivers and limits that shape them. Prevailing evidence
shows that the fast-slow continuum is the major structuring axis of life
history variation in several taxa, but also that this continuum alone
does not fully describe life history variation. We advocate for the
development of further theory to test hypotheses regarding which axes,
clusters, syndromes, and constraints shape said variation. Likely
candidates include different reproductive or developmental tactics (see
Outstanding Questions). As we make further progress in the era of
“empirical sufficiency”, we must also take more mechanistic
approaches. These approaches must be coupled with higher-quality data
and robust analytical methods. Ultimately, we argue that more time spent
on theory and hypothesis development will lead to more targeted efforts
to better understand how life history strategies are shaped by the
environment, ancestry, and bauplan. Concurrently, the search for
universal syndromes of life history across all currencies of measurement
must continue, encompassing the whole Tree of Life.