OUTSTANDING QUESTIONS
• Is there a universal characterisation of life histories across the
tree of life?
• Does the fast-slow continuum explain the majority of life-history
variation across all taxa? It does in Tetrapods (especially mammals and
birds), which are relatively over-studied, and only in recent years has
the fast-slow continuum been shown to be important in sessile and clonal
organisms (vascular plants, corals). Whether the fast-slow continuum is
the major structuring axis of life history variation has not been
studied in most invertebrates other than insects, where the fast-slow
continuum was identified [6], but seems to be less structuring than
in tetrapods [7].
• Are other axes of life history variation consistent among taxa? Traits
relating to reproductive or developmental tactics have repeatedly
emerged as the second most important axis of life history variation.
However, heterogeneity in the set of traits analysed so far prevents us
from concluding taxonomic universality.
• What, if any, are the implications of particular choices of data and
analytical approaches? Certainly the choice of multivariate data to
analyse, and the availability of particular measures by taxa, will vary.
If the impact of these choices on research outcomes is significant,
cognisance of such consequences is of paramount importance.
• Are there clearly defined clusters and boundaries of life history
variation across taxa that occupy distinct spaces in multidimensional
life history trait space? Biomechanical constraints limit the range of
covariation among life history traits [62]. Intuitively, certain
life history strategies should not exist if they defy physical or
evolutionary laws. How will human actions and climate change alter these
boundaries and shape rates of extinction/invasion?
TABLE 1 - Comparison of different types of demographic data in
the context of life history strategy comparative analyses.