Between categories and continua: growth-form organization in global leaf economics spectrum space

Stephen Antheny Mekwan 

The leaf economics spectrum (LES) describes a globally coordinated trade-off between
acquisitive and conservative plant resource-use strategies, yet how major plant growth forms
are organized within multidimensional LES space, and the extent to which observed patterns
reflect phylogenetic history, remains incompletely resolved. Using species-level trait data from
the TRY Plant Trait Database, we examined multidimensional trait organization across 3,206
vascular plant species representing trees, shrubs, herbs, graminoids, and climbers using four
core functional traits: specific leaf area, leaf nitrogen content, leaf dry matter content, and
vegetative height.
Principal component analysis identified a dominant acquisitive-conservative LES axis
explaining 50.3% of total trait variation, while a secondary height-associated axis explained an
additional 25.2%. Major growth forms occupied significantly differentiated yet strongly
overlapping regions of multidimensional trait space, with herbs and graminoids generally
associated with more acquisitive strategies than woody growth forms. Growth-form
differentiation remained significant across multivariate and phylogenetically informed analyses
despite strong phylogenetic structure in LES positioning. Extensive overlap among growth
forms and repeated occupation of similar trait regions across distantly related lineages
indicated that similar ecological strategies are not restricted to particular evolutionary
lineages.. Together, these findings suggest that global plant ecological strategies are
continuous, multidimensional, and evolutionarily structured, with major growth forms
representing overlapping regions of trait space rather than discrete functional categories.