Evolutionary lineage explains trait variation among 75 coexisting grass species

Abstract

Summary Evolutionary history plays a key role driving patterns of trait variation across plant species. For scaling and modeling purposes, grass species are typically organized into C3 vs C4 plant functional types (PFTs). Plant functional type groupings may obscure important functional differences among species. Rather, grouping grasses by evolutionary lineage may better represent grass functional diversity. We measured 11 structural and physiological traits in situ from 75 grass species within the North American tallgrass prairie. We tested whether traits differed significantly among photosynthetic pathways or lineages (tribe) in annual and perennial grass species. Critically, we found evidence that grass traits varied among lineages, including independent origins of C4 photosynthesis. Using a rigorous model selection approach, tribe was included in the top models for five of nine traits for perennial species. Tribes were separable in a multivariate and phylogenetically controlled analysis of traits, owing to coordination of important structural and ecophysiological characteristics. Our findings suggest grouping grass species by photosynthetic pathway overlooks variation in several functional traits, particularly for C4 species. These results indicate that further assessment of lineage‐based differences at other sites and across other grass species distributions may improve representation of C4 species in trait comparison analyses and modeling investigations.

Grass Evolutionary Lineages Can Be Identified Using Hyperspectral Leaf Reflectance

“…While we did not analyze leaf traits, in a recent analysis of grass leaf traits, the photosynthetic traits Vc max (maximum carboxylation rate) and C:N was found to differ significantly among grass lineages, illustrating linkages between leaf N/chlorophyll content and overall photosynthetic activity (Donnelly et al., 2023). The NIR region is highly sensitive to leaf structural traits.…”

“…The NIR region is highly sensitive to leaf structural traits. Leaf structural traits such as specific leaf area and leaf dry matter content, as well as and leaf thickness for perennial species, are significantly different among grass lineages (Donnelly et al., 2023) and may have contributed to spectral separation. In addition, leaf surface traits such as pubescence or waxiness, can strongly affect NIR reflectance.…”

“…These lineages sort along environmental gradients and exhibit a very different biogeographic distribution than classic C 3 –C 4 turnover would suggest (Griffith et al., 2020). Because each lineage evolved in a different ecological context, similarities among their morphological, biochemical, and physiological traits should be more accurately captured by lineage than by functional groupings based on photosynthetic pathway (Donnelly et al., 2023; Griffith et al., 2020).…”

Which Has a Greater Impact on Plant Functional Traits: Plant Source or Environment?

“…In this current investigation, “plant source” refers to the geographical location from where the plant materials were obtained. Plants from different sources may accumulate various genetic and adaptive characteristics during their evolution, directly affecting plant functional traits and adaptability [ 20 , 24 ]. However, most previous research has only focused on one single aspect in various factors or the interactions of multiple environmental factors [ 7 , 17 , 18 , 19 ].…”