OOS 14-4 - Trait variation of grasses across the North American Great Plains

Background/Question/Methods
Trait studies are useful for understanding how different plant lineages have evolved to inhabit and succeed in various environments. While grass species exhibit trait variation across different environments, it is less clear whether trait variation exists among entire lineages of grasses across macroecological scales. This trait variation can arise from species turnover within lineages, ecotypic turnover within species, and plastic variation. We measured five traits (SLA, LDMC, leaf thickness, C:N, and δ13C) on 52 species of grass representing 11 tribes across five grassland sites in North America. We grouped species by tribe and by site and tested whether trait values differed significantly across both factors. We also tested whether species that occurred at multiple sites exhibited intraspecific trait variation. Our goal was to determine how trait variation is shaped by differences in site and lineage, and how species vary intraspecifically across ecosystems.

Results/Conclusions
We found significant variation among sites for all traits when species were grouped by site and significant variation among tribes for all traits except C:N when species were grouped by tribe. Despite large differences in environmental factors among sites, it was surprising that trait values significantly differed by tribe. We also found that species occurring at multiple grassland sites exhibited statistically significant intraspecific trait variation. These results suggest that evolutionary history is a critically important factor to consider in trait analyses. The fact that trait differences were detected among both sites and tribes tells us that while species are locally adapted to their respective environment, evolutionary history plays a large role in the characterization of species’ traits.