Background/Question/Methods
Plant functional traits are properties that determine the adaptations to and fitness of plants in different environments. Understanding how and why they vary is essential because functional traits are the fundamental basis of biodiversity; they draw a concrete and descriptive portrait of species and of the way they relate to their environment.

Trait variation has been widely studied, with different fields working at different scales and focusing on different components of variation. However, despite the importance of functional traits, we can’t integrate the different components of trait variation because we do not know how traits vary across scales. It is essential to know the relative importance of the different scales of variation in order to link the different aspects of trait variation and to draw the big picture.

To address this deficiency, we partitioned the variance in two key leaf functional traits (Leaf mass per area - LMA and leaf dry matter content - LDMC) across six nested ecological scales (site, plot, species, tree, strata, leaf) in lowland tropical rainforests of Panama.

Results/Conclusions
We find that 1- there is more intra-specific variation than inter-specific variation, and 2- variance in both traits is uniformly distributed across all scales except the plot level, which shows virtually no variance despite high species turnover among plots. This contradicts a widely held belief that species-level variation is predominant in organizing species distribution and abundance. These results also indicate the presence of a tight environmental filter on trait composition which consequently act as a weak environmental filter on species composition.  These findings bring substantial support to the idea that community assembly occurs on a trait basis and highlights the importance of considering intra-specific variation.