Data from: Functional diversity promotes phytoplankton resource use efficiency

1.Understanding the relationship between biodiversity and ecosystem
functioning (BEF) is a central topic in ecology. Multi‐traits based
functional diversity has been proposed to improve mechanistic
understanding of the BEF relationship; however, how trait‐based functional
diversity affects ecosystem functioning and processes has rarely been
addressed in aquatic ecosystems. 2.Here, we examined the causal
relationships between three phytoplankton functional diversity indices
(FAD2, FDc, FRic) and Shannon diversity index versus resource use
efficiency for nitrogen (RUEN), phosphorus (RUEP), and silicate (RUESi),
with monthly long‐term datasets from the marine (Western English Channel,
2000 ‐ 2014) and freshwater (Lake Kasumigaura, 1984 ‐ 2012) ecosystems.
3.We employed Convergent Cross Mapping (CCM), a novel method developed for
identifying causality for nonlinear dynamical systems; this is in contrast
to linear approaches that cannot distinguish causality from correlation.
CCM found that FDc is the most robust functional diversity index among the
selected functional diversity indices (FAD2, FDc, FRic) in predicting
phytoplankton resource use efficiency and exhibited a much stronger causal
effect than the Shannon index. 4.Furthermore, scenario exploration
analysis indicates that most causal effects from phytoplankton diversity
indices on resource use efficiency (RUEN, RUEP, and RUESi) are on average
positive, and FDc exhibited the most consistent positive causal effects on
phytoplankton resource efficiency in both marine and freshwater
ecosystems. Thus, increasing FDc can enhance phytoplankton resource use
efficiency in aquatic ecosystems. 5.Synthesis. Our results show
significant causal effects of functional diversity on phytoplankton
resource use efficiency in both marine and freshwater ecosystems. Among
all selected functional diversity indices, FDc is the most robust
functional diversity index in promoting phytoplankton resource efficiency.
Our study provides empirical evidences in natural aquatic systems that
trait‐based functional diversity represents better species niche
partitioning than the Shannon index and thereafter enhances resource use
efficiency. This finding can improve our understanding on trophic transfer
and nutrient cycling in aquatic ecosystems.