Gaps in global alien plant trait data and how to fill them

Matthias Grenié , Helge Bruelheide, Wayne Dawson, Franz Essl, Mark van Kleunen, Ingolf Kühn, Holger Kreft, Petr Pyšek, Patrick Weigelt, Marten Winter

Aim

Functional traits help to understand the ecological processes underlying biological invasions. The extent to which trait data are available for alien plants at the global scale is unknown. In this study, we assess the availability of trait data and identify global gaps and biases

Location

Global

Time Period

Present

Major taxa studied

Vascular plants

Methods

We used the GloNAF database to get a global list of plants naturalized outside their native range and their distributions. We combined data from the four largest trait databases: AusTraits, BIEN, GIFT, and TRY, on which we performed taxonomic and trait harmonization. We studied the availability of trait data. Then, based on the distribution data, we tested to what extent trait knowledge was driven by ecological and socioeconomic variables.

Results

We found that the species-by-trait matrix (16,044 species for 2,764 traits) was only 1.4% filled, with most traits measured on very few species. Only ten traits were available for more than 50% of all alien plants. Four percent of the species had not a single trait measured, while 27% of species had data for the three key plant traits of leaf mass per area, seed mass, and plant height. We observed a strong latitudinal gradient in trait knowledge with areas in the Tropics showing lower trait knowledge than higher latitudes, especially in the Northern hemisphere. Growth form, range size, and invasion status were the strongest predictors of trait knowledge, with widespread, invasive tree species being better recorded than other species.

Main conclusions

We identified large trait data gaps at a global scale for alien plants, which limits our ability to study functional invasion ecology at large scales. These gaps are partly driven by uneven sampling and a lack of trait data integration across sources. We recommend that prioritizing the most invasion-relevant traits and distributing community efforts of plant and invasion scientists to sample them in a standardized way can help close these gaps.