# Trait overdispersion in dragonflies reveals the role and drivers of competition in community assembly across space and season There are 7 tables describing assemblages of dragonflies and damselflies in three study systems: Great Britain, Bavaria and Catalonia. All tables named "main analysis" describe assemblages built for the main analysis of the manuscript, using the parameters: *resSp* = 0.1 km, *resPh* = 30, *resTem* = 3, *samEf* = 4, *samCov* = 80, *Smin* = 4. Note that these parameters are described in the manuscript. * "Assemblages mainAnalysis FD.csv" decribes functional diversity of assemblages of Anisoptera and Zygoptera, for the three systems and based on both multitrait-FD and body size-FD. The tables: * "Assemblages mainAnalysis multitraitFD-env Anisoptera.csv" * "Assemblages mainAnalysis multitraitFD-env Zygoptera.csv" Contain multitrait FD for the three systems, respectively for Anisoptera and Zygoptera, and contain environmental data on the 10-year average temperature in the location and day of the year of the assemblage. The tables called phenoAnalysis describe assemblages built for the phenological analysis of the manuscript using the parameters: *resSp* = 0.1 km, *resPh* = 14 and *resTem* = 0, *samEf* = 4, *samCov* = 80, *Smin* = 3 There are four different files separated for Anisoptera and Zygoptera, and for multitrait FD and body size FD. ## Description of the data and file structure Description of variables within the tables: * Dataset: The study system of the assemblage. GB= Great Britain, Bavaria = Bavaria, Catalonia = Catalonia. * group: The taxonomic group (suborder) of the assemblage. Either Anisoptera (dragonflies) or Zygoptera (damselflies). * Day: average day of the year (1-365) of the observations that constitute the asemblage. * Lat: Latitude* * Long: Longitude* * Trait_set: Trait set used to measure FDses. Either based uniquely on body size (bodysizeFD) or a multi-trait measure based on body size, abdomen length, wing length, and the three RGB colour channels (multitraitFD). * FDis_SES: Standard effect size of functional diversity (FDses), measured using the metric FDis. * SES_cwm.body_volume.cm3: Standard effect size of community weighted means of body volume. * Forest: Proportion of forest landcover in the ~1x1 km cell of the assemblage. Calculated as the proportion of ~100x100m cells of forest landcover within a ~1x1km cell. * Temp: Summer temperature in the ~1x1 km cell of the assemblage. Units are degrees Celsius (°C). * tas: Air temperature in the day of the year and ~1x1 km cell of the assemblage. Units are kelvins (K). For Forest, Temp, and tas variables, NA represents missing values arising from methodological limitations when processing raster data. *Note that Lat and Long are described in different reference systems depending on the dataset: * GB= EPSG:27700 * Bavaria= EPSG:31468 * Catalonia = EPSG:32631 ## Sharing/Access information This data is derived from the following sources: * Databases of occurrence records were obtained: for Great Britain (GB) from the *British Dragonfly society*, for Bavaria from *Bayerische Artenschutzkartierung* ([www.lfu.bayern.de/natur/artendaten](http://www.lfu.bayern.de/natur/artendaten) and for Catalonia from *Institució Catalana d’Història Natural* (). * Temperature is derived from: [https://chelsa-climate.org/chelsa-w5e5-v1-0-daily-climate-data-at-1km-resolution ](https://chelsa-climate.org/chelsa-w5e5-v1-0-daily-climate-data-at-1km-resolution"Karger)"Karger, D. N., Lange, S., Hari, C., Reyer, C. P. O. and Zimmermann, N. E. 2022. CHELSA-W5E5 v1.0: W5E5 v1.0 downscaled with CHELSA v2.0." * Summer temperature corresponds to Bio 10, from CHELSA V1.2. "Karger, D. N., Conrad, O., Böhner, J., Kawohl, T., Kreft, H., Soria-Auza, R. W., Zimmermann, N. E., Linder, H. P. and Kessler, M. 2017. Climatologies at high resolution for the earth’s land surface areas. - Sci Data 4: 170122." * Forest is derived from

Our understanding of how biotic interactions influence animal community assembly is largely restricted to local systems due to the difficulty of obtaining ecologically meaningful assemblage data across large spatial extents. Here, we used thousands of spatio-phenologically high-resolution assemblages across three distinct European regions together with a functional diversity approach to understand community assembly of dragonflies and damselflies (Odonata), an insect group characterized by a pronounced competitive reproductive biology. We found that adult dragonfly, but not damselfly, assemblages were consistently composed of species morphologically more different than expected by chance based on the traits that enhance their inter-specific reproductive encounters. These results provide consistent evidence for the role of competition in the assembly of animal communities, which we interpret is most likely caused by the territorial reproductive biology of dragonflies. Support for competition varied both spatially and seasonally following theoretical expectations, as it was strongest in locations and seasonal moments with low thermal stress (i.e. warm conditions) and high niche packing. Our study illustrates how spatio-temporal diversity patterns arise from variation in assembly processes.