DOI: 10.5061/dryad.k9m20
title: Data from: Unraveling the interplay of community assembly processes acting on multiple niche axes across spatial scales

description: How the relative importance of community assembly processes varies with
 spatial scale is the focus of intensive debate, in part because inferring
 the scales at which specific niche-based processes act is difficult. One
 obstacle is that standard phylogenetic and functional diversity metrics
 may integrate the signals of multiple processes when combining separate
 niche axes into one variable (multiple-niche-axis metrics), potentially
 obscuring overlapping niche-based processes. We use simulations to
 evaluate the power of these metrics to detect competition and habitat
 filtering when these processes operate across multiple niche axes and vary
 in their relative importance. We then test for both processes at a range
 of spatial scales in a Neotropical bird assemblage. Simulations revealed
 that multiple-niche-axis metrics had low power to detect competition and
 habitat filtering when a mix of both processes acts across niche axes,
 whereas metrics focused on single-niche axes were better able to deal with
 this complexity. We found the same contrast in bird communities, where
 both competition and habitat filtering were detected at the scale of
 individual territories, but only by single-niche-axis metrics focused on
 specific niche axes (e.g., foraging traits). Our results suggest that
 multiple-niche-axis metrics may produce misleading evidence that
 niche-based processes are partitioned, particularly across scales, and
 highlight the importance of analyzing functional diversity patterns on
 individual niche axes when testing assembly models.
description: Wayqecha Peru Bird
 Community Census DataBird species
 presence/absence for 41 species at 72, 0.8 ha, survey points of radius 50
 m, arranged 120 m apart on a 6 by 12 point grid across a grassland–forest
 ecotone (See publication Fig. 1 and Fig. A1). Species were recorded as
 present at a survey point if detected by either sight or song. Spatial
 grid references for survey points are also given. Y coordinates are grid
 rows and X coordinates grid columns. This enables the calculation of
 species presence/absence at larger spatial scales by grouping together
 neighboring survey points (e.g. grouping the data for two neighboring
 survey points creates a survey area of 1.6 ha). Data are in .csv format.
 Column headings: Site: 0.8 ha survey point names. X: X coordinate on
 survey grid. Y: Y coordinate on survey grid. Other columns are species
 names (genus and species separated by an underscore): 1= species presence,
 0 = species absence.Wayqecha Peru Bird
 Community Functional TraitsSpecies average bill,
 tail, wing and tarsus trait values for 41 primarily insectivorous bird
 species from a cloudforest–grassland ecotone at Wayqecha Biological
 Station, Peru. Please refer to main text for additional details on trait
 collection methods. Data are in .csv format. Column headings: Species:
 Species name. Taxonomy follows Remsen et al. (2011). Bill.nares: Average
 length of bill (mm) measured from bill tip to anterior edge of nares.
 Bill.width: Average bill width (mm) measured at anterior edge of nares.
 Bill.depth: Average bill depth (mm) measured at anterior edge of nares.
 Wing.length: Average wing length (mm) measured on unflattened wing.
 Tail.length: Average tail length (mm) measured from the tip of the longest
 rectrix to the point at which the two central rectrices protrude from the
 skin. Tarsus.length: Average tarsus length (mm) measured as the distance
 from the notch at the knee to the third crease at the ankle. Sample.size:
 Number of individuals measured. Measured.on.Site: Y = measurements taken
 on individuals captured within the survey site at Wayqecha. N =
 measurements taken on museum specimens.Wayqecha Peru Bird
 Community Vegetation DataVegetation
 characteristics within a 20m x 20m square centered on each of the 72, 0.8
 ha bird survey points from a cloudforest–grassland ecotone at Wayqecha
 Biological Station, Peru. Please refer to publication main text for
 additional details on vegetation data collection methods. Data are in .csv
 format. Column headings: Site: 0.8 ha survey point names. X: X coordinate
 on survey grid. Y: Y coordinate on survey grid. Max.canopy.height: Maximum
 canopy height in meters, estimated by eye. Percentage.grass.cover:
 Estimated by eye. Percentage.shrub.cover: Estimated by eye.
 Percentage.tree.cover: Estimated by eye.