Geography, environmental conditions, and life history shape patterns of within-population phenotypic variation in North American birds

Abstract Intraspecific variation is a fundamental component of biodiversity, shaping species interactions and coexistence dynamics. While numerous mechanisms have been proposed to shape the degree of phenotypic variation within species, many remain largely untested or poorly explored at broad spatial and taxonomic scales. Using data from nearly 200,000 birds from 99 species captured across North America, we investigated hypothesized drivers of within-population phenotypic variation, using body mass and wing length as traits of interest. The magnitude of observed phenotypic variation was modulated by a combination of geographic, environmental, and life-history factors. This was true whether considering differences in within-population phenotypic variation within or among species. The impact of these non-mutually exclusive mechanisms has resulted in substantial variation in the observed magnitude of within-population phenotypic variation. These results provide empirical evidence for a set of long-standing hypotheses regarding the processes that regulate observed patterns of this understudied, but important, component of biodiversity. Data description The following file structure is contained in Data.zip. Data/ -L1/ --MAPS-master-2024-12-12.rds --consensus_tree-2025-01-10.rds -L2/ --cv_data_covs-2025-01-08.rds MAPS-master-2024-12-12.rds Each row corresponds to one individual captured as part of the Monitoring Avian Productivity and Survivorship (MAPS) program (DeSante et al. 2004). Data are curated and managed by The Institute for Bird Populations. DeSante, D. F., J. F. Saracco, D. R. O’Grady, K. M. Burton, and B. L. Walker. 2004. Methodological considerations of the Monitoring Avian Productivity and Survivorship (MAPS) program. Studies in Avian Biology:28–45. sci_name - Scientific name of speciescommon_name - Common name of speciessp_id - Numeric species IDcn_id - Numeric Species/station IDstation_id - Numeric banding station IDlat - Latitude banding station lng - Longitude banding stationlog_mass - log(mass) of individual birdlog_wing - log(length of unflattened wing chord) of individual bird consensus_tree-2025-01-10.rds Consensus phylogenetic tree for species used in this study of class phylo, which can be manipulated in R using the ape package. cv_data_covs-2025-01-08.rds trait - which trait the value is referring to, wing or masssci_name - Scientific name of speciessp_id - Numeric species IDstation_id - Numeric banding station IDcv_within_post_mean - Posterior mean within-population variation (CV) each species/stationcv_within_post_sd - Posterior sd within-population variation (CV) each species/stationcv_within_among_sp_post_mean - Posterior mean species-level within-population variation (CV)cv_within_among_sp_post_sd - Posterior sd species-level within-population variation (CV)lat - Latitude banding station lng - Longitude banding stationdistance_edge_km_buffer10 - Distance to range edgeDHI_spatial_var_10km - Spatial variation in DHIDHI_temporal_var_10km - Temporal variation in DHImigration_dist_km - Species migration distancerange_size_km2 - Species range sizeGenLength - Species generation length (i.e., generation time)HWI - Hang Wing Index