DOI: 10.5061/dryad.1g1jwsv6d
title: Bumble bee niche overlap along an elevation gradient: How traits can inform novel competitive pressures under climate change

description: Climate change-induced range shifts can disrupt interactions among species
 by moving them in and out of ecological communities. These disruptions can
 include impacts on competition for shared resources. Bumble bees (Bombus
 spp.) are important pollinators shifting their range upwards in elevation
 in response to climate change. These shifts could lead to altered
 competition among species and threaten co-existence. This could be
 particularly worrying at the tops of mountain ranges where bumble bees may
 no longer be able to move up to higher elevations to track climate change.
 To better understand this issue, we investigated changes in diet niche
 overlap among bumble bee species along a 2296m elevation gradient in the
 southern Rocky Mountains. Additionally, we investigated how morphological
 and phenological traits impact diet composition (flower species visited)
 among bumble bee species and explored a thought experiment on how the
 continued upward movement of bumble bee species under climate change into
 the mountaintop may affect trait overlap of newly co-occurring species. We
 found that diet niche overlap among bumble bee species increased with
 elevation. We also found that differences in morphological and
 phenological traits (body size, tongue length, date of activity) were
 correlated with differences in diet composition among bumble bee species.
 Finally, we described how the co-occurrence of bumble bee species from
 lower elevations with mountaintop species would lead to increased trait
 overlap and likely more species sharing similar flowers. These shifts
 could lead to increased competition for high-elevation restricted species
 on mountaintops and exacerbate the effects of climate change on
 high-elevation bumble bees.
description: # Bumble bee niche overlap along an elevation gradient: How traits can
 inform novel competitive pressures under climate change
 [https://doi.org/10.5061/dryad.1g1jwsv6d](https://doi.org/10.5061/dryad.1g1jwsv6d) ## Description of the data and file structure "Bombus_PikesPeak_07_24_24.csv" contains bumble bee and host flower interaction data collected between May and September for four years (2019-2022) on Pikes Peak, the highest mountain (4302m) in the southern Front Range of Colorado (38° 50' 15.59" N, -105° 02' 23.40 W"). Observations were made along an elevation gradient ranging from 1990m to 4286m on Pikes Peak. "BB_Diss_Traits_10-22-24.csv" contains bumble bee trait data for the species that were found in our study at Pikes Peak. Species-level phenology data is sourced from our observations at Pikes Peak. Species-level minimum, maximum, and average worker tongue length (mm, labium: prementum + glossa) is sourced from Macior 1974’s “Pollination ecology of the Front Range of the Colorado Rocky Mountains” and Medler 1962’s “Morphometric Studies on Bumble Bees”. For three bumble bee species for which we did not have tongue length data available from Macior 1974 (*Bombus fervidus*, *B. huntii*, and *B. rufocinctus*), we estimated minimum and maximum values by taking the mean +/- 2SD from Medler 1962. Finally, species-level minimum, maximum, and midpoint body size (mm) data are sourced from Williams et al. 2014’s “Bumble Bees of North America” guidebook. ### Files and variables #### File: BB\_Diss\_Traits\_10-22-24.csv **Description:** Bumble bee trait data ##### Variables * bb.species: Bumble bee scientific name (includes all observed bumble bee species at Pikes Peak) * wbsminwilliams: Minimum worker body size (mm) - Williams et al. 2014 * wbsmaxwilliams: Maximum worker body size (mm) - Williams et al. 2014 * wbsmidwilliams: Midpoint worker body size (mm) - Williams et al. 2014 * phenologyminw: Minimum worker phenology (day of year, 1 - 365) * phenologymaxw: Maximum worker phenology (day of year, 1 - 365) * phenologyavgw: Average worker phenology (day of year, 1 - 365) * wtonguedatasource: Source of tongue length data (Macior 1974 or Medler 1962) * wtonguemin: Minimum worker tongue length (mm) * wtonguemax: Maximum worker tongue length (mm) * wtonguemean: Mean worker tongue length (mm) * wtonguesd: Standard deviation of worker tongue length (mm) * wtonguesampsize: Sample size of worker tongue length #### File: Bombus\_PikesPeak\_07\_24\_24.csv **Description:** Bumble bee and flower interaction data ##### Variables * date: Date of observation (XX/XX/XXXX format) * year: Year of observation * dayofyear: Day of observation in a given year (ranges between 1 - 365) * time_field: Time recorded in the field for each observation * pol_sp: Bumble bee pollinator species observed * plantcode: Code for observed host plant species (Correspond with the full scientific name under "ack.nam" column) * ack.nam: Host plant species full scientific name (using Ackerfield 2015) * num_flow: Number of flowers/clusters of flowers observed * flow_clust: Individual flower or cluster of flowers observed (clust = cluster, flow = flower) * sex: Sex/caste of the observed bumble bee (female, male, or queen). If left blank, specimen was not identified to sex. * collector: Initials of the collector (AGG = Andrew Gaier, AK = Asia Kaiser, AWP = Anna Paraskevopoulos, CMS = Chloe Summer , DV = Diego Vázquez , JR = Julian Resasco, KB = Kaitlyn Barthell, ZC = Zander Constien) * lat: Latitude (decimal degrees) * lon: Longitude (decimal degrees) * ele_m: Elevation in meters NA: Not Applicable ## Code/software All analyses were conducted using R version 4.0.3 (R Core Team 2020). "10_22_24oikosmanuscriptcode.R" contains the script used for this study. Packages used in the script include "ggplot2", "bipartite", "bootstrapnet", "cowplot", "elevatr", "forcats", "ggmap", "ggrepel", "ggridges", "ggsn", "iNEXT", "reshape2", and "vegan".