DOI: 10.5061/dryad.n02v6wx8m
title: Two <em>Metschnikowia</em> nectar yeast species have similar volatile profiles, but elicit differential foraging in bee pollinators

description: Nectar yeasts are a highly specialized group of fungi that may play key
 roles in pollination ecology. Nectar yeasts lack an independent dispersal
 mechanism to access new habitats with fresh resources. Yeasts, bumblebee
 pollinators, and flowering plants likely take part in a series of diffuse
 mutualisms, wherein yeasts attract bees that provide phoretic travel
 between flowers. This interaction is thought to provide bees with improved
 foraging efficiency and plants with increased pollinator visitation and
 associated pollination services. However, the underlying mechanisms
 driving bee pollinator preferences for nectar with yeast and differences
 among yeast species in eliciting pollinator behavior are relatively
 unexplored. We used an integrative approach to elucidate the underpinnings
 of bee pollinator preference for nectars that contain yeasts. We conducted
 a survey of local flower nectar for the presence and species diversity of
 yeast. Using two prominent, local nectar yeast species (Metschnikowia
 reukaufii and Metschnikowia koreensis), we conducted observational field
 trials to ascertain the effects of the presence and identity of nectar
 yeast on bee visitation rates. We also analyzed the volatile profiles of
 both yeast species to explore if olfactory cues are associated with
 differential foraging behavior. We found that M. reukaufii was the most
 common nectar yeast in our study area in the Southeastern USA, as did
 previously published global surveys. Intriguingly, we found co-occurrence
 of multiple yeast species in 22% of samples, all of which contained M.
 reukaufii and another yeast typically from the Metschnikowia genus, such
 as M. koreensis. In a field trial, we found that bee pollinators had
 higher visitation to flowers supplemented with M. koreensis over sterile
 flowers, while no difference in bee foraging behavior was evident in
 response to M. reukaufii. Despite this behavioral difference, the volatile
 profiles of both yeast species were not significantly different from one
 another, indicating that some other mechanism, possibly related to
 gustation, underlies bee-yeast communication.  The ecology and
 species interactions of wild yeasts are poorly understood, yet they may
 play vital roles in many ecosystems. Our research highlights the
 importance of studying facultative mutualisms and the necessity of testing
 their underlying assumptions. Elucidating the mechanisms behind
 insect-microbe symbioses will open new horizons in pollinator ecology and
 conservation.
description: # Two *Metschnikowia* nectar yeast species have similar volatile profiles,
 but elicit differential foraging in bee pollinators Dataset DOI:
 [10.5061/dryad.n02v6wx8m](https://doi.org/10.5061/dryad.n02v6wx8m) ##
 Description of the data and file structure We used an integrative approach
 to elucidate the underpinnings of bee pollinator preference for nectars
 that contain yeasts. We conducted a survey of local flower nectar for
 presence and species diversity of yeast. Using two prominent, local nectar
 yeast species (*Metschnikowia reukaufii* and *Metschnikowia koreensis*),
 we conducted observational field trials to ascertain the effects of the
 presence and identity of nectar yeast on bee visitation rates. We also
 analyzed the volatile profiles of both yeast species to explore if
 olfactory cues were associated with differential foraging behavior. ###
 Files and variables ### Files and variables NAs or empty cells = missing
 or inappropriate data for all data files #### File:
 01_nectar_sampling_flower-data.csv **Description:** Data for flowers
 sampled for yeast presence across the Research Triangle, NC #####
 Variables * sample_id: unique flower sample ID * date_coll: date the
 sample was collected * date_bagged: the date the flower was bagged to
 prevent pollinator feeding (if applicable) * flower_com: common name of
 the flower * flower_sp: species of the flower * flower_family: family of
 the flower * gps_coord: gps coordinates of the sampling site * loc:
 location of sampling * loc_type: location type of sampling (rural, urban)
 * coll_notes: notes on the collection #### File:
 02_nectar_sampling_flower-data_readme.csv **Description:** Readme for
 nectar_sampling_flower_data.csv #### File:
 03_Compiled_Nectar_Sampling_9-19-24.csv **Description:** data of cultured
 nectar samples ##### Variables * sample_id: unique ID for each nectar
 sample * loc_type: whether the collection location was rural or urban *
 num_colonies: number of unique colonies isolated from the nectar sample *
 num_positive: number of unique colonies that were PCR positive and Sanger
 sequenced * num_unq_species: number of unique species found from the
 nectar sample * Genus 1: genus of first yeast found in sample * Species 1:
 species of first yeast found in sample * Genus 2: genus of second yeast
 found in sample * Species 2: species of second yeast found in sample ####
 File: 04_Compiled_Nectar_Sampling_9-19-24_readme.csv
 **Description:** Readme file for Compiled_Nectar_Sampling_9-19-24.csv ####
 File: 05_mf_obs_visitor_data_cl.csv **Description:** data of pollinator
 observations in experimental field trial with two species of nectar yeast.
 transcribed from audio recordings tracking pollinator activity in field
 plot ##### Variables * obs_id: Unique observed insect ID * date_trial:
 date of the trial * trial_id: unique ID of the trial * yeast_sp: yeast
 species used in the trial * yeast_strain: yeast strain used in the trial *
 plant_sp: plant species * poll_sp: pollinator species * plant_trt: plant
 treatment: y = inoculated with yeast; ny = inoculated with sterile nectar
 * plant_tot_fl: the total number of flowers on the plant for that trial *
 plant_id: plant ID * plant_loc: plant location in the plot for that trial
 * flower_num: the sequential number of flower visits for that unique
 observed pollinator * time_start: time between flower nectarings *
 time_end: counter for total number of observations * notes: notes about
 that observation * time_interval: time between flower nectarings *
 numbering: counter for total number of observations * time_start_sec: time
 started in seconds * time_end_sec: time ended in seconds * vst_dur:
 duration of each flower visit (time_end_sec – time_start_sec) *
 plant_sort: sorting rows to be kept for final analyses (data) vs those
 that were preliminary (prelim) * poll_class: general type of pollinator
 for that row #### File: 06_mf_obs_visitor_data_cl_readme.csv
 **Description:** Readme file for 05_mf_obs_visitor_data_cl.csv #### File:
 07_mf_byobs_plant_data_cl.csv **Description:** Plant data for experimental
 field trials ##### Variables * plant_id: unique plant ID * date_trial_1:
 date of trial 1 * plant_loc_1: location of the plant on the grid of trial
 1 * plant_trt_1: plant treatment for trial 1 * plant_tot_fl_1: total
 number of flowers on plant for trial 1 * yeast_sp_1: yeast species used in
 trial 1 * date_trial_2: date of trial 2 * plant_loc_2: location of the
 plant on the grid of trial 2 * plant_trt_2: plant treatment for trial 2 *
 plant_tot_fl_2: total number of flowers on plant for trial 2 * yeast_sp_2:
 yeast species used in trial 2 * date_trial_3: date of trial 3 *
 plant_loc_3 * plant_trt_3 * plant_tot_fl_3 * yeast_sp_3 * date_trial_4 *
 plant_loc_4 * plant_trt_4 * plant_tot_fl_4 * yeast_sp_4 * date_trial_5 *
 plant_loc_5 * plant_trt_5 * plant_tot_fl_5 * yeast_sp_5 * date_trial_6 *
 plant_loc_6 * plant_trt_6 * plant_tot_fl_6 * yeast_sp_6 * date_trial_7 *
 plant_loc_7 * plant_trt_7 * plant_tot_fl_7 * yeast_sp_7 * date_trial_8 *
 plant_loc_8 * plant_trt_8 * plant_tot_fl_8 * yeast_sp_8 #### File:
 08_mf_byobs_plant_data_cl_readme.csv **Description:** Readme file for
 07_mf_byobs_plant_data_cl.csv #### File:
 09_MKMR_comp_data_init_thresh_10.0.csv **Description:** Chemical analyses
 of volatiles from GCMS of two species of yeast ##### Variables * sample:
 yeast culture sample ID, combination of strain ID (s2_1 or s3_1) and
 replicate (a-e) * species: yeast species * date_dil: date the yeast
 culture was diluted * date_gcms: date the volatiles were analysed on the
 gc-ms * ret_time: retention time of the peak * area: area of the peak *
 chem_name: chemical names of the peak * qual: confidence in peak identify
 * com_chem_name: common chemical name (for standardization) * notes: any
 notes on the peak #### File: 10_MKMR_comp_data_init_thresh_10.0_readme.csv
 **Description:** Readme file of 09_MKMR_comp_data_init_thresh_10.0.csv
 #### File: 11_Metschnikowia_growth_assays_Counts.csv **Description:** Test
 of effect of refrigeration on yeast strain growth ##### Variables *
 strain: strain ID: s2_1 = M. reukaufii, s3_1 = M. koreensis * day: number
 of days kept at 4C * rep: replicate number * count: number of CFUs after
 24-72 hours after removal from 4C and growth at 25C #### File:
 12_Metschnikowia_growth_assays_Counts_readme.csv **Description:** Readme
 file for 11_Metschnikowia_growth_assays_Counts.csv #### File:
 bee-yeast_mss_analyses.R **Description:** R script for analyses in
 manuscript. This code cleans and integrates field observations, yeast
 volatile profiles, and growth assays to quantify how different yeast
 treatments affect bee visitation behavior, followed by mixed‐effects
 models testing treatment effects on visitation metrics and visit duration.
 #### File: bee-yeast_mss_figures.R **Description:** R script for figures
 in manuscript. This code cleans and merges nectar sampling data with yeast
 identity, bee visitation observations, and yeast volatile profiles to
 characterize yeast presence in nectar and prepare integrated datasets for
 comparing microbial composition, chemistry, and pollinator interactions.
 ## Code/software None ## Access information Other publicly accessible
 locations of the data: * none Data was derived from the following sources:
 * self