DOI: 10.5061/dryad.zcrjdfndn
title: A specialist bee and its host plants experience phenological shifts at different rates in response to climate change

description: Changes in climate can alter the phenology of organisms, potentially
 decoupling partners within mutualisms. Previous studies have shown that
 plant and pollinator phenologies are shifting over time, but these shifts
 have primarily been documented for generalists and within small geographic
 regions, and the specific climatic cues regulating these shifts are not
 well-understood. We examined phenological shifts in a specialist
 pollinator and its host plant species over a 117-year study period using a
 digitized dataset of over 4,000 unique collection records. We assess how
 climatic cues regulate these organisms’ phenologies using PRISM weather
 data associated with each record. We tested the hypothesis that rates of
 phenological change would be greater at northern latitudes. We found that
 the phenology of the specialist bee pollinator Habropoda laboriosa is
 changing over time, but at different rates across its range. Specifically,
 phenology is advancing to a greater degree in more northern populations,
 with increasing phenological advances of 0.04 days/year with each degree
 of latitude, and with a delay in phenology in more southern populations.
 In contrast, only one species in the host plant genus Vaccinium is
 experiencing phenological change over time. For this plant, rates of
 change are also variable across latitudes, but in a pattern opposite that
 of the bee; while phenology is advancing across its range, rates of
 advance are highest in more southern populations, with decreasing
 phenological advances of 0.01 days/year with each degree of latitude. The
 phenologies of both the bee and three of four Vaccinium spp. were
 regulated primarily by spring temperature, with phenologies overall
 advancing with increasing temperature, and with the strongest responses
 shown by the bee in northern populations. Our study provides partial
 support for the hypothesis that phenologies advance most at northern
 latitudes, but demonstrates that pollinators and plants do not adhere
 similarly to this prediction. Additionally, we illustrate the potential
 for phenological mismatch between a specialist pollinator and its host
 plants by showing that plants and pollinators are advancing their
 phenologies at different rates across space and time and with differing
 responses to changing climatic cues.
description: <b><i>Habropoda laboriosa
 records</i></b> We used Julian date of
 collection from each <i>H. laboriosa </i>specimen as a proxy
 for adult bee foraging phenology. Records of <i>H. laboriosa
 </i>were gathered online from the Symbiota Collections of Arthropods
 Network (SCAN). We also databased specimens housed in the Florida State
 Collection of Arthropods (FSCA). Only records that contained a clearly
 interpretable date<i> </i>were included for analysis. We
 removed one specimen that was georeferenced to the west coast, where no
 other <i>H. laboriosa </i>specimens have been collected or
 recorded. To prevent bias introduced by varying collection efforts and
 techniques, only one specimen representing a collection event was retained
 for analysis. Specimens were considered to be from the same collection
 event if they had both the same date of collection and location of
 collection. Collection techniques using bee bowls or other traps are more
 likely to collect multiple individuals on a given date than collection
 events using hand netting, and these differences may affect our analyses
 especially if collection methods changed in popularity and relative use
 over time. All <i>H. laboriosa </i>specimens represent the
 adult life stage when bees are foraging from flowers; this life stage is
 brief (3-7 weeks per year) and both males and females are foraging from
 flowers during these few weeks. We used the latitude, longitude, and date
 of collection from these specimen records in our analysis.
 <b><i>Vaccinium spp. records
 </i></b> We used Julian date of collection
 from each flowering <i>Vaccinium </i>spp. specimen as a proxy
 for flowering phenology. We collected herbaria specimen records of wild
 <i>Vaccinium </i>spp. with ranges that overlap with
 <i>H. laboriosa. Vaccinium</i> spp. that do not occur in
 <i>H. laboriosa</i>’s range were not included<i>
 </i>as we were primarily interested in the phenologies of these two
 taxa as they interact.<i> </i>We only used <i>Vaccinium
 </i>spp. that included 400 or more recorded specimens in the
 flowering stage. Plant species with fewer than 400 flowering records (n =
 72) were excluded as data were too limiting to draw conclusions about
 flowering phenology over time and space. Our final data set included the
 following species: <i>V. corymbosum</i>, <i>V.
 arboreum</i>, <i>V. stamineum</i>, and <i>V.
 pallidum. </i>Herbarium records of wild <i>Vaccinium
 </i>spp. were gathered online from the SEINet North American Plant
 Network (SEINet). Only those specimens with a clearly interpretable date
 of collection, a link to a reference photograph of the specimen, and
 geographic coordinates or county-level location of collection were
 included for analysis. Specimens without geographic coordinates but with a
 county-level location of collection were georeferenced to the center of
 the county that they were collected within. To prevent bias from different
 sampling or observation protocols over time, only one specimen per
 collection event was retained for analysis. Specimens with the same date
 of collection and location of collection were considered to be from the
 same collection event. To assess phenological shifts in
 plant flowering over time, as well as to determine how weather variables
 affect plant flowering, we only included <i>Vaccinium
 </i>specimens that were flowering at the time of collection or
 observation. Plants included in this study were designated to be flowering
 if their reference images contained one or more open flowers. Specimens
 with highly distorted images and those that were highly damaged, such that
 we were unable to determine whether or not the plant was flowering at the
 time of collection, were not included for analysis.
 <b><i>Weather data </i></b>
 We collected all weather data from PRISM using the “Data
 Explorer: Download Time Series Values in Bulk” feature. This feature
 provides time series data by location and date as values collected from
 within the PRISM standard 4 km grid cells. We collected data from PRISM
 for each cell that contained the collection coordinates of a specimen
 included in the study, and for each year corresponding to a collection
 event. For each cell, PRISM calculates annual, monthly, and seasonal
 (average of three months) variables including average temperature, maximum
 mean temperature, minimum mean temperature, total number of freezing days
 (days with any amount of time below 0°C), total precipitation as rainfall,
 and average solar radiation. We focused primarily on spring averages
 (average of Feb, March, and April) as these averaged variables allowed us
 to examine weather over the time period of interest (spring) while
 avoiding correlated predictor variables from multiple individual months.
 This period also overlaps well with the phenology of our study organisms
 as 96% of specimens were collected from February to May. For all analyses,
 we only included specimens and associated climate data from 1901 – 2018
 because PRISM climate estimates were only available for these years at the
 time of data collection. This 1901 – 2018 range included over 89% of all
 specimens that met all other criteria for inclusion in the study as
 previously described.
description: 1) For all datasets, variable names for columns 1:28 are Darwin
 Core terms. We provide the definition for each term in the README
 document. Theses definitions come directly from the Darwin
 Core website. 2) For all datasets, variable
 names for columns 29:275 are abbreviations for climate variables collected
 from PRISM using the “Data Explorer: Download Time Series Values in Bulk”
 feature. We provide a definition and units for each abbreviation in the
 README document. All definitions come directly from the Climate NA help page.