DOI: 10.5061/dryad.r77pc42
title: Data from: Effects of long-term variation in pollinator abundance and diversity on reproduction of a generalist plant

description: 1. Quantifying the benefits of pollinator abundance and diversity for
 plant reproduction is a critical challenge, especially given recent
 pollinator declines. Many studies test for pollen limitation (PL), but
 huge gaps remain in our understanding of how often and why plants
 experience PL. Most studies are limited to a few sites or years. Little
 existing research mechanistically links pollinator visitation with plant
 reproduction. Also, buffering against variability in visitation is a key
 but largely untested potential benefit of pollinator diversity. Long-term
 studies pairing visitation data with PL experiments are essential to
 addressing these gaps, but extremely rare. 2. I measured pollinator
 visitation, responses to pollen supplementation, and fruit weights in the
 generalist plant Scrophularia californica across multiple sites for 8
 years. I determined how often S. californica experienced significant PL
 and tested mechanistic models predicting PL and fruit (capsule) weight
 from visitation. I then used those models to simulate pollinator loss and
 evaluate the relative effects of changes in visit quantity and quality. I
 explored the stabilizing benefits of visitor diversity by quantifying both
 covariation among pollinators and effects of simulated species loss on
 variation in PL and capsule weights. 3. Scrophularia showed significant PL
 in only 26.9% of patch/year combinations tested. Visitation by the most
 abundant (Apis mellifera) and effective (Vespula pennsylvanica)
 pollinators strongly predicted PL and capsule weights. Both response
 curves were highly non-linear, but PL saturated more with increased
 visitation. Pollinator loss simulations predicted substantially increased
 PL and reduced capsule weights, mostly because of lower visit numbers
 rather than changes in visit quality. Visitation rates of individual
 pollinators varied substantially and without correlation. Simulated
 pollinator loss increased the spatial and temporal skew in visitation,
 resulting in higher predicted coefficients of variation for PL and capsule
 weights. 4. Synthesis. Previous work predicts a non-linear relationship
 between pollinator visitation and plant reproduction, but this is the
 first long-term study I am aware of that quantifies such a pattern. The
 analysis of covariance in pollinator visitation combined with my
 simulation results provide novel empirical support for another important
 hypothesis: that multiple pollinators can provide stabilizing benefits for
 plant reproduction.
description: Pollen supplementation
 dataAll data were collected
 at the Landels-Hill Big Creek Reserve, Monterey County, CA, U.S.A. First
 file: “Pollen supplementation data.csv”. The column headings represent:
 “Year”= year of study; “Patch”= location; “Plant”= identity of individual
 plant; “Aborted.hp”=whether the pollen-supplemented flower aborted (y) or
 set fruit and produced seeds (n); “Weight.hp”= weight in mg of capsule
 from pollen-supplemented flower; “Aborted.control”=whether the control
 (unsupplemented) flower aborted (y) or set fruit and produced seeds (n);
 “Weight.control”= weight in mg of capsule from control (unsupplemented)
 flower; “PLindex”=pollen limitation index, defined as the ratio of weights
 for supplemented relative to control capsules ; “lntranPLindex”=natural
 log-transformed PL index; TotalScroph= total abundance of Scrophularia
 californica flowers on the transect for this patch, in units of 500
 flowers; “Vvisit”= mean Vespula pennsylvanica visitors per transect count
 divided by total abundance of S. californica in units of 500 flowers;
 “Avisit”= mean Apis mellifera visitors per transect count divided by total
 abundance of S. californica in units of 500 flowers; “Bvisit”= mean Bombus
 visitors per transect count divided by total abundance of S. californica
 flowers in units of 500 flowers; “Growprecip”= total growing-year
 precipitation (Sept. 1- Aug. 31), in cm; “Time”=timing of
 pollen-supplementation experiments, measured in how many days later the
 supplementations began than in the earliest year (2007, on June
 23).Control flower
 dataSecond file: “Control
 flower data.csv”. The column headings represent: “Year”= year of study;
 “Patch”= location; “Plant”= identity of plant; “Weight”= capsule weight in
 mg (for control plants with two unsupplemented flowers, this value
 represents the mean capsule weight); TotalScroph= total abundance of
 Scrophularia californica flowers on the transect for this patch, in units
 of 500 flowers; “Vvisit”= mean Vespula pennsylvanica visitors per transect
 count divided by total abundance of S. californica in units of 500
 flowers; “Avisit”= mean Apis mellifera visitors per transect count divided
 by total abundance of S. californica in units of 500 flowers; “Bvisit”=
 mean Bombus visitors per transect count divided by total abundance of S.
 californica flowers in units of 500 flowers; “Growprecip”= total
 growing-year precipitation (Sept. 1- Aug. 31), in cm; “Time”=timing of
 pollen-supplementation experiments, measured in how many days later the
 supplementations began than in the earliest year (2007, on June
 23).Pollen transfer
 effectiveness dataThird file: “Pollen
 transfer effectiveness data.csv”. These data were all collected in 2003.
 The column headings represent: “Sample”=the specimen identifier;
 “Species”= visitor species (Apis= Apis mellifera, Bombus= Bombus spp.,
 Vespula= Vespula pennsylvanica); “Pollen”=were pollen grains found (y) or
 not (n) on the stigma; “Estgrains”=estimated number of pollen grains
 deposited (some numbers are fractions because values for stigmas that were
 more difficult to score represent means of two different
 counts).Visitation data
 2003-2014Fourth file: “Visitation
 data 2003-2014”. This file includes all patches with Scrophularia
 californica monitored for pollinator visitation from 2003-2014. The column
 headings represent: “Year”= year of study; “Patch”= location; TotalScroph=
 total abundance of Scrophularia californica flowers on the transect for
 this patch, in units of 500 flowers; “Vvisit”= mean Vespula pennsylvanica
 visitors per transect count divided by total abundance of S. californica
 in units of 500 flowers; “Avisit”= mean Apis mellifera visitors per
 transect count divided by total abundance of S. californica in units of
 500 flowers; “Bvisit”= mean Bombus visitors per transect count divided by
 total abundance of S. californica flowers in units of 500
 flowers.