DOI: 10.5061/dryad.1ns1rn95c
title: Soil moisture influences nectar robbing and plant fitness in a primrose species

description: Low soil moisture, a prominent indicator of a changing climate, has
 overarching impacts on plant reproduction both directly and indirectly by
 affecting the visitation rate of pollinators. However, the role of soil
 moisture in modifying the behaviors of species interacting with plants is
 less well explored, as are the mechanisms associated with those changes in
 behavior. Reduced soil moisture can disrupt mutualistic species
 interactions, potentially shifting them toward antagonism and negatively
 impacting plant fitness.  We investigated the effects and
 underlying mechanisms of soil moisture on the intensity of nectar robbing
 (a common behavioral interaction between plants and pollinators) in
 natural populations of Primula florindae on the southeast Tibetan Plateau.
 To understand the relationships between soil moisture and nectar robbing
 and the mechanisms involved, we explored within-population variation in
 nectar robbing, floral and nectar traits, and the diversity and evenness
 of the co-flowering plant community in areas with natural variation in
 soil moisture. We then used an experimental approach to test how nectar
 robbing affected male and female components of P. florindae reproduction.
 We found that plants growing in low moisture soil experienced higher
 nectar robbing. Low soil moisture was associated with reduced flower size,
 nectar production, and the diversity of nectariferous neighbor plants.
 However, the Partial Least Squares Path Model revealed that only flower
 size (an estimate of nectar accessibility) had a significant effect on the
 intensity of nectar robbing, with low soil moisture triggering a
 morphological mismatch between flowers and the primary pollinators
 bumblebees, prompting them to shift to nectar robbing behaviors. Nectar
 robbing reduced all components of male and female plant reproduction
 explored by up to 45%.  Synthesis: This study provides new
 insight into how soil moisture influences plant-animal interactions,
 influencing the behavior of floral visitors from mutualism to antagonism,
 and highlights that future soil water availability caused by global
 climate change may not only directly affect plants but also indirectly
 affect plants through changes in species interactions.
description: # Soil moisture influences nectar robbing and plant fitness in a primrose
 species Dataset DOI: [10.5061/dryad.1ns1rn95c](10.5061/dryad.1ns1rn95c) ##
 Description of the data and file structure This dataset was collected for
 revealing the effects and underlying mechanisms of soil moisture on the
 intensity of nectar robbing (a common behavioral interaction between
 plants and pollinators) and plant fitness in natural populations of
 *Primula florindae* on the southeast Tibetan Plateau. ### Files and
 variables #### File 1: **Soil moisture and nectar robbing intensity**
 **Description:** The data were used to test the direct effect of soil
 moisture on nectar robbing intensity‌ at the plot level. #### File 2:
 **PLS-PM analysis data** **Description:** The data were used to examine
 the pathways through which soil moisture affects nectar robbing based on
 partial least squares structural equation modeling (PLS-PM). #### File 3:
 **Flower longevity** **Description:** The data were used to examine the
 effects of nectar robbing treatment on floral longevity in *P. florindae*.
 #### File 4: **Pollen viability** **Description:** The data were used to
 examine the effects of nectar robbing treatment on pollen viability in *P.
 florindae*. #### File 5: **Pollen export** **Description:** The data were
 used to examine the effects of nectar robbing treatment on pollen export
 in *P. florindae*. #### File 6: **Seeds per fruit** **Description:** The
 data were used to examine the effects of nectar robbing treatment on seeds
 production in *P. florindae*. #### File 7: **Plant diversity in plots**
 **Description:** The data were used to analyze the diversity of nectar
 source plants within sampling plots. ##### Variables * "Year"
 refers to the year (2021 and 2022) when the effect of soil moisture on
 nectar robbing intensity is tested. * "Sampling date" refers to
 the specific date for measuring soil moisture and calculating nectar
 robbing rate. * "Plot" refers to the 2×2 m quadrats used for
 observing various indicators in the population of *Primula florindae*,
 with a total of 10 quadrats established. * "‌Soil moisture‌"
 refers to the soil water content measured at a depth of 6 cm using a soil
 three-parameter instrument‌. Measurement unit = VWC, %. * "‌Robbed
 flowers‌" refers to the number of nectar-robbed flowers recorded
 within each quadrat during the observation day‌. Measurement unit =
 number. * "‌Total flowers‌" refers to the total number of
 non-withered flowers recorded within the quadrats during the observation
 day‌. Measurement unit = number. * "Nectar robbing
 intensity" "Nectar robbing intensity"‌ refers to the
 proportion of nectar-robbed flowers within a quadrat, calculated as the
 total number of robbed flowers divided by the total number of non-withered
 flowers‌.  * "Species richness"‌ refers to the number of
 flowering species within the quadrat that share pollinators with *Primula
 florindae*. Measurement unit = number. * "Pielou evenness"
 refers to the evenness of flowering species within the quadrat that share
 pollinators with *Primula florindae*. * ‌"Shannon"‌ refers to
 the Shannon diversity index of flowering species within the quadrat that
 share pollinators with *Primula florindae*, which quantifies both species
 richness and evenness in the community‌.  * "Nectar volume"‌
 refers to the average volume of nectar produced per flower within the
 quadrat. Measurement unit = μL. * "Nectar sugar concentration"‌
 refers to the average sugar concentration in nectar produced per flower
 within the quadrat. Measurement unit = %. * "Corolla tube width"
 refers to the width of corolla tube, and was calculated as the mean of the
 maximum diameter measured on the first three open flowers on each
 individual within the quadrat, to the nearest 0.01 mm. Measurement unit =
 mm. * "Flower width" refers to the width of flower, and was
 calculated as the mean of the maximum diameter measured on the first three
 open flowers on each individual within the quadrat, to the nearest 0.01
 mm. Measurement unit = mm. * "Flower length" refers to the
 length of flower, and was calculated as the mean of the maximum length
 measured on the first three open flowers on each individual within the
 quadrat, to the nearest 0.01 mm. Measurement unit = mm. *
 ‌"Morph"‌ refers to the style-length polymorphism in *Primula
 florindae*, categorized as ‌long-styled (L-morph)‌ and ‌short-styled
 (S-morph)‌ morphs‌. * ‌"Treat"‌ refers to ‌nectar robbing‌ and
 ‌non-nectar robbing treatments in the study. * "Floral
 longevity" refers to the duration from start of flowering to flower
 wilting for each targeted flower. Measurement unit = day. * "Pollen
 viability" refers to the mean proportion of viable pollen
 grains. Measurement unit = %. * "Pollen export", the amount of
 pollen exported was calculated as the difference between the amounts from
 the anthers collected from the intact buds and that in the robbed or
 unrobbed treatment. Measurement unit = number. * "Seeds per
 fruit"  refers to the average number of seeds produced by per fruit.
 Measurement unit = number.