DOI: 10.5061/dryad.rfj6q57bw
title: Heterospecific pollen deposition is positively associated with reproductive success in a diverse hummingbird-pollinated plant community

description: Heterospecific pollen deposition (HPD) is ubiquitous across plant
 communities, especially for generalized species which use a diversity of
 pollinators, and may have negative effects on plant reproduction. However,
 it is unclear whether temporal changes in the co-flowering community
 result in changes in HPD patterns. Moreover, community-level studies are
 required to understand which factors influence HPD and how the
 reproduction of different species is affected. We investigated the
 temporal variation of HPD, its relationship with level of specialization
 on pollinators and floral phenotypic specialization, and its association
 with reproductive success (pollen limitation and fruit set) in 31
 hummingbird-pollinated plant species in a tropical Campo Rupestre. We
 found seasonality in HPD, with species flowering in the dry season having
 greater diversity of heterospecific pollen on stigmas and a higher
 frequency of stigmas containing heterospecific pollen, compared to the
 rainy season. Stigmas of ecologically generalized species had more
 heterospecific pollen, while the relationship for ecologically specialized
 species depended on floral phenotype. Surprisingly, and in contrast to
 theory, we found a positive relationship between HPD and reproductive
 success. Our results indicate benefits of generalization and facilitation,
 in which sharing pollinators brings greater reproductive success via
 increased conspecific pollen deposition, even if it incurs more HPD. We
 demonstrated how assessing HPD at a community-level can contribute to
 understanding the ecological causes and functional consequences of
 pollinator sharing.
description: <i>Study
 Area</i> Data was
 collected between August 2017 and July 2018 in a 50 ha area of
 <i>Campo Rupestre</i> on the JK campus of the Federal
 University of Vales do Jequitinhonha and Mucuri (UFVJM) in Diamantina/ MG
 (18°11'48.23"S, 43°34'8.74" W). The sampling area is
 continuous with Biribiri State Park, a permanent preservation area of more
 than 16,000 ha. The climate is characterized as mesothermal Cwb type,
 according to Köppen-Geiger classification, being temperate humid with dry
 winters (April to September) and wet summers (October to March). The
 average altitude is 1,281 m with an average temperature of 18.8°C and
 average annual rainfall of 1,498 mm. <i>Campos Rupestres</i>
 are regions with herbaceous shrub vegetation established in rocky outcrops
 with heterogeneity that allows the establishment of several plant species
 with common characteristics among hummingbird-pollinated
 plants. <i>Characterization of the
 plant-hummingbird community</i> The observations
 of plant species visited by hummingbirds were made every week over a year
 in two 500m x 10m transections, totalling one hectare of sampling area. In
 each transection, nine fixed plots of 2m<sup>2</sup> were used
 for the observation sessions. Each observation session lasted 20min.
 Observations took place twice a week, with a duration of three hours (nine
 observation sessions), with morning (09:00 – 12:00) and afternoon (13:00 –
 16:00) observations, totalling 288 observation hours. For interaction
 observations, 80x30 binoculars were used.
 <i>Ecological and phenotypic
 specialization</i> We focused on
 number of hummingbird partners as a measurement of ecological
 specialization. This is because interactions were recorded regardless of
 the flower availability of each plant species in each plot. A sampling
 effort of 15 hours per species (regardless of flower abundance) was shown
 to be sufficient to describe plant-hummingbird interactions
 (Vizentin-Bugoni et al. 2016). Accordingly, sampling effort was
 approximately 20 hours for each plant species, distributed across the
 phenology of each species.  We classified each species following the
 concept of ecological specialization (Ollerton et al. 2007, Ollerton
 2021): ecologically specialized (pollinated by one hummingbird species)
 and ecologically generalized (pollinated by more than one hummingbird
 species). The
 length and width of the opening of the corolla were measured as
 descriptors of phenotypic specialization. We measured corolla length and
 opening width from two flowers of five indviduals, totalling 10 flowers
 per species. To determine the accessibility of nectar to hummingbirds, we
 measured the effective length of the corolla, that is, from the receptacle
 to the corolla opening. We defined the corolla opening as the largest
 width of the floral tube entrance. Using these data we calculated the
 average corolla length and opening width for each
 species. <i>Pollen
 receipt patterns</i> Monthly collections of stigmas of the plant species were performed to evaluate conspecific pollen deposition (CPD) and heterospecific pollen deposition (HPD) for 12 months. We sampled HPD and CPD from 31 of the 57 hummingbird-visited species that were flowering during the collection period (we excluded species with less than three flowering individuals). The samples were collected at the end of flower anthesis (signs of wilting) and between 16:00 and 18:00 to ensure maximum pollen deposition. Two flowers were collected from five individuals per species, totalling 6-10 flowers per species per month. We used this sampling scheme in order to include more species per month (several species were represented only by 5-10 flowering individuals per month) and to avoid oversampling abundant species. We averaged samples per individual. The collection of stigmas was distributed along the flowering period of each plant species, sampling 20-116 stigmas per species. Slides of the stigmas were mounted using glycerin gelatin stained with basic fuchsin for better visualization of pollen under optical microscopy. In addition, slides with pollen from anthers of those 31 species were mounted to construct a reference pollen library. Pollen grains were identified and quantified according to morphological characteristics and classified as conspecific and heterospecific. We calculated the mean CPD/HPD intensity (amount of conspecific or heterospecific pollen) and HPD frequency (proportion of stigmas containing heterospecific pollen) per species (lumping all stigmas collected for the whole 12 months). We have not included CPD frequency because most stigmas contained conspecific pollen (96% of stigmas on average per species). Additionally, we also calculated the proportion of HPD relative to the total pollen load (HPD + CPD) per plant species (hereafter ‘HPD proportion’).
description: Datasets of “Heterospecific pollen deposition is positively
 associated with reproductive success in a diverse hummingbird-pollinated
 plant community” Published in Oikos
 DOI: https://doi.org/10.1111/oik.08714
 Authors: Sabrina Lopes, Pedro J Bergamo, Steffani Najara, Jeff
 Ollerton, Thiago Santos, André Rech Funding: PJB thanks
 CNPq (152417/2020-6 fellowship) and FAPERJ (E-26/201.867/2020). AR and SL
 thanks CNPq (Grant Proc. 400904/2019-5 and Scholarship Proc. 5682018
 respectively), SN thanks CAPES (Financial code 001), AR thanks FAPEMIG
 (Proc. RED-00253-16).  Two datasets are described
 here: 1) species_data.xlsx contains species-level
 metrics of pollen deposition, corolla morphology, interaction with
 hummingbird pollinators and reproductive success This
 dataset contains the following variables: 
 species
 plant species
 name genus plant genus name
 
 family 
 plant family name 
 HP_intensity
 mean intensity
 of heterospecific pollen deposition 
 
 HP_intensity_rounded mean intensity of heterospecific
 pollen deposition - rounded values 
 
 HP_frequency mean frequency of stigmas
 containing heterospecific pollen grains 
 
 CP_intensity mean intensity of conspecific
 pollen deposition CP_frequency 
 mean frequency of stigmas
 containing conspecific pollen grains 
 
 HP/CP_proportion proportion of intensity of
 heterospecific pollen deposition in relation to conspecific pollen
 deposition corolla_length
 corolla length
 in milimeters corolla_opening
 width of corolla
 opening in milimeters 
 richness_of_humingbird_pollinators number of hummingbird pollinator
 species partners specialization
 specialization
 (specialized if interacting with one hummingbird species; generalized if
 interacting with more than one hummingbird species) 
 
 pollen_limitation level of pollen limitation (ratio
 of the difference between fruit set after pollen supplementation and
 natural fruit set in relation to the fruit set after pollen
 supplementation)  pollen_limitation_rounded
 rounded values
 of the level of pollen limitation 
 
 natural_fruitset fruit set (fruits / flowers) of
 flowers exposed to pollinators  
 
 natural_fruitset_rounded rounded values of the level of
 natural fruit set 
 2) HP_temporal.xlsx This
 dataset contains the intensity and frequency of heterospecific pollen
 deposition of each plant species in each month: 
 species
 plant species
 name month month of data collection
 
 season 
 season (dry or rainy) 
 
 HP_intensity number of heterospecific pollen
 grains deposited onto stigmas 
 HP_frequency
 number of
 stigmas containing heterospecific pollen grains 
 
 HP_intensity_rounded number of heterospecific pollen
 grains deposited onto stigmas - rounded values 
 
 HP_frequency_rounded number of stigmas containing
 heterospecific pollen grains - rounded values