DOI: 10.5061/dryad.15dv41nzg
title: Nectar values from: Turnover in floral composition explains species diversity and temporal stability in the nectar supply of urban residential gardens

description: Residential gardens are a valuable habitat for insect pollinators
 worldwide, but differences in individual gardening practices substantially
 affect their floral composition. It is important to understand how the
 floral resource supply of gardens varies in both space and time so we can
 develop evidence-based management recommendations to support pollinator
 conservation in towns and cities. We surveyed 59 residential gardens in
 the city of Bristol, UK, at monthly intervals from March to October. For
 each of 472 garden surveys, we combined floral abundances with nectar
 sugar data to quantify the nectar production of each garden, investigating
 the magnitude, temporal stability, and diversity and composition of garden
 nectar supplies. We found that individual gardens differ markedly in the
 quantity of nectar sugar they supply (from 2 g to 1662 g), and nectar
 production is higher in more affluent neighbourhoods, but not in larger
 gardens. Nectar supply peaks in July (mid-summer), when more plant taxa
 are in flower, but temporal patterns vary among individual gardens. At
 larger spatial scales, temporal variability averages out through the
 portfolio effect, meaning insect pollinators foraging across many gardens
 in urban landscapes have access to a relatively stable and continuous
 supply of nectar through the year. Turnover in species composition among
 gardens leads to an extremely high overall plant richness, with 636 taxa
 recorded flowering. The nectar supply is dominated by non-natives, which
 provide 91% of all nectar sugar, while shrubs are the main plant life form
 contributing to nectar production (58%). Two thirds of nectar sugar is
 only available to relatively specialised pollinators, leaving just one
 third that is accessible to all. Synthesis and applications. By measuring
 nectar supply in residential gardens, our study demonstrates that
 pollinator-friendly management, affecting garden quality, is more
 important than the size of a garden, giving every gardener an opportunity
 to contribute to pollinator conservation in urban areas. For gardeners
 interested in increasing the value of their land to foraging pollinators
 we recommend planting nectar-rich shrubs with complementary flowering
 periods and prioritising flowers with an open structure in late summer and
 autumn.
description: <strong>Data: Nectar sugar production of plant taxa (data available from 01 August 2022)</strong> <strong>[N.B. See 'Related Works' for data on flower counts, garden level data and temporal stability simulations]</strong> <b>Nectar_sugar_per_taxon.xlsx </b>- nectar sugar values (micrograms of sugars per 24 hours per floral unit) and floral traits used in predictive modelling for each plant taxon. Tab 1 (‘Sugar_values’) = Nectar sugar production per 24 hours (<b>‘sugar_per_floral_unit_ug’</b>) for each <b>‘taxon’</b> as well as <b>‘genus’</b> plant<b> ‘family’</b>, <b>‘vernacular_name’</b>, <b>‘native_status’</b>, <b>‘life_form’</b>, ‘<b>flower_structure</b>’, ‘<b>floral_unit_definition</b>’, ‘<b>sugar_data_type</b>’, ‘<b>sugar_data_source</b>’ and ‘<b>comments</b>’. Tab 2 (‘Predictive_modelling’) = Floral traits <b>(‘plant_family’</b>,<b> ‘floral_unit_type’</b>,<b> ‘flower_shape’</b>,<b> ‘floral_unit_size’</b>) for each <b>‘taxon’</b>, with <b>‘sugar_per_floral_unit_ug’</b> given for species with empirical values (shown in <b>‘sugar_data_type’</b>). Flower shape source information is given in <b>‘Muller_class_BiolFlor’ </b>and<b> ‘Muller_class_source’</b>.