DOI: 10.5061/dryad.nvx0k6f48
title: Data from: Double mutualism: Dual rewards or redundancy? Insights from the interactions between mistletoes and their avian partners in the tropical hotspot of Southwest China

description: Mistletoes, recognized as keystone species, supply plentiful floral and
 fruit resources for birds, thereby facilitating mutualistic interactions
 in pollination and seed dispersal. Some avian species are “double
 mutualists”, engaging in both functions. However, their precise roles and
 effectiveness as mutualists remain inadequately understood. In this study,
 we conducted 690 hours of video-recorded observations of avian pollinators
 and dispersers of the mistletoe species Dendrophthoe pentandra
 (Loranthaceae) across three sites in the seasonal tropical forests of
 Xishuangbanna, a biodiversity hotspot in Southwest China. We also
 performed a phylogenetic analysis of avian traits, including beak length,
 body length, and body mass. Our findings documented a total of 833 visits
 by 13 bird species from 8 families, with 11 species probing flowers (528
 visits) and 7 species consuming fruits (43 visits). Three species –
 Dicaeum minullum, D. ignipectus, and Zosterops simplex – were identified
 as double mutualists, as they visited the plants during both the flowering
 and fruiting phases. Notably, double-mutualist birds accounted for 87.5%
 of flower visits and 95.5% of fruit visits. The generalist frugivore Z.
 simplex was the most frequent floral visitor, while the
 mistletoe-specialist frugivore D. minullum emerged as the primary
 pollinator and seed disperser across all sites, demonstrating the highest
 efficiency. All double-mutualist species exhibited high mobility and
 specialized morphology, characterized by small to medium-sized, slightly
 curved beaks and lower body mass, which contributed to greater
 effectiveness in pollination and seed dispersal, confirming their roles as
 “double mutualists” of this plant. Phylogenetic analysis indicated that
 ancestral mistletoe-associated birds typically possessed short to medium
 beaks and medium body masses, whereas double-mutualist birds appear to
 have evolved shorter beaks and smaller bodies. Our findings show that
 mistletoe-associated birds that perform both pollination and dispersal are
 morphologically adapted to the floral structure of mistletoes, fostering
 closer mutualistic relationships with host plants and enhancing fitness of
 both plants and their avian partners.
description: # Data from: Double mutualism: Dual rewards or redundancy? Insights from
 the interactions between mistletoes and their avian partners in the
 tropical hotspot of Southwest China Dataset DOI:
 [10.5061/dryad.nvx0k6f48](10.5061/dryad.nvx0k6f48) ## Description of the
 data and file structure host_mistletoe: dataset from section *Biological
 traits and reproductive phenology of mistletoe* of MATERIAL AND METHODS
 Raw_visit: dataset from section *Visitation of avian pollinators and
 frugivores* of MATERIAL AND METHODS fruit_crop_size: dataset from section
 *Fruit crop size and quantity of seeds removed* of MATERIAL AND METHODS
 mistletoe_bird_trait: dataset from section *Flower, fruit and bird
 morphology* of MATERIAL AND METHODS passerine: phylogeny from section
 *Phylogenetic relationships and ancestral state reconstruction of birds*
 of MATERIAL AND METHODS ### Files and variables #### File:
 host_mistletoe.xlsx **Description:** contains columns with data on the
 following: ##### Variables * site: site * plot: plot * host_id: host
 identifier * host_species: host species * host_family: host family *
 host_growth_form: growth form of host; It can be "Tree" or
 "Woody vine". * host_fruit_type: fruit type of host; It can be
 "fleshy" or "not fleshy". * host_deciduousness: host
 deciduousness; It can be "Evergreen" or "Deciduous". *
 host_DBH: diameter at breast height of host, unit: centimeter *
 host_height: host height, unit: meter * host_crown_size: host crown size,
 unit: square meter * host_latitude: latitude of host * host_longitude:
 longitude of host * host_elevation: elevation of host, unit: meter *
 host_infection_intensity: host infection intensity, defined as the number
 of mistletoes per host tree * mistletoe_id: mistletoe identifier *
 mistletoe_species: mistletoe species * mistletoe_height: mistletoe height,
 unit: meter * mistletoe_crown_size: mistletoe crown size, unit: square
 meter * mistletoe_light: light levels for each mistletoe; Light levels
 were visually assessed for each mistletoe on a standardized scale ranging
 from 0 to 10. A light score of 10 would be assigned to a mistletoe whose
 entire foliage was exposed to full sunlight throughout the day, and a
 score of 0 would be assigned when the entire foliage was in dense shade
 throughout the day. * Flowering2018: flowering period of the mistletoe in
 2018, unit: day; "n/a" in the column "Flowering2018"
 means no flowering was observed on this mistletoe in 2018. * Fruiting2018:
 fruiting period of the mistletoe in 2018, unit: day; "n/a" in
 the column "Fruiting2018" means no fruiting was observed on this
 mistletoe in 2018. * Flowering2019: flowering period of the mistletoe in
 2019, unit: day; "n/a" in the column "Flowering2019"
 means no flowering was observed on this mistletoe in 2019. * Fruiting2019:
 fruiting period of the mistletoe in 2019, unit: day; "n/a" in
 the column "Fruiting2019" means no fruiting was observed on this
 mistletoe in 2019. #### File: Raw_visit.xlsx **Description:** contains
 columns with data on the following: ##### Variables *  Site: site *
 Observers: observer * Years: years * Date: date * Host_ID: host
 identifier; "n/a" in the column "Host_ID" means the
 host identifier was not recorded. * Mistletoe_ID: mistletoe identifier;
 "n/a" in the column "Mistletoe_ID" means the mistletoe
 identifier was not recorded. * Bird_species: identified bird species *
 Behavior: specific behaviors of the bird; It contains two categorical
 variables: "probe_flower" and "forage_fruit".
 "probe_flower" means probing of corollas, indicative of
 potential pollination. "forage_fruit" means the plucking of
 fruits, suggestive of seed dispersal. * Number_of_flowers/fruits: the
 number of flowers probed or fruits consumed * duration: duration of each
 visit for each bird, unit: seconds * Phenophase: phenophase; It contains
 four categories: "Flowering2019", "Fruiting2019",
 "flowering2015", and
 "fruiting2015". "Flowering2019" means the visit
 happened in the flowering stage in 2019. "Fruiting2019" means
 the visit happened in the fruiting stage in
 2019. "flowering2015" means the visit happened in the flowering
 stage in 2015. "fruiting2015" means the visit happened in the
 fruiting stage in 2015.  * duration_per_visit: mean duration per flower at
 each visit for each bird, unit: seconds #### File: fruit_crop_size.xlsx
 **Description:** contains columns with data on the following: #####
 Variables * site: site * plot: plot * host_id: host identifier *
 mistletoe_id: mistletoe identifier * exocarp: the number of exocarps found
 in the traps * ripe_fruit: the number of ripe fruits found in the traps
 #### File: mistletoe_birds_trait.xlsx **Description:** contains columns
 with data on the following: ##### Variables * Bird_species: bird species *
 Gender: gender; "n/a" in the column "Gender" means the
 gender is not recorded in the specimen. * Specimen_Number: specimen number
 * BodyWeight(g): the weight of bird body, unit: gram; "n/a" in
 the column "BodyWeight(g)" means the body weight is not recorded
 in the specimen. * BodyLength(cm): the length of bird body, unit:
 centimeter; "n/a" in the column "BodyLength(cm)" means
 the body length is not recorded in the specimen. * BeakLength(mm): the
 length of bird beak, unit: millimeter #### File: passerine.nex
 **Description:** Phylogenetic tree of 14 avian species based on Bayesian
 methods