DOI: 10.5061/dryad.qv9s4mwpx
title: Benefits of extended maternal care in a mass-provisioning bee at the cusp of sociality

description: Many invertebrates exhibit parental care, posited as a precursor to
 sociality. For example, solitary foundresses of the facultative social
 orchid bee Euglossa viridissima guard their brood for 6+ weeks before
 offspring emerge, when the nest may become social. Guarding comes at the
 fitness cost of foregoing the production of additional offspring. Yet it
 is unclear whether guarding (extended maternal care: EMC) can enhance
 offspring survival such that it outweighs those fitness costs, or if it is
 a consequence of the selective benefits of sociality, including extended
 female longevity. Experimental removal of solitary foundresses from nests
 of E. viridissima revealed an immediate fitness loss: decreased offspring
 survival. A mathematical model exploring the trade-off between EMC versus
 non-guarding revealed that EMC is advantageous if the nest established is
 greater than a threshold of 1.7-12.5 days. For much of the parameter
 space, EMC may be a precursor to sociality. Below this threshold, our
 model suggests that social fitness gains (acquiring helper daughters) need
 to be invoked to explain the evolution of EMC. Enhanced survival of
 offspring through guarding and nest inheritance may nevertheless ease
 conditions for the evolution of sociality by favouring extended adult
 longevity and brood care in incipient social species like E.
 viridissima.
description: Removal Experiment: Nests with females that had finished brood
 production were randomly assigned to one of two categories: treatment (T)
 or control (C) in a paired design (see below), with n = 11 pairs of nests.
 Females in control nests remained with their brood whilst females in
 treatment nests were removed. Nest entrances were always naturally closed
 at the time of experimental female removal, which created similar starting
 conditions for control (C) and treatment (T) nests. A pair of nests (one
 C, one T) was initiated at approximately the same time (+/- 7 days) to
 account for seasonal variation in environmental conditions. Nests were
 then monitored for adult brood emergence and the presence of intruders
 three times a day until all broods had emerged or until the last brood
 cell was considered to have failed. Presence of
 Intruders: Nests of the Removal Experiment were monitored for the presence
 of Intruders three times a day until all brood had emerged or until the
 last brood cells were considered to have failed, as the number of days in
 which intruders were found within the nest divided by the number of
 observation days per nest. The number of days in which intruders were
 found in the nest, was used rather than the number of intruders per day to
 avoid counting the same intruder multiple times on the same day.
 Intranidal Behaviour: A total of 12 solitary nests (5 control
 nests from the removal experiment plus 7 additional nests that were not
 included in the removal experiment) were observed, while females were in
 the guarding phase. Nests were brought into a darkroom inside a laboratory
 at ambient temperature. Females were observed under a red light through
 the glass roof of their nest, with the nest entrance always closed
 naturally from within. Observations commenced on the day after a female
 had finished brood cell provisioning, and each nest was observed on 2.75 ±
 0.35 (mean ± SE) days (range 1-4 days). Once a new adult eclosed from the
 first brood cell, observations ceased. Observations were carried out
 across the day (09:00 to 17:00) to avoid diurnal bias and to record
 behaviours that might be related to daily weather conditions. Observations
 were performed at different stages of brood development. After bringing a
 nest into the lab, females were allowed to acclimatize to the new
 environment for five minutes, and then female behaviour was observed for
 two 15-minute periods, with a five-minute break between periods. Then a
 nest was returned to its original location in the field. All behaviours
 that occurred during observations were scored and their duration and
 number of occurrences were noted. Behaviours were then grouped into five
 categories: brood care (b) such as brood cell grooming and physical
 contact with brood cells, nest defence (d), including passive behaviours
 such as sitting at the nest entrance and active behaviours directed
 towards intruders, nest maintenance (m), self-grooming (g), and other
 (o). Modelling Alternative Strategies: <br>To
 evaluate whether the immediate solitary benefits of guarding are
 sufficient to account for its expression, we modelled the solitary
 pay-offs of two alternative strategies: guarding the brood by staying in
 the nest during the period of brood development (guarding strategy i.e.
 EMC), and deserting to found additional nests in which to produce more
 brood (deserting strategy).
description: # Benefits of extended maternal care in a mass-provisioning bee at the
 cusp of sociality
 [https://doi.org/10.5061/dryad.qv9s4mwpx](https://doi.org/10.5061/dryad.qv9s4mwpx) ## Description of the data and file structure ### Files and variables #### File: Final\_Sumission\_R\_Code\_18092024.txt **Description:** R Code for statistical analyses, figures, and modelling #### File: Final\_Submission\_SupplementaryMaterial\_DataFiles\_18092024.xlsx **Description:** Data files used for statistical analyses, figures, and modelling. R code indicates where each file was used This file contains datasets for graphs and statistics presented in the article and the Supplementary Material. ### Worksheet--&gt; Removal\_Experiment: Source data for descriptive statistics and analyses associated with the Removal Experiment variables, units, acronyms: treatment: treatment to which each nest was assigned --&gt; F= control (female present), NF= treatment (female removed) pair: identifier of nest pair, same letters = same nest pair n_successful_cells: number of cells that successfully emerged n_total_cells: total number of cells produced ratioSuc/total: number of successfully emerged cells divided by total number of cells ratioNonsuc/total: number of failed cells divided by total number of cells n_Nonsuc: number of failed cells(no adult bee emerged) nest_initiation_date: the date when the nest was initiated by the foundress female ### Worksheet--&gt;Removal\_Experiment\_Longformat: Source data Figure 2: Number of initially produced and successfully emerged brood cells in nests in which the mother was present or experimentally removed variables, units, acronyms: cells: indicates whether the following column ("numbers") shows the number of successfully emerged cells or the total number of cells numbers: number of cells in that nest pair and treatment ### Worksheet--&gt;Nest\_Intruders: Source data for descriptive statistics and analyses associated with nest intruders Source data Figure 3: Intensity of nest intrusion variables, units, acronyms: OtherAnimals: number of intruders categorized as "Others" Flies: number of intruders categorized as "Flies" Wasps: number of intruders categorized as "Wasps" Ants: number of intruders categorized as "Ants" OtherBees: number of intruders categorized as "Other bees" ConspecificsInNest: number of intruders categorized as "Other Euglossa" found in the nestbox ConspecificsStealing: the number of intruders categorized as "Other *Euglossa*" were observed stealing nesting material from inside the nestbox ("ConspecificsInNest" and "ConspecificsStealing" grouped together in further analyses) Sum: sum of all intruders day: number of days that the nest was observed days_after_brood_production: the number of days that the nest was observed after brood production was finished successfull_cells: number of successfully emerged cells ratio: "Sum" divided by "days_after_brood_production" ### Worksheet--&gt;Behaviour\_Data: Source data for descriptive statistics of Intranidal Behaviour observations variables, units, acronyms: independent_observation: number of observation session (o1= observation session 1) observation: identifier for observation session nest: an identifier for each nestbox female: identifier for each female days_after_brood_end: day (after the female finished brood production) of the observation session behaviour_category: category in which observed behaviour was grouped --&gt; m=nest maintenance, o=other, b= brood care, s= self hygienic behaviour, d= nest defence duration_in_s: duration of observed behaviour in seconds time_of_day: time that the observation session started date: date of observation session number_of_cells: total number of cells produced in the nest combine: variable that combines "behaviour_category" and "number_of_cells" ### Worksheet--&gt;Behaviour\_Summary: Source data for glmm analyses of Intranidal Behaviour observations variables, units, acronyms: n_cells: total number of cells produced in the nest days_brood: day (after the female finished brood production) of the observation session b_per_cell: brood care behaviour (in seconds) divided by n_cells d_per_cell: nest defence behaviour (in seconds) divided by n_cells m_per_cell: nest maintenance behaviour (in seconds) divided by n_cells o_per_cell: other behaviours (in seconds) divided by n_cells s_per_cell: self-hygienic behaviour (in seconds) divided by n_cells ### Modelling Alternative Strategies: R Code for theoretical modelling of the guarding vs deserting strategy, variables used in models are based on Table 1 of the article. R Code for Figure 4 (Curve indicating the evolutionary dynamics of guarding vs. deserting strategy). \---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ### Supplementary Material: #### Figure S1: Number of brood cells built per *Euglossa viridissima* nest across the study period Source data: Removal_Experiment #### Figure S2: Observation of nest pairs and the respective occurrence of intruders from the start of the experiment in October 2017 until the end of the experiment in December 2018 Source data: Nest_Invaders_Merge; Nest_Invaders_Timeline variables, units, acronyms: Nest_Invaders_Merge: Nest_initiation: the date when the nest was initiated by the foundress female Intruder: description of intruder observed in nest or nest identifier (treatment_nestbox --&gt; e.g., control_AA22) Date: Date on which intruder was observed (not applicable for nestboxes =NA) Month: Month in which intruder was observed (not applicable for nestboxes =NA) Year: Year in which intruder was observed (not applicable for nestboxes =NA) event: the combination of variables "Intruder" and "sequence" Intruder_type: Intruder category Date.comb: the combination of variables "Intruder_type" and "Date"; for nestboxes--&gt;combination of "Intruder-type" and "Nest_initiation" sequence: sequence of data entries, when dataset is sorted by: pair-&gt;Treatment-&gt; Intruder_type, each section of intruder observations starts with information about nestboxes of the respective nest pair Nest_Invaders_Timeline: event1: equals the variable "event" without "sequence" group: variable used to position the data entries along the y-axis of Figure S2 start: date of nest initiation (for nestboxes) and date when intruder was observed (for intruders) end: the date when observations ended (for nestboxes) and date when an intruder was observed (for intruders; equals "start") color: specifies colour used in Figure S2 Datafiles called "timeline.data.txt" and "timeline.total.txt" are created in the process, and then used for downstream code datafile "timeline.total" then needs to be manually split into two files: one containing timeline.lines (= information about nests); the other containing timeline.points (=information about intruders) #### Figure S3: Intensity of intrusion inside *Euglossa viridissima* nest boxes Source data: Nest_Intruders_Groups variables, units, acronyms: Intruders: Intruder category Occurence_total_period: total number of intruders within this category observed throughout the observation period ratio: "Occurence_total_period" divided by "days_after_brood_production" #### Figure S4: Time spent on brood care behaviour as a function of a) the number of brood cells and b) the age of the developing brood Source data: Behaviour_Summary #### Figure S5: R Code for Figure S5 #### Worksheet--&gt;Summary\_Fitness Source data for the extended model, including brood size variables, units, acronyms: nest.c: identifier nestbox for control nests T: time that control bees needed for brood production(started building the first cell, until the last cell was capped) B: total number of produced brood cells in control nests W: guarding time for control nests B.emerged: number of successfully emerged brood cells in control nests nest.t: identifier nestbox for treatment nests t: time that treatment bees needed for brood production(started building first cell, until the last cell was capped b: total number of produced brood cells in treatment nests b.emerged: number of brood cells that successfully emerged in treatment nests B.mean: the average values of B for each pair T.mean: the average values of T for each pair H: hatching rate of control nests (calculated as the number of emerged cells divided by the total number of cells) h: hatching rate of treatment nests (calculated as the number of emerged cells divided by the total number of cells) H2h: "H" divided by "h" #### Worksheet--&gt; OR41\_Sequencing: Or41 sequences of females were used for species identification and reference sequences of *E. dilemma*, *E. viridissima* and *E. mixta* \--&gt; lines starting with "&gt;" indicate reference species (Edil= *Euglossa dilemma*, Evir= *E. viridissima*, Mixta= *E. mixta*) or unique identifier of the sequences sample \--&gt; lines below show respective Sanger sequence at the olfactory receptor gene or41 #### General notes:  * "selfhygiene" behaviour in datasets and code is termed as "grooming" in the associated article * "other" behaviours in datasets and code are termed "unspecified behaviours" in the associated article