DOI: 10.5061/dryad.2ngf1vhvj
title: Data from: The magnitude of Allee effects varies across Allee mechanisms, but not taxonomic groups

description: The Allee effect is a density-dependent phenomenon in which individual
 fitness increases as population density increases at low population
 densities. Over the past few decades, a growing number of studies have
 identified Allee effects in populations using experimental approaches and
 statistical modelling techniques. These studies have investigated multiple
 Allee mechanisms (e.g., mate-finding, predation, resource limitation),
 across a range of systems and taxa (e.g., plants, vertebrates,
 invertebrates). This meta-analysis aims to synthesize studies that
 experimentally manipulated population density and measured either per
 capita population growth or fitness components, with the goal of
 determining whether the “magnitude” of the Allee effect (defined here as
 the correlation between population density and population growth or
 fitness) varies with Allee mechanism across taxonomic groups. A total of
 2305 studies were screened, and 62 of these studies met our meta-analysis
 inclusion criteria. Within these 62 studies, 155 effect sizes encompassing
 9 different Allee mechanisms were identified across 5 broad taxa. When
 grouped by Allee mechanism and taxa, the magnitude of the Allee effect
 differed across mechanisms, whereas taxonomic group was less useful at
 explaining variation in the magnitude of Allee effects. Of the nine Allee
 mechanisms identified, interspecific competition was associated with the
 strongest Allee effects, followed by fear, pollen limitation and mate
 limitation. These findings suggest that Allee effects may be more
 dependent on mechanism than taxa and may function similarly within
 different taxonomic groups. However, as the majority of experimental Allee
 effect studies included in this meta-analysis focused on plants and
 invertebrates, more research is needed on Allee effects in other taxonomic
 groups to confirm this conclusion. This first quantitative synthesis of
 Allee effect research in ecology offers novel insight into how Allee
 mechanisms affect the manifestation of Allee effects in populations,
 providing important information for ecologists and conservation managers.
description: Studies were screened to determine if they met the meta-analysis
 inclusion criteria (an experimental manipulation of population density).
 Data for these studies was obtained from supplementary material or from
 online repositories, or it was extracted from the candidate studies either
 directly (from text, tables etc.) or by reverse engineering figures using
 Engauge Digitize software.
description: Eva J. Muir, Marc J. Lajeunesse, Andrew, M. Kramer
 \--------------------------------------- Data for: The magnitude of Allee
 effects varies across Allee mechanisms, but not taxonomic groups
 \--------------------------------------- File list Scripts
 \===================== Allee_effect_meta_analysis_code.R Data
 \===================== Allee_effect_meta_analysis_effect_size.csv
 Allee_effect_meta_analysis_literature.csv
 Allee_effect_meta_analysis_raw_data.xslx
 \--------------------------------------- Description Scripts
 \===================== Allee_effect_meta_analysis_code_mechanism.R – R
 file to run the meta-analysis models for Allee mechanism, taxa, and Allee
 effect type. Creates a forest plot of effect sizes (Figure 2). Data
 \===================== Allee_effect_meta_analysis_effect_size.csv – a csv
 file containing the information for each study to run the meta-analysis
 models. \- SEARCH_ID: Serach ID (refer to
 Allee_effect_meta_analysis_literature.csv; WOS = Web of Science, SCO =
 SCOPUS, PRO= ProQuest) \- STUDY ID: Study ID (refer to
 Allee_effect_meta_analysis_effect_sizes.csv) \- EFFECT ID: Effect ID \-
 AUTHORS: Authors of original study that the data was extracted from \-
 YEAR: Year the original study was published \- DOI: The DOI of the study
 \- METHOD: Method used to calculate the effect size \- T_TEST: T value
 calculated from the test of quadratic significance (used to determine the
 method needed to calculate the effect size; NA means the data was not
 quadratic) \- DF: Degrees of freedom calculated from the test of quadratic
 significance (used to determine the method needed to calculate the effect
 size; NA means the data was not quadratic) \- P_VALUE: P value calculated
 from the test of quadratic significance (used to determine the method
 needed to calculate the effect size; NA means the data was not quadratic)
 \- N: Number of groups in the original study \- TAXA: Focal taxa of the
 original study \- MECHANISM: Allee mechanism identified in the original
 study \- ALLEE_TYPE: Allee effect type (demographic or component) \- Z:
 Fisher’s Z effect size \- V: Variance
 Allee_effect_meta_analysis_litearture.csv – an csv containing a list of
 all literature screened for inclusion in the meta-analysis. \- SEARCH_ID –
 Search ID number (WOS = Web of Science, SCO = SCOPUS, PRO= ProQuest) \-
 REVIEWER – Person who reviewed the study and determined whether or not to
 review the study for inclusion in the meta-analysis \- INCLUDE – Decision
 to review the study in detail \- AUTHORS – Authors of study \- TITLE –
 Title of study \- YEAR – Year of publication of study
 Allee_effect_meta_analysis_raw_data.xslx – an Excel workbook file
 containing the raw data extracted from the studies included in the
 meta-analysis. Each tab contains the data from one study, and the tab is
 named with the study ID number (refer to
 Allee_effect_meta_analysis_effect_sizes.csv for study IDs). The file also
 includes the formulas used to calculate the effect size for each study.
 Red cells indicate quadratic data that was removed from the analysis. All
 studies manipulated density: \- DENSITY - Densities used in the experiment
 \- DENSITY_2 - Squared density values \- LOW - Low density treatment (to
 be compared to a high density treatment) \- HIGH - High density treatment
 (to be compared to a low density treatment) Each study measured different
 response variables: \- PER CAPITA COCOON PRODUCTION - Number of cocoons
 produced per worm \- µ OF SEEDS - Mean number of seeds produced per flower
 in each floral treatment \- LARVAL SETTLEMENT - Proportion of larvae that
 successfully attached to substrate \- TIME TO ESTABLISHMENT - Time it took
 for bacteria colonies to establish \- NET DISTANCE TRAVELLED - Net
 distance travelled by individuals in mm \- SEEDS PER FRUIT - Number of
 seeds produced per fruit \- m EMBRYOS - Mean number of embryos produced
 per individual \- PARTURITION DATE - Number of days to reach parturition
 \- PROPORTION SEED SET - Proportion of flowers that produced seeds \-
 PROBABILITY OF EXTINCTION - Probability of a population going extinct \- m
 GROWTH RATE - Mean growth rate of different populations \- PERCENT LARVAL
 SURVIVAL - Percentage of larvae that survived in different populations \-
 PROPORTION SURVIVING JUVENILES - Proportion of juveniles that survived in
 different populations \- PROPORTION VIABLE SEEDS - Proportion of viable
 seeds produced by plants \- NUMBER OF EGGS PER INDIVIDUAL - Mean number of
 eggs produced by individuals in different populations \- PROPORTION EATEN
 - Proportion of individuals that died/were eaten \- NET REPRODUCTIVE RATE
 - Mean number of daughters produced per generation \- MEAN GROWTH - Mean
 population growth rate \- m OF EGGS - Mean number of eggs produced \-
 VISITS TO PLANT PER PLOT VISIT - Number of pollinator visits to each plant
 per plot visit \- VISITS TO PLANTS PER HOUR - Number of pollinator visits
 to each plant per hour \- VISITOR RICHNESS - Diversity of pollinators
 visiting each plot \- PROPORTION SURVIVAL - Proportion of individuals
 surviving in the population \- MEAN NUMBER OF SEEDS - Mean number of seeds
 produced per plant \- POPULATION GROWTH - Population growth \- m SEED SET
 - Mean number of seeds produced per plant \- SEED SET PER FLOWER - Mean
 number of seeds produced per flower \- PERCENT SEED SET - Percentage of
 plants that produced seeds \- PERCENT SURVIVAL - Percentage of surviving
 individuals in the population \- MEAN NUMBER OF GREEN FRUITS - Mean number
 of green fruits per flower and per plant \- PERCENT FERTILISATION SUCCESS
 - Percentage of gametes that were successfully fertilized \- m
 FERTILISATION - Mean fertilization rate \- LARVAL PER CAPITA GROWTH - Per
 capita population growth of larvae \- NUMBER OF SURVIVORS - Number of
 surviving individuals in the population \- REPRODUCTIVE SUCCESS - Number
 of nestlings that fledged from the nests each year \- PER FEMALE BREEDING
 PROB - Proportion of breeding adult females \- PER FEMALE BREEDING
 PRODUCTIVITY - Number of birds per adult female \- YEARLING SURVIVAL -
 Survival rate of yearlings \- JUVENILE SURVIVAL - Survival rate of
 juveniles \- ADULT SURVIVAL -Survival rate of adults \- MEAN TIME - Mean
 development time of larvae \- PER CAPITA BIRTH RATE - Number of births per
 individual \- TIME SPENT CALLING - Time spent calling for mates \- DENSITY
 & RELATIVE INTERACTION INDEX - Measures the intensity of facilitation
 between individuals \- REPRODUCTIVE OUTPUT - Number of new offspring
 produced over 2 weeks \- FECUNDITY - Weight of larvae \- BROODING LARVAE -
 Mean percentage of brooding larvae in the population \- MEAN BODY MASS -
 Mean body mass \- FLOWERING PLANTS - Number of flowering plants \- ACTIVE
 FLOWERS - Number of flowers per plant \- NEW LICE - Number of lice in the
 first and second infections \- FERTILISATION - Percentage of gametes
 successfully fertilized \- LARVAL PERIOD - Days taken for larvae to reach
 metamorphosis \- SEED SET - Number of seeds produced per plant \- PER
 CAPITA SURVIORSHIP - Number of individuals that survived parasitism \-
 POLLEN LIMITATION - Number of seeds produced per plant \- POPULATION
 GROWTH - Population growth rate \- GROWTH RATE - Increase in body size of
 individuals \- SETTLEMENT - Number of larvae that successfully attached to
 substrate