Data from: The magnitude of Allee effects varies across Allee mechanisms, but not taxonomic groups
Data files
Feb 16, 2024 version files 1.66 MB

Allee_effect_meta_analysis_effect_sizes.csv

Allee_effect_meta_analysis_literature.csv

Allee_effect_meta_analysis_raw_data.xlsx

README.md
Abstract
The Allee effect is a densitydependent 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., matefinding, predation, resource limitation), across a range of systems and taxa (e.g., plants, vertebrates, invertebrates). This metaanalysis 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 metaanalysis 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 metaanalysis 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.
README
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 metaanalysis models for Allee mechanism, taxa, and Allee effect type. Creates a forest plot of effect sizes (Figure 2).
Data
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Allee_effect_meta_analysis_effect_size.csv – a csv file containing the information for each study to run the metaanalysis 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 metaanalysis.
 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 metaanalysis
 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 metaanalysis. 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
Methods
Studies were screened to determine if they met the metaanalysis 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.