DOI: 10.5061/dryad.3f835vc
title: Data from: Applying Lanchester’s laws to the interspecific competition of coral reef fish

description: Lanchester’s laws of combat are a mathematical framework describing the
 relative contributions of individual fighting ability and group size to
 overall group fighting ability. Since 1993, several studies have attempted
 to apply this framework to interspecific dominance relationships between
 nonhuman animals. However, this prior work addressed only the corollaries
 of Lanchester’s laws rather than the laws themselves. Here, we directly
 test Lanchester’s linear and square law to explain interspecific
 competition of coral reef fish. First, we analyzed the relationship
 between body size and dominance to find a biologically accurate proxy of
 individual fighting ability. We then tested whether group fighting ability
 was linearly (linear law) or quadratically (square law) related to group
 size while accounting for the different fighting abilities of competing
 species. We found support for the linear law; however, both laws were
 outperformed by a simpler model that only included body size. After
 accounting for possible outliers and data limitations, we suggest that
 Lanchester’s linear law may prove useful for explaining interspecific
 competition in marine ecosystems.
description: Body to mass conversion
 dataThe a and b coefficients
 for body length-to-body mass conversion for the species of interest, as
 reported by Brooks (2011).body_to_mass_data.csvDominance matrix estimated from combined dataDominance matrix estimated after combining displacement data from live observation and video recordings.both_datasets_matrix.txtOne-on-one dominance matrix estimated from combined dataDominance matrix estimated exclusively from one-on-one interactions, including both those that were observed live and those that were recorded on video.both_datasets_one-on-one_matrix.txtDietary classificationDietary classification of the species of interest, as reported by Brooks (2011).diet.csvField body size dataBody size estimates of the species of interest as recorded during repeated observations in the field.FieldFishSize.csvVideos without interactionsNames of video files that were examined by one of the authors (K.L.) and found to contain no displacements. These contributed to the total length of footage watched, and helped estimate the "rarefaction-like" plot in Figure S4.kristens_videos.txtLive-only dominance matrixDominance matrix estimated exclusively from live observations.live_only_matrix.txtLive-only one-on-one dominance matrixDominance matrix estimated exclusively from one-on-one interactions that were observed live.live_only_one-on-one_matrix.txtLive fish interactionsA complete list of displacements that were observed live over the 9 days of fieldwork. Note that "Damselfish" refers to Dusky farmerfish (Stegastes nigricans) and "Melon Butterflyfish" refers to Oval butterflyfish (Chaetodon lunulatus).LiveFishInteraction_Feb9.csvPractice size estimatesPractice estimates of the sizes of different coral features (in cm) by J.M. ("J"), K.L. ("K"), and D.Č. ("D") to ensure inter-observer consistency.practice.csvVideo fish interactionsA complete list of displacements that were scored from 18.2 hours of video recordings. Note that "Damselfish" refers to Dusky farmerfish (Stegastes nigricans).ScoredFishInteraction_Feb19.csvVideo file lengthsLengths (in seconds) of the 239 video files listed in video_file_names.txt.video_file_lengths.txtVideo file namesNames of 239 video recordings collected from 6 underwater cameras.video_file_names.txtVideo-only dominance matrixDominance matrix estimated exclusively from video recordings.video_only_matrix.txtVideo-only one-on-one dominance matrixDominance matrix estimated exclusively from one-on-one interactions that were recorded on video.video_only_one-on-one_matrix.txtScript for summarizing field size estimatesR script used to calculate the mean and standard deviation of the number of size estimates that were recorded in the field and reported in FieldFishSize.csv for each of the species included.field_fish_size.RScript for tree subsamplingR script that subsamples the time-calibrated actinopterygian megaphylogeny from actinopt_12k_treePL.tre down to the species listed in FishSize.csv in order to produce small_tree.tre.get_small_tree.RScript for evaluating practice size estimatesR script used to perform paired t-tests on the practice size estimates reported in practice.csv.practice_measurements.RScript to calculate footage lengthR script used to calculate the total duration of the footage recorded and the duration of the footage scored from video_file_names.txt and video_file_lengths.txt.video_properties.RActinopterygian time tree of Rabosky et al. 2018Time-calibrated actinopterygian megaphylogeny of Rabosky et al. (2018; Nature 559:392) downloaded on September 22, 2018 from http://fishtreeoflife.org/downloads/, used to provide an ultrametric tree for phylogenetic generalized least squares.actinopt_12k_treePL.tre22-species phylogenetic treeUltrametric phylogeny of the species of interest created by subsampling actinopt_12k_treePL.tre using get_small_tree.R for use in phylogenetic generalized least squares.small_tree.treLanchester law testing (Rmd)R Markdown file with code for data clean-up, data preparation, and data analysis, used to conduct all the analyses reported in the manuscript and the supplement and to generate all the corresponding figures.Lanchester_law_testing.RmdLanchester law testing (HTML)HTML generated by knitting the corresponding markdown file, displaying notes, code, and code output.Lanchester_law_testing.htmlBody sizes from Randall (2005)Maximum attained body sizes of the species of interest reported by Randall (2005; "Reef and shore fishes of the South Pacific: New Caledonia to Tahiti and the Pitcairn Islands", University of Hawaii Press), along with their scientific as well as vernacular names and page references.FishSize.csv