DOI: 10.5061/dryad.sxksn035q
title: Data for: The costs and benefits of larger brains in fishes

description: The astonishing diversity of brain sizes observed across the animal
 kingdom is typically explained in the context of trade-offs: the benefits
 of a larger brain, such as enhanced cognitive ability, are balanced
 against potential costs, such as increased energetic demands. Several
 hypotheses have been formulated in this framework, placing different
 emphasis on ecological, behavioural, or physiological aspects of
 trade-offs in brain size evolution. Within this body of work, there exists
 considerable taxonomic bias towards studies of birds and mammals, leaving
 some uncertainty about the generality of the respective arguments. Here,
 we test three of the most prominent such hypotheses, the ´expensive
 tissue´, ´social brain´, and ´cognitive buffer´ hypotheses, in a large
 dataset of fishes, derived from a publicly available resource (FishBase).
 In accordance with predictions from the ´expensive tissue´ and the ´social
 brain´ hypothesis, larger brains co-occur with reduced fecundity and
 increased sociality in at least some Classes of fish. Contrary to
 expectations, however, lifespan is reduced in large-brained fishes, and
 there is a tendency for species that perform parental care to have smaller
 brains. As such, it appears that some potential costs (reduced fecundity)
 and benefits (increased sociality) of large brains are near universal to
 vertebrates, while others have more lineage-specific effects. We discuss
 our findings in the context of fundamental differences between the
 classically studied birds and mammals and the fishes we analyse here,
 namely divergent patterns of growth, parenting, and neurogenesis. As such,
 our work highlights the need for a taxonomically diverse approach to any
 fundamental question in evolutionary biology. This dataset includes all
 data used in the respective manuscript.
description: Using the R
 package <em>rfishbase</em> (version 3.1.6; (Boettiger et al.
 2021)), we downloaded information from FishBase (www.fishbase.se;
 (Froese and Pauly 2000)) using the package’s default commands and
 functions (all data initially downloaded during the second half of March
 2021). FishBase is a publicly available database and analysis tool with
 the aim ‘to provide key information on fishes of the world, that is both
 global and deep’ (Froese and Pauly 2000). For more than three decades,
 FishBase has pursued this goal by extracting data from the primary and
 secondary literature on fishes and collating it in a searchable digital
 repository. As such, a lot of information has been manually transcribed
 from scientific articles, books, and other forms of publishing into
 FishBase’s data structure, with the respective source being referenced in
 FishBase. It should thus be noted that the data found on FishBase is
 imperfect, either because existing information has not (yet) been
 included, information was included inaccurately (e.g. typos), or the
 information in the source material was already wrong (Froese and Pauly
 2000). There are ongoing efforts to make FishBase as error-free as
 possible, and by being an openly available database in which only already
 published information is included, at least two lines of checks exist:
 first, data need to pass reviewing processes during their initial
 publication. Second, once data enter FishBase, they are subject to the
 scrutiny of its users, which has repeatedly led to updates and corrections
 (Froese and Pauly 2000). FishBase is thus the most reliable and
 comprehensive source of information for the greatest number of fish
 species currently available (Froese and Pauly 2000). Our aim here was to
 collate a comprehensive dataset of brain sizes and corresponding variables
 of interest that relate to our questions about (i) associations between
 brain size and certain life history parameters, (ii) co-evolutionary links
 between breeding systems and brain size, (iii) and potential influences of
 habitat features on brain size evolution. To this end, we pre-screened all
 data available on FishBase for relevant information and selected those
 variables that we deemed most biologically meaningful. We did not trace
 entries on FishBase back to their sources. We selected two life history
 parameters (longevity and fecundity), two aspects of breeding systems
 (mating system and post-zygotic parental care), and two habitat features
 (a pelagic or demersal lifestyle and the presence or absence of migrations
 between marine and freshwater habitats) for our analyses. Specifically, we
 first extracted data for each species from FishBase’s ‘Species Table’
 using the <em>rfishbase</em> function ‘species’ (see (Froese
 and Pauly 2000) for descriptions of each of the FishBase-specific terms
 indicated by quotation marks). For each species, we included the
 scientific name (column name in the table: ‘Species’), habitat information
 (‘DemersPelag’ (indicating whether the species follows a demersal or
 pelagic lifestyle), ‘AnaCat’ (indicating whether the species migrates
 between marine and freshwater habitats or not)), life history information
 (‘LongevityWild, ‘LongevityCaptive’ (indicating lifespan estimates in
 years in the wild or in captivity, respectively)), and body size
 information (‘Length’ (length measurements in centimetres),
 ‘LengthTypeMaxM’ (indicating the type of length measurement provided; see
 Appendix S1), ‘Weight’ (weight measurements in grams)). This yielded a
 total of 34299 species entries. As FishBase’s ‘Orders Table’ is currently
 not available via <em>rfishbase</em>, we manually added
 information on higher taxonomic classifications from FishBase’s
 ‘Classification List’ (https://www.fishbase.se/tools/Classification/ClassificationList.php), yielding an entry for Genus, Family, Order, and Class for each of the 34299 species. Every species was classified as pelagic or demersal, and 4025 were classified as migratory between marine and freshwater habitats or as non-migratory. For 117 species, longevity data in years from both captivity and the wild was available, while at least one of these estimates was provided for 212 (captive) and 1341 (wild) species, respectively. We elected to use the larger of these two measurements wherever both were provided. A length measurement in centimetres was given for 30373 species, including information on the type of measuring procedure (e.g. standard length or fork length) in 30180 cases (see Appendix S1). Weight data in grams could be retrieved for 2184 species. Both length and weight data were provided as maximum values recorded for a given species. We then downloaded fecundity data using the <em>rfishbase</em> function ‘fecundity’ and including the columns ‘Species’, ‘FecundityMin’ (2300 entries for 1374 species), ‘FecundityMax’ (2607 entries for 1570 species), and ‘FecundityMean’ (112 entries for 88 species), where fecundity is given as the number of eggs/oocytes found in a single ripe female. We elected to use the maximum value provided in any of the fecundity data for each species, resulting in a total sample size of 1763 species. We downloaded information on the breeding system of each species using the <em>rfishbase</em> function ‘reproduction’ and including ‘Species’, ‘MatingSystem’ (995 species), ‘RepGuild1’ (10645 species), ‘RepGuild2’ (8218 species), and ‘ParentalCare’ (6761 species). We classified species as either monogamous or polygamous (pooling all species classified as polyandrous or promiscuous), and as either showing post-zygotic parental care (pooling all species that do not just scatter their eggs upon mating, see (Froese and Pauly 2000) for detailed descriptions of categories) or not performing care. This yielded a total of 995 species for which we had mating system information and 10655 species with information on post-zygotic parental care (also referred to as ‘parental care’ throughout the manuscript). Subsequently, we used the <em>rfishbase</em> function ‘brains’ to download a total of 5744 brain weights (‘BrainWeight’ in milligrams) and the weight of the corresponding donor individual (‘BodyWeight’ in grams) from FishBase, representing 1436 species (as above, we included ‘Species’ for later merging of information). Information on a donor individual’s sex was only available for 36 species and we thus omitted ‘Sex’ in our analyses. For each species for which multiple brain and donor weights were available, we chose to include in our species-comparisons only the data of the heaviest individual measured, making it more comparable to our other phenotypic information (maximum length, weight, lifespan, and fecundity). Notably, relative brain weight (brain weight divided by donor weight, referred to as ‘EncCoeff’ in FishBase) declines with body weight (and body length) both within and across species ((Kotrschal et al. 1998); Appendix S2). By considering only the data of the largest individual available, we minimise potential biases stemming from greater proportions of juveniles measured for some species.
description: ReadMe file for the article
 ‘The costs and benefits of larger brains in fishes’ in the
 <em>Journal of Evolutionary Biology</em>
 (JEB-2022-00020). <strong>Files:</strong> FischerJungwirth2022_JEB_S7_all.csv: includes information on 34299 species of fish FischerJungwirth2022_JEB_S7_indbrains.csv: includes information of individual brain donor individuals FischerJungwirth2022_JEB_S7_8speciesindbrains.csv: includes information of individual brain donor weights for 8 selected species with the largest sample size for a given Class FischerJungwirth2022_JEB_S7_Publicationdata.csv: includes information on publications on brain size FischerJungwirth2022_JEB_S8.R: R script to reproduce all analyses and figures <strong>Columns in all:</strong> SpecCode: FishBase’s unique code for each species Species: the species’ full scientific name Genus: the genus to which the species is assigned on FishBase Family: the family to which the species is assigned on FishBase Order: the order to which the species is assigned on FishBase Class: the Class to which the species is assigned on FishBase FamCode: FishBase’s unique code for each family Subfamily: the name of a given subfamily as assigned to the species on FishBase Marine: binary variable for whether the species is considered marine (1) or inhabits freshwater (0) Pelagic: binary variable for whether the species is considered pelagic (1) or demersal (0) Migratory: binary variable for whether the species is considered migratory (1) or not (0) Social: binary variable for whether the species is considered social (1) or solitary (0) Longevity: a single estimate of the species’ maximum lifespan in years logLongevity: ln transformed values of Longevity Length: a single estimate of the species’ maximum length in cm logLength: ln transformed values of Length LengthType: the type of measurement to derive the species’ maximum length (SL: standard length; TL: total length; FL: fork length; WD: disk width; NA: not specified) Weight: a single estimate of the species’ maximum weight in g derived from all available data logWeight: ln transformed values of Weight MaxWeightSpecies: a single estimate of the species’ maximum weight in g derived from FishBase’s species table MaxWeightIndWithBrain: the body weight in g of the heaviest brain donor individual for a given species BrainWeightMaxWeightIndWithBrain: the brain weight in mg of the heaviest brain donor individual for a given species logBrain: ln transformed values of BrainWeightMaxWeightIndWithBrain RelBrainSize: the weight of the brain of the heaviest individual per species for which a brain weight was available divided by that individual's weight MaxFecundity: the maximum number of eggs/oocytes recorded for the species logFecundity: ln transformed values of MaxFecundity MaxLarvalSize: the maximum size in mm at hatching or first feeding of the larvae for the species DevTime: the minimum time in days it takes the species from egg laying to hatching EggSize: the species' maximum recorded egg size in mm diameter logEggSize: ln transformed values of EggSize Monogamy: binary variable for whether the species is considered monogamous (1) or polygamous/promiscuous (0) ParentalCare: binary variable for whether the species is performs some post-zygotic parental care (1) or only scatters its eggs (0) <strong>Columns in indbrains:</strong> SpecCode: FishBase’s unique code for each species Species: the species’ full scientific name Genus: the genus to which the species is assigned on FishBase Family: the family to which the species is assigned on FishBase Order: the order to which the species is assigned on FishBase Class: the Class to which the species is assigned on FishBase BodyWeight: the donor individual’s body weight in g BrainWeight: the donor individual’s brain weight in mg CountEntries: cumulative count of the number of brain weights recorded for the species (0 = no brain weight measurements available) <strong>Columns in 8speciesindbrains:</strong> SpecCode: FishBase’s unique code for each species Species: the species’ full scientific name Genus: the genus to which the species is assigned on FishBase Family: the family to which the species is assigned on FishBase Order: the order to which the species is assigned on FishBase Class: the Class to which the species is assigned on FishBase BodyWeight: the donor individual’s body weight in g BrainWeight: the donor individual’s brain weight in mg SL: the donor individual’s standard length in cm TL: the donor individual’s total length in cm SampleSize: the number of brain weights recorded for the species <strong>Publicationdata:</strong> Year: the year in which at least one paper on brain size was published Nr publ: count of publications for a given taxon for a given year Cum.Nr.publ: cumulative count of publications for a given taxon Taxon: taxonomic group for which the publications were found (mammal, bird, or fish)