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Anisogamy is unrelated to the intensity of sexual selection

Citation

Mokos, Judit et al. (2021), Anisogamy is unrelated to the intensity of sexual selection, Dryad, Dataset, https://doi.org/10.5061/dryad.fqz612jpp

Abstract

Males and females often display different behaviours and, in the context of reproduction, these behaviours are labelled sex roles. The Darwin–Bateman paradigm argues that the root of these differences is anisogamy (i.e., differences in size and/or function of gametes between the sexes) that leads to biased sexual selection, and sex differences in parental care and body size. This evolutionary cascade, however, is contentious since some of the underpinning assumptions have been questioned. Here we investigate the relationships between anisogamy, sexual size dimorphism, sex difference in parental care and intensity of sexual selection using phylogenetic comparative analyses of 64 species from a wide range of animal taxa. The results question the first step of the Darwin–Bateman paradigm, as the extent of anisogamy does not appear to predict the intensity of sexual selection. The only significant predictor of sexual selection is the relative inputs of males and females into the care of offspring. We propose that ecological factors, life-history and demography have more substantial impacts on contemporary sex roles than the differences of gametic investments between the sexes.

Methods

We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [1] statement to search systematically the literature using the exact same method given by Janicke et al. (2016) [2], to augment Janicke et al’s dataset. We searched the ISI Web of Knowledge (Web of Science Core Collection, from 1945 to 2017) in 2017 3rd of March the following “topic” search terms and format: (“Bateman*” OR “opportunit*for selection” OR“opportunit*for sexual selection”OR“selection gradient*”), where asterisk (*) represents any group of characters, including no character. We obtained 754 candidate publications for further investigation. We compared these studies to Janicke’s database, and we checked all the items absent in their database. We were able to extend the dataset of Janicke et al. only with one new species (Lamprotornis superbus where data was extract from the supplementary material of Apakupakul and Rubenstein(2015)), otherwise, we used their data. Hermaphrodite species (Physa acuta, Biomphalaria glabrata) were excluded. Overall, our dataset contains data from 64 species. 

1. Moher D et al. 2009 Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement (Chinese edition). J. Chinese Integr. Med. 7, 889–896. (doi:10.3736/jcim20090918)

2.  Janicke T, Ha derer IK, Lajeunesse MJ, Anthes N. 2016 Darwinian sex roles confirmed across the animal kingdom. Sci. Adv. 2, e1500983–e1500983. (doi:10.1126/sciadv.1500983)

 

This dataset contains the following information: 

 

 

 

name description notes

species

species latin name  
sperm_head_length sperm head length  (μm)  
sperm_head_length_reference reference of sperm head length  (μm)  
sperm_total_length sperm length  (μm)  
sperm_total_length_reference reference of sperm total length  (μm)  
testis_mass combined testis mass (g)  
testis_mass_reference reference of combined testis mass (g)  
other_testis_size other testis size data  
other_testis_size_reference reference of  
egg_mass fresh egg mass (g) fresh egg mass or newborn mass (g)
egg_mass_reference reference of fresh egg mass (g)  
other_egg_size other egg size data  
other_egg_size_reference reference of other egg size data  
clutch_size clutch size  
clutch_size_reference reference of clutch size  
male_body_mass male body mass (g)  
male_body_mass_reference reference of male body mass (g)  
female_body_mass female body mass (g)  
female_body_mass_references reference of female body mass (g)  
female_body_length female body length (mm)  
female_body_length_reference reference of female body length (mm)  
male_body_length male body length (mm)  
male_body_length_reference reference of male body length (mm)  
other_body_size other body size data  
other_body_size_reference reference of other body size data  
sexual_size_dimorphism log(male size) - log(female size)  
sexual_size_dimorphism_how_was_measured what kind of body size  
dI_lnCVR effect size of opportunity of selection  
dI_lnCVR_VAR measurement error variance for dIs_lnCVR  
dIs_lnCVR effect size of opportunity of sexual selection  
dIs_lnCVR_VAR measurement error variance for dIs_lnCVR  
dbeta_g effect size of Bateman gradient  
dbeta_g_VAR measurement error variance for dbeta_g  
selection_indices_reference_Janicke_et_al reference of selection (from Janicke)  
sperm_mass sperm mass (g)  
sperm_mass_reference reference of sperm mass (g)  
sperm_volume sperm head volume (μm3)  
sperm_volume_reference reference of sperm head volume (μm3)  
parental_care parental care bias: if care: 0 - just female, 1- shared but rather female care, 2- equal care, 3-shared but rather male care, 4- just male care, - no parental care  
parental_care_reference reference of parental care  
     

 

Usage Notes

To represent the phylogenetic relationships between species, we used the most recent comprehensive phylogeny (timetree.org [3] that included all but seven species in our dataset. 

Species added to the phylogeny trees.
Added species    Source
Colpula lativentris    [4]
Gerris gilettei    [4]
Hippocampus subelongatus    [5]
Ischnura gemina    [6]
Labidomera clivicollis
Megabruchidius dorsalis    [7]
[7]
Strongylocentrotus purpuratus    [8]
 

 

4.    Li M, Tian Y, Zhao Y, Bu W. 2012 Higher level phylogeny and the first divergence time estimation of heteroptera (insecta: Hemiptera) based on multiple genes. PLoS One 7. (doi:10.1371/journal.pone.0032152)
5.    Teske PR, Beheregaray LB. 2009 Evolution of seahorses’ upright posture was linked to Oligocene expansion of seagrass habitats. Biol. Lett. 5, 521–3. (doi:10.1098/rsbl.2009.0152)
6.    Swaegers J, Janssens SB, Ferreira S, Watts PC, Mergeay J, McPeek MA, Stoks R. 2014 Ecological and evolutionary drivers of range size in Coenagrion damselflies. J. Evol. Biol. 27, 2386–2395. (doi:10.1111/jeb.12481)
7.    Kergoat GJ, Le Ru BP, Genson G, Cruaud C, Couloux A, Delobel A. 2011 Phylogenetics, species boundaries and timing of resource tracking in a highly specialized group of seed beetles (Coleoptera: Chrysomelidae: Bruchinae). Mol. Phylogenet. Evol. 59, 746–760. (doi:10.1016/j.ympev.2011.03.014)
8.    Lee YH. 2003 Molecular phylogenies and divergence times of sea urchin species of Strongylocentrotidae, Echinoida. Mol. Biol. Evol. 20, 1211–1221. (doi:10.1093/molbev/msg125)
 

Funding

Campus scholarship of the Hungarian government, Award: EFOP-3.4.2-VEKOP-15-2015-00001

UNKP grant

UNKP grant, Award: ELTE/8083/10(2017)

National Scientific Research Fund

National Scientific Research Fund, Award: OTKA K128289

Hungary's Economic Development and Innovation Operative Programme

Hungary's Economic Development and Innovation Operative Programme, Award: GINOP 2.3.2-15-2016-00057

NKFIH grant

NKFIH grant, Award: KH 130430

Hungarian Ministry of Human Capacities, Award: 20385-3/2018/FEKUSTRAT

Royal Society, Wolfson Merit Award

Royal Society, Wolfson Merit Award, Award: APEX APX\R1\191045

NKFIH grant

NKFIH grant, Award: NKFIH-2558-1/2015

Hungarian government, Award: ÉLVONAL-KKP 126949