DOI: 10.5061/dryad.rr3667m
title: Data from: Multicellularity drives the evolution of sexual traits

description: From the male peacock's tail plumage to the floral displays of
 flowering plants, traits related to sexual reproduction are often complex
 and exaggerated. Why has sexual reproduction become so complicated? Why
 have such exaggerated sexual traits evolved? Early work posited a
 connection between multicellularity and sexual traits such as anisogamy
 (i.e., the evolution of small sperm and large eggs). Anisogamy then drives
 the evolution of other forms of sexual dimorphism. Yet, the relationship
 between multicellularity and the evolution of sexual traits has not been
 empirically tested. Given their extensive variation in both multicellular
 complexity and sexual systems, the volvocine green algae offer a tractable
 system for understanding the interrelationship of multicellular complexity
 and sex. Here we show that species with greater multicellular complexity
 have a significantly larger number of derived sexual traits, including
 anisogamy, internal fertilization, and secondary sexual dimorphism. Our
 results demonstrate that anisogamy repeatedly evolved from isogamous
 multicellular ancestors and that anisogamous species are larger and
 produce larger zygotes than isogamous species. In the volvocine algae, the
 evolution of multicellularity likely drives the evolution of anisogamy,
 and anisogamy subsequently drives secondary sexual dimorphism.
 Multicellularity may set the stage for the overall diversity of sexual
 complexity throughout the Tree of Life.
description: combined_chloroplast_collectionSystematic sample of Bayesian trees. Every 1,000th post-burnin tree from the four runs was included, for a total of 600 trees.Volvocine tree, ultrametricVolvocine phylogenetic tree, created from the phylogram using a penalized likelihood function.combined_chloroplast.con.clado.nexVolvocine tree, phylogramBayesian phylogram of volvocine and outgroup taxa.combined_chloroplast.con.tre.nexChloroplast data matrixData matrix for volvocine chloroplast phylogenetic tree.combined_chloroplast.fasta.nexDataset 1Genbank accession numbers of chloroplast genes for ingroup and outgroup taxa.Dataset 2Continuous multicellularity metrics and discrete character states for sexual traits and associated references for volvocine taxa. For heterothallic species, only one strain of a mating pair has been given.Table A1PCR primers used in this study. *indicates a reverse primerTable A2The best partition and nucleotide substitution scheme as determined by PartitionFinder version 2.1.1 (Lanfear et al. 2016). “Position” refers to codon position.Table A3Model fit and parameter estimates for analyses of discrete traits. For phylogenetic signal, the D value was calculated (D &lt; 0 indicates stronger phylogenetic signal than a Brownian motion model; D = 0 indicates Brownian motion; D = 1 indicates random, non-phylogenetic distribution of states among taxa). Significant P-values associated with a given model indicate that the model is rejected. For discrete traits, the first state listed in the column header is state 0, and subsequent states are state 1 or state 2. The value q is the transition rate between the two states (ancestral state on the left, derived state on the right). Bayes factors (BF), taking phylogenetic uncertainty into account, were estimated based on twice the difference between the highest harmonic mean log likelihood for each model (ER, equal rates; SYM, symmetric rates; ARD, all rates different), calculated from nine independent MCMC runs for each model. Interpretation of Bayes factors is as follows: 0 to 2 barely worth mentioning, 2 to 6 positive, 6 to 10 strong, &gt;10 very strong (Kass and Raftery 1995).Table A4Model fit and parameter estimation for analyses of continuous traits. Phylogenetic signal was assessed using Blomberg’s K (2003) and Pagel’s λ (Pagel 1999). Statistical significance for these indices was based on comparison to a non-phylogenetic model (K = 0, λ = 0), with a significant P-value indicating rejection of the non-phylogenetic model.Table A5Correlations between internal fertilization and anisogamy and oogamy using Pagel’s test (1994)Table 1Phylogenetic t-test for sexual traits, using three continuous metrics of multicellular complexity (rounds of cell division, percent somatic cells, natural logarithm-transformed body length). A phylogenetic t-test comparing natural logarithm-transformed zygote diameter of isogamous and anisogamous algae is included. When multiple metrics were used, p-values were adjusted for multiple comparisons following Benjamini and Hochberg (1995).