Group size frequency distribution of six <i>Chaetodon</i> spp. at Lizard Island.

<p>Numbers in parentheses indicate sample size of total observations of groups.</p

Predominantly pairing species in current study: Sex composition of pairs.

<p>Predominantly pairing species in current study: Sex composition of pairs.</p

Predominantly solitary species and solitary <i>C</i>. <i>lunulatus</i> in current study: Sex composition of individuals.

<p>Predominantly solitary species and solitary <i>C</i>. <i>lunulatus</i> in current study: Sex composition of individuals.</p

Dichotomous social systems (pair bonding vs. solitary living) among individuals of <i>Chaetodon lunulatus</i> and among species of <i>Chaetodon</i> at Lizard Island (current study) do not co-vary with other attributes (previously established), controlling for these variables while comparatively studying pair bonding.

<p>Phylogeny data sourced from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194465#pone.0194465.ref061" target="_blank">61</a>], where species clades (CH) and ancestral state nodes and probabilities (in parentheses) are shown. <i>Notes</i>: † = current study. *Parental care is unstudied in Lizard Island populations and is presumed absent based on unequivocal reporting of pelagic spawning within Chaetodontidae. ^Mating systems of these populations at Lizard Island are presumed based on reports at other locations [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194465#pone.0194465.ref063" target="_blank">63</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194465#pone.0194465.ref087" target="_blank">87</a>].</p

Ancestral reconstruction of social behavior in the family Chaetodontidae summarized on a published maximum clade credibility chronogram [61].

<p>Pie charts at nodes represent the posterior probabilities of state reconstructions, summarized from 10,000 stochastic character maps across 1000 randomly sampled topologies from the BEAST posterior distribution of trees [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194465#pone.0194465.ref061" target="_blank">61</a>]. Within the family, pairing is reconstructed as the ancestral character with several subsequent independent transitions to solitary behavior or gregarious grouping and few reversals to pairing (inset). Within the study group (highlighted in blue for solitary and pink for pairing), pairing is ancestral, with one potential origin of solitary sociality in the common ancestor to <i>C</i>. <i>trifascialis</i>, <i>C rainfordi</i>, and <i>C</i>. <i>plebeius</i>. Time axis is in millions of years before present with major epochs identified (P: Pleistocene to Recent epoch).</p

Differences in social behaviors between predominantly paired and solitary grouped <i>Chaetodon</i> spp. and <i>C</i>. <i>lunulatus</i> individuals.

<p>(A) Time spent proximate swimming with another conspecific (mean % ± standard error). (B) Time spent parallel swimming with another conspecific (mean % ± standard error). (C) Agonism towards partner vs. non-partner conspecifics among pairs (mean % ± standard error). (D) Percentage of pairs displaying partner fidelity after six weeks. Asterisks indicate significant differences between groups. N/A = not applicable.</p