Butterflyfishes as a System for Investigating Pair Bonding

Abstract

For many animals, affiliative relationships such as pair bonds form the foundation of society, and are highly adaptive. Animal systems amenable for comparatively studying pair bonding are important for identifying underlying biological mechanisms, but mostly exist in mammals. Better establishing fish systems will enable comparison of pair bonding mechanisms across taxonomically distant lineages that may reveal general underlying principles. We examined the utility of wild butterflyfishes (f: Chaetodontidae; g: Chaetodon) for comparatively studying pair bonding. Stochastic character mapping inferred that within the family, pairing is ancestral, with at least seven independent transitions to group formation and seven transition to solitary behavior from the late Miocene to recent. In six sympatric and wide-spread species representing a clade with one ancestrally reconstructed transition from paired to solitary grouping, we then verified social systems at Lizard Island, Australia. In situ observations confirmed that Chaetodon baronessa, C. lunulatus, and C. vagabundus are predominantly pair bonding, whereas C. rainfordi, C. plebeius, and C. trifascialis are predominantly solitary. Even in the predominantly pair bonding species, C. lunulatus, a proportion of adults (15 %) are solitary. Importantly, inter-and intra-specific differences in social systems do not co-vary with other previously established attributes (geographic occurrence, parental care, diet, or territoriality). Hence, the proposed butterflyfish populations are promising for comparative analyses of pair bonding and its mechanistic underpinnings. Avenues for further developing the system are proposed, including determining whether the utility of these species applies across their geographic disruptions.

Evolutionary diversity as a catalyst for biological discovery

“…For example, divergent mating and parental care behaviors are exhibited between closely-related species of Hymenopteran insects (ants, bees, and wasps), butterflyfishes, cichlid fishes, poison frogs (Dendrobatidae), African mole rats, Microtine voles, Peromyscus mice, and primates (Emlen & Oring, 1977; Ferkin, 1990; French et al, 2017; Jasarevic et al, 2013; Kidd et al, 2012; Lukas & Clutton-Brock, 2013; Nowicki et al, 2017a; Opie et al, 2013; Roland & O’Connell, 2015; Toth & Rehan, 2017). Diverse patterns of flocking behavior are frequently exhibited between closely-related species of birds, such as Estrildidae finches and Emberizidae songbirds; and divergent group burrowing behaviors are exhibited between closely-related species of South American Ctenomys tuco-tuco rodents (Anacker & Beery, 2013; Beery et al, 2008; Goodson et al, 2009; Goodson et al, 2012).…”

Pair bond endurance promotes cooperative food defense and inhibits conflict in coral reef butterflyfishes

“…Both partners of naturally occurring pair bonds of C. lunulatus (n = 9) and C. baronessa (n = 10) were identified and monitored through time using unique body markings (as per 31 ), which were photographed and printed on water-proof paper to assist observers (see Supplementary Figure S1 online for example photographs). Pairs were assumed to have been enduring, based on previous research showing a high level of partner endurance in these species at the study location 49 . Prior to experimentation, one individual from each pair was haphazardly chosen as the focal individual for the experiment.…”