Coevolution of social and communicative complexity in lemurs

Abstract

The endemic lemurs of Madagascar (Lemuriformes: Primates) exhibit great social and communicative diversity. Given their independent evolutionary history, lemurs provide an excellent opportunity to identify fundamental principles in the coevolution of social and communicative traits. We conducted comparative phylogenetic analyses to examine patterns of interspecific variation among measures of social complexity and repertoire sizes in the vocal, olfactory and visual modality, while controlling for environmental factors such as habitat and number of sympatric species. We also examined potential trade-offs in signal evolution as well as coevolution between body mass or brain size and communicative complexity. Repertoire sizes in the vocal, olfactory and visual modality correlated positively with group size, but not with environmental factors. Evolutionary changes in social complexity presumably antedated corresponding changes in communicative complexity. There was no trade-off in the evolution of signals in different modalities and neither body mass nor brain size correlated with any repertoire size. Hence, communicative complexity coevolved with social complexity across different modalities, possibly to service social relationships flexibly and effectively in pair- and group-living species. Our analyses shed light on the requirements and adaptive possibilities in the coevolution of core elements of social organization and social structure in a basal primate lineage. This article is part of the theme issue ‘Cognition, communication and social bonds in primates’.

Benefits but not the dual functions of submissive signals differ between two Malagasy primates

“…Lemurs evolved group living independently from anthropoid primates [24] and deviate from them in several morphological and social traits, such as the lack of sexual dimorphism, sex bias in adult sex ratios, strict female dominance and mild genital masculinization, which have been referred to as the lemur syndrome [27,44]. Nevertheless, these two lineages exhibit a convergent pattern in aspects of social evolution as, for example, the coevolution of communicative complexity and sociality [3,44]. In the two investigated lemur species, the dual function of subordination signalling resembled, in principle, that of macaques, apparently suggesting convergent evolution in the function of these signals.…”

“…Communication is an essential tool to mediate social behaviour and should, hence, have co-evolved with a species' social organization and structure [1][2][3]. In particular, group-living species characterized by stable long-term memberships evolved behavioural strategies such as formalized dominance relationships, defined as asymmetries in aggression by one animal towards another animal, to limit the costs of conflicts [4,5].…”

Hidden social complexity behind vocal and acoustic communication in non-avian reptiles

“…The social complexity hypothesis for communicative complexity (SCHCC) posits that the evolution of communication is driven by the need of social interactions, therefore, animals living in a more complex social system are expected to have more complex communicative means to sustain their higher social needs. SCHCC has been examined and supported by finding that group size positively correlates with the number of call types in prominently vocal and social animals, including birds [86], primates [87], bats [88], dolphins [89] and whales [90]. Nevertheless, SCHCC has not been examined in vocal non-avian reptiles.…”

Communicative roots of complex sociality and cognition: preface to the theme issue

“…The next two papers examine associations between social and communicative complexity across a range of primate species. Fichtel & Kappeler [27] use a phylogenetic analysis of lemurs to show that repertoire sizes in vocal, olfactory and visual modalities are positively associated with group size, but not environmental factors, arguing that communicative complexity in lemurs changed in response to evolutionary changes in social complexity. Aureli et al [28] focus on spider monkeys and highlight some of the challenges of accurately measuring social, communicative and cognitive complexity within and between species.…”