AVPR1b variation and the emergence of adaptive phenotypes in Platyrrhini primates

Abstract

Platyrrhini (New World monkeys, NWm) are a group of primates characterized by behavioral and reproductive traits that are otherwise uncommon among primates, including social monogamy, direct paternal care, and twin births. As a consequence, the study of Platyrrhine primates is an invaluable tool for the discovery of the genetic repertoire underlying these taxon‐specific traits. Recently, high conservation of vasopressin (AVP) sequence, in contrast with high variability of oxytocin (OXT), has been described in NWm. AVP and OXT functions are possible due to interaction with their receptors: AVPR1a, AVPR1b, AVPR2, and OXTR; and the variability in this system is associated with the traits mentioned above. Understanding the variability in the receptors is thus fundamental to understand the function and evolution of the system as a whole. Here we describe the variability of AVPR1b coding region in 20 NWm species, which is well‐known to influence behavioral traits such as aggression, anxiety, and stress control in placental mammals. Our results indicate that 4% of AVPR1b sites may be under positive selection and a significant number of sites under relaxed selective constraint. Considering the known role of AVPR1b, we suggest that some of the changes described here for the Platyrrhini may be a part of the genetic repertoire connected with the complex network of neuroendocrine mechanisms of AVP–OXT system in the modulation of the HPA axis. Thus, these changes may have promoted the emergence of social behaviors such as direct paternal care in socially monogamous species that are also characterized by small body size and twin births.

The association study of polymorphic variants of hypothalamic-pituitary-adrenal system genes (AVPR1B, OXTR) and aggressive behavior manifestation: a focus on social environment

“…Other scientific groups also point to the involvement of AVPR1B gene variants in developing aggression even in childhood [23]. Moreover, our findings seem to be in line with evolutionary data obtained in Platyrrhini [47], which indicated that 4% of AVPR1B sites may be under positive selection for accumulation of certain prosocial traits. In addition, the same research group reported that a positive selection related to domestication was attributed to the fixation of specific sites in the AVPR1B gene [29].…”

Concordant evidence for positive selection on genes related to self-domestication in bonobos and early humans.

“…Previous research has identified positive selection on the protein-coding parts of this gene region in New World primates, using nonsynonymous to synonymous rate ratio tests. In that study, the authors used comparative analyses to demonstrate associations between positive selection and mating and parental care systems in New World primates (Fam et al, 2019). Previous molecular evolution research on bonobos showed changes in the binding region of avpr1a , a vasopressin receptor closely related to avpr1b (Staes et al, 2021).…”

From molecular variations to behavioral adaptations: Unveiling adaptive epistasis in primate oxytocin system

“…We have emphasized that these taxon‐specific traits should be considered with caution. They likely represent a simplification of the reality found in nature since they do not consider intraspecific variation or changes in the usual behavior/trait of the animals promoted by specific and transient environmental conditions (Fam et al, 2019). In addition, according to French et al (2018), primate monogamy is not a single trait but a combination of various social elements, such as living in pairs, preferring specific partners, distress when separated, protecting against potential threats to fidelity, and jointly caring for offspring.…”

“…However, this approach is a valuable starting point for unraveling the link between taxon‐specific genetic repertoires and adaptive phenotypes that characterize different taxonomic groups (Fam et al, 2019). Furthermore, using the candidate gene strategy helps to minimize non‐causal correlations, as it involves selecting genes that have been previously associated with the phenotypic traits in question, such as OT and parental care.…”