Abstract
The ultimate-level factors that drive the evolution of mating systems have been well studied, but an evolutionarily conserved neural mechanism involved in shaping behaviour and social organization across species has remained elusive. Here, we review studies that have investigated the role of neural arginine vasopressin (AVP), vasotocin (AVT), and their receptor V1a in mediating variation in territorial behaviour. First, we discuss how aggression and territoriality are a function of population density in an inverted-U relationship according to resource defence theory, and how territoriality influences some mating systems. Next, we find that neural AVP, AVT, and V1a expression, especially in one particular neural circuit involving the lateral septum of the forebrain, are associated with territorial behaviour in males of diverse species, most likely due to their role in enhancing social cognition. Then we review studies that examined multiple species and find that neural AVP, AVT, and V1a expression is associated with territory size in mammals and fishes. Because territoriality plays an important role in shaping mating systems in many species, we present the idea that neural AVP, AVT, and V1a expression that is selected to mediate territory size may also influence the evolution of different mating systems. Future research that interprets proximate-level neuro-molecular mechanisms in the context of ultimate-level ecological theory may provide deep insight into the brain-behaviour relationships that underlie the diversity of social organization and mating systems seen across the animal kingdom.
Highlights
Understanding the causes and consequences of animal behaviour is a fundamental goal in biology [1]
Because territoriality plays an important role in shaping mating systems in many species, we present the idea that neural arginine vasopressin (AVP), Arginine Vasotocin (AVT), and V1a expression that is selected to mediate territory size may influence the evolution of different mating systems
Within species, neural AVP, AVT, and V1a are often associated with territorial behaviour
Summary
Understanding the causes and consequences of animal behaviour is a fundamental goal in biology [1]. Inter-species variation in teleost fishes Similar to the situation described above for cricetid rodents, expression in neural AVT and V1a in the brains of males varies across fish species with characteristically different male territory sizes (in the brain region homologous to the mammalian lateral septum: the ventral nucleus of the ventral telencephalon [area Vv]; see [80]). A recent study by Oldfield et al [150] compared males of two heroine cichlid species with different mating systems: the Cuatro Ciénegas cichlid, Herichthys minckleyi, in which males are polygynous and maintain large territories, and the Rio Grande cichlid, H. cyanoguttatus, in which males form monogamous pair-bonds with females and defend small, temporary nesting territories [38] These authors found that neural expression of V1a2 in males was associated with territory size. This neural mechanism underlying variation in territory sizeis at least in part conserved between mammals and teleost fishes even though patterns of territoriality have clearly evolved independently [6,38]
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