Interspecific interactions drive cultural co-evolution and acoustic convergence in syntopic species

• Published in: The Journal of animal ecology Vol. 81; no. 3; pp. 594 - 604
• Main Author: Laiolo, Paola
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing 01-05-2012; Blackwell Publishing Ltd; Blackwell
• Subjects: Acoustics; Aggression; Aggressive behavior; aggressiveness; Allopatric populations; Animal and plant ecology; Animal ecology; Animal vocalization; Animal, plant and microbial ecology; Animals; Biodiversity; Biological and medical sciences; Biological Evolution; biotic interactions; Bird songs; Character displacement; Climate; Coadaptation; Coexistence; Communication; Congeners; Convergence; Ecological genetics; Ecosystem; Evolution; Evolutionary biology; Evolutionary ecology; Fundamental and applied biological sciences. Psychology; Galerida cristata; General aspects; geographical mosaic of co‐evolution; Habitat; Human ecology; interference competition; Male; Natural selection; Passeriformes - genetics; Passeriformes - physiology; Plastics; Playback; Social Behavior; Social interaction; social learning; Species; Species Specificity; Syllables; Territoriality; Territory; Vocalization behavior; Vocalization, Animal - physiology; Wildlife habitats; Competition; interference competition; Syntopic species; Interference; Environmental factor; Social learning; Coevolution; Convergence; geographical mosaic of co-evolution; biotic interactions; Aggressiveness; Biotic factor; Interspecific relation
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/j.1365-2656.2011.01946.x

1. Antagonistic interactions have been favourite subjects of studies on species co-evolution, because coexistence among competing species often results in quantifiable character displacement. A common output for competitive interactions is trait divergence, although the opposite phenomenon, convergence, has been proposed to evolve in some instances, for example in the communication behaviour of species that maintain mutually exclusive territories. 2. I use here experimental and observational evidence to study how species interactions drive heterospecific signal convergence and analyse how convergence feeds back to the interaction itself, in the form of aggressive behaviour. I recorded the learned territorial signals of two non-hybridizing larks, Galerida cristata and G. theklae, and used allopatric populations as controls for evaluating acoustic convergence in syntopy. Acoustic variation was analysed with respect to social conditions controlling for other potential agents of natural selection, habitat and climate. 3. Interspecific convergence of Galerida calls peaked in syntopy. Although call acoustic structure was affected by climate and habitat, it matched gradients of density and proximity to congeners even at small local scales. The process of cultural transmission, in which individuals may acquire components of behaviour by copying neighbours, enhances the correlation between call acoustics and the local social milieu. 4. Territories were defended against both species, but playback stimuli of convergent congener calls elicited a stronger aggressive reaction than congener calls from allopatric locations. 5. This study shows that learned behaviours may co-evolve as a consequence of antagonistic interactions, determining reciprocal cultural evolution or cultural co-evolution. As for (biological) coevolution, the distribution of competing species influences whether a particular area becomes a syntopic environment in which convergence is occurring, or an allopatric environment lacking interactions and reciprocal change. Because of their plastic nature, cultural coadaptations may rapidly shift in response to fluctuating social selection, thus propelling dynamic interactions and fine adjustments to the local environment.