SHY-LARKS · Comparative analysis of intraspecific song variability in lark species (Alaudidae) with different degree of population fragmentation

Final Activity Report Summary - SHY-LARKS (Comparative analysis of intraspecific song variability in lark species (Alaudidae) with different degree of population fragmentation)

Culture is defined in very diverse ways by different disciplines. Some cultural anthropologist states that culture is uniquely a human phenomenon mediated by linguistics. In contrast, in the general field of biological sciences, culture is defined as any variation acquired and maintained by social learning (or imitation, social facilitation, imprinting, etc.). Cultural transmission is strikingly similar to genetic one in some characteristics (the occurrence and interplay of variation, selective pressure, heritability, drift), although it differs in its Lamarckian process of transmission (acquired cultural traits can be transmitted to the next generation). Bird song is a classical example of culturally transmitted character, which proved to be extremely susceptible to change over evolutionary times. Among oscine passerines, geographic song differentiation (dialect formation) is a well-documented phenomenon. So far, most studies on song geographic variation pointed to patchy populations isolated by natural habitat barriers. In a context of rapid landscape change, it has been shown that anthropogenic habitat fragmentation can be responsible for changes in distribution, abundance, persistence and structure of populations. Few studies analysed bird acoustic differentiation in relation to habitat fragmentation and anthropogenic habitat barriers, although dialects are a well-documented by-product of spatial isolation processes. In our study, we found that changes in bird vocalizations could be used as an early warning system to detect man-made ecological disturbances, such has habitat loss and fragmentation. We analysed the songs and calls of hundreds of individuals Dupont's lark Chersophilus duponti, a threatened and declining lark species typical of Iberian shrub steppes. We found that acoustic variability was significantly linked to isolation (lack of landscape connectivity) and habitat loss, whose origins are anthropogenic. In fragmented habitats, song-sharing among male neighbours was enhanced whereas song-sharing among non-neighbours dropped. Ruling out other explanations such as the stage of the breeding season and competition intensity, we hypothesise that changes in song-sharing is due to lack of interaction between individuals isolated by habitat barriers. Habitat loss in the steppe matrix markedly affected song-type sharing mechanisms in Dupont's lark, and at the same time conditioned the transmission of its territorial call. Hence, the occurrence of anthropogenic habitat barriers seems to hinder cultural transmission of cultures over distances. All in all, communication systems of habitat-sensitive species might be used as a behavioural indicator of anthropogenic environmental deterioration. Because of their rapidly evolving cultural nature, bird vocalisations might become an early warning system detecting the effects of fragmentation over relatively short times and before other indicators, such as genetic markers, show any change.

Data: CORDIS, © European Union