Distance-based ReDundancy Analysis (dbRDA).

<p><b>A</b>: Results of dbRDA applied to the acoustic distances among recordings, with factor “Time” as an explanatory variable. <b>B</b>: Results of dbRDA applied to the acoustic distances among recordings, with factor “Site” as an explanatory variable (A: Aoupinié, K: Koghis, M: Mandjélia). The length of the arrows represents residuals: each arrow connects the position of a recording predicted by the time in which it was done or the site in which it was done (where the arrow starts) to its real position based on raw data (real acoustic composition where the arrow ends).