Phylogenetic Signal in the Song of Crests and Kinglets (Aves: Regulus)

Abstract

Abstract. Territorial song structures are often the most prominent characters for distinguishing closely related taxa among songbirds. Learning processes may cause convergent evolution of passerine songs, but phylogenetic information of acoustic traits can be investigated with the help of molecular phylogenies, which are not affected by cultural evolutionary processes. We used a phylogeny based on cytochrome b sequences to trace the evolution of territorial song within the genus Regulus. Five discrete song units are defined as basic components of regulid song via sonagraphic measurements. Traits of each unit are traced on a molecular tree and a mean acoustic character difference between taxon pairs is calculated. Acoustic divergence between regulid taxa correlates strongly with genetic distances. Syntax features of complete songs and of single units are most consistent with the molecular data, whereas the abundance of certain element types is not. Whether song characters are innate or learned was interpreted using hand-reared birds in aviary experiments. We found that convergent character evolution seems to be most probable for learned acoustic traits. We conclude that syntax traits of whole verses or subunits of territorial song, especially innate song structures, are the most reliable acoustic traits for phylogenetic reconstructions in Regulus.

Song dialects on the Atlantic islands: goldcrests of the Azores (Regulus regulus azoricus, R. r. sanctae-mariae, R. r. inermis)

“…The Azorean subspecies have been considered recent descendants from western European populations (Volsøe 1951;Knecht and Scheer 1971). This has recently been confirmed by molecular data (Pa¨ckert et al 2003). The song of Azorean goldcrests has not been fully investigated to date.…”

“…On the Canary Islands, for example, most songbird taxa differ largely in morphological and acoustic characters from their continental relatives, as in the cases of blue tits, Parus teneriffae (Schottler 1995;Martens 1996;Salzburger et al 2002), the Canarian robin, Erithacus rubecula superbus (Stock and Bergmann 1988), the Canarian chiffchaff, Phylloscopus canariensis (Helbig et al 1996) and, on Madeira, the Madeiran firecrest Regulus ignicapillus madeirensis (Pa¨ckert et al 2001(Pa¨ckert et al , 2003. Geographic isolation of the Azorean archipelago is even more extreme than in the latter because of the greater distances between the Azores and the European, African and American continents.…”

Social complexity as a proximate and ultimate factor in communicative complexity

“…greater signal complexity in lineages that have had more time to evolve) and similarities in the level of communicative complexity (high or low) among close relatives compared with more distantly related species. There is evidence that signal complexity tends to increase with lineage age and vary among taxa as a function of phylogenetic relationships in the chemical signals of ants [138] and Drosophila [139], in the vocal signals of birds [140][141][142] and frogs [143], and the visual signals of darter fishes [144] and Anolis lizards [40]. We should add that interpretations of phylogenetic signal should be made cautiously because it can reflect a number of different biological factors (e.g.…”

Phenotypic divergence during speciation is inversely associated with differences in seasonal migration

“…Specifically, as suggested above, most migratory divides comprise one taxon in the east and another in the west. This is often not the case for widespread non-migratory groups such as boreal chickadees, black-capped chickadees [56], rubycrowned kinglets, and golden-crowned kinglets [67]. During the glacial advances, these species would likely have experienced similar periods of allopatry to taxa that form divides, occupying both eastern and western refugia (as inferred from their widespread current ranges).…”