Browsing by Subject "Passeriformes"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Open Access
    Diversification across an altitudinal gradient in the Tiny Greenbul (Phyllastrephus debilis) from the Eastern Arc Mountains of Africa
    (BioMed Central Ltd, 2011) Fuchs, Jérôme; Fjeldså, Jon; Bowie, Rauri
    BACKGROUND:The Eastern Arc Mountains of Africa have become one of the focal systems with which to explore the patterns and mechanisms of diversification among montane species and populations. One unresolved question is the extent to which populations inhabiting montane forest interact with those of adjacent lowland forest abutting the coast of eastern Africa. The Tiny Greenbul (Phyllastephus debilis) represents the only described bird species within the Eastern Arc/coastal forest mosaic, which is polytypic across an altitudinal gradient: the subspecies albigula (green head) is distributed in the montane Usambara and Nguru Mountains whereas the subspecies rabai (grey head) is found in Tanzanian lowland and foothill forest. Using a combination of morphological and genetic data, we aim to establish if the pattern of morphological differentiation in the Tiny Greenbul (Phyllastrephus debilis) is the result of disruptive selection along an altitudinal gradient or a consequence of secondary contact following population expansion of two differentiated lineages. RESULTS: We found significant biometric differences between the lowland (rabai) and montane (albigula) populations in Tanzania. The differences in shape are coupled with discrete differences in the coloration of the underparts. Using multi-locus data gathered from 124 individuals, we show that lowland and montane birds form two distinct genetic lineages. The divergence between the two forms occurred between 2.4 and 3.1 Myrs ago.Our coalescent analyses suggest that limited gene flow, mostly from the subspecies rabai to albigula, is taking place at three mid-altitude localities, where lowland and montane rainforest directly abut. The extent of this introgression appears to be limited and is likely a consequence of the recent expansion of rabai further inland. CONCLUSION: The clear altitudinal segregation in morphology found within the Tiny Greenbul is the result of secondary contact of two highly differentiated lineages rather than disruptive selection in plumage pattern across an altitudinal gradient. Based on our results, we recommend albigula be elevated to species rank.
  • Thumbnail Image
    Item
    Open Access
    Meaningful call combinations and compositional processing in the southern pied babbler
    (2016) Engesser, Sabrina; Ridley, Amanda R; Townsend, Simon W
    Human language is syntactic in its nature: meaningful words are assembled into larger meaningful phrases or sentences. How unique this ability is to humans remains surprisingly unclear. A considerable body of work has indicated that birds are capable of combining sounds into large, elaborate songs, but there is currently no evidence suggesting that these structures are syntactic. Here, we provide important evidence for this ability in a highly social bird. Specifically, pied babblers combine two functionally distinct vocalizations into a larger sequence, the function of which is related to the function of its parts. Our work adds important evidence to the variation and distribution of combinatorial vocal mechanisms outside humans and provides insights into potentially early forms of human syntactic communication.
  • Thumbnail Image
    Item
    Open Access
    Sexual conflict predicts morphology and behavior in two species of penduline tits
    (BioMed Central Ltd, 2010) van Dijk, Rene; Pogany, Akos; Komdeur, Jan; Lloyd, Penn; Szekely, Tamas
    BACKGROUND:The evolutionary interests of males and females rarely coincide (sexual conflict), and these conflicting interests influence morphology, behavior and speciation in various organisms. We examined consequences of variation in sexual conflict in two closely-related passerine birds with contrasting breeding systems: the Eurasian penduline tit Remiz pendulinus (EPT) exhibiting a highly polygamous breeding system with sexually antagonistic interests over parental care, and the socially monogamous Cape penduline tit Anthoscopus minutus (CPT). We derived four a priori predictions from sexual conflict theory and tested these using data collected in Central Europe (EPT) and South Africa (CPT). Firstly, we predicted that EPTs exhibit more sexually dimorphic plumage than CPTs due to more intense sexual selection. Secondly, we expected brighter EPT males to provide less care than duller males. Thirdly, since song is a sexually selected trait in many birds, male EPTs were expected to exhibit more complex songs than CPT males. Finally, intense sexual conflict in EPT was expected to lead to low nest attendance as an indication of sexually antagonistic interests, whereas we expected more cooperation between parents in CPT consistent with their socially monogamous breeding system. RESULTS: Consistent with our predictions EPTs exhibited greater sexual dimorphism in plumage and more complex song than CPTs, and brighter EPT males provided less care than duller ones. EPT parents attended the nest less frequently and less simultaneously than CPT parents. CONCLUSIONS: These results are consistent with sexual conflict theory: species in which sexual conflict is more manifested (EPT) exhibited a stronger sexual dimorphism and more elaborated sexually selected traits than species with less intense sexual conflict (CPT). Our results are also consistent with the notion that EPTs attempt to force their partner to work harder as expected under sexual conflict: each member of the breeding pair attempts to shift the costs of care to the other parent. More brightly colored males benefit more from desertion than dull ones, because they are more likely to remate with a new female. Taken together, the comparison between two closely related species with contrasting breeding systems suggest that sexual conflict over care has influenced the evolution of behavior and morphology in penduline tits.