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Plumage Variation (plumage + variation)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

INCIPIENT SPECIATION DESPITE LITTLE ASSORTATIVE MATING: THE YELLOW-RUMPED WARBLER HYBRID ZONE

EVOLUTION, Issue 12 2009
Alan Brelsford
Hybrid zones between recently diverged taxa are natural laboratories for speciation research, allowing us to determine whether there is reproductive isolation between divergent forms and the causes of that isolation. We present a study of a classic avian hybrid zone in North America between two subspecies of the yellow-rumped warbler (Dendroica coronata). Although previous work has shown very little differentiation in mitochondrial DNA across this hybrid zone, we identified two nuclear loci (one sex-linked and one autosomal) that show fixed differences across the hybrid zone, in a close concordance with patterns of plumage variation. Temporal stability and limited width of the hybrid zone, along with substantial linkage disequilibrium between these two diagnostic markers in the center of the zone, indicate that there is moderate reproductive isolation between these populations, with an estimated strength of selection maintaining the zone of 18%. Pairing data indicate that assortative mating is either very weak or absent, suggesting that this reproductive isolation is largely due to postmating barriers. Thus, despite extensive hybridization the two forms are distinct evolutionary groups carrying genes for divergent adaptive peaks, and this situation appears relatively stable. [source]

Phylogenetic relationships, diversification and biogeography in Neotropical Brotogeris parakeets

JOURNAL OF BIOGEOGRAPHY, Issue 9 2009
Camila C. Ribas
Abstract Aim, We present a molecular phylogenetic analysis of Brotogeris (Psittacidae) using several distinct and complementary approaches: we test the monophyly of the genus, delineate the basal taxa within it, uncover their phylogenetic relationships, and finally, based on these results, we perform temporal and spatial comparative analyses to help elucidate the historical biogeography of the Neotropical region. Location, Neotropical lowlands, including dry and humid forests. Methods, Phylogenetic relationships within Brotogeris were investigated using the complete sequences of the mitochondrial genes cyt b and ND2, and partial sequences of the nuclear intron 7 of the gene for Beta Fibrinogen for all eight species and 12 of the 17 taxa recognized within the genus (total of 63 individuals). In order to delinetae the basal taxa within the genus we used both molecular and plumage variation, the latter being based on the examination of 597 skin specimens. Dates of divergence and confidence intervals were estimated using penalized likelihood. Spatial and temporal comparative analyses were performed including several closely related parrot genera. Results,Brotogeris was found to be a monophyletic genus, sister to Myiopsitta. The phylogenetic analyses recovered eight well-supported clades representing the recognized biological species. Although some described subspecies are diagnosably distinct based on morphology, there was generally little intraspecific mtDNA variation. The Amazonian species had different phylogenetic affinities and did not group in a monophyletic clade. Brotogeris diversification took place during the last 6 Myr, the same time-frame as previously found for Pionus and Pyrilia. Main conclusions, The biogeographical history of Brotogeris implies a dynamic history for South American biomes since the Pliocene. It corroborates the idea that the geological evolution of Amazonia has been important in shaping its biodiversity, argues against the idea that the region has been environmentally stable during the Quaternary, and suggests dynamic interactions between wet and dry forest habitats in South America, with representatives of the Amazonian biota having several independent close relationships with taxa endemic to other biomes. [source]

Continuous, age-related plumage variation in male Kirtland's Warblers

JOURNAL OF FIELD ORNITHOLOGY, Issue 1 2007
John R. Probst
ABSTRACT The ability to age individual birds visually in the field based on plumage variation could provide important demographic and biogeographical information. We describe an approach to infer ages from a distribution of plumage scores of free-ranging male Kirtland's Warblers (Dendroica kirtlandii). We assigned ages to males using a scoring scheme (0,12 points) based on variation in plumage coloration, brightness, and contrast on three dorsal and three ventral body regions presumed to be age-related. The distribution of total additive plumage scores for 875 breeding males was normally distributed, indicating no distinct age classes. Thus, we developed provisional plumage-age classes of second year (SY) and after second-year (ASY), and compared them to the total plumage scores of a smaller subsample of known age (N= 92) and minimum age (N= 143) males. Plumage scores of known-age male Kirtland's Warblers increased nonlinearly with age (rs= 0.67), but with some overlap. The median plumage score for SY males (median = 5.0) was significantly lower than for third-year (TY) males (median = 7.0) and after third-year (3 year and older) males (median = 8.0), indicating that the plumage of male Kirtland's Warblers becomes more distinctive and brighter with age. Linear discriminant function analysis differentiated ASY male Kirtland's Warbler from SY males with 78.3% accuracy. Investigators could use the distribution of plumage scores and approximate age structures to document changes in male age structure during colonization, use, and abandonment of habitats by Kirtland's Warblers or other species that occupy early successional habitats. Aging free-ranging birds based on a plumage scoring scheme may be especially critical for demographic studies of less-studied species where it is unlikely that a banding program will be initiated, but where plumage-age inferences or management decisions must be made. SINOPSIS Describimos una forma para inferir la edad a través de una distribución de marcadores en machos silvestres de la reinita Dendroica kirtlandii. Utilizando dicho acercamiento, asignamos edad relativa a machos basándonos en un esquema de puntuación (0,12) para la coloración del plumaje, su brillantez, y contraste en tres localidades del dorso y la parte ventral, que han sido relacionadas con la edad de estos. La distribución de las puntuaciones de 875 machos fue normal, lo que indica que no hubo forma de distinguir las diferentes edades. Por ende, desarrollamos un divisiones de clases, basándonos en diferencias en el plumaje para individuos de segundo año (SA) y posterior al segundo año (PSA) y los comparamos a las puntuaciones de una pequeña muestra de aves (N= 92) cuya edad era conocida y a otra en que sabíamos la edad mínima (N= 143). La puntuación total para individuos de edad conocida aumento de forma no-lineal con la edad (Rs = 0.67), con un pequeño solapamiento en el plumaje total. La puntuación para machos de segundo año (SA) (mediana = 5.0) fue significativamente menor que para aves de tercer año (mediana = 7.0) y esta a su vez que para aves mayores a tres años (mediana = 8.0), lo que indica que el plumaje de los machos, en las aves estudiadas, se torna más brillante con la edad. Un análisis lineal de función discriminativa pudo diferenciar entre aves PSA y SA con un 78.3% de exactitud. Los investigadores han utilizado estas diferencias en el plumaje para clasificar entre los grupos machos territoriales que no han sido anillados. También pudieran utilizar estas particularidades y diferencias en el plumaje para aproximar la estructura de edades entre machos silvestres y hacer inferencias sobre la demografía y reclutamiento de aves en habitats de diferente calidad. [source]