RESUMO
Detailed osteological descriptions of the craniomandibular complex of passerine birds are lacking for most species, limiting our understanding of their diversity and evolution. Cowbirds (genus Molothrus) are a small but widespread group of New World nine-primaried songbirds, well-known for their unique brooding parasitic behavior. However, detailed osteological data for cowbirds and other Icteridae are currently scarce and several features of their skulls remain undescribed or poorly known. To address this issue, a detailed comparative osteology of cowbird skulls is presented here for the first time based on data from x-ray microcomputed tomography, dry skeletal data, and multivariate analyses of linear morphometric data. Cowbird skulls offer some functional insights, with many finch-like features probably related to a seed-rich diet that distinguishes them from most other icterids. In addition, features previously overlooked in earlier studies might provide valuable phylogenetic information at different levels of passerine phylogeny (Passerida, Emberizoidea, Icteridae, and Agelaiinae), including some of the otic region and nasal septum. Comparisons among cowbirds show that there is substantial cranial variation within the genus, with M. oryzivorus being the most divergent cowbird species. Within the genus, distantly related species share similar overall skull morphology and proportions, but detailed osteological data allow species identification even in cases of strong convergence. Further efforts are warranted to furnish baseline data for future studies of this iconic group of Neotropical birds and to fully integrate it into phylogenetic comparative frameworks.
Assuntos
Crânio , Microtomografia por Raio-X , Animais , Crânio/anatomia & histologia , Filogenia , Masculino , Osteologia , Feminino , Aves Canoras/anatomia & histologia , Evolução Biológica , Passeriformes/anatomia & histologiaRESUMO
The Sedge Wren Cistothorus platensis (Latham, 1790) is a widely distributed bird species, occurring in natural grasslands through the American continent. Most knowledge on its biology has been obtained in temperate regions, and no information on its home range in tropical grasslands is available. The goal of this study was to examine the home ranges of Sedge Wrens at the Parque Nacional da Chapada dos Veadeiros, central Cerrado, Brazil. Fourteen banded males were studied in a patch of shrubby grassland (campo sujo) between February and December 2008. The mean size of home ranges of five males monitored during the whole period was 6.10 ± 2.09 ha (Minimum Convex Polygon) and 4.57 ± 1.92 ha (Kernel 95%). Home ranges were larger in the dry season (non-breeding period) than in the rainy season (that encompassed both the breeding and non-breeding periods). The overlap between home ranges of neighboring males was small. Sedge Wrens did not establish home ranges on recently burned grasslands. Five banded males were recorded during the entire study period, suggesting the existence of resident individuals. Nine of the 14 males did not persist in the same site throughout the year. There was no evidence of polygyny, as only lone birds or pairs were detected. Our study indicates that Sedge Wrens inhabiting grasslands of the Cerrado are monogamous and have larger home ranges than in temperate regions.
A corruíra-do-campo Cistothorus platensis (Latham, 1790) apresenta ampla distribuição geográfica, ocorrendo ao longo de todo o continente americano. Informações sobre sua biologia têm sido obtidas principalmente em regiões temperadas, e o conhecimento sobre suas áreas de vida em campos tropicais é inexistente. O objetivo deste trabalho foi estudar as áreas de vida de C. platensis no Parque Nacional da Chapada dos Veadeiros, Cerrado do Brasil central. Quatorze machos foram anilhados em um campo sujo e cinco deles puderam ser acompanhados continuamente entre fevereiro e dezembro de 2008. O tamanho médio das áreas de vida (n = 5) foi de 6,10 ± 2,09 ha (Mínimo Polígono Convexo) e 4,57 ± 1,92 ha (Kernel 95%) e variaram significativamente entre as estações estudadas. As áreas de vida foram maiores na estação seca (período não-reprodutivo) do que na estação chuvosa (que abrangeu os períodos reprodutivo e não-reprodutivo). Houve baixa sobreposição entre áreas de machos vizinhos. As aves estudadas não estabeleceram áreas de vida em trechos de campo recentemente queimados. Alguns indivíduos foram registrados durante todo o período do estudo, sendo assim considerados residentes. Entretanto, nove dos 14 machos não persistiram no local. Não houve evidência de poliginia, uma vez que somente casais ou aves solitárias foram registradas. Este estudo indica que C. platensis habitando campos naturais no Cerrado são monogâmicos e têm áreas de vida maiores do que em regiões temperadas.
Assuntos
Animais , Aves Canoras/anatomia & histologia , Aves Canoras/crescimento & desenvolvimento , Condições Sociais , PastagensRESUMO
The Sedge Wren Cistothorus platensis (Latham, 1790) is a widely distributed bird species, occurring in natural grasslands through the American continent. Most knowledge on its biology has been obtained in temperate regions, and no information on its home range in tropical grasslands is available. The goal of this study was to examine the home ranges of Sedge Wrens at the Parque Nacional da Chapada dos Veadeiros, central Cerrado, Brazil. Fourteen banded males were studied in a patch of shrubby grassland (campo sujo) between February and December 2008. The mean size of home ranges of five males monitored during the whole period was 6.10 ± 2.09 ha (Minimum Convex Polygon) and 4.57 ± 1.92 ha (Kernel 95%). Home ranges were larger in the dry season (non-breeding period) than in the rainy season (that encompassed both the breeding and non-breeding periods). The overlap between home ranges of neighboring males was small. Sedge Wrens did not establish home ranges on recently burned grasslands. Five banded males were recorded during the entire study period, suggesting the existence of resident individuals. Nine of the 14 males did not persist in the same site throughout the year. There was no evidence of polygyny, as only lone birds or pairs were detected. Our study indicates that Sedge Wrens inhabiting grasslands of the Cerrado are monogamous and have larger home ranges than in temperate regions.(AU)
A corruíra-do-campo Cistothorus platensis (Latham, 1790) apresenta ampla distribuição geográfica, ocorrendo ao longo de todo o continente americano. Informações sobre sua biologia têm sido obtidas principalmente em regiões temperadas, e o conhecimento sobre suas áreas de vida em campos tropicais é inexistente. O objetivo deste trabalho foi estudar as áreas de vida de C. platensis no Parque Nacional da Chapada dos Veadeiros, Cerrado do Brasil central. Quatorze machos foram anilhados em um campo sujo e cinco deles puderam ser acompanhados continuamente entre fevereiro e dezembro de 2008. O tamanho médio das áreas de vida (n = 5) foi de 6,10 ± 2,09 ha (Mínimo Polígono Convexo) e 4,57 ± 1,92 ha (Kernel 95%) e variaram significativamente entre as estações estudadas. As áreas de vida foram maiores na estação seca (período não-reprodutivo) do que na estação chuvosa (que abrangeu os períodos reprodutivo e não-reprodutivo). Houve baixa sobreposição entre áreas de machos vizinhos. As aves estudadas não estabeleceram áreas de vida em trechos de campo recentemente queimados. Alguns indivíduos foram registrados durante todo o período do estudo, sendo assim considerados residentes. Entretanto, nove dos 14 machos não persistiram no local. Não houve evidência de poliginia, uma vez que somente casais ou aves solitárias foram registradas. Este estudo indica que C. platensis habitando campos naturais no Cerrado são monogâmicos e têm áreas de vida maiores do que em regiões temperadas.(AU)
Assuntos
Animais , Aves Canoras/anatomia & histologia , Aves Canoras/crescimento & desenvolvimento , Condições Sociais , PastagensRESUMO
Populations may become isolated by distance, geographic barriers or both. Isolated populations often diverge in behavioral, morphological and genetic traits as a result of reduced inter-population gene flow. Highland species commonly present naturally fragmented distributions that confine populations to the highest mountain peaks, isolated by mountain passes and distance. The endemic Timberline Wren (Thryorchilus browni) inhabits the highlands of the Talamanca mountain range, including western Panama, and the highest peak in the Central Volcanic mountain range of Costa Rica. Using microsatellites and song recordings we studied the effect of a geographic barrier and distance on song, genetic and morphological divergence among four populations in Costa Rica. A lowland mountain pass resulted in the largest genetic, vocal, and morphological (bill length) differences among populations, likely due to reduce the gene flow. Cultural drift and assortative mating by females selecting songs from their own population likely accentuates the effect of isolation and limited gene flow between populations. This pattern of population divergence has been found in other Neotropical highland birds, but over larger geographical scales. We conclude that mountain passes and distance both reduce gene flow between populations in recently-isolated highland species with restricted distributions.
Assuntos
Biodiversidade , Isolamento Reprodutivo , Aves Canoras/fisiologia , Vocalização Animal/fisiologia , Animais , Bico/anatomia & histologia , Costa Rica , Especiação Genética , Geografia , Masculino , Repetições de Microssatélites/genética , Panamá , Fenótipo , Aves Canoras/anatomia & histologiaRESUMO
We studied the phylogeography and plumage variation of the Russet-crowned Warbler (Myiothlypis coronata), from Venezuela to Bolivia, with focus on populations from Ecuador and northern Peru. We analyzed sequences of mitochondrial and nuclear genes, geographic distributions, as well as photographs of specimens deposited at museum collections. Phylogenetic analyses identified three major lineages formed by populations from: Venezuela and Colombia (M. c. regulus), Ecuador and northern Peru (M. elata, M. castaneiceps, M. orientalis, M. c. chapmani), and central Peru and Bolivia (M. c. coronata). We found further population structure within M. c. regulus and M. c. coronata, and population structure and complexity of plumage variation within the Ecuador-northern Peru lineage. Time-calibrated trees estimated that most intraspecific variation originated during the Pleistocene; however, this pattern may not be attributed to an increase in diversification rate during that period. We discuss these results in the context of the importance of geographic-ecological barriers in promoting lineage diversification along the Andes and put forward a preliminary taxonomic proposal for major lineages identified in this study.
Assuntos
Plumas , Aves Canoras/anatomia & histologia , Aves Canoras/genética , Variação Anatômica , Distribuição Animal , Animais , Teorema de Bayes , DNA Mitocondrial , Evolução Molecular , Especiação Genética , Variação Genética , Funções Verossimilhança , Modelos Biológicos , Filogenia , Filogeografia , Pigmentação , Isolamento Reprodutivo , América do SulRESUMO
Cyphorhinus arada, an Amazonian endemic, shows considerable geographic variation in plumage that has led to the recognition of eight subspecies. These include C. a. arada, C. a. salvini, C. a. modulator, C. a. transfluvialis, C. a. interpositus, C. a. griseolateralis, C. a. urbanoi and C. a. faroensis. However, a thorough taxonomic revision of the Cyphorhinus arada complex has never been undertaken, so we revise the taxonomy based on morphological and vocal characters. We analyzed a total of 515 museum specimens and 146 voice recordings representing and encompassing the distributions of all named taxa, including those currently considered not valid. Vocal analyses showed major variation within the complex, from which several trends could be identified between populations. We concluded that six species (C. arada, C. transfluvialis, C. modulator, C. salvini, C. interpositus and C. griseolateralis) should be recognized under the Phylogenetic Species Concept based on the diagnosis of stable plumage and vocal patterns of each.
Assuntos
Aves Canoras/classificação , Distribuição Animal , Estruturas Animais/anatomia & histologia , Estruturas Animais/crescimento & desenvolvimento , Animais , Tamanho Corporal , Ecossistema , Feminino , Masculino , Tamanho do Órgão , Filogenia , Aves Canoras/anatomia & histologia , Aves Canoras/genética , Aves Canoras/crescimento & desenvolvimentoRESUMO
Turdus ignobilis is a widely distributed thrush species throughout northern South America and the Amazon, inhabiting a diverse set of habitats ranging from floodplain forests, white sand "campinas", to highland forests (Andes and Tepuis). There are currently six known subspecies of T. ignobilis, which vary extensively phenotypically and also ecologically, but whose interspecific limits and evolutionary history have never been investigated before. In this study, we used molecular data and plumage characters to review the taxonomy and uncover the evolutionary relationships of the six T. ignobilis subspecies described to date. We estimated gene and species trees based on both mitochondrial (ND2 and COI) and nuclear (TGFB2 and G3PDH) genes, which recovered, with high statistical support, the polyphyly of Turdus ignobilis, as currently defined. Therefore, based on our results, we propose a new taxonomic treatment that splits T. ignobilis into at least three separate species based on both molecular data and plumage characters. Each newly recognized species inhabit a distinct habitat type, with "true" T. ignobilis occurring in highland habitats of the Tepuis and the Andes, while T. arthuri and T. debilis are tied to "white-sand forest" and várzea floodplain forests in lowland Amazonia, respectively.
Assuntos
Filogenia , Aves Canoras/classificação , Aves Canoras/genética , Animais , Núcleo Celular/genética , Ecossistema , Evolução Molecular , Plumas/anatomia & histologia , Feminino , Florestas , Genes Mitocondriais/genética , Masculino , Fenótipo , Filogeografia , Aves Canoras/anatomia & histologia , América do Sul , Fator de Crescimento Transformador beta2/genéticaRESUMO
Cyclarhis gujanensis is a little bird which feeds on high number of large preys, such frogs, lizards, snakes, bats and birds. As there are few studies on the cranial anatomy of this species, we aimed to describe the cranial myology to contribute to the anatomical knowledge of this species and to make some assumptions about functional anatomy. Thus, we described the muscles from the jaw apparatus (external and internal adductor muscles, the muscles of the pterygoid system and the depressor muscles of the mandible). The adductor system is the greatest and multipinulated, particularly in its origin in the caudal portion of the temporal fossa. The depressor jaw muscles systems are enlarged with many components in complexity. The most of jaw apparatus muscles are short, but the strength (biting or crushing forces) from short feeding apparatus fibers probably is increased by high number of components and pinnulation. These anatomical aspects of the muscles indicate a considerable force in the jaws, without which C. gujanensis probably could not cut their prey into smaller pieces. However, functional approaches to analysis of forces of the muscle fibers are needed to corroborate / refute the hypotheses mentioned above.
Assuntos
Arcada Osseodentária/anatomia & histologia , Músculo Esquelético/anatomia & histologia , Crânio/anatomia & histologia , Aves Canoras/anatomia & histologia , Animais , Músculos da Mastigação/anatomia & histologiaRESUMO
AbstractCyclarhis gujanensis is a little bird which feeds on high number of large preys, such frogs, lizards, snakes, bats and birds. As there are few studies on the cranial anatomy of this species, we aimed to describe the cranial myology to contribute to the anatomical knowledge of this species and to make some assumptions about functional anatomy. Thus, we described the muscles from the jaw apparatus (external and internal adductor muscles, the muscles of the pterygoid system and the depressor muscles of the mandible). The adductor system is the greatest and multipinulated, particularly in its origin in the caudal portion of the temporal fossa. The depressor jaw muscles systems are enlarged with many components in complexity. The most of jaw apparatus muscles are short, but the strength (biting or crushing forces) from short feeding apparatus fibers probably is increased by high number of components and pinnulation. These anatomical aspects of the muscles indicate a considerable force in the jaws, without which C. gujanensis probably could not cut their prey into smaller pieces. However, functional approaches to analysis of forces of the muscle fibers are needed to corroborate / refute the hypotheses mentioned above.
ResumoO pitiguari (C. gujanensis) é um pássaro neotropical que se alimenta de uma ampla variedade de presas grandes, tais como lagartos, anuros, morcegos e aves. Como são escassos os estudos sobre a anatomia craniana desta espécie, descrevemos a miologia craniana para contribuir com o seu conhecimento anatômico e inferir hipóteses sobre sua anatomia funcional. Foram descritos os músculos adutores mandibulares, externos e internos, do sistema pterigóideo e depressores da mandíbula. O sistema adutor, com a função de elevar a mandíbula, é o mais desenvolvido, particularmente em sua origem na porção caudal da fossa temporal. O músculo depressor da mandíbula possui vários componentes. A maioria dos músculos do aparato mandibular tem tamanho pequeno, porém a ave possui um grande potencial para dilacerar, e essa força provavelmente se deve ao grande número de componentes e pinulações neles presentes. Esses aspectos anatômicos da musculatura indicam uma força considerável nas maxilas, sem a qual C. gujanensis provavelmente não conseguiria cortar suas presas em pedaços menores. No entanto, mais estudos, tanto em abordagens funcionais como análises de forças das fibras musculares, são necessários para corroborar/refutar as hipóteses mencionadas acima.
Assuntos
Animais , Arcada Osseodentária/anatomia & histologia , Músculo Esquelético/anatomia & histologia , Crânio/anatomia & histologia , Aves Canoras/anatomia & histologia , Músculos da Mastigação/anatomia & histologiaRESUMO
Cyclarhis gujanensis is a little bird which feeds on high number of large preys, such frogs, lizards, snakes, bats and birds. As there are few studies on the cranial anatomy of this species, we aimed to describe the cranial myology to contribute to the anatomical knowledge of this species and to make some assumptions about functional anatomy. Thus, we described the muscles from the jaw apparatus (external and internal adductor muscles, the muscles of the pterygoid system and the depressor muscles of the mandible). The adductor system is the greatest and multipinulated, particularly in its origin in the caudal portion of the temporal fossa. The depressor jaw muscles systems are enlarged with many components in complexity. The most of jaw apparatus muscles are short, but the strength (biting or crushing forces) from short feeding apparatus fibers probably is increased by high number of components and pinnulation. These anatomical aspects of the muscles indicate a considerable force in the jaws, without which C. gujanensis probably could not cut their prey into smaller pieces. However, functional approaches to analysis of forces of the muscle fibers are needed to corroborate / refute the hypotheses mentioned above.(AU)
O pitiguari (C. gujanensis) é um pássaro neotropical que se alimenta de uma ampla variedade de presas grandes, tais como lagartos, anuros, morcegos e aves. Como são escassos os estudos sobre a anatomia craniana desta espécie, descrevemos a miologia craniana para contribuir com o seu conhecimento anatômico e inferir hipóteses sobre sua anatomia funcional. Foram descritos os músculos adutores mandibulares, externos e internos, do sistema pterigóideo e depressores da mandíbula. O sistema adutor, com a função de elevar a mandíbula, é o mais desenvolvido, particularmente em sua origem na porção caudal da fossa temporal. O músculo depressor da mandíbula possui vários componentes. A maioria dos músculos do aparato mandibular tem tamanho pequeno, porém a ave possui um grande potencial para dilacerar, e essa força provavelmente se deve ao grande número de componentes e pinulações neles presentes. Esses aspectos anatômicos da musculatura indicam uma força considerável nas maxilas, sem a qual C. gujanensis provavelmente não conseguiria cortar suas presas em pedaços menores. No entanto, mais estudos, tanto em abordagens funcionais como análises de forças das fibras musculares, são necessários para corroborar/refutar as hipóteses mencionadas acima.(AU)
Assuntos
Animais , Arcada Osseodentária/anatomia & histologia , Músculo Esquelético/anatomia & histologia , Crânio/anatomia & histologia , Aves Canoras/anatomia & histologia , Músculos da Mastigação/anatomia & histologiaRESUMO
Many migratory songbirds spend their non-breeding season in tropical humid forests, where climate change is predicted to increase the severity and frequency of droughts and decrease rainfall. For conservation of these songbirds, it is critical to understand how resources during the non-breeding season are affected by seasonal patterns of drying, and thereby predict potential long-term effects of climate change. We studied habitat quality for a declining tropical forest-dwelling songbird, the wood thrush (Hylocichla mustelina), and tested the hypothesis that habitat moisture and arthropod abundance are drivers of body condition during the overwintering period. We examined habitat moisture, abundance of arthropods and fruit, and condition of individual birds (n = 418) in three habitat types--mature forest, mature forest with increased presence of human activity, and riparian scrub--from October to April. We found a strong pattern of habitat drying from October (wet season) to March (prior to spring migration) in all habitats, with concurrent declines in arthropod and fruit abundance. Body condition of birds also declined (estimated ~5 % decline over the wintering period), with no significant difference by habitat. Relatively poor condition (low body condition index, low fat and pectoral muscles scores) was equally apparent in all habitat types in March. Climate change is predicted to increase the severity of dry seasons in Central America, and our results suggest that this could negatively affect the condition of individual wood thrushes.
Assuntos
Constituição Corporal , Mudança Climática , Florestas , Estações do Ano , Aves Canoras/fisiologia , Migração Animal/fisiologia , Animais , Artrópodes/fisiologia , Belize , Conservação dos Recursos Naturais , Densidade Demográfica , Aves Canoras/anatomia & histologiaRESUMO
Mobile organisms are expected to show population differentiation only over fairly large geographical distances. However, there is growing evidence of discrepancy between dispersal potential and realized gene flow. Here we report an intriguing pattern of differentiation at a very small spatial scale in the forest thrush (Turdus lherminieri), a bird species endemic to the Lesser Antilles. Analysis of 331 individuals from 17 sampling sites distributed over three islands revealed a clear morphological and genetic differentiation between these islands isolated by 40-50 km. More surprisingly, we found that the phenotypic divergence between the two geographic zones of the island of Guadeloupe was associated with a very strong genetic differentiation (Fst from 0.073-0.153), making this pattern a remarkable case in birds given the very small spatial scale considered. Molecular data (mitochondrial control region sequences and microsatellite genotypes) suggest that this strong differentiation could have occurred in situ, although alternative hypotheses cannot be fully discarded. This study suggests that the ongoing habitat fragmentation, especially in tropical forests, may have a deeper impact than previously thought on avian populations.
Assuntos
Fluxo Gênico , Genética Populacional , Aves Canoras/anatomia & histologia , Aves Canoras/genética , Animais , DNA Mitocondrial/genética , Evolução Molecular , Florestas , Genótipo , Geografia , Guadalupe , Ilhas , Repetições de Microssatélites , Modelos Genéticos , Fenótipo , Análise de Sequência de DNARESUMO
The tropical Andes are a global hotspot of avian diversity that is characterized by dramatic elevational shifts in community composition and a preponderance of recently evolved species. Bird habitats in the Andes span a nearly twofold range of atmospheric pressure that poses challenges for respiration, thermoregulation, water balance and powered flight, but the extent to which physiological constraints limit species' elevational distributions is poorly understood. We report a previously unknown hybrid zone between recently diverged flycatchers (Aves, Tyrannidae) with partially overlapping elevational ranges. The southern Anairetes reguloides has a broad elevational range (0-4200 m), while the northern Anairetes nigrocristatus is restricted to high elevations (>2200 m). We found hybrids in central Peru at elevations between ~3100 and 3800 m, with A. nigrocristatus above this elevation and A. reguloides below. We analysed variation in haematology, heart mass, morphometrics, plumage and one mitochondrial and three nuclear loci across an elevational transect that encompasses the hybrid zone. Phenotypic traits and genetic markers all showed steep clines across the hybrid zone. Haemoglobin concentration, haematocrit, mean cellular haemoglobin concentration and relative heart mass each increased at altitude more strongly in A. reguloides than in A. nigrocristatus. These findings suggest that A. nigrocristatus is more resistant than A. reguloides to high-altitude hypoxic respiratory stress. Considering that the ancestor of the genus is suggested to have been restricted to high elevations, A. reguloides may be secondarily adapted to low altitude. We conclude that differential respiratory specialization on atmospheric pressure combined with competitive exclusion maintains replacement along an elevational contour, despite interbreeding.
Assuntos
Adaptação Fisiológica/genética , Altitude , Fluxo Gênico , Genética Populacional , Aves Canoras/genética , Animais , Núcleo Celular/genética , DNA Mitocondrial/genética , Evolução Molecular , Marcadores Genéticos , Genótipo , Haplótipos , Hibridização Genética , Peru , Fenótipo , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA , Aves Canoras/anatomia & histologiaRESUMO
BACKGROUND: The Neotropics are exceptionally diverse, containing roughly one third of all extant bird species on Earth. This remarkable species richness is thought to be a consequence of processes associated with both Andean orogenesis throughout the Tertiary, and climatic fluctuations during the Quaternary. Phylogeographic studies allow insights into how such events might have influenced evolutionary trajectories of species and ultimately contribute to a better understanding of speciation. Studies on continentally distributed species are of particular interest because different populations of such taxa may show genetic signatures of events that impacted the continent-wide biota. Here we evaluate the genealogical history of one of the world's most broadly-distributed and polytypic passerines, the rufous-collared sparrow (Zonotrichia capensis). RESULTS: We obtained control region DNA sequences from 92 Zonotrichia capensis individuals sampled across the species' range (Central and South America). Six additional molecular markers, both nuclear and mitochondrial, were sequenced for a subset of individuals with divergent control region haplotypes. Median-joining network analysis, and Bayesian and maximum parsimony phylogenetic analyses all recovered three lineages: one spanning Middle America, the Dominican Republic, and north-western South America; one encompassing the Dominican Republic, Roraima (Venezuela) and La Paz (Bolivia) south to Tierra del Fuego, Argentina; and a third, including eastern Argentina and Brazil. Phylogenetic analyses suggest that the Middle American/north-western South American clade is sister to the remaining two. Bayesian and maximum likelihood coalescent simulations used to study lineage demographic history, diversification times, migration rates and population expansion together suggested that diversification of the three lineages occurred rapidly during the Pleistocene, with negligible gene flow, leaving genetic signatures of population expansions. CONCLUSIONS: The Pleistocene history of the rufous-collared sparrow involved extensive range expansion from a probable Central American origin. Its remarkable morphological and behavioral diversity probably represents recent responses to local conditions overlying deeper patterns of lineage diversity, which are themselves produced by isolation and the history of colonization of South America.
Assuntos
Filogeografia , Aves Canoras/classificação , Aves Canoras/genética , Migração Animal , Animais , Evolução Biológica , Núcleo Celular/genética , DNA Mitocondrial/genética , Genética Populacional , Aves Canoras/anatomia & histologia , América do SulRESUMO
Egg mimicry by obligate avian brood parasites and host rejection of non-mimetic eggs are well-known textbook examples of host-parasite coevolution. By contrast, reciprocal adaptations and counteradaptations beyond the egg stage in brood parasites and their hosts have received less attention. The screaming cowbird (Molothrus rufoaxillaris) is a specialist obligate brood parasite whose fledglings look identical to those of its primary host, the baywing (Agelaioides badius). Such a resemblance has been proposed as an adaptation in response to host discrimination against odd-looking young, but evidence supporting this idea is scarce. Here, we examined this hypothesis by comparing the survival rates of young screaming cowbirds and non-mimetic shiny cowbirds (Molothrus bonariensis) cross-fostered to baywing nests and quantifying the similarity in plumage colour and begging calls between host and cowbird fledglings. Shiny cowbirds suffered higher post-fledging mortality rates (83%) than screaming cowbirds (0%) owing to host rejection. Visual modelling revealed that screaming cowbirds, but not shiny cowbirds, were indistinguishable from host young in plumage colour. Similarly, screaming cowbirds matched baywings' begging calls more closely than shiny cowbirds. Our results strongly support the occurrence of host fledgling mimicry in screaming cowbirds and suggest a role of visual and vocal cues in fledgling discrimination by baywings.
Assuntos
Comportamento Alimentar , Reprodução , Aves Canoras/fisiologia , Aves Canoras/parasitologia , Animais , Argentina , Percepção Auditiva , Evolução Biológica , Cor , Feminino , Masculino , Modelos Biológicos , Comportamento de Nidação , Estações do Ano , Aves Canoras/anatomia & histologia , Espectrografia do Som , Especificidade da Espécie , Percepção Visual , Vocalização AnimalRESUMO
The faunas associated with oceanic islands provide exceptional examples with which to examine the dispersal abilities of different taxa and test the relative contribution of selective and neutral processes in evolution. We examine the patterns of recent differentiation and the relative roles of gene flow and selection in genetic and morphological variation in the yellow warbler (Dendroica petechia aureola) from the Galápagos and Cocos Islands. Our analyses suggest aureola diverged from Central American lineages colonizing the Galápagos and Cocos Islands recently, likely less than 300 000 years ago. Within the Galápagos, patterns of genetic variation in microsatellite and mitochondrial markers suggest early stages of diversification. No intra-island patterns of morphological variation were found, even across steep ecological gradients, suggesting that either (i) high levels of gene flow may be homogenizing the effects of selection, (ii) populations may not have had enough time to accumulate the differences in morphological traits, or (iii) yellow warblers show lower levels of 'evolvability' than some other Galápagos species. By examining genetic data and morphological variation, our results provide new insight into the microevolutionary processes driving the patterns of variation.
Assuntos
Evolução Biológica , Variação Genética , Genética Populacional , Filogenia , Seleção Genética , Aves Canoras/anatomia & histologia , Aves Canoras/genética , Animais , Sequência de Bases , Teorema de Bayes , Tamanho Corporal/fisiologia , Costa Rica , DNA Mitocondrial/genética , Equador , Fluxo Gênico/genética , Funções Verossimilhança , Modelos Lineares , Repetições de Microssatélites/genética , Modelos Genéticos , Dados de Sequência Molecular , Análise de Componente Principal , Alinhamento de Sequência , Análise de Sequência de DNA , Aves Canoras/fisiologiaRESUMO
The climatic variability hypothesis (CVH) states that species are geographically more widespread at higher latitudes because individuals have a broader range of physiological tolerance or phenotypic flexibility as latitude and climatic variability increase. However, it remains unclear to what extent climatic variability or latitude, acting on the phenotype, account for any observed geographical gradient in mean range size. In this study, we analyzed the physiological flexibility within the CVH framework by using an intraspecific population experimental approach. We tested for a positive relationship between digestive-tract flexibility (i.e., morphology and enzyme activities) and latitude and climatic and natural diet variability in populations of rufous-collared sparrows (Zonotrichia capensis) captured in desert (27°S), Mediterranean (33°S), and cold-temperate (41°S) sites in Chile. In accordance with the CVH, we observed a positive relationship between the magnitude of digestive-tract flexibility and environmental variability but not latitude. The greatest digestive flexibility was observed in birds at middle latitudes, which experience the most environmental variability (a Mediterranean climate), whereas individuals from the most stable climates (desert and cold-temperate) exhibited little or no digestive-tract flexibility in response to experimental diets. Our findings support the idea that latitudinal gradients in geographical ranges may be strongly affected by the action of regional features, which makes it difficult to find general patterns in the distribution of species.
Assuntos
Ecossistema , Trato Gastrointestinal/anatomia & histologia , Trato Gastrointestinal/enzimologia , Aves Canoras/anatomia & histologia , Aves Canoras/fisiologia , Animais , Antígenos CD13/metabolismo , Chile , Clima , Dieta , Isótopos de Nitrogênio/química , Estações do Ano , Sacarase/metabolismo , alfa-Glucosidases/metabolismoRESUMO
The tyrant flycatchers represent a monophyletic radiation of predominantly insectivorous passerine birds that exhibit a plethora of stereotyped prey capture techniques. However, little is known about their retinal organization. Using retinal wholemounts, we estimated the total number and topography of neurons in the ganglion cell layer in the generalist yellow-bellied elaenia (Elaenia flavogaster) and the up-hover-gleaner mouse-colored tyrannulet (Phaeomyias murina) with the optical fractionator method. The mean estimated total number of neurons in the ganglion cell layer was 4,152,416 +/- 189,310 in E. flavogaster and 2,965,132 +/- 354,359 in P. murina. Topographic maps of isocounting lines revealed a similar distribution for both species: a central fovea and a temporal area surrounded by a poorly defined horizontal streak. In addition, both species had increased numbers of giant ganglion cells in the dorsotemporal retina forming an area giganto cellularis. In E. flavogaster, these giant ganglion cells were also distributed across the nasal and ventral retinal peripheries, which is in agreement with the generalist habits of this species. However, in P. murina these cells were rarely seen along the nasal and ventral peripheries, possibly reflecting a lesser need to perceive movement because this species captures stationary insects resting on foliage. Thus, we suggest that the retinas of the tyrant flycatchers in the present study show a general common pattern of neuron distribution in the ganglion cell layer irrespective of their foraging habits. We also suggest that the distribution of giant ganglion cells is indicative of the visual requirements of the species.
Assuntos
Comportamento Apetitivo , Células Ganglionares da Retina/citologia , Neurônios Retinianos/citologia , Aves Canoras/anatomia & histologia , Animais , Contagem de Células , Comportamento Exploratório , FotomicrografiaRESUMO
During the reproductive season Blue-black grassquit (Volatinia jacarina) males are found in clusters, wherein they exhibit a distinctive display that consists of repeated, vertical leaps while simultaneously producing a brief vocalization. The main objective of this study was to describe details of the species' reproductive behavior in a "Cerrado" area of central Brazil and compare these data with some studies carried out in other areas. The data obtained concerning different aspects of nesting, laying and hatching were generally similar to those obtained in previous studies in other areas. However, we found that the typical clutch size of two eggs per nest is lower, and egg and nestling mortality rates higher in our area than what has been reported elsewhere. Our results suggest that males differ in time expended with different activities according to their reproductive condition and also provide extensive parental care. We found that display execution rates peak in the early morning and in the late afternoon and are higher in the middle of the breeding season. We also found that there is an inverse relation between the height of the display leap and the height of the perch.
Assuntos
Reprodução/fisiologia , Comportamento Sexual Animal/fisiologia , Aves Canoras/fisiologia , Animais , Brasil , Feminino , Masculino , Comportamento de Nidação/fisiologia , Oviposição , Estações do Ano , Aves Canoras/anatomia & histologiaRESUMO
Crossbills (Aves: Loxia) and several conifers have coevolved in predator-prey arms races over the last 10,000 years. However, the extent to which coevolutionary arms races have contributed to the adaptive radiation of crossbills or to any other adaptive radiation is largely unknown. Here we extend our previous studies of geographically structured coevolution by considering a crossbill-conifer interaction that has persisted for a much longer time period and involves a conifer with more variable annual seed production. We examined geographic variation in the cone and seed traits of two sister species of pines, Pinus occidentalis and P. cubensis, on the islands of Hispaniola and Cuba, respectively. We also compared the Hispaniolan crossbill (Loxia megaplaga) to its sister taxa the North American white-winged crossbill (Loxia leucoptera leucoptera). The Hispaniolan crossbill is endemic to Hispaniola whereas Cuba lacks crossbills. In addition and in contrast to previous studies, the variation in selection experienced by these pines due to crossbills is not confounded by the occurrence of selection by tree squirrels (Tamiasciurus and Sciurus). As predicted if P. occidentalis has evolved defenses in response to selection exerted by crossbills, cones of P. occidentalis have scales that are 53% thicker than those of P. cubensis. Cones of P. occidentalis, but not P. cubensis, also have well-developed spines, a known defense against vertebrate seed predators. Consistent with patterns of divergence seen in crossbills coevolving locally with other conifers, the Hispaniolan crossbill has evolved a bill that is 25% deeper than the white-winged crossbill. Together with phylogenetic analyses, our results suggest that predator-prey coevolution between Hispaniolan crossbills and P. occidentalis over approximately 600,000 years has caused substantial morphological evolution in both the crossbill and pine. This also indicates that cone crop fluctuations do not prevent crossbills and conifers from coevolving. Furthermore, because the traits at the phenotypic interface of the interaction apparently remain the same over at least several hundred thousand years, divergence as a result of coevolution is greater at lower latitude where crossbill-conifer interactions have been less interrupted by Pleistocene events.