Variable Antshrike Research Articles

Molecular diversity and polyparasitism of avian trypanosomes in the Brazilian Atlantic Rainforest.

The current study proposes to investigate the diversity and phylogeny of trypanosomes parasitizing wild birds from the Brazilian Atlantic Forest. Cytological examination was carried out by light microscopy of blood smears and positive birds were selected for amplification of the 18S rDNA sequence through PCR. The resulting amplicons were subjected to purification, cloning, and sequencing analysis. Phylogenetic reconstruction was conducted, including all avian trypanosomes representative's lineages. A total of ten bird samples from species of Turdus flavipes (N=1/12), T. albicollis (N=1/8), Tachyphonus coronatus (N=6/121), Thamnophilus caerulescens (N=1/22) and Synallaxis spixi (N=1/8) were positive for Trypanosoma spp. In the six specimens of T. coronatus, five distinct lineages of Trypanosoma spp. 18S-rRNA were observed in ninety sequences obtained, and using the strategy of cloning independent PCR, it was possible to observe that two of them were related to T. avium (JB01/JB02), and three were closed related to T. bennetti (JB03/ JB04/JB05). Addionaly, all fifteen sequences obtained from T. caerulescens/ S. spixi/T. flavipes/T. albicollis were identical. The present research is the first study to access molecular diversity and polyparasitism by avian trypanosomes in Brazil. The current research exhibits the wide genetic variability in avian trypanosomes and its non-specific relationship with its avian hosts.

Use of response guilds of understory birds in threatened subtropical forest to monitor selective logging impact

Unplanned logging is one of the greatest current threats to native forests biodiversity. About 90% of the piedmont forest in the Southern Andean Yungas has been converted to other land-use types and the remaining forests fragments are being intensively logged without management plans. Bird species, especially understory birds, are good indicators of forest diversity and integrity. The aim of this study was to identify understory bird species associated with changes in the forest structure caused by selective logging and to explore whether it is possible to use these species as a monitoring tool. We observed that Sittasomus griseicapillus, Turdus rufiventris, Lepidocolaptes angustirostris, Casiornis rufus, Thraupis sayaca, and Tolmomyias sulphurescens were associated to unlogged sites with higher density of timber-yielding and standing dead trees. Thamnophilus caerulescens, Leptotila megalura, Synallaxis scutata, Poecilotriccus plumbeiceps, and Catharus ustulatus were favoured by logging activities and associated with understory visual obstruction. Mean cut-off abundance thresholds were 2.74 ind/ha for the avian guild associated with unlogged forest and 1.79 ind/ha for the guild associated with logged forest. Sustainable forest management schemes need to retain the understory visual obstruction at values similar to those of unlogged forest (43.75%), together with an adequate density (≥10 ind/ha) of standing dead trees with at least 19.5 cm in DBH, and a minimum of 210 ind/ha of timber tree species. Bird species identified in this study can be used in monitoring schemes to evaluate the implementation of these guidelines.

Immature ticks on wild birds and the molecular detection of a novel Rickettsia strain in the Ibitipoca State Park, southeastern Brazil.

Birds are recognized hosts of ticks, especially for the immature stages which may harbor various species and strains of Rickettsia. To explore landscapes inhabited by birds and their ticks would expand the knowledge on host-parasite relationships and the rickettsiae. The aim of this paper was to record the diversity of ticks collected on wild birds and assess the phylogenetic position of a novel Rickettsia strain detected in immature ticks. Birds were captured in the Ibitipoca State Park, located in the Minas Gerais state, southeastern Brazil, as part of a long-term research project on the ecology of ticks, birds and Rickettsia. We found three tick species parasitizing birds: Amblyomma aureolatum (63 larvae, 10 nymphs), Haemaphysalis leporispalustris (28 larvae, seven nymphs) and Amblyomma romarioi (27 larvae). Among these, A. aureolatum was the most abundant species including 54% (73/135) of the collected ticks. New tick-host records were: A. romarioi on Turdus amaurochalinus and H. leporispalustris on Thamnophilus caerulescens, Saltator similis and Zonotrichia capensis. Of the 82 ticks tested for Rickettsia spp. by PCR, two larvae (2.5%) of A. romarioi were infected with 'Candidatus Rickettsia paranaensis', a novel putative Rickettsia species closely related to Rickettsia africae, Rickettsia sibirica and Rickettsia parkeri, as corroborated by our phylogenetic analysis. Finally, we present a list of all records of immature stages of H. leporispalustris on passerine birds in Brazil.

Testing the simple and complex versions of Gloger’s rule in the Variable Antshrike (Thamnophilus caerulescens, Thamnophilidae)

AbstractGloger’s rule is a classic ecogeographical principle that, in its simplest version, predicts animals should be darker in warmer and wetter climates. In a rarely tested more complex version, it also predicts animals should be more rufous in warmer and drier climates. The Variable Antshrike (Thamnophilus caerulescens) is a widely distributed South American passerine that presents an impressive amount of plumage color variation and occupies a wide variety of climatic conditions. Moreover, genetic and vocal evidence indicate ongoing hybridization in south-central Bolivia among 3 populations with very distinct plumages. We collected color data from 232 specimens from throughout this species’ distribution to test the predictions of Gloger’s rule. We found a negative correlation between brightness and precipitation, consistent with the simple version of Gloger’s rule. In contrast, we found that birds were darker in cooler climates, contrary to the simple version of Gloger’s rule, but consistent with recent findings in other taxa. We found support for both predictions of the complex Gloger’s rule and suggest it might be driven by background matching. We conclude by concurring with a recent suggestion that the simple version of Gloger’s rule should be reformulated exclusively in terms of humidity.

A simple index to quantify and compare the magnitude of intraspecific geographic plumage colour variation in typical antbirds (Aves: Passeriformes: Thamnophilidae)

AbstractIntraspecific geographic phenotypic variation is a crucial theme in evolutionary biology. Comparing its magnitude across species can provide insights into its ecological and genetic correlates. Here, we developed an index, which we dub the V index, to quantify intraspecific plumage colour variation in typical antbirds (Thamnophilidae), a family which has long interested ornithologists due to a high prevalence of intraspecific variation. The V index is based on a bivariate colour space defined by brightness and redness. Its value for each species equals the mean area occupied by each of its subspecies in that colour space, divided by the area of the species. Lower values indicate greater intraspecific geographic variation. Based on this index, Thamnophilus caerulescens (Variable Antshrike) was exceptionally geographically variable compared to other thamnophilids, as previously suggested based on qualitative evidence. In general, we found that the most variable species had disjunct distributions and deep phylogeographic structure, suggesting an effect of historical population dynamics in producing geographic variation. The V index can be adapted for use with other taxa, traits, and taxonomic levels, and we expect it will instigate novel ways of thinking about phenotypic variation in birds and other animals.

Phylogeography of the Variable Antshrike (Thamnophilus caerulescens), a South American passerine distributed along multiple environmental gradients

The Neotropics show a wealth of distributional patterns shared by many co-distributed species. A distinctive pattern is the so-called “circum-Amazonian distribution,” which is observed in species that do not occur in Amazonia but rather along a belt of forested habitats spanning south and east of Amazonia, the Andean foothills, and often into the Venezuelan Coastal Range and the Tepuis. Although this pattern is widespread across animals and plants, its underlying biogeographic mechanisms remain poorly understood. The Variable Antshrike (Thamnophilus caerulescens) is a sexually dimorphic suboscine passerine that exhibits extreme plumage variation and occurs along the southern portion of the circum-Amazonian belt. We describe broad-scale phylogeographic patterns of T. caerulescens and assess its demographic history using DNA sequences from the mitochondrion and ultraconserved elements (UCEs). We identified three genomic clusters: a) northern Atlantic Forest; b) southeastern Cerrado and central-southern Atlantic Forest, and c) Chaco and Andes. Our results were consistent with Pleistocene divergence followed by gene flow, mainly between the latter two clusters. There were no genetic signatures of rapid population expansions or bottlenecks. The population from the northern Atlantic Forest was the most genetically divergent group within the species. The demographic history of T. caerulescens was probably affected by series of humid and dry periods throughout the Quaternary that generated subtle population expansions and contractions allowing the intermittent connection of habitats along the circum-Amazonian belt. Recognizing the dynamic history of climate-mediated forest expansions, contractions, and connections during the South American Pleistocene is central toward a mechanistic understanding of circum-Amazonian distributions.

Experimental food supplementation increases reproductive effort in the Variable Antshrike in subtropical Brazil.

Food limitation may interact with nest predation and influence nesting patterns, such as breeding season length and renesting intervals. If so, reproductive effort should change with food availability. Thus, when food is limited, birds should have fewer attempts and shorter seasons than when food is not limiting. Here we experimentally test that increased food availability results in increased reproductive effort in a fragmented landscape in the Variable Antshrike (Thamnophilus caerulescens) in southern Brazil. We followed nesting pairs in a naturally fragmented habitat and experimentally supplemented food for half of those pairs. Birds were seen, but evidence of nesting was never found in two small fragments, even though these fragments were larger than individual territories. Pairs with supplemented food were more likely to increase clutch size from two to three eggs and tended to renest sooner (20 d on average) than control pairs. Also, fragment size was associated with breeding patterns, although fragment replicates were unavailable. Nest duration, nest success and breeding season length were all greater, while renesting intervals were shorter, in the largest fragments. Simulations showed that only the largest fragments were able to have a net production of young. Food availability clearly influenced reproductive effort and as a consequence, because of the interaction with predation risk, forest fragments of varying sizes will have complex reproductive dynamics.

Territoriality of Six Thamnophilidae Species In A Cloud Forest In Southeastern Brazil

ABSTRACT Territorial systems of Neotropical birds remain poorly understood, especially considering the effect of interspecific interactions. Studies on territorial behavior provide information about demography and life history, and are useful for the refinement of conservation strategies. We assessed territories of six species of antbirds (Thamnophilidae) from August 2010 to May 2011 at Pedra Azul State Park, a protected area in southeastern Brazil, in a 30-ha sampling grid. Birds were captured, marked, and followed through the study area. Territory sizes of Plain Antvireo (Dysithamnus mentalis), Ferruginous Antbird (Drymophila ferruginea), Ochre-rumped Antbird (Drymophila ochropyga), White-bibbed Antbird (Myrmeciza loricata), White-shouldered Fire-eye (Pyriglena leucoptera), and Variable Antshrike (Thamnophilus caerulescens) were estimated by the convex polygon method. We found 46 territories of the six species. We compared and evaluated the effect of body size on territories among the species. Males and...

Using gap‐crossing capacity to evaluate functional connectivity of two Atlantic rainforest birds and their response to fragmentation

Abstract One of the main consequences of habitat loss and fragmentation is the increase in patch isolation and the consequent decrease in landscape connectivity. In this context, species persistence depends on their responses to this new landscape configuration, particularly on their capacity to move through the interhabitat matrix. Here, we aimed first to determine gap‐crossing probabilities related to different gap widths for two forest birds (Thamnophilus caerulescens, Thamnophilidae; and Basileuterus culicivorus, Parulidae) from the Brazilian Atlantic rainforest. These values were defined with a playback technique and then used in analyses based on graph theory to determine functional connections among forest patches. Both species were capable of crossing forest gaps between patches, and these movements were related to gap width. The probability of crossing 40 m gaps was 50% for both species. This probability falls to 10% when the gaps are 60 m (for B. culicivorus) or 80 m (for T. caerulescens). Actually, birds responded to stimulation about two times more distant inside forest trials (control) than in gap‐crossing trials. Models that included gap‐crossing capacity improved the explanatory power of species abundance variation in comparison to strictly structural models based merely on patch area and distance measurements. These results highlighted that even very simple functional connectivity measurements related to gap‐crossing capacity can improve the understanding of the effect of habitat fragmentation on bird occurrence and abundance.

Territory size of three Antbirds (Aves, Passeriformes) in an Atlantic Forest fragment in southeastern Brazil

Territory size is an important ecological attribute of populations that has been considered a factor determines population density. Antbirds is a large group of mainly insectivorous Neotropical passerines, usually well represented in bird communities from forested landscapes in Neotropical region. Territory sizes for three Antbirds, Thamnophilus caerulescens (Vieillot, 1816) (Variable Antshrike), Dysithamnus mentalis (Temmink, 1823) (Plain Antvireo) e Pyriglena leucoptera (Vieillot, 1818) (White-shouldered Fire-eye), were mapped and their area estimated by the convex polygon method in a 50 ha forest fragment, in southeastern Brazil. The three species presented small territories of similar sizes (< 2 ha) both during the non-reproductive and the reproductive seasons of 2000-2001. Territories overlapped considerably among species but not intraspecifically. Territory sizes increased with body mass of the three species studied (P. leucoptera > T. caerulescens > D. mentalis). We failed to find any effect on territory size for the three species associated with forest edge or distance to the dirt road.

Mitochondrial Variation in Bolivian Populations of the Variable Antshrike (Thamnophilus Caerulescens)

AbstractThe Variable Antshrike (Thamnophilus caerulescens) is arguably the most polytypic thamnophilid, with males ranging from almost entirely jet black to nearly white. The four subspecies that occur in Bolivia are strikingly divergent in male plumage: T. c. aspersiventer (black with white-barred belly), T. c. connectens (black back and bib with white belly), T. c. dinellii (gray throat and back with rufous belly), and T. c. paraguayensis (light gray with white belly). To assess the genetic structure of those taxa in Bolivia, sequence variation at the mitochondrial cytochrome-b gene was screened in 126 individuals collected across transects spanning the plumage and vocal variation in the four forms. A 95-km-wide cline in haplotype frequencies from T. c. aspersiventer to T. c. dinellii was centered in the Serrania Cochabamba across an ecotone from humid to dry Andean foothill habitats. Thamnophilus caerulescens connectens is not a valid taxon, instead representing an introgressed population near the dinellii tail of the T. c. aspersiventer-T. c. dinellii hybrid zone. Although direct contact between T. c. dinellii and T. c. paraguayensis remains undocumented, the mitochondrial data were consistent with introgression along a broad cline extending across most of southern Bolivia. Overall, the transitions in mitochondrial frequencies were remarkably concordant with clinal changes in vocalizations among those same populations (Isler et al. 2005). Both studies highlight the need for increased sampling, in both the geographic extent and number of individuals per population, to address adequately the potential for clinal variation between populations that are not isolated geographically. A more restricted sampling design in the present study might have led to the erroneous conclusion that T. c. aspersiventer, T. c. dinellii, and T. c. paraguayensis have reciprocally monphyletic mitochondrial lineages, making them full species according to some species concepts.

MITOCHONDRIAL VARIATION IN BOLIVIAN POPULATIONS OF THE VARIABLE ANTSHRIKE (THAMNOPHILUS CAERULESCENS)

Abstract The Variable Antshrike (Thamnophilus caerulescens) is arguably the most polytypic thamnophilid, with males ranging from almost entirely jet black to nearly white. The four subspecies that occur in Bolivia are strikingly divergent in male plumage: T. c. aspersiventer (black with white-barred belly), T. c. connectens (black back and bib with white belly), T. c. dinellii (gray throat and back with rufous belly), and T. c. paraguayensis (light gray with white belly). To assess the genetic structure of those taxa in Bolivia, sequence variation at the mitochondrial cytochrome-b gene was screened in 126 individuals collected across transects spanning the plumage and vocal variation in the four forms. A 95-km-wide cline in haplotype frequencies from T. c. aspersiventer to T. c. dinellii was centered in the Serrania Cochabamba across an ecotone from humid to dry Andean foothill habitats. Thamnophilus caerulescens connectens is not a valid taxon, instead representing an introgressed population near the din...

Bird species richness in natural forest patches in southeast Brazil

Studies of populations in fragmented habitats have become essential tools in biodiversity conservation. This study was conducted at 14 natural forest patches (“capões”) in the Serra da Canastra National Park, with the purpose of evaluating bird species richness of these patches in relation to patch area and distance to other patches. In this study, area and isolation did not explain much of the variation in bird richness and abundance when all species were considered. However, when only forest-dependent species were considered, both area and isolation were significantly related to patch richness, suggesting that the distribution of these birds is highly related to forest patch area and is limited by dispersal ability of the species through the matrix. But, some individuals of some forest-dependent species (Thamnophilus caerulescens, and Basileuterus leucophrys) were also found in the very small (0.05 ha) or most isolated (430 to 700 m) patches. This fact may be related to an adaptation of these species to the naturally fragmented landscape, since this is a landscape which have not been altered considerably in the last two centuries. Our results showed that this natural landscape of small and isolated forest patches imbedded in a grassland matrix may support populations of several forest-dependent species of birds, increasing the regional biodiversity.