Natalia C. García

Continental-scale analysis reveals deep diversification within the polytypic Red-crowned Ant Tanager (Habia rubica, Cardinalidae).

We explored the phylogeographic patterns of intraspecific diversity in the Red-crowned Ant Tanager (Habia rubica) throughout its continent-wide distribution, in order to understand its evolutionary history and the role of evolutionary drivers that are considered to promote avian diversification in the Neotropics. We sampled 100 individuals of H. rubica from Mexico to Argentina covering the main areas of its disjunct distribution. We inferred phylogenetic relationships through Bayesian and maximum parsimony methodologies based on mitochondrial and nuclear markers, and complemented genetic analyses with the assessment of coloration and behavioral differentiation. We found four deeply divergent phylogroups within H. rubica: two South American lineages and two Mexican and Middle American lineages. The divergence event between the northern and southern phylogroups was dated to c. 5.0 Ma, seemingly related to the final uplift of the Northern Andes. Subsequently, the two South American phylogroups split c. 3.5 Ma possibly due to the development of the open vegetation corridor that currently isolates the Amazonian and Atlantic forests. Diversification throughout Mexico and Middle America, following dispersion across the Isthmus of Panama, was presumably more recent and coincident with Pleistocene climatic fluctuations and habitat fragmentations. The analyses of vocalizations and plumage coloration showed significant differences among main lineages that were consistent with the phylogenetic evidence. Our findings suggest that the evolutionary history of H. rubica has been shaped by an assortment of diversification drivers at different temporal and spatial scales resulting in deeply divergent lineages that we recommend should be treated as different species.

Intraspecific and interspecific vocal variation in three Neotropical cardinalids (Passeriformes : Fringillidae) and its relationship with body mass

Abstract Several studies, of a large number of bird species, have shown that song frequencies have a strong negative relationship with body size. However, mixed results were obtained at the intraspecific level or when comparing closely related species. Here, we compared the vocalisations of the monotypic Glaucous-blue Grosbeak (Cyanoloxia glaucocaerulea), three of five subspecies of the Ultramarine Grosbeak (Cyanocompsa brissonii) and all four subspecies of the Blue-black Grosbeak (Cyanocompsa cyanoides). These taxa of Neotropical cardinalids differ significantly in body size, so we compared them to examine the allometric relationship of body size with song frequencies, using body mass as a proxy of body size. The maximum frequency and the emphasised frequency (i.e. the frequency of the song of highest amplitude) showed the expected negative correlation with body mass, supporting the idea that the aforementioned relationship stands when comparing closely related lineages in Cyanoloxia and Cyanocompsa. We also found that the duration of notes, rate of production of notes and duration of inter-note interval correlated with body mass: heavier species had longer notes produced at a lower rate and separated by longer intervals. The correlation of temporal variables with body mass suggests that body size could also influence the temporal structure of song. Our findings highlight once again the importance of considering the role of avian morphology when studying the evolution of song, even if differences in frequency and temporal variables of songs are small.

Stability and change through time in the dialects of a Neotropical songbird, the Rufous-collared Sparrow

Abstract Behavioural characters that are learned can show temporal variation resulting from changes introduced in new generations during the learning process. The song of the Rufous-collared Sparrow (Zonotrichia capensis) shows significant geographical variation associated with habitat, delimiting song dialects. To study the temporal stability or change in dialects of Rufous-collared Sparrows at a microgeographical scale, we compared recordings made at Reserva El Destino, in north-eastern coastal Buenos Aires Province, Argentina, during 1987 and 2000 with recordings made during 2010 and 2011. We found that the geographical boundaries of the dialects remained stable over the period of 24 years. As we did not detect gross changes in the habitat of the study area over that period, we conclude that habitat is an important factor in maintaining geographical boundaries of dialects. Within the dialects, variation in some variables detected between 1987 and 2000 persisted to 2010–11 whereas other variables showed reversal over that period. These findings are consistent with the hypothesis that some changes in song were the result of neutral variation, whereby changes resulting from random factors, such as copying error, could have been maintained or introduced across generations. Our results show that comparing more than two points in time is fundamental to a better understanding of temporal variation of song and its possible causes.

Barcoding the butterflies of southern South America: Species delimitation efficacy, cryptic diversity and geographic patterns of divergence

Because the tropical regions of America harbor the highest concentration of butterfly species, its fauna has attracted considerable attention. Much less is known about the butterflies of southern South America, particularly Argentina, where over 1,200 species occur. To advance understanding of this fauna, we assembled a DNA barcode reference library for 417 butterfly species of Argentina, focusing on the Atlantic Forest, a biodiversity hotspot. We tested the efficacy of this library for specimen identification, used it to assess the frequency of cryptic species, and examined geographic patterns of genetic variation, making this study the first large-scale genetic assessment of the butterflies of southern South America. The average sequence divergence to the nearest neighbor (i.e. minimum interspecific distance) was 6.91%, ten times larger than the mean distance to the furthest conspecific (0.69%), with a clear barcode gap present in all but four of the species represented by two or more specimens. As a consequence, the DNA barcode library was extremely effective in the discrimination of these species, allowing a correct identification in more than 95% of the cases. Singletons (i.e. species represented by a single sequence) were also distinguishable in the gene trees since they all had unique DNA barcodes, divergent from those of the closest non-conspecific. The clustering algorithms implemented recognized from 416 to 444 barcode clusters, suggesting that the actual diversity of butterflies in Argentina is 3%–9% higher than currently recognized. Furthermore, our survey added three new records of butterflies for the country (Eurema agave, Mithras hannelore, Melanis hillapana). In summary, this study not only supported the utility of DNA barcoding for the identification of the butterfly species of Argentina, but also highlighted several cases of both deep intraspecific and shallow interspecific divergence that should be studied in more detail.

Vocal variation in relation to genetic structure in an Atlantic forest woodcreeper (Xiphorhynchus fuscus): evolutionary and taxonomic implications

AbstractThe analysis of intra-specific geographical variation is central to the study of the evolutionary and speciation processes, providing insights into the mechanisms leading to current diversity patterns. In the last decades, analyses of within-species variation moved its focus from phenotypic traits to the analysis of variation in genetic markers. Modern phylogeographic studies could be significantly improved by including detailed phenotypic variation analyses, allowing a better understanding of the biological processes driving similar or opposing patterns in phenotype and molecular markers differentiation. Here, we analyze vocal variation within the Lesser Woodcreeper (Xiphorhynchus fuscus), an Atlantic forest suboscine passerine, in relation to the genetic lineages previously described for this species. Our results show that two of the genetic clades within this species have their own vocal type, while the other two lineages share a common type. This finding supports the notion that the same events which modeled part of the genetic structure within X. fuscus also led to the accumulation of vocal differences. It also provides evidence to support the elevation of the subspecies atlanticus to a species-level taxon.ZusammenfassungStimmliche Variation in Relation zur genetischen Struktur bei einer Baumsteigerart (Xiphorhynchus fuscus) atlantischer Wälder und ihre Bedeutung für Evolution und Taxonomie Für Studien der Evolution und von Artbildungsprozessen ist die Untersuchung intraspezifischer geografischer Variation von zentraler Bedeutung und ermöglicht Rückschlüsse auf die Mechanismen, welche zu den derzeitigen Diversitätsmustern geführt haben. Bei Analysen innerartlicher Variation hat sich während der letzten Jahrzehnte der Schwerpunkt von phänotypischen Merkmalen zur Analyse der Variation genetischer Marker verlagert. Die Einbeziehung detaillierter Analysen phänotypischer Variation wäre ein signifikanter Gewinn für heutige phylogeografische Untersuchungen und würde zu einem besseren Verständnis der biologischen Prozesse führen, welche ähnliche oder entgegengesetzte Muster bei der Differenzierung phänotypischer und molekularer Marker entstehen lassen. Hier untersuchen wir die stimmliche Variation beim Blasskehl-Baumsteiger (Xiphorhynchus fuscus), einer suboszinen Singvogelart atlantischer Wälder, in Relation zu den bisher beschriebenen genetischen Abstammungslinien für diese Art. Unsere Ergebnisse zeigen, dass zwei der genetischen Kladen innerhalb der Art ihren eigenen Stimmtyp besitzen, während sich die zwei übrigen Abstammungslinien einen gemeinsamen Typ teilen. Dies bestätigt die Theorie, dass dieselben Ereignisse, welche Teile der genetischen Struktur innerhalb von X. fuscus geprägt haben, auch zur Herausbildung stimmlicher Unterschiede geführt haben. Außerdem dient dies als Beleg zur Untermauerung der Erhebung der Unterart atlanticus zu einem Taxon auf Artebene.

Viewing geometry affects sexual dichromatism and conspicuousness of noniridescent plumage of Swallow Tanagers (Tersina viridis)

ABSTRACT Some types of plumage color are difficult to characterize spectrophotometrically because the properties of the reflected light change with viewing geometry (i.e. the relative positions of the light source and the observer, and the orientation of the feather). This is the case for the noniridescent plumage coloration of the Swallow Tanager (Tersina viridis), which seems to change from a human perspective as the angle between the light source and the observer varies. In this study, we measured plumage reflectance with different angles of illumination and/or observation, and used avian visual models to evaluate the change in sexual dichromatism and conspicuousness with viewing geometry from a birds perspective. We also calculated different color parameters to assess how these changed with viewing conditions. Sexual dichromatism showed large changes, with its maximum coinciding with the angle combination between illuminant and observer that produced both the highest conspicuousness for males and the highest crypsis for females. The conspicuousness of males also varied with viewing geometry, and was consistently less when viewed by the visual system of a potential avian predator (VS) than by that of a conspecific (UVS). The change in perceived coloration was mainly related to large variation in hue and chroma in the plumage of males as the relative angle between the illumination and observation probes changed. Our results show that viewing geometry can alter color perception, even for noniridescent plumage coloration. Therefore, the relative position of the light source and the observer should be considered in studies of avian visual communication, particularly for species with plumage coloration similar to that of Swallow Tanagers.

Dissecting the roles of body size and beak morphology in song evolution in the “blue” cardinalids (Passeriformes: Cardinalidae)

ABSTRACT Certain vocal signals can be difficult or challenging to produce due to constraints on vocal mechanics. In the case of birdsong, both body size and beak morphology have been shown to constrain spectral and temporal song parameters. Therefore, variation within a clade in both these morphological traits could exert an important effect in vocal evolution and diversity. However, given the allometric relationship between body size and beak size, it is not always easy to separate the effects they may have. Additionally, different habitats impose different sources of sound attenuation and degradation, and birdsong seems to be adapted to minimize habitat-specific sound degradation. Here, we analyze vocal variation in relation to both body size and beak morphology in 13 of 14 species in the “blue” clade of the Cardinalidae, controlling for habitat characteristics. On one hand, we found the predicted negative correlation of body size with song frequencies, but no effect of body size on temporal variables. On the other hand, we found no relationship between different beak dimensions (corrected by body size) and song frequencies, but we found that beak length was correlated negatively with note rate and positively with the duration of the interval between notes. Similar results have been found previously, but mostly in species with trilled songs, in which notes are equal and produced at a constant rate. Our results show that different morphological variables, even if strongly correlated, can exert differential constraints in a complex behavioral trait such as song. A better understanding of the relevance of these proximate factors in shaping vocal evolution is fundamental to understanding the causes of avian vocal diversity.