Gustavo S. Cabanne

Nuclear and mitochondrial phylogeography of the Atlantic forest endemic Xiphorhynchus fuscus (Aves: Dendrocolaptidae): Biogeography and systematics implications

We studied the intraspecific evolutionary history of the South American Atlantic forest endemic Xiphorhynchusfuscus (Aves: Dendrocolaptidae) to address questions such as: Was the diversification of this birds populations associated to areas of avian endemism? Which models of speciation (i.e., refuges, river as barriers or geotectonism) explain the diversification within X. fuscus? Does the genetic data support subspecies as independent evolutionary units (species)? We used mitochondrial (n=34) and nuclear (n=68) DNA sequences of X. fuscus to study temporal and spatial relationships within and between populations. We described four main monophyletic lineages that diverged during the Pleistocene. The subspecies taxonomy did not match all the evolutionary lineages; subspecies atlanticus was the only one that represented a monophyletic and isolated lineage. The distribution of these lineages coincided with some areas of endemism for passerines, suggesting that those areas could be regions of biotic differentiation. The ancestor of X. fuscus diverged approximately 3 million years ago from Amazonian taxa and the phylogeographic pattern suggested that X. fuscus radiated from northeastern Brazil. Neither the riverine nor the geotectonic vicariance models are supported as the primary cause for diversification of geographic lineages, but rainforest contractions and expansions (ecological vicariance) can explain most of the spatial divergence observed in this species. Finally, analyses of gene flow and divergence time estimates suggest that the endangered subspecies atlanticus (from northeastern Brazil) can be considered a full species under the general lineage species concept.

The genetic effects of Late Quaternary climatic changes over a tropical latitudinal gradient: diversification of an Atlantic Forest passerine

The increase in biodiversity from high to low latitudes is a widely recognized biogeographical pattern. According to the latitudinal gradient hypothesis (LGH), this pattern was shaped by differential effects of Late Quaternary climatic changes across a latitudinal gradient. Here, we evaluate the effects of climatic changes across a tropical latitudinal gradient and its implications to diversification of an Atlantic Forest (AF) endemic passerine. We studied the intraspecific diversification and historical demography of Sclerurus scansor, based on mitochondrial (ND2, ND3 and cytb) and nuclear (FIB7) gene sequences. Phylogenetic analyses recovered three well‐supported clades associated with distinct latitudinal zones. Coalescent‐based methods were applied to estimate divergence times and changes in effective population sizes. Estimates of divergence times indicate that intraspecific diversification took place during Middle–Late Pleistocene. Distinct demographic scenarios were identified, with the southern lineage exhibiting a clear signature of demographic expansion, while the central one remained more stable. The northern lineage, contrasting with LGH predictions, exhibited a clear sign of a recent bottleneck. Our results suggest that different AF regions reacted distinctly, even in opposite ways, under the same climatic period, producing simultaneously favourable scenarios for isolation and contact among populations.

Phylogeography of an Atlantic forest passerine reveals demographic stability through the last glacial maximum

In this study we analyzed the phylogeographic pattern and historical demography of an endemic Atlantic forest (AF) bird, Basileuterus leucoblepharus, and test the influence of the last glacial maximum (LGM) on its population effective size using coalescent simulations. We address two main questions: (i) Does B. leucoblepharus present population genetic structure congruent with the patterns observed for other AF organisms? (ii) How did the LGM affect the effective population size of B. leucoblepharus? We sequenced 914 bp of the mitochondrial gene cytochrome b and 512 bp of the nuclear intron 5 of beta-fibrinogen of 62 individuals from 15 localities along the AF. Both molecular markers revealed no genetic structure in B. leucoblepharus. Neutrality tests based on both loci showed significant demographic expansion. The extended Bayesian skyline plot showed that the species seems to have experienced demographic expansion starting around 300,000 years ago, during the late Pleistocene. This date does not coincide with the LGM and the dynamics of population size showed stability during the LGM. To further test the effect of the LGM on this species, we simulated seven demographic scenarios to explore whether populations suffered specific bottlenecks. The scenarios most congruent with our data were population stability during the LGM with bottlenecks older than this period. This is the first example of an AF organism that does not show phylogeographic breaks caused by vicariant events associated to climate change and geotectonic activities in the Quaternary. Differential ecological, environmental tolerances and habitat requirements are possibly influencing the different evolutionary histories of these organisms. Our results show that the history of organism diversification in this megadiverse Neotropical forest is complex.

Phylogeography and genetic structure of two Patagonian shag species (Aves: Phalacrocoracidae).

We compared the phylogeographic and genetic structure of two sympatric shag species, Phalacrocorax magellanicus (rock shag) and Phalacrocorax atriceps (imperial shag), from Patagonia (southern South America). We used multilocus genotypes of nuclear DNA (microsatellite loci) from 324 individuals and mitochondrial DNA sequences (ATPase) from 177 individuals, to evaluate hypotheses related to the effect of physical and non-physical barriers on seabird evolution. Despite sharing many ecological traits, the focal species strongly differ in two key aspects: P. magellanicus has a strong tendency to remain at/near their breeding colonies during foraging trips and the non-breeding season, while P. atriceps exhibits the converse pattern. Both species showed similar mtDNA genetic structure, where colonies from the Atlantic Coast, Pacific Coast and Fuegian region were genetically divergent. We also found similarities in the results of Bayesian clustering analysis of microsatellites, with both species having four clusters. However population differentiation (e.g. Fst, Φst) was higher in P. magellanicus compared to P. atriceps, and average membership probabilities of individuals to specific clusters (Q-values) were also higher in the former. Phalacrocorax magellanicus has strong phylogeographic structure, consistent with the impact of Pleistocene glaciations, with diagnostic haplotypes associated with each of the three mentioned regions. The same pattern was not as evident for P. atriceps. Migration rate estimators were higher for P. atriceps than for P. magellanicus; however both species followed an n-island-like model of gene flow, this implies that dispersal occurs across the continental land mass that separates Atlantic and Pacific Oceans. Our results supported the hypothesis that non-physical barriers are important drivers of the genetic and phylogeographic structure in seabirds, and also that physical barriers constitute effective but not absolute impediments to gene flow.

Range expansion, density and conservation of the Araucaria Tit-spinetail Leptasthenura setaria (Furnariidae) in Argentina: the role of araucaria Araucaria angustifolia (Araucariaceae) plantations

Summary The Araucaria Tit-spinetail Leptasthenura setaria (Furnariidae) is a globally Near Threatened species. Its habitat, the araucaria (Araucaria angustifolia) rainforest of south-east Brazil and north-east Argentina, is highly fragmented and reduced to nearly 10% of its original range. The species has also been recorded in commercial araucaria plantations that comprise about 80% of its suitable habitat in Argentina. This situation provides an opportunity for the conservation of the Araucaria Tit-spinetail in a human-modified landscape. We assessed the occurrence of the species in the region and estimated its density and total population size in araucaria plantations in Argentina. We discuss the value of plantations in the conservation of the bird, and evaluate its conservation status in Argentina using IUCN criteria. The density of the tit-spinetail in araucaria plantations, estimated by a distance sampling method, was 9 birds ha 21 . The overall population size in commercial plantations appears to be large (.7,000 birds), showing that araucaria plantations play an important role in the conservation of the bird. However, plantations must not replace the native araucaria forest because the former are an intrinsically fragmented habitat influenced primarily by economic factors and forestry practices. The longterm conservation and restoration of araucaria rainforest in Argentina and Brazil must be guaranteed to conserve the Araucaria Tit-spinetail and other species associated with this rainforest. Based on the restricted and very fragmented habitat, the Araucaria Tit-spinetail should be regarded as Vulnerable in Argentina.

The niche and phylogeography of a passerine reveal the history of biological diversification between the Andean and the Atlantic forests

The Atlantic Forest is separated from the Andean tropical forest by dry and open vegetation biomes (Chaco and Cerrado). Despite this isolation, both rainforests share closely related lineages, which suggest a past connection. This connection could have been important for forest taxa evolution. In this study, we used the Saffron-billed Sparrow (Arremon flavirostris) as a model to evaluate whether the Andean and the Atlantic forests act as a refugia system, as well as to test for a history of biogeographic connection between them. In addition, we evaluated the molecular systematic of intraspecific lineages of the studied species. We modeled the current and past distribution of A. flavirostris, performed phylogeographic analyses based on mitochondrial and nuclear genes, and used Approximate Bayesian Computation (ABC) analyses to test for biogeographic scenarios. The major phylogeographic disjunction within A. flavirostris was found between the Andean and the Atlantic forests, with a divergence that occurred during the Mid-Pleistocene. Our paleodistribution models indicated a connection between these forest domains in different periods and through both the Chaco and Cerrado. Additionally, the phylogeographic and ABC analyses supported that the Cerrado was the main route of connection between these rainforests, but without giving decisive evidence against a Chaco connection. Our study with A. flavirostris suggest that the biodiversity of the Andean and of the Atlantic forests could have been impacted (and perhaps enriched?) by cycles of connections through the Cerrado and Chaco. This recurrent cycle of connection between the Andean and the Atlantic Forest could have been important for the evolution of Neotropical forest taxa. In addition, we discussed taxonomic implications of the results and proposed to split the studied taxon into two full species.

How Past Vicariant Events Can Explain the Atlantic Forest Biodiversity

Gisele Pires Mendonca Dantas1, Gustavo Sebastian Cabanne3 and Fabricio Rodrigues Santos2 1Instituto de Biociencias – Universidade de Sao PauloRua do Matao, Cidade Universitaria, Sao Paulo, SP 2Instituto de Ciencias BiologicasUniversidade Federal de Minas GeraisAv. Antonio Carlos, Belo Horizonte, MG 3Museo Argentino de Ciencias Naturales, “Bernadino Rivadavia”, Av. Angel Gallardo 470, Buenos Aires 1,2Brazil 3Argentina

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.

Forest corridors between the central Andes and the southern Atlantic Forest enabled dispersal and peripatric diversification without niche divergence in a passerine

The central Andean rainforests and the Atlantic Forest are separated by the Chaco and the Cerrado domains. Despite this isolation, diverse evidence suggests that these rainforests have been connected in the past. However, little is known about the timing and geographic positions of these connections, as well as their effects on diversification of species. In this study, we used the Black-goggled Tanager (Trichothraupis melanops, Thraupidae) as a model to study whether the Andean and the Atlantic forests have acted as a refugia system, and to evaluate biogeographic hypotheses of diversification and connection between these rainforests. We compared alternative biogeographic scenarios by using Approximate Bayesian Computation (ABC), modeled range shifts across time, and assessed niche divergence between regions. The results indicated that the major phylogeographic gap within T. melanops is located between these rainforests. The ABC analysis supported peripatric diversification, with initial dispersal from the Atlantic Forest to the Andes during the Mid-Pleistocene. Also, the results supported an Andean-Atlantic forests connection through the current Cerrado-Chaco transition, linking the southern Atlantic Forest with the central Andes. Our findings, taken together with other studies, support that the connection between these biomes has been recurrent, and that has occurred mostly through the Cerrado and/or the Cerrado-Chaco transition. The data also support that the connection dynamic has played an important role in the biological diversification, by promoting peripatric divergence in some forest taxa restricted to both biomes.