Gustavo A. Bravo

A phylogenetic approach to disentangling the role of competition and habitat filtering in community assembly of Neotropical forest birds

1. Methods that assess patterns of phylogenetic relatedness, as well as character distribution and evolution, allow one to infer the ecological processes involved in community assembly. Assuming niche conservatism, assemblages should shift from phylogenetic clustering to evenness with decreasing geographic scale because the relative importance of mechanisms that shape assemblages is hypothesized to be scale-dependent. Whereas habitat filtering is more likely to act at regional scales because of increased habitat heterogeneity that allows sorting of ecologically similar species in contrasting environments, competition is more likely to act at local scales because low habitat heterogeneity provides few opportunities for niche partitioning. 2. We used species lists to assess assemblage composition, data on ecologically-relevant traits, and a molecular phylogeny, to examine the phylogenetic structure of antbird (Thamnophilidae) assemblages at three different geographical scales: regional (ecoregions), intermediate (100-ha plots) and local (mixed-flocks). In addition, we used patterns of phylogenetic beta diversity and beta diversity to separate the factors that structure antbird assemblages at regional scales. 3. Contrary to previous findings, we found a shift from phylogenetic evenness to clustering with decreasing geographical scale. We argue that this does not reject the hypothesis that habitat filtering is the predominant force in regional community assembly, because analyses of trait evolution and structure indicated a lack of niche conservatism in antbirds. 4. In some cases, phylogenetic evenness at regional scales can be an effect of historical biogeographic processes instead of niche-based processes. However, regional patterns of beta diversity and phylogenetic beta diversity suggested that phylogenetic structure in our study cannot be explained by the history of speciation and dispersal of antbirds, further supporting the habitat-filtering hypothesis. 5. Our analyses suggested that competitive interactions might not play an important role locally, which would provide a plausible explanation for the high alpha diversity of antbirds in Amazonia. 6. Finally, we emphasize the importance of including trait information in studies of phylogenetic community structure to adequately assess the mechanisms that determine species co-existence.

Adaptive processes drive ecomorphological convergent evolution in antwrens (Thamnophilidae).

Phylogenetic niche conservatism (PNC) and convergence are contrasting evolutionary patterns that describe phenotypic similarity across independent lineages. Assessing whether and how adaptive processes give origin to these patterns represent a fundamental step toward understanding phenotypic evolution. Phylogenetic model‐based approaches offer the opportunity not only to distinguish between PNC and convergence, but also to determine the extent that adaptive processes explain phenotypic similarity. The Myrmotherula complex in the Neotropical family Thamnophilidae is a polyphyletic group of sexually dimorphic small insectivorous forest birds that are relatively homogeneous in size and shape. Here, we integrate a comprehensive species‐level molecular phylogeny of the Myrmotherula complex with morphometric and ecological data within a comparative framework to test whether phenotypic similarity is described by a pattern of PNC or convergence, and to identify evolutionary mechanisms underlying body size and shape evolution. We show that antwrens in the Myrmotherula complex represent distantly related clades that exhibit adaptive convergent evolution in body size and divergent evolution in body shape. Phenotypic similarity in the group is primarily driven by their tendency to converge toward smaller body sizes. Differences in body size and shape across lineages are associated to ecological and behavioral factors.

DNA sequence data reveal a subfamily-level divergence within Thamnophilidae (Aves: Passeriformes).

The Thamnophilidae is a diverse radiation of insectivorous passerine birds that comprises nearly 220 species and is mostly restricted to the lowlands and lower montane forests of the Neotropics. Current classification within Thamnophilidae relies primarily on morphological variation, but recent incorporation of molecular and vocal data has promoted changes at various taxonomic levels. Here we demonstrate that the genus Terenura is polyphyletic because Terenura callinota, T. humeralis, T. spodioptila, and T. sharpei are phylogenetically distant from the type species of the genus, Terenura maculata. More importantly, the former four species are not particularly closely related to any other thamnophilids and represent a clade that is sister to all other members of the family. Because no genus name is available for this previously undetected lineage in the Thamnophilidae, we describe the genus Euchrepomis for callinota, humeralis, spodioptila, and sharpei, and erect the subfamily Euchrepomidinae. We discuss the taxonomic and evolutionary significance of this divergent lineage. This study highlights the importance of taxonomic coverage and the inclusion of type taxa to redefine classifications to reflect accurately evolutionary relationships.

Inferring speciation history in the Andes with reduced‐representation sequence data: an example in the bay‐backed antpittas (Aves; Grallariidae; Grallaria hypoleuca s. l.)

In the Andes, humid‐forest organisms frequently exhibit pronounced genetic structure and geographic variation in phenotype, often coincident with physical barriers to dispersal. However, phylogenetic relationships of clades have often been difficult to resolve due to short internodes. Consequently, even in taxa with well‐defined genetic structure, the temporal and geographic sequences of dispersal and vicariance events that led to this differentiation have remained opaque, hindering efforts to test the association between diversification and earth history and to understand the assembly of species‐rich communities on Andean slopes. Here, we use mitochondrial DNA and thousands of short‐read sequences generated with genotyping by sequencing (GBS) to examine the geographic history of speciation in a lineage of passerine birds found in the humid forest of the Andes, the ‘bay‐backed’ antpitta complex (Grallaria hypoleuca s. l). Mitochondrial DNA genealogies documented genetic structure among clade but were poorly resolved at nodes relevant for biogeographic inference. By contrast, relationships inferred from GBS loci were highly resolved and suggested a biogeographic history in which the ancestor originated in the northern Andes and dispersed south. Our results are consistent with a scenario of vicariant speciation wherein the range of a widespread ancestor was fragmented as a result of geologic or climatic change, rather than a stepping‐stone series of dispersal events across pre‐existing barriers. However, our study also highlights challenges of distinguishing dispersal‐mediated speciation from static vicariance. Our results further demonstrate the substantial evolutionary timescale over which the diverse biota of the Andes was assembled.

THE AVIAN BIOGEOGRAPHY OF AN AMAZONIAN HEADWATER: THE UPPER UCAYALI RIVER, PERU

Abstract The Ucayali River is a major tributary of the Amazon, but it narrows considerably toward its headwater at the base of the Andes. This region, the upper Ucayali Valley, is of biological interest for the large number of closely related birds elsewhere separated from each other by major rivers that come into close proximity and potential contact. Between 2006–2011, we conducted the first modern ornithological inventory of the upper Ucayali River and sampled localities in all major avian habitats on either side of the river. We document the continued importance of the Ucayali River as a biogeographic barrier, even at the headwater, but also find that some mixing occurs, both in the form of taxa crossing to the “wrong” bank and in the potential intergradation of distinct forms. We describe the biogeography of birds in the region, characterize the avifaunas of major habitats, and discuss in detail species of particular biogeographical interest.

Inundicola Bravo, Isler, and Brumfield 2013 is a junior synonym of Akletos Dunajewski 1948 (Aves: Passeriformes: Thamnophilidae)

In examining the history of generic names given to species in the polytypic genus Myrmeciza (Isler et al. 2013), we did not uncover the genus Akletos . This name had been applied by Dunajewski (1948) to a new species, Akletos peruvianus , represented by a single specimen collected by Fiedler on 16 March 1934 at what is now Cumaria, Ucayali, Peru, and deposited in the Museum and Institute of Zoology of the Polish Academy of Sciences (MIZ 34107). The species was said to be similar to Attila Lesson, which at the time was placed in the family Cotingidae. The holotype was later identified as Myrmeciza melanoceps by Stresemann (Mayr 1956) as reported by Mlikovský (2009) who also confirmed the identification. To provide further confirmation and documentation, Dominika Mierzwa of the Museum and Institute of Zoology of the Polish Academy of Sciences provided digital photographs of the type, clearly a female, an example of which is included herein. Thus, the generic name Inundicola Bravo, Isler, and Brumfield 2013 is a junior synonym of Akletos Dunajewski 1948. The generic descriptions provided in Isler et al. 2013 are amended as follows.

Systematics of the obligate ant-following clade of antbirds (Aves: Passeriformes: Thamnophilidae)

ABSTRACT Results of a comprehensive molecular phylogeny of the family Thamnophilidae were consistent with earlier findings that almost all obligate army-ant-followers of the family form a monophyletic group that contains five well-supported clades and encompasses six currently recognized genera: Phaenostictus, Pithys, Willisornis, Gymnopithys, Rhegmatorhina, and Phlegopsis. A comparative analysis of seven suites of morphological, behavioral, and ecological traits within the context of the phylogeny reinforced the validity of five of these genera, but results for the sixth, Gymnopithys, were internally inconsistent and required the description of a new genus, Oneillornis.